Comparative efficacy and toxic effects of carvacryl acetate and carvacrol on sheep gastrointestinal nematodes and mice

Anthelmintic activity on Haemonchus contortus and toxicity of benzoyl-carvacrol: a study in vitro, in silico and in vivo

Carvacrol is isolated from essential oils and possesses activity against gastrointestinal nematodes of small ruminants. Benzoylation has been proposed to improve its pharmacological and pharmacokinetic properties. The objectives of this study were to evaluate the ovicidal activity of benzoyl-carvacrol (BC) against Haemonchus contortus, the in silico interaction of BC with the β-tubulin protein and the toxicity of this compound. Carvacrol was subjected to benzoylation and analyzed by gas chromatography coupled to mass spectrometry (GC/MS). The activity of BC and carvacrol was evaluated against H. contortus in the egg hatching test. The in silico study was based on molecular docking with the β-tubulin and thiabendazole used as control. The acute toxicity test was performed with BC and carvacrol by up-and-down procedure (limit test: 2,000 mg/kg) in Wistar rats. GC/MS confirmed the benzoylation. BC and carvacrol inhibited egg hatching by 99.70 and 98.89% at concentrations of 3.16 and 1 mg/mL, respectively, and interacted with β-tubulin. No mortality was caused by compounds, but rats treated with carvacrol demonstrated intoxication signs. These findings indicated that BC showed effect on H. contortus and can potentially interact with β-tubulin of nematodes in addition to presenting toxicological safety in laboratory animals.

Harnessing Plant-Derived Terpenoids for Novel Approaches in Combating Bacterial and Parasite Infections in Veterinary and Agricultural Settings

The rising resistance to conventional antimicrobial therapies in veterinary contexts poses a formidable challenge. While various innovative treatment strategies for pathogenic infections have emerged, their success still needs to be improved, warranting continued research. Recent investigations into natural products as potential sources for biologically active therapeutics have gained traction. Phytochemicals present a promising alternative in combating a spectrum of pathogens, including bacteria, fungi and parasites. One such class of phytochemicals with mounting potential is the structurally diverse terpenes. These chemicals contribute to plants' characteristic odour and medicinal effects and have been widely investigated in the scientific literature for their exceptional antibacterial activity. Their efficacy is demonstrated through diverse mechanisms, encompassing damage to bacterial membranes, suppression of virulence factors, and interference with enzymes, toxins, and biofilm formation. This review comprehensively examines terpenes' in vitro and in vivo activity and their derivatives against pathogens, elucidating their potential against antimicrobial resistance (AMR) and the underlying mechanisms specific to each terpene class. The findings underscore the burgeoning potential of terpene therapy as a viable alternative or supplementary approach to conventional antibiotics in addressing bacterial and parasitic infections in livestock and companion animals.

Morphological effects of acetylcarvacrol on thyroid of Wistar rats subjected to repeated dose dermal and oral toxicity tests

Acetylcarvacrol is a semi-synthetic product derived from carvacrol and has known activity against ticks. In vertebrates, the thyroid has been used as a bioindicator in toxicity studies due to its sensitivity to external factors. Thus, the objective of this study was to evaluate the toxic effects of acetylcarvacrol in Wistar rats subjected to repeated dose dermal and oral toxicity tests by means of histopathological analysis of the thyroid. For each test, the rats were divided into 4 groups containing 5 animals. In the topical treatment test, acetylcarvacrol was applied to the trichotomized back of each animal at concentrations of 26, 52 and 104 μL/mL for 21 days. In the oral test, the animals were fed acetylcarvacrol by gavage at concentrations of 26, 52 and 104 μL/mL for 30 days. The control groups were treated only with the vehicles. A significant increase in interstitial tissue vascularization was observed in the group treated topically with the highest concentration of acetylcarvacrol compared to the control. No significant changes were observed between the treatment and control groups in the oral experiment. The comparison between the treated groups and their respective controls also showed no differences in the colloid, the follicle and the follicular cells. The reduced occurrence of changes in this tissue suggests relative safety for use in the control of ticks, although caution is needed when using it at high concentrations or for long periods of time.

Preclinical safety assessment in rats after dermal exposure to acetylcarvacrol, a potential acaricide against the brown dog tick

Carvacrol, a phenolic monoterpene found in essential oils of plants of the Lamiaceae family, emerges as an alternative acaricide of plant origin. Its acetylation was proposed to obtain a derivative compound with a better pharmacological profile and lower toxicity to non-target organisms. The present study aimed to assess the preclinical safety of acetylcarvacrol after dermal application in Wistar rats, through the examination of hematological and biochemical parameters, as well as histopathological analysis of the skin, liver and kidney. For this, twenty rats were distributed into four groups with five animals each. Three groups received treatment with different concentrations of the substance (26, 52, and 104 µL/mL) based on the lethal concentration for Rhipicephalus sanguineus ticks, and one group (Control) received only the vehicle. Acetylcarvacrol was applied daily to a trichotomized skin area for 21 days. No changes in hematological parameters were observed. Regarding biochemical analysis, a slight increase in urea and alanine transaminase levels was noted. No significant changes were observed in the kidney and liver, although the rats had developed cumulative irritant contact dermatitis at the application site, as corroborated by the histopathological analysis of the skin. In general, the results showed that the dermal application of acetylcarvacrol in the experimental conditions described here is safe. However, it can cause signs of mild systemic toxicity and skin irritation at high concentrations, suggesting that this product should be used in lower therapeutic doses and that the development of less aggressive formulations, including the combination with other acaricides, is desirable.

The recent discovery of a promising pharmacological scaffold derived from carvacrol: A review

Carvacrol, called CA, is a dynamic phytoconstituent characterized by a phenol ring abundantly sourced from various natural reservoirs. This versatile scaffold serves as a pivotal template for the design and synthesis of novel drug molecules, harboring promising biological activities. The active sites positioned at C-4, C-6, and the hydroxyl group (-OH) of CA offer fertile ground for creating potent drug candidates from a pharmacological standpoint. In this comprehensive review, we delve into diverse synthesis pathways and explore the biological activity of CA derivatives. We aim to illuminate the potential of these derivatives in discovering and developing efficacious treatments against a myriad of life-threatening diseases. By scrutinizing the structural modifications and pharmacophore placements that enhance the activity of CA derivatives, we aspire to inspire the innovation of novel therapeutics with heightened potency and effectiveness.

Effect of the Combination of Synthetic Anthelmintics with Carvacryl Acetate in Emulsions with and without a Sodium Alginate Matrix on Haemonchus contortus

The present study aimed to evaluate the effect of nanoemulsions using combined synthetic anthelmintics, thiabendazole (TBZ), levamisole (LEV), and ivermectin (IVM), with carvacryl acetate (CA) against Haemonchus contortus, and also tested the presence and absence of alginate (ALG). The anthelmintic effect of the CA/TBZ nanoemulsion was evaluated in the egg hatch test (EHT). The effects of CA/IVM and CA/LEV nanoemulsions were evaluated in the larval development test (LDT). The emulsions CA/TBZ/ALG and CA/TBZ showed a multimodal profile, with most particles on the nanometric scale. The encapsulation efficiency in CA/TBZ/ALG was 80.25%, and that in CA/LEV/ALG was 89.73%. In the EHT, CA/TBZ and CA/TBZ/ALG showed mean combination indices (CIs) of 0.55 and 0.36, respectively, demonstrating synergism in both. In LDT, CA/IVM had an average CI of 0.75, and CA/LEV and CA/LEV/ALG showed CI values of 0.4 and 0.93, respectively. It was concluded that CA/TBZ showed a synergistic interaction, and CA/TBZ/ALG showed an enhanced effect. In addition, the matrix brought stability to the product, encouraging its improvement to obtain higher efficacy.

Comparative toxicological evaluation of carvacrol, acetylcarvacrol anda fipronil-based pesticide in human blood cells

Plant-derived chemicals are promising substances to control arthropod pests, although synthetic ones are still the most frequently used. Thus, comparative toxicological studies are needed to determine if natural substances are safe alternatives to replace the use of synthetic chemicals. This study aimed to compare the toxicity of carvacrol (natural origin), acetylcarvacrol (semi-synthetic) and a fipronil-based pesticide (synthetic). We assessed the effects of these chemicals on hemolytic activity, erythrocytes morphology and leucocyte viability using whole blood from human subjects. Additionally, DNA damage was evaluated through comet and DNA fragmentation assays. Fipronil and carvacrol caused hemolysis at concentrations ranging from 0.5 to 2.0%, whereas acetylcarvacrol did not cause hemolysis at 0.5 and 0.75%. Fipronil and carvacrol caused severe alterations in erythrocytes' morphology at 2%, such as ghost erythrocytes, elliptocyte-like shape and rouleau-like shape, presenting only 3.3 and 8.3% normal cells, respectively, at this concentration. However, 73.3% erythrocytes incubated with 2% acetylcarvacrol exhibited normal morphology. Fipronil considerably reduced leucocytes viability, decreasing it to 78% at 2%. Carvacrol and acetylcarvacrol showed no differences in leucocyte viability for 0.5 to 1.0%, but a decrease was observed for 2% carvacrol. The comet assay showed similar DNA damage for fipronil and carvacrol, but it was significantly lower for 1 and 2% acetylcarvacrol. Incubation with genomic DNA showed that only fipronil caused fragmentation of this molecule. Thus, we conclude that carvacrol and fipronil can present similar toxicity at higher concentrations. However, acetylation of carvacrol significantly reduced its toxicity to human blood cells compared with the other chemicals.

Nanoemulsion Improves the Anti-Inflammatory Effect of Intraperitoneal and Oral Administration of Carvacryl Acetate

Carvacryl acetate (CA) is a monoterpene obtained from carvacrol, which exhibits anti-inflammatory activity. However, its low solubility in aqueous media limits its application and bioavailability. Herein, we aimed to develop a carvacryl acetate nanoemulsion (CANE) and assess its anti-inflammatory potential in preclinical trials. The optimized nanoemulsion was produced by ultrasound, and stability parameters were characterized for 90 days using dynamic light scattering after hydrophilic-lipophilic balance (HLB) assessment. To evaluate anti-inflammatory activity, a complete Freund's adjuvant-induced inflammation model was established. Paw edema was measured, and local interleukin (IL)-1β levels were quantified using ELISA. Toxicity was assessed based on behavioral changes and biochemical assays. The optimized nanoemulsion contained 3% CA, 9% surfactants (HLB 9), and 88% water and exhibited good stability over 90 days, with no signs of toxicity. The release study revealed that CANE followed zero-order kinetics. Dose-response curves for CA were generated for intraperitoneal and oral administration, demonstrating anti-inflammatory effects by both routes; however, efficacy was lower when administered orally. Furthermore, CANE showed improved anti-inflammatory activity when compared with free oil, particularly when administered orally. Moreover, daily treatment with CANE did not induce behavioral or biochemical alterations. Overall, these findings indicate that nanoemulsification can enhance the anti-inflammatory properties of CA by oral administration.

Toxicity assessment of carvacrol and its acetylated derivative in early staged zebrafish (Danio rerio): Safer alternatives to fipronil-based pesticides?

Fipronil is a broad-spectrum pesticide presenting high acute toxicity to non-target organisms, particularly to aquatic species. Natural compounds stand out as promising alternatives to the use of synthetic pesticides such as fipronil. Thus, our study aimed to compare the toxicity of carvacrol (natural), acetylcarvacrol (semisynthetic), and fipronil (synthetic) to early staged zebrafish. We conducted a series of toxicity assays at concentrations ranging from 0.01 μM to 25 μM for fipronil and 0.01 μM to 200 μM for carvacrol and acetylcarvacrol, depending on the assay, after 7-days post-fertilization (dpf). The potency (EC50) of fipronil was ∼1 μM for both deformities and mortality at 7 dpf, whereas EC50 was >50 μM for carvacrol and >70 μM for acetylcarvacrol. Fipronil at 0.1 and 1 μM caused a decrease in body length and swim bladder area of larvae at 7dpf, but no difference was observed for either carvacrol or acetylcarvacrol. Based upon the visual motor response test, fipronil induced hypoactivity in larval zebrafish at 1 μM and acetylcarvacrol induced hyperactivity at 0.1 μM. Anxiolytic-type behaviors were not affected by any of these chemicals. All chemicals increased the production of reactive oxygen species at 7 dpf, but not at 2 dpf. Genes related to swim bladder inflation, oxidative stress, lipid metabolism, and mitochondrial activity were measured; only fipronil induced upregulation of atp5f1c. There were no changes were observed in oxygen consumption rates of fish and apoptosis. Taken together, our data suggest that carvacrol and its derivative may be safer replacements for fipronil due to their lower acute toxicity.

The Antibacterial Effect of Selected Essential Oils and Their Bioactive Constituents on Pseudomonas savastanoi pv. savastanoi: Phytotoxic Properties and Potential for Future Olive Disease Control

Plant pathogenic bacteria pose a significant threat to olive cultivation, leading to substantial economic losses and reduced yield. The efficacy of antimicrobial agents against these pathogens is of great interest for sustainable disease management strategies. As such, the management of olive knot disease is one of the major challenges in olive protection. In the presented study, through a series of in vitro assays, we investigated the antimicrobial effect of six essential oils (EOs) and their most concentrated constituents against causative agent of olive knot disease-Pseudomonas savastanoi pv. savastanoi, highlighting the high potential of Origanum compactum EO and its constituent carvacrol. Carvacrol exhibited the highest potential for practical application, demonstrating membrane disruption as its mechanism of action even at the lowest concentration. The bactericidal effect of antimicrobials was confirmed in a time-kill assay, where concentrations of MIC, 2× MIC, and 4× MIC were evaluated. Some of the applied treatments resulted in inhibition equal or higher than copper-based treatment. Additionally, we assessed the phytotoxicity of carvacrol by foliar application on olive cv. Leccino. The appearance of phytotoxic injuries majorly occurred on the young leaves of olive plants, with the highest proportion of damaged canopy observed when the 2× MIC concentration was applied. Due to its great efficiency against P. savastanoi pv. savastanoi in vitro, these findings highlight the potential of carvacrol as a molecule of interest for the development of environmentally friendly biopesticides. This study also contributes to the advancement of disease management practices in olive cultivation, leading to enhanced crop protection.

Radioprotective Effects of Carvacrol and/or Thymol against Gamma Irradiation-Induced Acute Nephropathy: In Silico and In Vivo Evidence of the Involvement of Insulin-like Growth Factor-1 (IGF-1) and Calcitonin Gene-Related Peptide

Radiotherapy (RT) is an effective curative cancer treatment. However, RT can seriously damage kidney tissues resulting in radiotherapy nephropathy (RN) where oxidative stress, inflammation, and apoptosis are among the common pathomechanisms. Carvacrol and thymol are known for their antioxidative, anti-inflammatory, and radioprotective activities. Therefore, this study investigated the nephroprotective potentials of carvacrol and/or thymol against gamma (γ) irradiation-induced nephrotoxicity in rats along with the nephroprotection mechanisms, particularly the involvement of insulin-like growth factor-1 (IGF-1) and calcitonin gene-related peptide (CGRP). Methods: Male rats were injected with carvacrol and/or thymol (80 and 50 mg/kg BW in the vehicle, respectively) for five days and exposed to a single dose of irradiation (6 Gy). Then, nephrotoxicity indices, oxidative stress, inflammatory, apoptotic biomarkers, and the histopathological examination were assessed. Also, IGF-1 and CGRP renal expressions were measured. Results: Carvacrol and/or thymol protected kidneys against γ-irradiation-induced acute RN which might be attributed to their antioxidative, anti-inflammatory, and antiapoptotic activities. Moreover, both reserved the γ -irradiation-induced downregulation of CGRP- TNF-α loop in acute RN that might be involved in the pathomechanisms of acute RN. Additionally, in Silico molecular docking simulation of carvacrol and thymol demonstrated promising fitting and binding with CGRP, IGF-1, TNF-α and NF-κB through the formation of hydrogen, hydrophobic and alkyl bonds with binding sites of target proteins which supports the reno-protective properties of carvacrol and thymol. Collectively, our findings open a new avenue for using carvacrol and/or thymol to improve the therapeutic index of γ-irradiation.

Combinations of amitraz with essential oils from Lippia sidoides and Thymus vulgaris, thymol and thymol acetate for Rhipicephalus microplus control: studies under laboratory and field conditions

This study aimed to assess the effect of combining amitraz with essential oils (EOs) from Thymus vulgaris and Lippia sidoides, as well as the monoterpenes thymol and thymol acetate, on Rhipicephalus microplus in laboratory conditions, and to select the most effective combination for testing in field conditions. The chemical analysis showed that EOs were mainly composed of monoterpenes, with thymol and p-cymene as the major compounds. In larval (LIT) and adult (AIT) immersion tests using different concentrations of the oils and terpenes mixed with amitraz, the results showed that both EOs and thymol improved the efficacy of amitraz against larvae and engorged females of R. microplus, whereas thymol acetate only enhanced activity against larvae. The most favorable outcome was obtained with the EO of L. sidoides combined with amitraz, resulting in 99 % and 100 % efficacy against larvae and engorged females, respectively. Furthermore, the combination of amitraz with thymol showed presented an efficacy of 94 % and 91 % against larvae and engorged females, respectively. Thus, for the other tests, the combination of thymol + amitraz was chosen due to the ease of working with pure thymol in bioassays, and easier standardization. The immersion test (thymol + amitraz) with semi-engorged females showed 100 % efficacy for the combination of thymol + amitraz, while in tests with different solvents (thymol + amitraz), ethanol being the most effective solvent among those tested (ethanol, Triton, and Tween), resulting in 95 % efficacy on engorged females. In the field test, in treatments with amitraz and thymol + amitraz, efficacy of 54 % and 74 % was observed on day + 3 and 33 % and 43 % on day + 7, respectively. Assessing the reproductive biology of females recovered from animals treated with amitraz or amitraz + thymol, in day + 7, efficacies of 33 % and 52 %, respectively, were observed. EOs from T. vulgaris and L. sidoides and thymol improved the acaricidal activity of amitraz on larvae and engorged females of R. microplus under laboratory conditions, while thymol acetate only enhanced activity against larvae. Thymol increased the efficacy of amitraz under field conditions, however for the development of a commercially available acaricide to R. microplus control, additional studies are needed to increase the efficacy. Further research is needed (by changing concentrations, adding other compounds and/or developing formulations) to increase acaricidal efficacy and develop new effective products to combat R. microplus infestations in cattle.

Invitro and in vivo anthelmintic efficacy of peppermint (Mentha x piperita L.) essential oil against gastrointestinal nematodes of sheep

Nowadays, the exclusive use of commercial anthelmintics for the treatment of gastrointestinal nematode infections in ruminants is less sustainable due to anthelmintic resistance, as well as the problem of drug residues in animal products and the environment. Therefore, an integrated therapeutic approach is needed, including the search for alternatives to synthetic anthelmintic drugs. The aim of this study was to evaluate the possibility of using the essential oil of peppermint (Mentha x piperita L.) in the control of gastrointestinal nematodes in sheep. For this purpose, the in vitro and in vivo anthelmintic efficacy of this oil and the toxic effects on the hosts were examined. In the in vitro egg hatch test, ovicidal activity varied from 21.0-90.3% depending on the concentration of essential oil used (0.0125, 0.025, 0.049, 0.195, 0.781, 3.125, 12.5, and 50 mg/mL). To some extent, anthelmintic efficacy was confirmed in the in vivo fecal egg count reduction test at a mean dose of 150 mg/kg, with an average reduction of nematode eggs of 26.9 and 46.0% at Days 7 and 14 after treatment, respectively. Furthermore, no toxic effects of applied oil were observed on sheep behavior, kidney, or liver function. The main compounds identified by gas chromatography-mass spectrometry analyzes were menthol (32.6%), menthone (22.0%), menthyl-acetate (10.0%), and isomenthone (9.39%). Due to their complex chemical compositions, numerous bioactive ingredients, and natural origin, herbal formulations represent a potentially valuable alternative for the control of gastrointestinal nematodes in sheep. In this context, the results of the present study showed that peppermint essential oil is one of the promising candidates. Further studies should be performed to collect more data on the safety profile of M. piperita EO in treated animals to find the most appropriate formulation for use in field conditions and to test it against resistant gastrointestinal nematode populations.

Evaluation of a Phytogenic Feed Supplement Containing Carvacrol and Limonene on Sheep Performance and Parasitological Status on a Hungarian Milking Sheep Farm

There is currently worldwide interest in phytogenic feed supplements (PFSs) because they can lead to improved animal production. The scope of the present study was to observe the impact of a feed supplement containing carvacrol (CAR) and limonene (LIM) on the performance and parasitological status of sheep. The feed supplement decreased the plasma levels of β-hydroxybutyrate (p < 0.001), triglycerides (p = 0.014), nonesterified fatty acids (p = 0.021), and fructosamine (p = 0.002) in lactating ewes after 42 days of supplementation, while the average live weight (p = 0.002) and average daily weight gain (p = 0.001) of their twin suckling lambs increased significantly by the end of the study. In another experiment, fattening lambs fed the same supplement showed a decrease in fecal egg number of gastrointestinal nematodes (p = 0.02) but no differences in live weight, average daily gain, or mean number of Haemonchus contortus nematodes in the abomasum. The results highlighted that the inclusion of carvacrol and limonene in the feed of lactating ewes effectively increased the weight gain of the suckling lambs, presumably due to the ewes' improved energy, but further studies are needed to elucidate the effects of carvacrol and limonene against gastrointestinal parasites.

Enhancing the antischistosomal activity of carvacryl acetate using nanoemulsion

Aim: To formulate a carvacryl acetate nanoemulsion (CANE) and test its antischistosomal activity. Materials & methods: CANE was prepared and tested in vitro on Schistosoma mansoni adult worms and both human and animal cell lines. Next, CANE was administered orally to mice infected with either a prepatent infection or a patent infection of S. mansoni. Results: CANE was stable during 90 days of analysis. CANE showed in vitro anthelmintic activity, and no cytotoxic effects were observed. In vivo, CANE was more effective than the free compounds in reducing worm burden and egg production. Treatment with CANE was more effective for prepatent infections than praziquantel. Conclusion: CANE improves antiparasitic properties and may be a promising delivery system for schistosomiasis treatment.

A Potential Anthelmintic Phytopharmacological Source of Origanum vulgare (L.) Essential Oil against Gastrointestinal Nematodes of Sheep

The development of anthelmintic resistance in sheep gastrointestinal nematodes (GINs) requires novel strategies for the sustainable control of these parasites. This study aimed to evaluate the anthelmintic efficacy of the Origanum vulgare (L.) essential oil (EO) against sheep GINs and to evaluate the possibility of its use in control practice. The in vitro egg hatch test was conducted at eight different concentrations (50, 12.5, 3.125, 0.781, 0.195, 0.049, 0.025, and 0.0125 mg/mL) of the tested EO. For the in vivo fecal egg count reduction test, the EO of O. vulgare was administrated orally at a mean single dose of 150 mg/kg to sheep from two farms in Southern Italy, whereby potential toxic effects to the hosts were also evaluated. In the egg hatch test, the inhibition of egg hatchability varied from 71.3% to 93.7%, depending on the concentration used. The high anthelmintic potential was confirmed in the fecal egg count reduction test with an average reduction of nematode eggs in feces of 43.2% and 60.1% on days 7 and 14 after treatment, respectively. In addition, no toxic effects were noticed during the clinical examination of sheep or by observing blood count and liver or kidney function test results. The obtained results suggest the strong activity of the O. vulgare EO against sheep GINs, probably due to a high percentage of carvacrol (76.21%), whereby it can be considered safe for sheep at the dose tested in vivo. Therefore, it is suitable for use in veterinary practice as a part of an integrated strategy for the control of sheep GINs.

The Antimicrobial and Toxicity Influence of Six Carrier Oils on Essential Oil Compounds

Essential oil compounds have been identified as alternative antimicrobials; however, their use is limited due to their toxicity on human lymphocytes, skin, and reproduction. Carrier oils can reduce the toxicity of essential oils, which raises the question as to whether such activity would extend to the essential oil compounds. Thus, this study aimed to investigate the antimicrobial and toxicity activity of essential oil compounds in combination with carrier oils. The antimicrobial properties of the essential oil compounds, alone and in combination with carrier oils, were determined using the broth microdilution assay. The toxicity was determined using the brine shrimp lethality assay. Antimicrobial synergy (ΣFIC ≤ 0.50) occurred in 3% of the samples when tested against the ESKAPE pathogens. The compound thymoquinone in combination with the carrier oil Prunus armeniaca demonstrated broad-spectrum synergistic activity and a selectivity index above four, highlighting this combination as the most favorable. The carrier oils reduced the toxicity of several compounds, with Calendula officinalis and P. armeniaca carrier oils being responsible for the majority of the reduced toxicity observed. This study provides insight into the interactions that may occur when adding a carrier oil to essential oil compounds.

Does in Vitro and in Vivo Exposure To Medicinal Herbs Cause Structural Cuticular Changes in Haemonchus Contortus?

The health and production of small ruminants in constantly menaced by parasitic infections, especially those caused by the blood-sucking gastrointestinal nematode Haemonchus contortus. The aim of this study was to assess the structural cuticular changes in adult H. contortus induced by the use of extracts from local medicinal plants and to examine their ovicidal activity. Previous studies have confirmed the beneficial effect of herbal mixtures in preventing haemonchosis in lambs by lowering fecal egg production and improving immunocompetence. We exposed adult H. contortus to Herbmix (a mixture of medicinal plants) under in vivo and in vitro conditions for observation by scanning electron microscopy (SEM). For the in vivo observations, adult worms were isolated from the abomasa of experimentally infected lambs from a Herbmix group and a control group. Surface structure did not differ significantly between the exposed and control groups. The ovicidal activity of an aqueous Herbmix extract was assessed in vitro, establishing the inhibition of hatching with an ED₅₀ of 6.52 mg/mL. Adult worms for in vitro examination were isolated from experimentally infected lambs and incubated in Herbmix aqueous extracts for 24 h. SEM observations indicated that none of the worms had prominent ultrastructural changes on their cuticles. This study suggests that previously demonstrated antiparasitic effects of medicinal plants did not negatively affect adult parasites by damaging their external structures.

Experimental treatment of cystic echinococcosis: Combination therapy with carvacrol and thymol versus albendazole

Cystic echinococcosis is a worldwide zoonotic disease caused by Echinococcus granulosus sensu lato (s.l.), which produces serious health and economic problems. For human treatment, chemotherapy with albendazole (ABZ), a derivative of benzimidazoles, is widely used. However, due to its low efficacy and the lack of alternatives to ABZ, novel compounds are urgently needed. Aromatic plants exhibit powerful pharmacological activities, are accessible, have a relatively low cost, and have generally mild toxicities, making them an effective choice to traditional therapies. In particular, the pharmaceutical properties of aromatic plants are partially attributed to essential oils (EOs). The aim of the present study was to assess the in vitro and in vivo effects of the combined carvacrol and thymol against E. granulosus sensu stricto (s.s.). The greatest protoscolicidal effect was observed with the 9:1 and 5:5 (carvacrol:thymol) combinations which caused a marked decrease in viability after 6 days post-incubation, agreeing with the ultrastructural changes obtained. Permeation of the cysts and loss of turgidity was observed with the incubation with the different combinations of carvacrol:thymol. In the clinical efficacy study, the combination of thymol (40 mg/kg) and carvacrol (40 mg/kg) caused a tendency to diminish the weight of the cysts in comparison with the control group. On the other hand, the treatment of infected mice with ABZ, thymol or carvacrol, caused a significant decrease in the weight of the cysts. In conclusion, we here demonstrated the efficacy of different concentrations of combined carvacrol and thymol against E. granulosus s.s. protoscoleces and murine cysts, where short periods of treatment were sufficient to achieve a pharmacological effect. Moreover, we observed a reduction in the weight of the cysts in experimentally infected mice after treatment with carvacrol and thymol. The strategy used has an advantage over synthetic drugs because natural compounds are generally safe and non-toxic. Moreover, the combination of two drugs with different modes of action would cause a reduction in the doses and treatment times. Based on the promising results obtained in vitro, in the future, different doses of the combined drugs will be assayed in vivo to determine the potential of these compounds for the treatment of cystic echinococcosis.

The mechanism of ferroptosis regulating oxidative stress in ischemic stroke and the regulation mechanism of natural pharmacological active components

Cerebrovascular diseases, such as ischemic stroke, pose serious medical challenges worldwide due to their high morbidity and mortality and limitations in clinical treatment strategies. Studies have shown that reactive oxygen species (ROS)-mediated inflammation, excitotoxicity, and programmed cell death of each neurovascular unit during post-stroke hypoxia and reperfusion play an important role in the pathological cascade. Ferroptosis, a programmed cell death characterized by iron-regulated accumulation of lipid peroxidation, is caused by abnormal metabolism of lipids, glutathione (GSH), and iron, and can accelerate acute central nervous system injury. Recent studies have gradually uncovered the pathological process of ferroptosis in the neurovascular unit of acute stroke. Some drugs such as iron chelators, ferrostatin-1 (Fer-1) and liproxstatin-1 (Lip-1) can protect nerves after neurovascular unit injury in acute stroke by inhibiting ferroptosis. In addition, combined with our previous studies on ferroptosis mediated by natural compounds in ischemic stroke, this review summarized the progress in the regulation mechanism of natural chemical components and herbal chemical components on ferroptosis in recent years, in order to provide reference information for future research on ferroptosis and lead compounds for the development of ferroptosis inhibitors.

In vitro anthelmintic activity of an R-carvone nanoemulsions towards multiresistant Haemonchus contortus

This work aimed to evaluate the in vitro anthelmintic effect of carvone nanoemulsions on Haemonchus contortus. Three R-carvone nanoemulsions were prepared: uncoated R-carvone nanoemulsions homogenized in a sonicator (UNAlg-son) and homogenized in an ultrahomogenizer (UNAlg-ultra) and sodium alginate-coated R-carvone (CNAlg-ultra). The physicochemical characterizations of the nanoemulsions were carried out. The anthelmintic activity was evaluated using egg hatch test (EHT), larval development test (LDT) and adult worm motility test (AWMT). Changes in cuticle induced in adult H. contortus were evaluated by scanning electron microscopy (SEM). The results were subjected to analysis of variance and compared using the Tukey test (P < 0.05). The effective concentration to inhibit 50% (EC50) of egg hatching and larval development was calculated. The particle sizes were 281.1 nm (UNAlg-son), 152.7 nm (UNAlg-ultra) and 557.8 nm (CNAlg-ultra), and the zeta potentials were −15 mV (UNAlg-son), −10.8 mV (UNAlg-ultra) and −24.2 mV (CNAlg-ultra). The encapsulation efficiency was 99.84 ± 0.01%. SEM of the nanoemulsions showed an increase in size. In EHT, the EC50 values of UNAlg-son, UNAlg-ultra and CNAlg-ultra were 0.19, 0.02 and 0.17 mg mL−1, respectively. In LDT, they were 0.29, 0.31 and 0.95 mg mL−1 for UNAlg-son, UNAlg-ultra and CNAlg-ultra, respectively. The adult motility inhibition was 100% after 12 h of exposure to UNAlg-ultra and CNAlg-ultra, while for UNAlg-son, it was 79.16%. SEM showed changes in the buccal capsule and cuticular damage. It was concluded that R-carvone nanoemulsions showed antiparasitic action demonstrating promise for the control of infections caused by gastrointestinal nematodes in small ruminants.

Assessment of anthelmintic potentials of Myrtus communis against Haemonchus contortus and Heligmosomoides polygyrus

Anthelmintic resistance in grazing livestock systems has been spreading worldwide in prevalence and severity. Therefore, alternative measures including the use of herbal anthelmintic is considered as one of the successful approaches for the control of anthelmintic resistance. In the present report, we describe the chemical constituents of Myrtus communis essential oil, its in vitro anthelmintic effect against the most pathogenic gastrointestinal parasite of sheep; Haemonchus contortus and its in vivo anthelmintic potential using an in vivo gastrointestinal parasite model of rodents; i.e. Heligmosomoides polygyrus. Chromatographic analyzes of the essential oil (EO) extracted from the leaves of M. communis have shown that this oil was composed mainly of a α-pinene (33.59%), eucalyptol (23.85%) and limonene (14.70%). Regarding the in vitro anthelmintic potential, the ovicidal effect was confirmed in an egg hatch inhibition assay at IC₅₀ = 0.7 mg/mL and with 95.83% of immobility of adult worm's after 8 h of exposure to 2 mg/mL of M. communis EO. The anthelmintic capacity of M. communis EO was also confirmed by in vivo assays conducted against the murine parasite H. polygyrus. In fact, at 1200 mg/kg bw of M. communis EO, a reduction of 99.70% in faecal egg counts was observed after 7 days of oral treatment, together with a 71.12% reduction in total worm counts. Based on the obtained results, M. communis EO showed relevant in vitro and in vivo anthelmintic effects against gastro-intestinal parasites.

Nematicidal effect of a lectin preparation from Artocarpus heterophyllus (Moraceae) on larvae and adults of Haemonchus contortus

Haemonchus contortus is a hematophagous parasite that causes damage to ruminant production worldwide. This study reported the in vitro nematicidal effect of a lectin preparation (LP) isolated from Artocarpus heterophyllus seeds on larvae and adults of H. contortus. The protein extraction was in phosphate-buffered saline followed by protein precipitation with ammonium sulfate 70% and dialysis. The dialyzed protein fraction was chromatographed to obtain isolated LP. The LP was characterized by hemagglutinating activity (HA) assays, protein dosage and polyacrylamide gel electrophoresis. The motility index of H. contortus in the third larval stage (unsheathed L3 larvae) and adult stage was evaluated. The HA inhibition of LP by mannose and galactose as well as the electrophoretic profile indicated the presence of the lectins ArtinM and Jacalin. The motility index of H. contortus was significantly reduced (p < 0.001) during the first 8 h of LP exposure, both in larvae (lowest index 8.3% with LP at 1 mg mL-1) and female adults (lowest index 20% with LP at 500 μg mL-1; index 40% with LP at 1 mg mL-1). This research revealed that the LP has potential for being utilized in the development of natural nematicides.

Impact of Sainfoin (Onobrychis viciifolia) Pellets on Parasitological Status, Antibody Responses, and Antioxidant Parameters in Lambs Infected with Haemonchus contortus

Our study analyzed the parasitological status, antibody responses, and antioxidant parameters of lambs experimentally infected with a gastrointestinal nematode during the consumption of sainfoin pellets (SFPs) for 14 d. Twenty-four lambs infected with Haemonchus contortus were separated into two groups: untreated animals (control) and animals treated with SFPs (600 g dry matter/d). SFP treatment began on day (D) 30 post-infection. The number of eggs per gram (EPG) of feces was quantified on D18, D23, D26, D30, D33, D37, D40, and D44. The mean reductions in EPG on D40 and D44 were 33.6 and 36.7%, respectively. The number of abomasal worms was lower for the SFP than the control group (p < 0.05). SFP treatment did not significantly affect either the total or the local antibody response (p > 0.05). The blood activity of glutathione peroxidase was affected by the treatment (p < 0.022). Adult worms were selected for scanning electron microscopy after necropsy, but surface structures of adult H. contortus females did not differ between the groups. The treatment of lambs with SFPs directly affected the dynamics of infection, probably indirectly by mobilizing the antioxidant defensive system and antibody response thus improving animal resistance.

Anthelmintic Properties of Essential Oils to Control Gastrointestinal Nematodes in Sheep-In Vitro and In Vivo Studies

Herbal products such as essential oils may play a promising role in the treatment of infections caused by gastrointestinal nematodes (GINs). The aim of this study was to evaluate the in vitro potential of 11 essential oils (EOs) and one binary combination of isolated EO compounds, as well as the in vivo anthelmintic efficacy of two EO formulations. Four GIN genera were identified in the coproculture examination: Haemonchus, Trichostrongylus, Teladorsagia and Chabertia. The in vitro egg hatch test (EHT) was performed at six different concentrations (50, 12.5, 3.125, 0.781, 0.195 and 0.049 mg/mL) for each EO, whereas in the in vivo faecal egg count reduction test (FECRT), each EO sample was diluted in sunflower oil and orally administrated at a dose of 100 mg/kg to the different group of animals. In the EHT, the EOs of Origanum vulgare, Foeniculum vulgare, Satureja montana, Satureja hortensis and two types of Thymus vulgaris were the most effective. The dominant compounds of these EOs were carvacrol, thymol, anethol, p-cymene and γ-terpinene, indicating their importance for the anthelmintic activity. In the FECRT, both T. vulgaris EO type 1 and linalool:estragole combination show an anthelmintic potential with a mean effect on FECR of approximately 25%. The results suggest the possible role of tested EOs as anthelmintic agents in sheep farms, although further in vivo tests are needed.

The combination of carvacrol and albendazole enhanced the efficacy of monotherapy in experimental alveolar echinococcosis

Alveolar echinococcosis is a helminthic zoonosis caused by the larval stage of Echinococcus multilocularis. When surgical resection of the parasite is not feasible, pharmacological treatment with albendazole is the only option. Due to the difficulties in achieving the success of treatment, it is necessary to find new drugs to improve the treatment of this disease. In the present work, the efficacy of carvacrol alone or combined with albendazole was evaluated against E. multilocularis metacestodes. The association of carvacrol with albendazole produced a greater in vitro effect than the compounds incubated separately. The most effective treatment was the combination of 10 μg/ml of carvacrol and 1 μg/ml of albendazole. In the clinical efficacy study, treatment of infected mice with carvacrol (40 mg/kg) and albendazole (25 mg/kg) reduced the weight of metacestodes by 29 % and 50 %, respectively; while the combination of drugs had an efficacy of 83 %. These results coincided with the tissue damage observed at the ultrastructural level. In conclusion, carvacrol and albendazole combination enhanced the efficacy of monotherapy. This strategy would allow to improve the efficacy of the treatment without increasing the doses of albendazole or lengthen the treatment period, reducing the occurrence of adverse effects.

Effects of essential oil components exposure on biological parameters of Caenorhabditis elegans

The extensive use of essential oil components in an increasing number of applications can substantially enhance exposure to these compounds, which leads to potential health and environmental hazards. This work aimed to evaluate the toxicity of four widely used essential oil components (carvacrol, eugenol, thymol, vanillin) using the in vivo model Caenorhabditis elegans. For this purpose, the LC₅₀ value of acute exposure to these components was first established; then the effect of sublethal concentrations on nematodes' locomotion behaviour, reproduction, heat and oxidative stress resistance and chemotaxis was evaluated. The results showed that all the components had a concentration-dependent effect on nematode survival at moderate to high concentrations. Carvacrol and thymol were the two most toxic compounds, while vanillin had the mildest toxicological effect. Reproduction resulted in a more sensitive endpoint than lethality to evaluate toxicity. Only pre-exposure to carvacrol and eugenol at the highest tested sublethal concentrations conferred worms oxidative stress resistance. However, at these and lower concentrations, both components induced reproductive toxicity. Our results evidence that these compounds can be toxic at lower doses than those required for their biological action. These findings highlight the need for a specific toxicological assessment of every EOC application.

Scanning electron microscopy of different vulval structures in a Mexican Haemonchus contortus isolate

Haemonchus contortus is a parasite species that affects the health and production of grazing small ruminants in different parts of the world. Scanning electron microscopy (SEM) is an important tool for the study of parasites' morphology and taxonomy as it generates images that appear 3D and are generally easier to interpret than optical microscopy images. This study used the SEM to describe the vulval types of adult H. contortus from a Mexican isolate. A total of 14 adult H. contortus females were obtained from two artificially infected goats. Females were fixed and processed by critical point drying and observed with SEM. A collection of SEM images was obtained from these parasites and those images were used to identify the structures previously described by optical microscopy studies. Two different types of vulval structures were described in this Mexican H. contortus isolate: Type 1 (vulval flap), Type 2 (epiptygma). An unusual vulval structure was reported in a single individual. The Type 1 included vulval flaps of different sizes and spatial dispositions, as well as one or more knobs in different positions around the vulva. The Type 2 shows differences in the epiptygma. The present study suggests that the Mexican H. contortus isolate used in donor animals possess intraspecific polymorphism in vulval structures.

Carvacryl acetate nanoencapsulated with chitosan/chichá gum exhibits reduced toxicity in mice and decreases the fecal egg count of sheep infected with gastrointestinal nematodes

The nanoencapsulation of biocomposites with anthelmintic action has been proposed as an alternative for improving their efficiency. Thus, the current study aimed to evaluate the efficacy of carvacryl acetate nanoencapsulated with biopolymers (nCVA) in the control of sheep gastrointestinal nematodes. CVA was nanoencapsulated with chitosan/chichá gum and characterized in terms of its efficacy of encapsulation (EE), yield and zeta potential. The acute toxicity of nCVA was evaluated in mice. For the fecal egg count reduction test, 40 animals were divided into four groups (n = 10) and orally administered the following treatments: G1, 250 mg kg−1 CVA; G2, 250 mg kg−1 nCVA; G3, chitosan/chichá gum (negative control) and G4, 2.5 mg kg−1 monepantel (positive control). Feces were collected on days 0 and 16 posttreatment to determine the eggs per gram of feces (epg). The EE and yield of nCVA were 72.8 and 57.5%, respectively. The nanoparticles showed a size of 764.5 ± 302.5 nm, and the zeta potential at pH 3.2 was +22.0 mV. nCVA presented a 50% lethal dose (LD50) of 2609 mg kg−1. By 16 days posttreatment, CVA, nCVA and monepantel reduced the epg by 52.9.7, 71.5 and 98.7%, respectively, and the epg of sheep treated with nCVA differed from that of the negative control (P > 0.05) but did not differ from that of sheep treated with CVA. In conclusion, the nanoencapsulation of CVA reduced its toxicity, and nCVA showed anthelmintic activity.

Anthelmintic resistance: is a solution possible?

More than 50 years after anthelmintic resistance was first identified, its prevalence and impact on the animal production industry continues to increase across the world. The term "anthelmintic resistance" (AR) can be briefly defined as the reduction in efficacy of a certain dose of anthelmintic drugs (AH) in eliminating the presence of a parasite population that was previously susceptible. The main aim of this study is to examine anthelmintic resistance in domestic herbivores. There are numerous factors playing a role in the development of AR, but the most important is livestock management. The price of AH and the need to treat a high number of animals mean that farmers face significant costs in this regard, yet, since 1981, little progress has been made in the discovery of new molecules and the time and cost required to bring a new AH to market has increased dramatically in recent decades. Furthermore, resistance has also emerged for new AH, such as monepantel or derquantel. Consequently, ruminant parasitism cannot be controlled solely by using synthetic chemicals. A change in approach is needed, using a range of preventive measures in order to achieve a sustainable control programme. The use of nematophagous fungi or of plant extracts rich in compounds with anthelmintic properties, such as terpenes, condensed tannins, or flavonoids, represent potential alternatives. Nevertheless, although new approaches are showing promising results, there is still much to do. More research focused on the control of AR is needed.

Efficacy of carvacryl acetate in vitro and following oral administration to mice harboring either prepatent or patent Schistosoma mansoni infections

Schistosomiasis is a major public health problem that afflicts more than 240 million individuals globally, particularly in poor communities. Treatment of schistosomiasis relies heavily on a single oral drug, praziquantel, and there is interest in the search for new antischistosomal drugs. This study reports the anthelmintic evaluation of carvacryl acetate, a derivative of the terpene carvacrol, against Schistosoma mansoni ex vivo and in a schistosomiasis animal model harboring either adult (patent infection) or juvenile (prepatent infection) parasites. For comparison, data obtained with gold standard antischistosomal drug praziquantel are also presented. Initially in vitro effective concentrations of 50% (EC₅₀) and 90% (EC₉₀) were determined against larval and adult stages of S. mansoni. In an animal with patent infection, a single oral dose of carvacryl acetate (100, 200, or 400 mg/kg) caused a significant reduction in worm burden (30-40%). S. mansoni egg production, a process responsible for both life cycle and pathogenesis, was also markedly reduced (70-80%). Similar to praziquantel, carvacryl acetate 400 mg/kg had low efficacy in pre-patent infection. In tandem, although carvacryl acetate had interesting in vitro schistosomicidal activity, the compound exhibited low efficacy in terms of reduction of worm load in S. mansoni-infected mice.

The ATP bioluminescence assay: a new application and optimization for viability testing in the parasitic nematode Haemonchus contortus

The parasitic gastrointestinal nematode Haemonchus contortus causes serious economic losses to agriculture due to infection and disease in small ruminant livestock. The development of new therapies requires appropriate viability testing, with methods nowadays relying on larval motility or development using procedures that involve microscopy. None of the existing biochemical methods, however, are performed in adults, the target stage of the anthelmintic compounds. Here we present a new test for the viability of H. contortus adults and exsheathed third-stage larvae which is based on a bioluminescent assay of ATP content normalized to total protein concentration measured using bicinchoninic acid. All the procedure steps were optimized to achieve maximal sensitivity and robustness. This novel method can be used as a complementary assay for the phenotypic screening of new compounds with potential antinematode activity in exsheathed third-stage larvae and in adult males. Additionally, it might be used for the detection of drug-resistant isolates.

Acaricidal activity of essential oils of Cinnamomum zeylanicum and Eremanthus erythropappus, major compounds and cinnamyl acetate in Rhipicephalus microplus

This study aimed to chemically characterize the essential oils (EOs) of Cinnamomum zeylanicum (cinnamon) and Eremanthus erythropappus (candeia) and evaluate their acaricidal activity, together with that of their major compounds and cinnamyl acetate derivative, against Rhipicephalus microplus. Essential oil compounds were identified through gas chromatography. The larval packet test (LPT) at concentrations ranging from 0.31 to 10.0 mg/mL and the adult immersion test (AIT) at concentrations between 2.5 and 60.0 mg/mL were performed. (E)-cinnamaldehyde and α-bisabolol were the major compounds in cinnamon (86.93%) and candeia (78.41%) EOs, respectively. In the LPT, the EOs of cinnamon and candeia and the compounds (E)-cinnamaldehyde, α-bisabolol and cinnamyl acetate resulted in 100% mortality at concentrations of 2.5, 2.5, 5.0, 10.0 and 10.0 mg/mL respectively. In the AIT, percentage control values > 95% were observed for cinnamon and candeia EOs, (E)-cinnamaldehyde and α-bisabolol at the concentrations of 5.0, 60.0, 20.0, and 20.0 mg/mL, respectively, whereas cinnamyl acetate showed low activity. We conclude that EOs and their compounds showed high acaricidal activity, whereas the acetylated derivative of (E)-cinnamaldehyde presented less acaricidal activity on R. microplus engorged females.

Effect of essential oil blends and a nonionic surfactant on rumen fermentation, anti-oxidative status, and growth performance of lambs

This study aimed to evaluate the effect of essential oils (OEO; XEO) and an emulsifier on rumen fermentation, anti-oxidative status, and the growth performance of lambs. A finishing study was conducted using 35 females and 35 males Suffolk × Canadian Arcott crossbreed lambs, fed a 16:84 forage:concentrate pelleted barley-based with either Control; Bovatec (0.018% Bovatec); Emulsifier (0.25% of Emulsifier); OEO (0.11% of blend 1); XEO (0.0125% of blend 2); OEO + Emulsifier; or XEO + Emulsifier. The rumen fluid of all lambs was sampled via stomach tubing to measure ruminal pH, volatile fatty acid (VFA), and NH3 concentrations and enumerate protozoa. Ruminal pH, molar proportions of individual VFA (except for acetate), and ammonia concentration were similar among treatments. The acetate and total VFA concentrations were lower (P = 0.03) for lambs receiving OEO, while protozoa numbers were increased (P = 0.01). No changes were observed in blood glutathione peroxidize or total superoxide dismutase, but there was a tendency for a reduction in thiobarbituric acid reactive substances in lambs fed diets containing OEO or XEO. No differences among diets were observed in coccidia oocyst counts (OPG) in feces, however, the prevalence of coccidia in lambs was reduced (Cramer's V = 0.081) with OEO. Lambs fed OEO had the highest (P < 0.01) dry matter intake (DMI) (1.48 kg/d), whereas those fed XEO had the lowest (1.30 kg/d). Average daily gain (ADG), feed conversion (DMI/ADG), and carcass measurements (hot carcass weight, carcass dressing percentages) were not affected by EO or EM. Results from this study suggest that EO may alter rumen fermentation and protozoa counts and increase DMI. However, these responses did not appear to be enhanced by Emulsifier as its inclusion with essential oils did not enhance fermentation or growth responses.

Repellent activity of acetylcarvacrol and its effects on salivary gland morphology in unfed Rhipicephalus sanguineus sensu lato ticks (Acari: Ixodidae)

Rhipicephalus sanguineus sensu lato (s.l.), commonly known as brown dog tick, is a widely distributed tick species that is substantially important for human and veterinary medicine. Therefore, it is the target of different control methods. Carvacrol and its semisynthetic derivative, acetylcarvacrol, are promising chemical compounds for alternative tick control. Thus, this study aimed to compare the repellent activities of carvacrol and acetylcarvacrol at different concentrations and drying times. Additionally, morphological alterations found in salivary glands were evaluated through histological techniques after exposure to acetylcarvacrol. The impact of the morphological changes on the development and survival of acini/cells in salivary glands was measured by a semiquantitative analysis. The repellent action of both compounds did not differ when evaluated at different concentrations, although acetylcarvacrol increased its effects as the concentration raised. Regarding the different drying times, acetylcarvacrol maintained its effects after 3 hours of exposure, while the efficacy of carvacrol decreased during this time period. Salivary glands of unfed R. sanguineus s.l. females showed dose-dependent alterations in the size and shape of acini as well as cytoplasmic vacuolization. Loss of the acinar cell limit, rupture of secretory granules and nuclear changes in the cells were also observed in the treated groups. Thus, our results demonstrated the potential of acetylcarvacrol to act as repellent against R. sanguineus s.l. Additionally, the morphological alterations found in salivary glands may interfere with the feeding process of ticks, which contributes to mitigate infestation by this species.

Anthelmintic effect of essential rhizome oil from Hedychium coronarium Koenig (Zingiberaceae) introduced in Northeastern Brazil

Hedychium coronarium is native to Tropical Asia and has been introduced into several Brazilian biomes. Significant biological properties described for the essential oil (EO) from this species' rhizomes include antimicrobial, larvicidal, anti-inflammatory, antioxidant, phytotoxic, and anthelmintic activities. The primary constituents identified in this study by GC-MS in the EO were monoterpenes 1,8-cineole (33.5%), β-pinene (17.0%), α-terpineol (7.7%), α-pinene (7.3%), limonene (5.2%), and p-cymene (4.9%), comprising 75.6% of total oil compounds. The main monoterpenes' EO and standards were tested against N2 (susceptible) and UVR15 (resistant) adult nematode Caenorhabditis elegans strains, with varying dead rates in motility tests.. Nematocidal activity was not attributed to 1,8-cineole and β-pinene, the main H. coronarium rhizome oil components, as both exhibited an inhibitory concentration (IC₅₀) ≥ 5 mg/mL. On the other hand, the α-pinene (IC₅₀, 1.69 mg/mL) and (S)-(-)-limonene (IC₅₀, 1.66 mg/mL) standards demonstrated more efficient action than rhizome oil in motility tests, with significant adult C. elegans nematode mortality rates. These results support the hypothesis that the combination of H. coronarium EO constituents can be helpful as a nematicidal product, due to their synergistic action.

Action of Carvacrol on Parascaris sp. and Antagonistic Effect on Nicotinic Acetylcholine Receptors

Parascaris sp. is the only ascarid parasitic nematode in equids and one of the most threatening infectious organisms in horses. Only a limited number of compounds are available for treatment of horse helminthiasis, and Parascaris sp. worms have developed resistance to the three major anthelmintic families. In order to overcome the appearance of resistance, there is an urgent need for new therapeutic strategies. The active ingredients of herbal essential oils are potentially effective antiparasitic drugs. Carvacrol is one of the principal chemicals of essential oil from Origanum, Thymus, Coridothymus, Thymbra, Satureja and Lippia herbs. However, the antiparasitic mode of action of carvacrol is poorly understood. Here, the objective of the work was to characterize the activity of carvacrol on Parascaris sp. nicotinic acetylcholine receptor (nAChR) function both in vivo with the use of worm neuromuscular flap preparations and in vitro with two-electrode voltage-clamp electrophysiology on nAChRs expressed in Xenopus oocytes. We developed a neuromuscular contraction assay for Parascaris body flaps and obtained acetylcholine concentration-dependent contraction responses. Strikingly, we observed that 300 µM carvacrol fully and irreversibly abolished Parascaris sp. muscle contractions elicited by acetylcholine. Similarly, carvacrol antagonized acetylcholine-induced currents from both the nicotine-sensitive AChR and the morantel-sensitive AChR subtypes. Thus, we show for the first time that body muscle flap preparation is a tractable approach to investigating the pharmacology of Parascaris sp. neuromuscular system. Our results suggest an intriguing mode of action for carvacrol, being a potent antagonist of muscle nAChRs of Parascaris sp. worms, which may account for its antiparasitic potency.

A Systematic Review on Comparative Analysis, Toxicology, and Pharmacology of Medicinal Plants Against Haemonchus contortus

Background:Haemonchus contortus is an important pathogenic nematode parasite and major economic constraint of small ruminants in tropics and subtropics regions. This review is an attempt to systematically address the; (a) efficacy of different plants against H. contortus by in vitro and in vivo proof; (b) toxicology, mechanism of action, and active phyto-compounds involve in anti-haemonchiasis activity; (c) and comparative analysis of plant species evaluated both in vitro and in vivo.

Methods: Online databases (Google Scholar, PubMed, Scopus, and ScienceDirect) were searched and published research articles (1980–2020) were gathered and reviewed.

Results: A total of 187 plant species were reported belonging to 59 families and 145 genera with Asteraceae and Fabaceae being frequently used. Out of the total plant species, 171 species were found to be evaluated in vitro and only 40 species in vivo. Twenty-four species were commonly evaluated for in vitro and in vivo anti-haemonchiasis activity. Among the reported assays, egg hatching test (EHT) and fecal egg count reduction (FECR) were the most widely used assays in vitro and in vivo, respectively. Moreover, sheep were the frequently used experimental model in vivo. After comparative analysis, Lachesiodendron viridiflorum, Corymbia citriodora, Calotropis procera, and Artemisia herba-alba were found highly effective both in vitro and in vivo. L. viridiflorum inhibited enzymatic activities and metabolic processes of the parasite and was found to be safe without toxic effects. C. citriodora was moderately toxic in vivo, however, the plant extract produced promising nematicidal effects by causing muscular disorganization and changes in the mitochondrial profile. Additionally, C. procera and A. herba-alba despite of their high anti-haemonchiasis activity were found to be highly toxic at the tested concentrations. C. procera caused perforation and tegumental disorganization along with adult worm paralysis. Nineteen compounds were reported, among which anethole and carvone completely inhibited egg hatching in vitro and significantly reduced fecal egg count, decreased male length, and reproductive capacity of female in vivo.

Conclusion: This review summarized different medicinal plants owing to nematicidal activities against H. contortus eggs, larvae, and adult worms. Plants like L. viridiflorum, C. citriodora, C. procera, and A. herba-alba, while compounds anethole and carvone having promising nematicidal activities and could be an alternative source for developing novel drugs after further investigation.

Antifungal Activity of Novel Formulations Based on Terpenoid Prodrugs against C. albicans in a Mouse Model

Carvacrol (CAR), a phenolic monoterpenoid, has been extensively investigated for its antimicrobial and antifungal activity. As a result of its poor physicochemical properties, water soluble carvacrol prodrugs (WSCPs) with improved water solubility were previously synthesized and found to possess antimicrobial activity. Here, three novel CAR analogs, WSCP1, WSCP2, and WSCP3, were tested against fluconazole (FLU)-sensitive and -resistant strains where they showed greater antifungal activity than CAR against C. albicans. The probable mechanism by which the CAR prodrugs exert the antifungal activity was studied. Results from medium acidification assays demonstrated that the CAR and its synthetically designed prodrugs inhibit the yeast plasma membrane H+-ATPase (Pma1p), an essential target in fungi. In other words, in vitro data indicated that CAR analogs can prove to be a better alternative to CAR considering their improved water solubility. In addition, CAR and WSCP1 were developed into intravaginal formulations and administered at test doses of 50 mg/kg in a mouse model of vulvovaginal candidiasis (VVC). Whereas the CAR and WSCP1 formulations both exhibited antifungal efficacy in the mouse model of VVC, the WSCP1 formulation was superior to CAR, showing a remarkable decrease in infection by ~120-fold compared to the control (infected, untreated animals). Taken together, a synthetically designed prodrug of CAR, namely WSCP1, proved to be a possible solution for poorly water-soluble drugs, an inhibitor of an essential yeast pump in vitro and an effective and promising antifungal agent in vivo.

Essential oils from Ocimum basilicum cultivars: analysis of their composition and determination of the effect of the major compounds on Haemonchus contortus eggs

The continuous use of synthetic anthelmintics against gastrointestinal nematodes (GINs) has resulted in the increased resistance, which is why alternative methods are being sought, such as the use of natural products. Plant essential oils (EOs) have been considered as potential products for the control of GINs. However, the chemical composition and, consequently, the biological activity of EOs vary in different plant cultivars. The aim of this study was to evaluate the anthelmintic activity of EOs from cultivars of Ocimum basilicum L. and that of their major constituents against Haemonchus contortus. The EOs from 16 cultivars as well the pure compound linalool, methyl chavicol, citral and eugenol were used in the assessment of the inhibition of H. contortus egg hatch. In addition, the composition of three cultivars was simulated using a combination of the two major compounds from each. The EOs from different cultivars showed mean Inhibition Concentration (IC50) varying from 0.56 to 2.22 mg/mL. The cultivar with the highest egg-hatch inhibition, Napoletano, is constituted mainly of linalool and methyl chavicol. Among the individual compounds tested, citral was the most effective (IC50 0.30 mg/mL). The best combination of compounds was obtained with 11% eugenol plus 64% linalool (IC50 0.44 mg/mL), simulating the Italian Large Leaf (Richters) cultivar. We conclude that different cultivars of O. basilicum show different anthelmintic potential, with cultivars containing linalool and methyl chavicol being the most promising; and that citral or methyl chavicol isolated should also be considered for the development of new anthelmintic formulations.

Combination of entomopathogenic nematodes with acaricides or essential oil of Lippia triplinervis against Rhipicephalus microplus (Acari: Ixodidae)

This study aimed to evaluate the combination effect of Heterorhabditis bacteriophora HP88 and H. indica LPP1, with the acaricides deltamethrin, amitraz and chlorfenvinphos, and the essential oil (EO) of Lippia triplinervis, against engorged females of Rhipicephalus microplus. In order to verify the effect of acaricides and EO, the adult immersion test was used, and in the groups treated only with entomopathogenic nematodes (EPNs), 150 infective juveniles were used per female. In the treatments with nematodes in combination with the acaricides or EO, the females were immersed in the solutions (acaricide or EO) and then transferred to Petri dishes for application of the nematodes. The treatment with acaricides resulted in a control percentage lower than 70%, except in the group treated with chlorfenvinphos in the second experiment (84.3%). The control percentage was 73% for L. triplinervis EO, and greater than 90% in all the groups treated with nematodes. For treatments with EPNs combined with the acaricides or EO, the efficacy was greater than 95% (except for deltamethrin + HP88), and reached 100% in the treatment with LPP1 + amitraz. It can be concluded that the EPNs at the concentrations tested were compatible with the acaricides deltamethrin, amitraz and chlorfenvinphos, and with the EO of L. triplinervis. These combinations enhance the effect of these control agents.

In vitro and in vivo antibacterial activity assays of carvacrol: A candidate for development of innovative treatments against KPC-producing Klebsiella pneumoniae

Dissemination of carbapenem-resistant Klebsiella pneumoniae poses a threat to the successful treatment of bacterial diseases and increases the need for new antibacterial agents development. The objective of this study was to determine the antimicrobial activity of carvacrol against multidrug-resistant K. pneumoniae. Carbapenemase production was detected by MALDI-TOF. The PCR and sequencing showed that the bla_KPC-2,bla_OXA-48, bla_NDM-1, bla_CTX-M-8 genes were present in carbapenem-resistant K. pneumoniae strains. The polymyxin-resistant K. pneumoniae strain exhibited alterations in mgrB gene. The antimicrobial activity of carvacrol was evaluated in vitro using broth microdilution and time-kill methods. For this, carbapenem-resistant K. pneumoniae and polymyxin-resistant strains, were evaluated. The in vitro results showed that carvacrol had antimicrobial activity against all isolates evaluated. The survival curves showed that carvacrol eradicated all of the bacterial cells within 4 h. The antimicrobial effect of carvacrol in vivo was determined using a mouse model of infection with Klebsiella pneumoniae carbapenemase (KPC). The treatment with carvacrol was associated with increased survival, and significantly reduced bacterial load in peritoneal lavage. In addition, groups treated with carvacrol, had a significant reduction in the total numbers of white cell and significantly increased of platelets when compared to the untreated group. In vivo and in vitro studies showed that carvacrol regimens exhibited significant antimicrobial activity against KPC-producing K. pneumoniae, making it an interesting candidate for development of alternative treatments.

Combination of synthetic anthelmintics and monoterpenes: Assessment of efficacy, and ultrastructural and biophysical properties of Haemonchus contortus using atomic force microscopy

The resistance of Haemonchus contortus to synthetic anthelmintics is of increasing concern; and different strategies are being evaluated to improve parasite control. The present study investigated the in vitro effects of combinations of synthetic compounds and monoterpenes. Additionally, the chemical association of the best combinations and their impact on the ultrastructural and biophysical properties of H. contortus eggs was evaluated. We assessed the efficacy of the monoterpenes, carvacrol, thymol, r-carvone, s-carvone, citral, and p-cymene and the anthelmintics, albendazole and levamisole using the egg hatch test (EHT) and the larval migration inhibition test (LMIT), respectively. The minimum effective concentrations of the monoterpenes, according to the EHT (efficacy ranging from 4.4%-11.8%) and LMIT (efficacy ranging from 5.6%-7.4%), were used in combination with different concentrations of synthetic compounds, and the IC₅₀ and synergism rate (SR) were calculated. Fourier-transform infrared spectroscopy (FTIR) was used to analyze the chemical association between the best combinations as revealed by the in vitro tests (albendazole and levamisole with r-carvone or s-carvone). Atomic force microscopy (AFM) was used to assess the ultrastructural and biophysical properties of H. contortus eggs treated with the albendazole and r-carvone combination. Among the monoterpenes, the highest efficacies were exhibited by carvacrol (IC₅₀ = 185.9 μg/mL) and thymol (IC₅₀ = 187.0 μg/mL), according to the EHT, and s-carvone and carvacrol (IC₅₀ = 1526.0 and 1785.3 μg/mL, respectively), according to the LMIT. According to the EHT, albendazole showed a slight statistically significant synergism in combination with r-carvone (SR = 3.8) and s-carvone (SR = 3.0). According to the LMIT, among the monoterpenes, r-carvone (SR = 1.7) and s-carvone (SR = 1.7) showed an increase in efficacy with levamisole; however, this was not statistically significant. The FTIR spectra of albendazole and levamisole, in association with r-carvone and s-carvone, indicated the presence of chemical interactions between the synthetic and natural molecules, contributing to the possible synergistic effects of these associations. Eggs treated with albendazole and r-carvone showed an increase in roughness and a decrease in height, suggesting that the treatment induced damage to the egg surface and an overflow of its internal contents. Overall, the combination of albendazole with r-carvone and s-carvone was efficacious against H. contortus, demonstrating a chemical association between the compounds; the significant changes in the egg ultrastructure justify this efficacy.

Sublethal concentrations of acetylcarvacrol affect reproduction and integument morphology in the brown dog tick Rhipicephalus sanguineus sensu lato (Acari: Ixodidae)

Rhipicephalus sanguineus sensu lato (s.l.), also known as the brown dog tick, is among the main tick species involved in the transmission of pathogens to humans and other animals and, therefore, the target of numerous control methods. However, due to the disadvantages of synthetic acaricides, the use of alternative products such as plant derivatives has been encouraged. This study aimed to evaluate the acaricidal potential of acetylcarvacrol and to determine its efficacy at sublethal doses for the control of R. sanguineus s.l. female ticks. In addition, as acetylcarvacrol was applied topically, morphological alterations in the integument were assessed. Acetylation of carvacrol was performed by reaction with acetic anhydride in a sodium hydroxide solution, being confirmed by infrared spectroscopy. The lethal concentration for 50 and 90% (LC₅₀ and LC₉₀) of unfed ticks and the efficacy of acetylcarvacrol in engorged females were determined after the Adult Immersion Test (AIT). For the evaluation of effects of acetylcarvacrol in the integument, routine histological techniques were employed after the AIT. The LC₅₀ and LC₉₀ in unfed females were 2.8 and 7.2 μL/mL, respectively. Regarding reproductive performance, after treatment with 8.0 μL/mL acetylcarvacrol 90.9% control was achieved, as ticks showed the lowest egg production index (EPI), hatching rate (HR), and fecundity rate (FR). In the integument, considerable morphological alterations were observed both in cuticle and epithelium. Thus, acetylcarvacrol affected R. sanguineus s.l. external coating and reproduction when applied at sublethal concentrations, probably contributing to a long-term control.

In vitro effects of Moringa oleifera seed lectins on Haemonchus contortus in larval and adult stages

Haemonchus contortus is a hematophagous parasite causing damage to the production of ruminant animals throughout the world. This study evaluated the in vitro effect of proteins from Moringa oleifera (WSMoL - Water Soluble M. oleifera Lectin and cMoL - coagulant M. oleifera Lectin) on the motility of infective larvae and adult male and female worms of H. contortus. The specific activity of total proteases and the morphology of the worms exposed to the lectins were observed. Both lectins inhibited motility of all parasite stages tested. WSMoL and cMoL at 500 μg mL^-1 interfered in the motility of larvae. Values of 11.1% and 8.1% were the lowest motility indices of larvae with sheath, and 30.6% and 16.4% were the lowest motility indices of exsheathed larvae treated with WSMoL and cMoL, respectively. In 1 mg mL^-1 solutions of WSMoL and of cMoL, the motility index of adult male worms was 23.3% (p < 0.001) and 20% (p < 0.001), while the motility index of adult female worms was 63.3% (p > 0.05) and 26.6% (p < 0.001), respectively. Greater proteolytic activity was detected in extracts obtained from adult worms, male and female, after incubation with the lectins. Morphological changes caused by the lectins were revealed by changes in the crests of the cuticle, in the longitudinal striations and at the vulva.

Chemical characterization and in vitro biological activity of Cymbopogon citratus extracts against Haemonchus spp. and Trichostrongylus spp. nematodes from sheep

Medicinal plants have been the focus of several studies due to their nematicide properties which can be used to control nematodes in sheep. No study has examined the morphological effects of Cymbopogon citratus on nematodes. Thus, this study evaluated the chemical composition, nematicidal activity and effects of C. citratus extracts on the morphology of eggs and infective larvae (L3) of sheep. Aqueous and methanolic extracts and fractions of C. citratus were obtained and analysed in vitro. The C. citratus extracts were effective against Haemonchus spp. and Trichostrongylus spp. larvae and eggs. Ten fractions were obtained from C. citratus, six of which had high ovicidal activity at 1000 μg mL-1, and two fractions had high activity at all tested concentrations. The phytochemical analysis identified the presence of compounds such as terpenoids, various ketones, esters, and fatty acids. The ultrastructural analysis showed deformations of the cuticle and wilting along the body of the nematodes at all concentrations. The muscular layer, intestinal cells and the mitochondria profile showed damage compared to the typical pattern. Ultra-thin sections of eggs treated with methanolic fractions of C. citratus presented modifications. This study showed the biological activity and effects of C. citratus on the gastrointestinal nematodes in sheep.

Acetylation of carvacrol raises its efficacy against engorged cattle ticks Rhipicephalus (Boophilus) microplus (Acari: Ixodidae)

The effects of acetylcarvacrol on the reproductive performance of engorged female R. microplus were evaluated. Carvacrol was acetylated by a reaction with acetic anhydride, confirmed by the identification of its melting point and by infrared spectroscopy. Based on the median lethal concentration, females were exposed to sublethal concentrations (3.7, 4.6 and 5.0 μL/mL) of acetylcarvacrol by means of the adult immersion test. The following parameters were evaluated: female weight before oviposition, pre-oviposition period, egg mass weight, egg production index, incubation period, hatching rate, fecundity rate, percentage of reduction in oviposition, percentage of reduction in hatching and product efficacy. The greatest efficacy was observed in the group treated with the highest concentration (91.69%) due to the greater weight reduction in egg mass (34.91 ± 0.02 mg) and the lower hatching rate (7.23 ± 15.50%). Therefore, this compound is a promising alternative for the control of R. microplus infestations.

From formulation to in vivo model: A comprehensive study of a synergistic relationship between vancomycin, carvacrol, and cuminaldehyde against Enterococcus faecium

Vancomycin-resistant Enterococcus faecium (VRE) has become endemic in healthcare settings, reducing treatment options for enterococcal infections. New antimicrobials for VRE infections are a high priority, but the development of novel antibiotics is time-consuming and expensive. Essential oils (EOs) synergistically enhance the activity of some existing antibiotics, suggesting that EO-antibiotic combinations could resensitise resistant bacteria and maintain the antibiotic repertoire. The mechanism of resensitisation of bacteria to antibiotics by EOs is relatively understudied. Here, the synergistic interactions between carvacrol (1.98 mM) and cuminaldehyde (4.20 mM) were shown to reestablish susceptibility to vancomycin (0.031 mg/L) in VRE, resulting in bactericidal activity (4.73 log₁₀ CFU/ml reduction). Gene expression profiling, coupled with β-galactosidase leakage and salt tolerance assays, suggested that cell envelope damage contributes to the synergistic bactericidal effect against VRE. The EO-vancomycin combination was also shown to kill clinical isolates of VRE (2.33-5.25 log₁₀ CFU/ml reduction), and stable resistance did not appear to develop even after multiple passages. The in vivo efficacy of the EO-vancomycin combination was tested in a Galleria mellonella larvae assay; however, no antimicrobial action was observed, indicating that further drug development is required for the EO-vancomycin combination to be clinically useful for treatment of VRE infections.

Anthelmintic activity of nanoencapsulated carvacryl acetate against gastrointestinal nematodes of sheep and its toxicity in rodents

The objective of this study was to evaluate the efficacy of carvacryl acetate (CVA) and nanoencapsulated CVA (nCVA) on gastrointestinal nematodes of sheep. The CVA was nanoencapsulated with chitosan/gum arabic and the efficacy of nanoencapsulation (EE), yield, zeta potential, nanoparticle morphology and release kinetics at pH 3 and 8 were analyzed. Acute and subchronic toxicity were evaluated in rodents and reduction of egg counts in the faeces (FECRT) of sheep. The sheep were divided into four groups (n = 10): G1, 250 mg/kg CVA; G2, 250 mg/kg nCVA; G3, polymer matrix and G4: 2.5 mg/kg monepantel. EE and nCVA yield were 65% and 57%, respectively. The morphology of the nanoparticles was spherical, size (810.6±286.7 nm), zeta potential in pH 3.2 (+18.3 mV) and the 50% release of CVA at pHs 3 and 8 occurred at 200 and 10 h, respectively. nCVA showed LD50 of 2,609 mg/kg. CVA, nCVA and monepantel reduced the number of eggs per gram of faeces (epg) by 57.7%, 51.1% and 97.7%, respectively. The epg of sheep treated with CVA and nCVA did not differ from the negative control (P>0.05). Nanoencapsulation reduced the toxicity of CVA; however, nCVA and CVA presented similar results in the FECRT.