Antileishmanial activity of essential oil from Chenopodium ambrosioides and its main components against experimental cutaneous leishmaniasis in BALB/c mice

Natural endoperoxides as promising anti-leishmanials

BACKGROUND

The discovery of artemisinin, an endoperoxide, encouraged the scientific community to explore endoperoxides as potential anti-parasitic molecules. Although artemisinin derivatives are rapidly evolving as potent anti-malarials, their potential as anti-leishmanials is emerging gradually. The treatment of leishmaniasis, a group of neglected tropical diseases is handicapped by lack of effective vaccines, drug toxicities and drug resistance. The weak antioxidant defense mechanism of the Leishmania parasites due to lack of catalase and a selenium dependent glutathione peroxidase system makes them vulnerable to oxidative stress, and this has been successful exploited by endoperoxides.

PURPOSE

The study aimed to review the available literature on the anti-leishmanial efficacy of natural endoperoxides with a view to achieve insights into their mode of actions.

METHODS

We reviewed more around 110 research and review articles restricted to the English language, sourced from electronic bibliographic databases including PubMed, Google, Web of Science, Google scholar etc. RESULTS: Natural endoperoxides could potentially augment the anti-leishmanial drug library, with artemisinin and ascaridole emerging as potential anti-leishmanial agents. Due to higher reactivity of the cyclic peroxide moiety, and exploiting the compromised antioxidant defense of Leishmania, endoperoxides like artemisinin and ascaridole potentiate their leishmanicidal efficacy by creating a redox imbalance. Furthermore, these molecules minimally impair oxidative phosphorylation; instead inhibit glycolytic functions, culminating in depolarization of the mitochondrial membrane and depletion of ATP. Additionally, the carbon-centered free radicals generated from endoperoxides, participate in chain reactions that can generate even more reactive organic radicals that are toxic to macromolecules, including lipids, proteins and DNA, leading to cell cycle arrest and apoptosis of Leishmania parasites. However, the precise target(s) of the toxic free radicals remains open-ended.

CONCLUSION

In this overview, the spectrum of natural endoperoxide molecules as major anti-leishmanials and their mechanism of action has been delineated. In view of the substantial evidence that natural endoperoxides (e.g., artemisinin, ascaridole) exert a noxious effect on different species of Leishmania, identification and characterization of other natural endoperoxides is a promising therapeutic option worthy of further pharmacological consideration.

Eugenol-Rich Essential Oil from Pimenta dioica: In Vitro and In Vivo Potentialities against Leishmania amazonensis

Pimenta dioica L. is one the most recognized species with diverse biological activities. In this study, in vitro activity and in vivo efficacy of essential oil from P. dioica (EO-Pd) was evaluated. The main compound was also included in the animal studies and its in silico prediction related to biological activities, molecular ligands, drug likeness, and ADME (absorption, distribution, metabolism, and excretion) properties are listed. The chemical composition analyzed by GC-MS retrieved 45 components, which the most abundant compound was the eugenol (80.1%). The EO-Pd was able to inhibit the growth of L. amazonensis (IC50 = 9.7 ± 0.7 and 11.3 ± 2.1 µg/mL, promastigotes and amastigotes, respectively). The cytotoxicity assay showed a CC50 of 104.5 ± 0.9 µg/mL and a selectivity index of 9. In the model of cutaneous leishmaniasis in BALB/c mice, the effect of EO-Pd and eugenol was observed after treatment at 30 mg/kg by intralesional route with 5 administrations every 4 days. In the in silico predictions, some targets that justified the antileishmanial activity of eugenol and good drug like properties for this compound, were obtained. This study showed for first time the potential of EO-Pd to inhibit L. amazonensis, which could be linked to the activity of major compound eugenol.

Chemical Composition and Antiplasmodial Activity of the Essential Oil of Rhododendron subarcticum Leaves from Nunavik, Québec, Canada

Dwarf Labrador tea, Rhododendron subarcticum Harmaja, is a popular medicinal plant in use by First Nations of Northern Canada, but its phytochemistry has remained largely unexplored. We have isolated and characterized the essential oil from a population of this species harvested near the treeline in Nunavik, Québec. Analyses by gas chromatography-mass spectrometry (GC-MS) and gas chromatography/flame-ionization detection (GC/FID) led to the identification of 53 compounds; the main secondary metabolites were ascaridole (64.7% of the total FID area) and p-cymene (21.1%). Such a composition resembles a chemotype observed for R. tomentosum, a close relative found mainly in Europe and Asia, but has never been attributed to R. subarcticum. Growth inhibition assays against different strains of Plasmodium falciparum (3D7, Dd2), the parasite responsible for the most severe form of malaria, were conducted with either the R. subarcticum's essential oil or the isolated ascaridole. Our results show that the essential oil's biological activity can be attributed to ascaridole as its IC₅₀ is more than twice that of ascaridole [ascaridole's IC₅₀ values are 147.3 nM (3D7) and 104.9 nM (Dd2)].

Salt-Tolerant Plants as Sources of Antiparasitic Agents for Human Use: A Comprehensive Review

Parasitic diseases, especially those caused by protozoans and helminths, such as malaria, trypanosomiasis, leishmaniasis, Chagas disease, schistosomiasis, onchocerciasis, and lymphatic filariasis, are the cause of millions of morbidities and deaths every year, mainly in tropical regions. Nature has always provided valuable antiparasitic agents, and efforts targeting the identification of antiparasitic drugs from plants have mainly focused on glycophytes. However, salt-tolerant plants (halophytes) have lately attracted the interest of the scientific community due to their medicinal assets, which include antiparasitic properties. This review paper gathers the most relevant information on antiparasitic properties of halophyte plants, targeting human uses. It includes an introduction section containing a summary of some of the most pertinent characteristics of halophytes, followed by information regarding the ethnomedicinal uses of several species towards human parasitic diseases. Then, information is provided related to the antiprotozoal and anthelmintic properties of halophytes, determined by in vitro and in vivo methods, and with the bioactive metabolites that may be related to such properties. Finally, a conclusion section is presented, addressing perspectives for the sustainable exploitation of selected species.

Antileishmanial Anthracene Endoperoxides: Efficacy In Vitro, Mechanisms and Structure-Activity Relationships

Leishmaniasis is a vector-borne disease caused by protozoal Leishmania parasites. Previous studies have shown that endoperoxides (EP) can selectively kill Leishmania in host cells. Therefore, we studied in this work a set of new anthracene-derived EP (AcEP) together with their non-endoperoxidic analogs in model systems of Leishmania tarentolae promastigotes (LtP) and J774 macrophages for their antileishmanial activity and selectivity. The mechanism of effective compounds was explored by studying their reaction with iron (II) in chemical systems and in Leishmania. The correlation of structural parameters with activity demonstrated that in this compound set, active compounds had a LogPOW larger than 3.5 and a polar surface area smaller than 100 Å2. The most effective compounds (IC50 in LtP < 2 µM) with the highest selectivity (SI > 30) were pyridyl-/tert-butyl-substituted AcEP. Interestingly, also their analogs demonstrated activity and selectivity. In mechanistic studies, it was shown that EP were activated by iron in chemical systems and in LtP due to their EP group. However, the molecular structure beyond the EP group significantly contributed to their differential mitochondrial inhibition in Leishmania. The identified compound pairs are a good starting point for subsequent experiments in pathogenic Leishmania in vitro and in animal models.

Mexican Oregano (Lippia berlandieri Schauer and Poliomintha longiflora Gray) Essential Oils Induce Cell Death by Apoptosis in Leishmania (Leishmania) mexicana Promastigotes

Leishmaniasis is a neglected vector-borne disease; there are different manifestations of the diseases and species involved, and cutaneous leishmaniasis caused by Leishmania (L.) mexicana is the most prevalent in Mexico. Currently, the drugs available for the treatment of leishmaniasis are toxic, expensive, and often ineffective; therefore, it is imperative to carry out research and development of new therapeutic alternatives, with natural products being an attractive option. In particular, oregano is a plant with worldwide distribution; in Mexico, two species: Lippia berlandieri Schauer and Poliomintha longiflora Gray are endemic. Both essential oils (EO’s) have been reported to have antimicrobial activity attributed to their main components, thymol and carvacrol. In this research, the leishmanicidal effect and mechanism of cell death induced by L. berlandieri EO, P. longiflora EO, thymol, and carvacrol in L. mexicana promastigotes were determined in vitro. Additionally, the cytotoxic activity in mammalian cells was evaluated. L. berlandieri EO presented higher leishmanicidal activity (IC₅₀ = 41.78 µg/mL) than P. longiflora EO (IC₅₀ = 77.90 µg/mL). Thymol and carvacrol were the major components of both Mexican oregano EO’s. Thymol presented higher leishmanial inhibitory activity (IC₅₀ = 22.39 µg/mL), above that of carvacrol (IC₅₀ = 61.52 µg/mL). All the EO’s and compounds evaluated presented lower cytotoxic activity than the reference drug; thymol was the compound with the best selectivity index (SI). In all cases, apoptosis was identified as the main mechanism of death induced in the parasites. The leishmanicidal capacity of the Mexican oregano EO is an accessible and affordable alternative that can be further explored.

Ascaridole exerts the leishmanicidal activity by inhibiting parasite glycolysis

BACKGROUND

The global burden of leishmaniasis is exacerbated by the limited repertoire of drugs, resulting in an urgent need to develop new therapeutic alternatives. Endoperoxides like ascaridole have emerged as promising anti-parasitic candidates, and its effectiveness was established in an animal model of cutaneous leishmaniasis (CL). However, its impact on Leishmania donovani parasites, causative of visceral leishmaniasis (VL) remains to be established.

PURPOSE

This study aimed to delineate the underlying mechanisms contributing towards the leishmanicidal effect of ascaridole in terms of its impact on the cellular redox status and metabolic bioenergetics of L. donovani parasites.

METHODOLOGY

The anti-promastigote activity of ascaridole was established by a cell viability assay in L. donovani [MHOM/IN/1983/AG83] and anti-amastigote activity by microscopy and ddPCR (droplet digital polymerase chain reaction). The cellular redox status, mitochondrial membrane potential (MMP), annexin V positivity and cell cycle arrest was evaluated by flow cytometry, while cellular and mitochondrial bioenergetics was assessed using Agilent XFp Analyzer, and the levels of ATP was measured by chemiluminescence.

RESULTS

Ascaridole demonstrated strong anti-promastigote and anti-amastigote activities in l. donovani, IC₅₀ (half maximal Inhibitory concentration) being 2.47 ± 0.18 µM and 2.00±0.34 µM respectively, while in J774.A1 and murine peritoneal macrophages, the CC₅₀ (half maximal cytotoxic concentration) was 41.47 ± 4.89 µM and 37.58 ± 5.75 µM respectively. Ascaridole disrupted the redox homeostasis via an enhanced generation of reactive oxygen species (ROS), lipid peroxidation and concomitant depletion of thiols. However, it failed to increase the generation of mitochondrial superoxide, which minimally impacted on mitochondrial respiration and was corroborated by energy metabolism studies. Instead, ascaridole inhibited glycolysis of promastigotes, caused a loss in MMP, which translated into ATP depletion. In promastigotes, ascaridole enhanced annexin-V positivity and caused a cell cycle arrest at sub- G₀/G₁ phase.

CONCLUSION

In summary, ascaridole displays its leishmanicidal activity possibly due to its ability to auto-generate free radicals following cleavage of its endoperoxide bridge that led to disruption of the redox homeostasis, inhibition of glycolysis and culminated in an apoptotic like cell death.

Mosquitocidal activities of Chenopodium botrys whole plant n-hexane extract against Culex quinquefasciatus

This research aimed to investigate various mosquitocidal activities of Chenopodium botrys whole- plant n-hexane extract against Culex quinquefasciatus. The extract showed remarkable larvicidal, pupicidal, adulticidal, oviposition deterrent and adult emergence inhibitory activities against Cx. quinquefasciatus. During the larvicidal and pupicidal activities, the 24-hour lethal concentration (LC50) of extract against 2nd instar larvae, 4th instar larvae and pupae were 324.6, 495.6 and 950.8 ppm, respectively. During the CDC (Centers for Disease Control and Prevention) bottle bioassay for adulticidal activity, the median knockdown times (KDT50) at 1.25% concentration was 123.4 minutes. During the filter paper impregnation bioassay for adulticidal activity, the KDT50 value at 0.138 mg/cm2 concentration was 48.6 minutes. The extract was fractionated into 14 fractions through silica gel column chromatography which were then combined into six fractions on the basis of similar retention factor (Rf) value. These fractions were screened for adulticidal activity by applying CDC bottle bioassay. The fraction obtained through 60:40 to 50:50% n-hexanes-chloroform mobile phase with 0.5 Rf value showed 100% adulticidal activity at 0.2% concentration. During oviposition deterrent activity, the highest concentration (1000 ppm) showed 71.3 ± 4.4% effective repellence and 0.6 ± 0.1 oviposition activity index. During adult emergence inhibition activity, the median emergence inhibition (EI50) value was 312.3 ppm. From the outcome of the present investigation, it is concluded that the n-hexane extract of C. botrys whole- plant possesses strong larvicidal, pupicidal, adulticidal, oviposition deterrent and adult emergence inhibitory activities against Cx. quinquefasciatus.

Confusion Syndrome During COVID-19: The "Herb" That Hides the Forest?

We report the case of potential Dysphania ambrosioides (Silverweed) intoxication in the context of SARS-COV-2 infection in a patient admitted for delirium with Glasgow Coma Score (GCS) of 13/15. This herb was used as an antipyretic to treat COVID-19 persistent fever. The clinical presentation of our patient raised several questions related to the viral or herbal intoxication origin of the confusion syndrome. To our knowledge, this is the first description of toxic encephalopathy after D. ambrosioides ingestionin an adult patient.

Ethnomedical uses, chemical constituents, and evidence-based pharmacological properties of Chenopodium ambrosioides L.: extensive overview

Background

The Chenopodium genus is a plant family widely spread worldwide that includes various plant species reputed to possess several medicinal virtues in folk medicines. Chenopodium ambrosioides L. is among the most used plants in traditional medicines worldwide. This review aimed to highlight ethnomedicinal uses, phytochemical status, and pharmacological properties of C. ambrosioides L.

Main body of the abstract

The analysis of relevant data highlights various ethnomedicinal uses against human and veterinary diseases in forty countries. Most indications consisted of gastrointestinal tract dysfunctioning troubles and worms parasitemia. Around 330 chemical compounds have been identified in different plant parts, especially in its essential oil fractions (59.84%). However, only a few compounds—mainly monoterpenes and glycosides—have been isolated and characterized. Experimental pharmacological studies validated a large scale of significant health benefits. It appeared that many monoterpenes are antioxidant, insecticidal, trypanocidal, analgesic, antifungal, anti-inflammatory, anti-arthritic, acaricidal, amoebicidal, anthelmintic, anticancer, antibacterial, antidiabetic, antidiarrheal, antifertility, antifungal, anti-leishmanial, antimalarial, antipyretic, antisickling, antischistosomal, antiulcer, anxiolytic, immunomodulatory, molluscicidal, and vasorelaxant agents.

Short conclusion

Thus, the Chenopodium ambrosioides species necessitates further chemical studies to isolate and characterize new bioactive secondary metabolites and pharmacological investigations to precise the mechanisms of action before clinical trials.

Pharmacological Assessment of the Carvacrol Chemotype Essential Oil FromPlectranthus amboinicusGrowing in Cuba

Plant-derived products are employed in various public health practices and have been considered as a major source of medicines. The genus Plectranthus (Lamiaceae) has been widely respected for its nutritional properties, its essential oil, and its therapeutic values. In the present work, the chemical characterization, antimicrobial, antiparasitic, and cytotoxic properties of the essential oil from Plectranthus amboinicus (Lour.) Spreng and its main compound carvacrol were studied. Twenty-one components were identified in the oil by gas chromatography coupled with a mass spectrometric detector. In this oil, carvacrol constitutes the major compound (71%), which represented the more abundant chemotype. The essential oil did not inhibit growth of Escherichia coli, Staphylococcus aureus, Candida albicans, Trypanosoma cruzi, or Leishmania infantum, but displayed activity against Plasmodium falciparum (half-maximal inhibitory concentration [IC50] = 5.9 µg/mL), Trypanosoma brucei (IC50= 34.9 µg/mL), and Leishmania amazonensis (IC50= 58.2 µg/mL), and the human tumor-derived cell lines MCF-7 (IC50= 29.1 µg/mL), MDA-MB-231 (IC50= 41.5 µg/mL), and 22Rv1 (IC50= 29.6 µg/mL), but no cytotoxicity was observed against nonmalignant macrophages. The antiproliferative activity of the oil could be attributed to carvacrol. However, this compound showed certain level of cytotoxicity, which suggests unspecific activity. This study provides evidence about antimicrobial and anticancer potential of the essential oil from P. amboinicus against protozoa and neoplastic diseases, particularly as an antimalarial natural product.

Effect of essential oils on Leishmania amazonensis: a systematic review

This systematic review investigated the evidence for the therapeutic potential of essential oils (EOs) against Leishmania amazonensis. We searched available scientific publications from 2005 to 2019 in the PubMed and Web of Science electronic databases, according to PRISMA statement. The search strategy utilized descriptors and free terms. The EOs effect of 35 species of plants identified in this systematic review study, 45.7% had half of the maximal inhibitory concentration (IC50) 10 < IC50 ⩽ 50 μg mL−1 and 14.3% had a 10 < IC50μg mL−1 for promastigote forms of L. amazonensis. EOs from Cymbopogon citratus species had the lowest IC50 (1.7 μg mL−1). Among the plant species analyzed for activity against intracellular amastigote forms of L. amazonensis, 39.4% had an IC50 10 < IC50 ⩽ 50 μg mL−1, and 33.3% had an IC50 10 < IC50μg mL−1. Aloysia gratissima EO showed the lowest IC50 (0.16 μg mL−1) for intracellular amastigotes. EOs of Chenopodium ambrosioides, Copaifera martii and Carapa guianensis, administered by the oral route, were effective in reducing parasitic load and lesion volume in L. amazonensis-infected BALB/c mice. EOs of Bixa orellana and C. ambrosioides were effective when administered intraperitoneally. Most of the studies analyzed in vitro and in vivo for the risk of bias showed moderate methodological quality. These results indicate a stimulus for the development of new phytotherapy drugs for leishmaniasis treatment.

Traditional Herbal Medicine in Mesoamerica: Toward Its Evidence Base for Improving Universal Health Coverage

The quality of health care in Mesoamerica is influenced by its rich cultural diversity and characterized by social inequalities. Especially indigenous and rural communities confront diverse barriers to accessing formal health services, leading to often conflicting plurimedical systems. Fostering integrative medicine is a fundamental pillar for achieving universal health coverage (UHC) for marginalized populations. Recent developments toward health sovereignty in the region are concerned with assessing the role of traditional medicines, and particularly herbal medicines, to foster accessible and culturally pertinent healthcare provision models. In Mesoamerica, as in most regions of the world, a wealth of information on traditional and complementary medicine has been recorded. Yet these data are often scattered, making it difficult for policy makers to regulate and integrate traditionally used botanical products into primary health care. This critical review is based on a quantitative analysis of 28 survey papers focusing on the traditional use of botanical drugs in Mesoamerica used for the compilation of the "Mesoamerican Medicinal Plant Database" (MAMPDB), which includes a total of 12,537 use-records for 2188 plant taxa. Our approach presents a fundamental step toward UHC by presenting a pharmacological and toxicological review of the cross-culturally salient plant taxa and associated botanical drugs used in traditional medicine in Mesoamerica. Especially for native herbal drugs, data about safety and effectiveness are limited. Commonly used cross-culturally salient botanical drugs, which are considered safe but for which data on effectiveness is lacking constitute ideal candidates for treatment outcome studies.

Carvacrol loaded nanostructured lipid carriers as a promising parenteral formulation for leishmaniasis treatment

Leishmaniasis are a group of neglected infectious diseases caused by protozoa of the genus Leishmania with distinct presentations. The available leishmaniasis treatment options are either expensive and/or; cause adverse effects and some are ineffective for resistant Leishmania strains. Therefore, molecules derived from natural products as the monoterpene carvacrol, have attracted interest as promising anti-leishmania agents. However, the therapeutic use of carvacrol is limited due to its low aqueous solubility, rapid oxidation and volatilization. Thus, the development of nanostructured lipid carriers (NLCs) was proposed in the present study as a promising nanotechnology strategy to overcome these limitations and enable the use of carvacrol in leishmaniasis therapy. Carvacrol NLCs were obtained using a warm microemulsion method, and evaluated regarding the influence of lipid matrix and components concentration on the NLCs formation. NLCs were characterized by DSC and XRD as well. In addition, to the in vitro carvacrol release from NLCs, the in vitro cytotoxicity and leishmanicidal activity assays, and the in vivo pharmacokinetics evaluation of free and encapsulated carvacrol were performed. NLCs containing carvacrol were obtained successfully using a warm microemulsion dilution method. The NLCs formulation with the lowest particle size (98.42 ± 0.80 nm), narrowest size distribution (suitable for intravenous administration), and the highest encapsulation efficiency was produced by using beeswax as solid lipid (HLB=9) and 5% of lipids and surfactant. The in vitro release of carvacrol from NLCs was fitted to the Korsmeyer and Peppas, and Weibull models, demonstrating that the release mechanism is probably the Fickian diffusion type. Moreover, carvacrol encapsulation in NLCs provided a lower cytotoxicity in comparison to free carvacrol (p<0.05), increasing its in vitro leishmanicidal efficacy in the amastigote form. Finally, the in vivo pharmacokinetics of carvacrol after IV bolus administration suggests that this phenolic monoterpene undergoes enterohepatic circulation and therefore presented a long half-life (t_1/2) and low clearance (Cl). In addition, C₀, mean residence time (MRT) and V_dss of encapsulated carvacrol were higher than free carvacrol (p < 0.05), favoring a higher distribution of carvacrol in the target tissues. Thus, it is possible to conclude that the developed NLCs are a promising delivery system for leishmaniasis treatment.

Bixa orellana L. (Bixaceae) and Dysphania ambrosioides (L.) Mosyakin & Clemants (Amaranthaceae) Essential Oils Formulated in Nanocochleates against Leishmania amazonensis

Leishmaniasis is a group of neglected tropical diseases caused by protozoan parasites of the Leishmania genus. The absence of effective vaccines and the limitations of current treatments make the search for effective therapies a real need. Different plant-derived essential oils (EOs) have shown antileishmanial effects, in particular from Bixa orellana L. (EO-Bo) and Dysphania ambrosioides (L.) Mosyakin & Clemants (EO-Da). In the present study, the EO-Bo and EO-Da, formulated in nanocochleates (EO-Bo-NC and EO-Da-NC, respectively), were evaluated in vitro and in vivo against L. amazonensis. The EO-Bo-NC and EO-Da-NC did not increase the in vitro inhibitory activity of the EOs, although the EO-Bo-NC showed reduced cytotoxic effects. In the animal model, both formulations (30 mg/kg/intralesional route/every 4 days/4 times) showed no deaths or weight loss greater than 10%. In the animal (mouse) model, EO-Bo-NC contributed to the control of infection (p < 0.05) in comparison with EO-Bo treatment, while the mice treated with EO-Da-NC exhibited larger lesions (p < 0.05) compared to those treated with EO-Da. The enhanced in vivo activity observed for EO-Bo-NC suggests that lipid-based nanoformulations like nanocochleates should be explored for their potential in the proper delivery of drugs, and in particular, the delivery of hydrophobic materials for effective cutaneous leishmaniasis treatment.

In vitro and in silico anti-dengue activity of compounds obtained from Psidium guajava through bioprospecting

BACKGROUND

For decades, bioprospecting has proven to be useful for the identification of compounds with pharmacological potential. Considering the great diversity of Colombian plants and the serious worldwide public health problem of dengue-a disease caused by the dengue virus (DENV)-in the present study, we evaluated the anti-DENV effects of 12 ethanolic extracts derived from plants collected in the Colombian Caribbean coast, and 5 fractions and 5 compounds derived from Psidium guajava.

METHODS

The cytotoxicity and antiviral effect of 12 ethanolic extracts derived from plants collected in the Colombian Caribbean coast was evaluated in epithelial VERO cells. Five fractions were obtained by open column chromatography from the ethanolic extract with the highest selectivity index (SI) (derived from P. guajava, SI: 128.2). From the fraction with the highest selectivity (Pg-YP-I-22C, SI: 35.5), five compounds were identified by one- and two-dimensional nuclear magnetic resonance spectroscopy. The antiviral effect in vitro of the fractions and compounds was evaluated by different experimental strategies (Pre- and post-treatment) using non-toxic concentrations calculated by MTT method. The DENV inhibition was evaluated by plate focus assay. The results were analyzed by means of statistical analysis using Student's t-test. Finally the antiviral effect in Silico was evaluated by molecular docking.

RESULTS

In vitro evaluation of these compounds showed that three of them (gallic acid, quercetin, and catechin) were promising antivirals as they inhibit the production of infectious viral particles via different experimental strategies, with the best antiviral being catechin (100% inhibition with a pre-treatment strategy and 91.8% with a post-treatment strategy). When testing the interactions of these compounds with the viral envelope protein in silico by docking, only naringin and hesperidin had better scores than the theoretical threshold of - 7.0 kcal/mol (- 8.0 kcal/mol and - 8.2 kcal/mol, respectively). All ligands tested except gallic acid showed higher affinity to the NS5 protein than the theoretical threshold.

CONCLUSION

Even though bioprospecting has recently been replaced by more targeted tools for identifying compounds with pharmacological potential, our results show it is still useful for this purpose. Additionally, combining in vitro and in silico evaluations allowed us to identify promising antivirals as well as their possible mechanisms of action.

Chemical Constituents with Leishmanicidal Activity from a Pink-Yellow Cultivar of Lantana camara var. aculeata (L.) Collected in Central Mexico

Lantana camara (L.) is employed by several ethnical groups to treat numerous diseases. Although there are no ethnomedical reports on its use against leishmaniasis, organic extracts prepared from L. camara were shown to display leishmanicidal activity. In the present study, we carried out a bioassay-guided fractionation of the dichloromethane extract from Mexican L. camara in order to identify the compounds responsible for the leishmanicidal activity. Eighteen chromatographic fractions (FI⁻FXVIII) were evaluated in vitro against Leishmania mexicana and L. amazonensis. FII, FX, FXI, FXV, and FXVI showed significant activity against both Leishmania strains, the most potent of which was FXV. Eicosane (1), squalene (2), β-ionone (3), caryophyllene oxide (4), β-caryophyllene (5), hexanoic acid (6), tiglic acid (7), a mixture of lantanilic (8) and camaric (9) acids, and lantadene B (10) were identified and obtained from the active fractions and evaluated for their leishmanicidal activity. The mixture of lantanilic (8) and camaric (9) acids (79%/21%) was the most potent one (half maximal inhibitory concentration (IC₅₀) = 12.02 ± 0.36 μM). This study indicates that this cultivar of L. camara has high potential for the development of phytomedicines or as a source of natural products, which might represent lead compounds for the design of new drugs against leishmaniasis.

Active Essential Oils and Their Components in Use against Neglected Diseases and Arboviruses

The term neglected diseases refers to a group of infections caused by various classes of pathogens, including protozoa, viruses, bacteria, and helminths, most often affecting impoverished populations without adequate sanitation living in close contact with infectious vectors and domestic animals. The fact that these diseases were historically not considered priorities for pharmaceutical companies made the available treatments options obsolete, precarious, outdated, and in some cases nonexistent. The use of plants for medicinal, religious, and cosmetic purposes has a history dating back to the emergence of humanity. One of the principal fractions of chemical substances found in plants are essential oils (EOs). EOs consist of a mixture of volatile and hydrophobic secondary metabolites with marked odors, composed primarily of terpenes and phenylpropanoids. They have great commercial value and were widely used in traditional medicine, by phytotherapy practitioners, and in public health services for the treatment of several conditions, including neglected diseases. In addition to the recognized cytoprotective and antioxidative activities of many of these compounds, larvicidal, insecticidal, and antiparasitic activities have been associated with the induction of oxidative stress in parasites, increasing levels of nitric oxide in the infected host, reducing parasite resistance to reactive oxygen species, and increasing lipid peroxidation, ultimately leading to serious damage to cell membranes. The hydrophobicity of these compounds also allows them to cross the membranes of parasites as well as the blood-brain barrier, collaborating in combat at the second stage of several of these infections. Based on these considerations, the aim of this review was to present an update of the potential of EOs, their fractions, and their chemical constituents, against some neglected diseases, including American and African trypanosomiasis, leishmaniasis, and arboviruses, specially dengue.

Activation of Anthracene Endoperoxides in Leishmania and Impairment of Mitochondrial Functions

Leishmaniasis is a vector-borne disease caused by protozoal Leishmania. Because of resistance development against current drugs, new antileishmanial compounds are urgently needed. Endoperoxides (EPs) are successfully used in malaria therapy, and experimental evidence of their potential against leishmaniasis exists. Anthracene endoperoxides (AcEPs) have so far been only technically used and not explored for their leishmanicidal potential. This study verified the in vitro efficiency and mechanism of AcEPs against both Leishmania promastigotes and axenic amastigotes (L. tarentolae and L. donovani) as well as their toxicity in J774 macrophages. Additionally, the kinetics and radical products of AcEPs’ reaction with iron, the formation of radicals by AcEPs in Leishmania, as well as the resulting impairment of parasite mitochondrial functions were studied. Using electron paramagnetic resonance combined with spin trapping, photometry, and fluorescence-based oximetry, AcEPs were demonstrated to (i) show antileishmanial activity in vitro at IC₅₀ values in a low micromolar range, (ii) exhibit host cell toxicity in J774 macrophages, (iii) react rapidly with iron (II) resulting in the formation of oxygen- and carbon-centered radicals, (iv) produce carbon-centered radicals which could secondarily trigger superoxide radical formation in Leishmania, and (v) impair mitochondrial functions in Leishmania during parasite killing. Overall, the data of different AcEPs demonstrate that their structures besides the peroxo bridge strongly influence their activity and mechanism of their antileishmanial action.

Interaction of ascaridole, carvacrol, and caryophyllene oxide from essential oil of Chenopodium ambrosioides L. with mitochondria in Leishmania and other eukaryotes

The antileishmanial activity of the essential oil (EO) from Chenopodium ambrosioides L. has been demonstrated in vitro and in animal models, attributed to the major components of the EO. This study focused on the effects of the three major EO compounds carvacrol, caryophyllene oxide (Caryo), and the antileishmanial endoperoxide ascaridole (Asc) on mitochondrial functions in Leishmania tarentolae promastigotes (LtP). EO and Caryo were able to partially inhibit the leishmanial electron transport chain, whereas other components failed to demonstrate a direct immediate effect. Caryo demonstrated inhibition of complex III activity in LtP and in isolated complex III from other species. The formation of superoxide radicals was studied in Leishmania by electron spin resonance spectroscopy in the presence of iron chelators wherein selected compounds failed to trigger a significant immediate additional superoxide production in LtP. However, upon prolonged incubation of Leishmania with Asc and especially in the absence of iron chelators (allowing the activation of Asc), an increased superoxide radical production and significant impairment of mitochondrial coupling in Leishmania was observed. Prolonged incubation with all EO components resulted in thiol depletion. Taken together, the major components of EO mediate their leishmanicidal activity via different mitochondrial targets and time profiles. Further studies are required to elucidate possible synergistic effects of carvacrol and Asc and the influence of minor compounds.

In Vitro Anti-Leishmanial Activity of Essential Oils Extracted from Vietnamese Plants

Leishmania mexicana is one of the pathogens causing cutaneous leishmaniasis which is associated with patient morbidity. In our researches for new safe and effective treatments, thirty-seven essential oils (EOs) extracted from Vietnamese plants were screened in vitro for the first time on Leishmania mexicana mexicana (Lmm) promastigotes at the maximum concentration of 50 nL/mL. Active EOs were also analyzed for cytotoxicity on mammalian cell lines (WI38, J774) and their selectivity indices (SI) were calculated. Their composition was determined by GC-MS and GC-FID. Our results indicated that EOs extracted from Cinnamomum cassia, Zingiber zerumbet, Elsholtzia ciliata and Amomum aromaticum, possessed a moderate anti-leishmanial activity, with IC₅₀ values of 2.92 ± 0.08, 3.34 ± 0.34, 8.49 ± 0.32 and 9.25 ± 0.64 nL/mL respectively. However, they also showed cytotoxicity with SI < 10. The most promising EO was extracted from Ocimum gratissimum, displaying an IC₅₀ of 4.85 ± 1.65 nL/mL and SI > 10. It contained 86.5% eugenol, which was demonstrated to be effective on Lmm with IC₅₀ of 2.57 ± 0.57 nL/mL and not toxic on mammalian cells, explaining the observed activity.

In Vitro and In Vivo Evaluation of Essential Oil from Artemisia absinthium L. Formulated in Nanocochleates against Cutaneous Leishmaniasis

Background: Leishmaniasis is a zoonotic disease caused by protozoan parasites from Leishmania genus. Currently, there are no effective vaccines available and the available therapies are far from ideal. In particular, the development of new therapeutic strategies to reduce the infection caused by Leishmania amazonensis could be considered desirable. Different plant-derived products have demonstrated antileishmanial activity, including the essential oil (EO) from Artemisia absinthium L. (EO-Aa), Asteraceae. Methods: In the present study, the EO-Aa formulated in nanocochleates (EO-Aa-NC) was investigated in vitro against intracellular amastigotes of L. amazonensis and non-infected macrophages from BALB/c mice. In addition, the EO-Aa-NC was also evaluated in vivo against on experimental cutaneous leishmaniasis, which body weight, lesion progression, and parasite load were determined. Results: EO-Aa-NC displayed IC₅₀ values of 21.5 ± 2.5 μg/mL and 27.7 ± 5.6 μg/mL against intracellular amastigotes of L. amazonensis and non-infected peritoneal macrophage, respectively. In the animal model, the EO-Aa-NC (30 mg/kg/intralesional route/every 4 days 4 times) showed no deaths or weight loss greater than 10%. In parallel, the EO-Aa-NC suppressed the infection in the murine model by approximately 50%, which was statistically superior (p < 0.05) than controls and mice treated with EO-Aa. In comparison with Glucantime^®, EO-Aa-NC inhibited the progression of infection as efficiently (p > 0.05) as administration of the reference drug. Conclusions: Encochleation of EO-Aa resulted in a stable, tolerable, and efficacious antileishmanial formulation, facilitating systemic delivery of EO, with increased activity compared to administration of the free EO-Aa. This new formulation shows promising potential to future studies aimed at a new therapeutic strategy to treat leishmaniasis.

Evaluation of the in vivo leishmanicidal activity of amphotericin B emulgel: An alternative for the treatment of skin leishmaniasis

The American Cutaneous Leishmaniasis (ACL) is an infectious disease that can be fatal. The first line of treatment is pentavalent antimonies. However, due to its potential to develop resistance, Amphotericin B (AmB) started to be used as an alternative medicine. Current treatments are limited, a fact that has led to a growing interesting in developing new therapies. This study aims to evaluate the therapeutic potential in vivo of an amphotericin B + oleic acid (OA) emulgel in the treatment of cutaneous leishmaniasis in an experimental model. Strains of Leishmania major MHOM/IL/80/Friendlin of Leishmania major were used. The animals were inoculated subcutaneously. After the development of leishmanial, nodular or ulcerative lesions, the animals were divided into three groups (control, Group A and Group B) and treated twice a day for twelve days. The weight of the animals was measured and the size of the lesions was observed. A histopathological analysis was performed with skin fragments of lesions and with the spleen of animals treated with different treatments (emulgel, AmB 3% emulgel and AmB 3% plus OA 5% emulgel). It was observed that when subjected to treatment with AmB 3% emulgel during the study period using both formulations, with enhancer and without enhancer, ulcerative lesions regress gradually or even complete cure. The quantification of the average number of parasites recovered from the inoculation site was made after the treatment in each group and the differences were considered significant. The treatment with AmB 3% and OA 5% emulgel had the best in vivo therapeutic response, showing good prospects for cutaneous leishmaniasis therapy as an alternative therapy.

Combinations of ascaridole, carvacrol, and caryophyllene oxide against Leishmania

To date there are no vaccines against Leishmania and chemotherapy remains the mainstay for the control of leishmaniasis. The drugs currently used for leishmaniasis therapy are significantly toxic, expensive, and result in a growing frequency of refractory infections. In this study, we evaluated the effect of combinations of the main components of essential oil from Chenopodium ambrosioides (ascaridole, carvacrol, and caryophyllene oxide) against Leishmaniaamazonensis. Anti-leishmanial effects of combinations of pure compounds were evaluated in vitro and the fractional inhibitory concentration (FIC) indices were calculated. BALB/c mice infected with L. amazonensis were treated with different concentrations of ascaridole-carvacrol combinations by intralesional doses every 4 days. Disease progression and parasite burden in infected tissues were determined. In vitro experiments showed a synergistic effect of the combination of ascaridole-carvacrol against promastigotes of Leishmania with a FIC index of 0.171, while indifferent activities were observed for ascaridole-caryophyllene oxide (FIC index=3.613) and carvacrol-caryophyllene oxide (FIC index=2.356) combinations. The fixed ratio method showed that a 1:4 ascaridole-carvacrol ratio produced a better anti-protozoal activity on promastigotes, lower cytotoxicity, and synergistic activity on intracellular amastigotes (FIC index=0.416). Significant differences (p<0.05) in lesion size and parasite burden were demonstrated in BALB/c mice experimentally infected and treated with the ascaridole-carvacrol combinations compared with control animals. Carvacrol showed significant higher anti-radical activity in the DPPH assay compared with caryophyllene oxide. Electron spin resonance spectroscopy in combination with spin trapping suggested the presence of carbon-centered radicals after activation of ascaridole by Fe(2+). The intensity of the signals is preferably decreased upon addition of carvacrol. The ascaridole-carvacrol combination could represent a future alternative to monotherapeutic anti-leishmanial agents.

Chemistry and Leishmanicidal Activity of the Essential Oil from Artemisia absinthium from Cuba

Historically, natural products have been a rich source of lead molecules in drug discovery. In particular, products to treat infectious diseases have been developed and several reports about potentialities of essential oils (EO) against Leishmania could be found. In this study, we report the chemical characterization, anti-leishmanial effects and cytotoxicity of the EO from Artemisia absinthium L. Chemical analysis revealed the EO to be composed of 18 compounds, 11 of which were identified, accounting for 64.1% of the composition. The main component of the EO was trans-sabinyl acetate, which made up 36.7%. In vitro anti-leishmanial screening showed that the A. absinthium EO inhibited the growth of promastigotes (14.4 ± 3.6 μg/mL) and amastigotes (13.4 ± 2.4 μg/mL) of L. amazonensis; while cytotoxicity evaluation caused 6 fold higher values than those for the parasites. In a model of experimental cutaneous leishmaniasis in BALB/c mice, five doses of EO at 30 mg/kg by intralesional route demonstrated control of lesion size and parasite burden ( p< 0.05) compared with animals treated with glucantime and untreated mice. In conclusion, in vitro and in vivo results showed the potential of EO from A. absinthium as a promising source for lead or active compounds against Leishmania, which could be explored.

Chemistry and multibeneficial bioactivities of carvacrol (4-isopropyl-2-methylphenol), a component of essential oils produced by aromatic plants and spices

Aromatic plants produce organic compounds that may be involved in the defense of plants against phytopathogenic insects, bacteria, fungi, and viruses. One of these compounds, called carvacrol, which is found in high concentrations in essential oils such as oregano, has been reported to exhibit numerous bioactivities in cells and animals. This integrated overview surveys and interprets our present knowledge of the chemistry and analysis of carvacrol and its beneficial bioactivities. These activities include its antioxidative properties in food (e.g., lard, sunflower oil) and in vivo and the inhibition of foodborne and human antibiotic-susceptible and antibiotic-resistant pathogenic bacteria, viruses, pathogenic fungi and parasites, and insects in vitro and in human foods (e.g., apple juice, eggs, leafy greens, meat and poultry products, milk, oysters) and food animal feeds and wastes. Also covered are inhibitions of microbial and fungal toxin production and the anti-inflammatory, analgesic, antiarthritic, antiallergic, anticarcinogenic, antidiabetic, cardioprotective, gastroprotective, hepatoprotective, and neuroprotective properties of carvacrol as well as metabolic, synergistic, and mechanistic aspects. Areas for future research are also suggested. The collated information and suggested research might contribute to a better understanding of agronomical, biosynthetic, chemical, physiological, and cellular mechanisms of the described health-promoting effects of carvacrol, and facilitate and guide further studies needed to optimize the use of carvacrol as a multifunctional food in pure and encapsulated forms, in edible antimicrobial films, and in combination with plant-derived and medical antibiotics to help prevent or treat animal and human diseases.