Antifungal activity of plant-derived essential oils on Candida tropicalis planktonic and biofilms cells

Insights into the antibacterial effectiveness of linalool against Shigella flexneri on pork surface: Changes in bacterial growth and pork quality

Shigella flexneri has the ability to contaminate pork and cause foodborne diseases. This study aimed to examine the effectiveness of linalool (a natural preservative) against S. flexneri and explore its potential application in contaminated pork. The results showed that linalool was capable of damaging the cell membrane and binding to the DNA of S. flexneri, and inhibiting biofilm formation and disrupting mature biofilms. The antibacterial effectiveness of linalool on the surface of pork was further demonstrated by analyzing the physicochemical properties of the pork (i.e., weight loss rate, pH value, color index, and TVB-N value) and its protein profiles. Linalool did not completely kill S. flexneri in pork at minimum bactericidal concentration (MBC) concentration and its antibacterial effect of linalool was stronger during the initial stage of storage. During storage, linalool influenced the abundance of specific proteins in the pork, particularly those involved in pathways related to fat metabolism. These findings offer novel insights into the antibacterial efficacy of linalool and its underlying mechanism in pork.

Natural products of plant origin: an emerging therapeutic for dermatomycosis

Dermatomycosis or superficial mycosis is considered one of the chronic fungal infections and a global challenge for the public health system. The severity of dermatomycosis is proportionately increasing with the emerging population of immunocompromised individuals, and it is becoming more prevalent, even life-threatening, in several tropical countries. In this context, improper long-term treatment with synthetic antifungal drugs and their related side effects imposes additional challenges in treating dermatomycosis. Thus, the present scenario highlights the need for a novel and accurate treatment with minimal or no side effects. The multifaceted therapeutic properties of various natural products have garnered the interest of scientific communities in recent years. Generally, plant-based products have low toxicity levels and offer diverse formulations and unique biomolecules for clinical applicability against dermatomycosis. Thus, this study presents an overview of the pathogenesis and different treatment strategies for dermatomycosis. In addition, we highlight the implementation of natural products of plant origin for treating dermatomycosis infections and reducing adverse events. Further, their mode of action and role in the development of pharmaceutical drugs are discussed.

Oxidative Stress-Mediated Repression of Virulence Gene Transcription and Biofilm Formation as Antibacterial Action of Cinnamomum burmannii Essential Oil on Staphylococcus aureus

This work aimed to identify the chemical compounds of Cinnamomum burmannii leaf essential oil (CBLEO) and to unravel the antibacterial mechanism of CBLEO at the molecular level for developing antimicrobials. CBLEO had 37 volatile compounds with abundant borneol (28.40%) and showed good potential to control foodborne pathogens, of which Staphylococcus aureus had the greatest inhibition zone diameter (28.72 mm) with the lowest values of minimum inhibitory concentration (1.0 μg/mL) and bactericidal concentration (2.0 μg/mL). To unravel the antibacterial action of CBLEO on S. aureus, a dynamic exploration of antibacterial growth, material leakage, ROS formation, protein oxidation, cell morphology, and interaction with genome DNA was conducted on S. aureus exposed to CBLEO at different doses (1/2-2×MIC) and times (0-24 h), indicating that CBLEO acts as an inducer for ROS production and the oxidative stress of S. aureus. To highlight the antibacterial action of CBLEO on S. aureus at the molecular level, we performed a comparative association of ROS accumulation with some key virulence-related gene (sigB/agrA/sarA/icaA/cidA/rsbU) transcription, protease production, and biofilm formation in S. aureus subjected to CBLEO at different levels and times, revealing that CBLEO-induced oxidative stress caused transcript suppression of virulence regulators (RsbU and SigB) and its targeted genes, causing a protease level increase destined for the biofilm formation and growth inhibition of S. aureus, which may be a key bactericidal action. Our findings provide valuable information for studying the antibacterial mechanism of essential oil against pathogens.

Antifungal activity of cercosporamide produced by Phaeosphaeriaceae GV-1 against pathogenic fungi

Fungal infections affect millions of people worldwide, and the several cases are related to invasive infections, which is a problem mainly for immunocompromised people, such as transplant and cancer patients with high mortality and morbidity rates. In addition, the number of emerging and multidrug-resistant fungal species has increased in the last decade. The search for new antifungal compounds is necessary, due to the increase in cases of resistance and the toxicity of drugs used in fungal infection treatment. This work aimed to study the antifungal activity of cercosporamide produced by Phaeosphaeriaceae GV-1. Cercosporamide was tested against pathogenic fungi by determining the minimum inhibitory (MIC) and minimum fungicidal (MFC) concentrations, using the broth microdilution method. Cercosporamide showed antifungal activity in vitro against 13 of 16 strains of medical importance tested, with the most susceptible species being Candida tropicalis, with MIC and MFC of 15.6 μg/mL. Thus, cercosporamide might be considered a promising therapeutic antifungal agent.

Revisiting the Therapeutic Effects of Essential Oils on the Oral Microbiome

The extensive use of antibiotics has resulted in the development of drug-resistant bacteria, leading to a decline in the efficacy of traditional antibiotic treatments. Essential oils (EOs) are phytopharmaceuticals, or plant-derived compounds, that possess beneficial properties such as anti-inflammatory, antibacterial, antimicrobial, antiviral, bacteriostatic, and bactericidal effects. In this review, we present scientific findings on the activity of EOs as an alternative therapy for common oral diseases. This narrative review provides a deeper understanding of the medicinal properties of EOs and their application in dentistry. It not only evaluates the effectiveness of these oils as antibacterial agents against common oral bacteria but also covers general information such as composition, methods of extraction, and potential toxicity. Further nonclinical and clinical studies must be conducted to determine their potential use and safety for treating oral diseases.

Impact of Litsea cubeba inter-row cover on the structure of bacterial community in the tea plantation

Purpose

The application of bio-control plants in the agricultural processes is one of the effective ways to solve the traditional agricultural synthetic pesticide residues. This study will investigate the effect of bio-control plant Litsea cubeba branch inter-row cover on soil bacterial community, soil-enriched metabolites, and soil mineral nutrition in tea plantation, which will provide a basis for the use of bio-control plant in agroecological farming systems.

Methods

The fruit-bearing (F-Pr) and vegetative (F-Ab) branches of Litsea cubeba were inter-row covered (the use of plants for partial coverage of soil between the rows) in the tea plantation. And we determined the soil microbial community, soil mineral nutriment, and soil-enriched metabolites composition with the methods of 16S rRNA gene sequencing, inductively coupled plasma-atomic emission spectroscopy (ICP-AEC), inductively coupled plasma-optical emission spectrometry (ICP-OES), and gas chromatography-mass spectrometry (GS-MS). We also predict the function of soil bacteria with the Tax4Fun software.

Results

Litsea cubeba inter-row cover modified the soil microbial structure and diversity; Litsea cubeba inter-row cover significantly decreased the relative abundance of Acidobacteria, Chloroflexi, and Planctomycetes while increased the relative abundance of Proteobacteria. Litsea cubeba inter-row cover significantly antagonized the plant pathogen community, and its OTUs number decreased from 907 ± 81 in the control to 337 ± 25 in F-Pr treatment; compared with F-Pr treatment, F-Ab treatment had weaker effect on the abundance of nutrition metabolism and transport, carbohydrate utilization, and nitrate reduction A. The aluminum element in the F-Pr treatment was significantly reduced, while phosphorus was increased. The soil-enriched metabolites of F-Pr treatment contained some antibacterial substance, including 14.2 ± 3.32% citronellol, 10.38 ± 4.79% alpha-terpineol, and 8.25 ± 2.62% (+)-2-bornanone, which was the main environment factor that affects the soil bacterial structure and diversity.

Conclusion

Litsea cubeba inter-row cover significantly affected bacterial structure and diversity, slightly increased the soil pH, and improved soil aluminum and phosphorus status; soil-enriched metabolites were the major environment factor affecting soil bacterial community and should be considered in the application of bio-control plants; Litsea cubeba vegetative branch inter-row cover will be a feasible measure for integrated pest management in tea plantation.

Natural Compounds in the Battle against Microorganisms-Linalool

The purpose of this article is to present recent studies on the antimicrobial properties of linalool, the mechanism of action on cells and detoxification processes. The current trend of employing compounds present in essential oils to support antibiotic therapy is becoming increasingly popular. Naturally occurring monoterpene constituents of essential oils are undergoing detailed studies to understand their detailed effects on the human body, both independently and in doses correlated with currently used pharmaceuticals. One such compound is linalool, which is commonly found in many herbs and is used to flavor black tea. This compound is an excellent fragrance additive for cosmetics, enhancing the preservative effect of the formulations used in them or acting as an anti-inflammatory on mild skin lesions. Previous studies have shown that it is extremely important due to its broad spectrum of biological activities, i.e., antioxidant, anti-inflammatory, anticancer, cardioprotective and antimicrobial. Among opportunistic hospital strains, it is most active against Gram-negative bacteria. The mechanism of action of linalool against microorganisms is still under intensive investigation. One of the key aspects of linalool research is biotransformation, through which its susceptibility to detoxification processes is determined.

Natural Compounds: A Hopeful Promise as an Antibiofilm Agent Against Candida Species

The biofilm communities of Candida are resistant to various antifungal treatments. The ability of Candida to form biofilms on abiotic and biotic surfaces is considered one of the most important virulence factors of these fungi. Extracellular DNA and exopolysaccharides can lower the antifungal penetration to the deeper layers of the biofilms, which is a serious concern supported by the emergence of azole-resistant isolates and Candida strains with decreased antifungal susceptibility. Since the biofilms’ resistance to common antifungal drugs has become more widespread in recent years, more investigations should be performed to develop novel, inexpensive, non-toxic, and effective treatment approaches for controlling biofilm-associated infections. Scientists have used various natural compounds for inhibiting and degrading Candida biofilms. Curcumin, cinnamaldehyde, eugenol, carvacrol, thymol, terpinen-4-ol, linalool, geraniol, cineole, saponin, camphor, borneol, camphene, carnosol, citronellol, coumarin, epigallocatechin gallate, eucalyptol, limonene, menthol, piperine, saponin, α-terpineol, β–pinene, and citral are the major natural compounds that have been used widely for the inhibition and destruction of Candida biofilms. These compounds suppress not only fungal adhesion and biofilm formation but also destroy mature biofilm communities of Candida. Additionally, these natural compounds interact with various cellular processes of Candida, such as ABC-transported mediated drug transport, cell cycle progression, mitochondrial activity, and ergosterol, chitin, and glucan biosynthesis. The use of various drug delivery platforms can enhance the antibiofilm efficacy of natural compounds. Therefore, these drug delivery platforms should be considered as potential candidates for coating catheters and other medical material surfaces. A future goal will be to develop natural compounds as antibiofilm agents that can be used to treat infections by multi-drug-resistant Candida biofilms. Since exact interactions of natural compounds and biofilm structures have not been elucidated, further in vitro toxicology and animal experiments are required. In this article, we have discussed various aspects of natural compound usage for inhibition and destruction of Candida biofilms, along with the methods and procedures that have been used for improving the efficacy of these compounds.

Identification of Secondary Metabolites from Mexican Plants with Antifungal Activity against Pathogenic Candida Species

In the last three decades, invasive fungal infections caused by Candida species have become an important public health problem, because they are associated with high rates of morbidity and mortality in immunocompromised and hospitalized patients. The diagnosis and treatment of candidiasis are difficult and usually inefficient. Accordingly, a diversity of available drugs, currently employed to attack candidiasis, frequently induce resistance in patients promoting toxicity due to long-term treatments. Therefore, development of accurate diagnoses and novel antifungals is of high priority to improve life’s quality and expectancy of individuals infected with this pathogen. Plants are invaluable sources of new biologically active compounds. Among the plants used in Mexico in traditional herbolary medicine which have empirically been demonstrated to have antifungal activity are Pedilanthus tithymaloides, Thymus vulgaris, and Ocimum basilicum. In the present study, we analyzed whether these plants contain metabolites with antifungal activity against five Candida species. The extracts from the different plant organs were obtained by macerating them in ethyl alcohol or hexane and filtering. The obtained extracts were preserved in amber flasks at 4°C until used. The minimum inhibitory concentrations (MICs) of the active compound were determined by a microdilution assay. In addition, the following secondary metabolites were identified: linalool (3,7-dimethylocta-1,6-dien-3-ol), eugenol (4-allyl-2-methoxyphenol), limonene (1-methyl-4-(1-methylethenyl)-cyclohexene), and borneol ([(2R)-1,7,7-trimethyl-2-bicyclo[2.2.1]heptanyl] formate). All these compounds were found in the three plants, traditionally used in everyday life, and proved to be effective against Candida species and therefore a viable alternative to conventional antifungals.

Antifungal and Modulatory Activity of Lemon Balm (Lippia alba (MILL.) N. E. BROWN) Essential Oil

Fungal diseases and the progressive development of resistance are a challenge. In this context, Lippia alba (lemon balm) is a species used in folk medicine, being described with antimicrobial potential. The aim of this study was to determine the antifungal activity and modulating effect of the essential oil of Lippia alba (Mill.) N.E. Brown leaves (LaEO). The antifungal activity of LaEO on eight Candida strains was determined by minimum inhibitory concentration (MIC) and minimum lethal concentration (MLC), minimum biofilm inhibition concentration (MBIC), minimum biofilm eradication concentration (MBEC) and time-kill. The checkerboard technique was used to determine the modulating effect of LaEO on antifungal activity. The results indicate the presence of 11 constituents, with a predominance of carvone (58.15%) and limonene (25.37%). LaEO was able to inhibit the growth of all tested microorganisms, with MIC and MLC ranging from 0.078 to 1.25 mg/mL and MBIC and MBEC ranging from 0.156 to 5 mg/mL. The time-kill assay showed that LaEO was able to eliminate the strains after two hours of exposure and the best association was observed for the combination of LaEO and ketoconazole. The results of the study indicate that LaEO has excellent antifungal activity with potential biotechnological application.

Metabolic profile of Candida albicans and Candida parapsilosis interactions within dual-species biofilms

Within the oral cavity, the ability of Candida species to adhere and form biofilms is well recognized, especially when C. albicans is considered. Lately, a knowledge gap has been identified regarding dual-species communication of Candida isolates, as a way to increase virulence, with evidences being collected to support the existence of interactions between C. albicans and C. parapsilosis. The present work evaluated the synergistic effect of the two Candida species, and explored chemical interactions between cells, evaluating secreted extracellular alcohols and their relation with yeasts´ growth and matrix composition. Four clinical strains of C. albicans and C. parapsilosis species, isolated from single infections of different patients or from co-infections of a same patient, were tested. It was found that dual-species biofilms negatively impacted the growth of C. parapsilosis and their biofilm matrix, in comparison with mono-species biofilms, and had minor effects on the biofilm biomass. Alcohol secretion revealed to be species- and strain-dependent. However, some dual-species cultures produced much higher amounts of some alcohols (E-nerolidol and E, E-Farnesol) than the respective single cultures, which proves the existence of a synergy between species. These results show evidence that interactions between Candida species affect the biofilm matrix, which is a key element of oral biofilms.

Evaluation of anticandidal activities and phytochemical examination of extracts prepared from Vitex agnus-castus: a possible alternative in treating candidiasis infections

BACKGROUND

Candidiasis infection is associated with high morbidity and mortality. Fungicidal resistance of some commercially used fungicides ascended the need for a naturally effective alternative. The current study aimed to evaluate the fungicidal activity of Vitex agnus-castus extracts in vitro against some Candida species.

METHODS

The bioactive compounds contained in the crude and alcoholic extracts were compared, and the antioxidant activity was tested, as well. The phytochemical analysis was carried out by Fourier Transform-Infrared Spectroscopy (FTIR) and Gas Chromatography-Mass Spectrometry (GC/MS). The scavenger activity of the tested extracts was tested, as well. The anticandidal activity was tested to detect the effect of the tested extracts on the mycelial growth of Candida albicans, Candida krusei, Candida parapsilosis, Candia tropicalis, Candida famata, Candida rhodotorula, and Candida dublinesis. The minimum inhibitory concentrations were calculated for all reported activities. The Scanning Electron Microscopy (SEM) and the Transmission Electron Microscopy (TEM) were used to detect the morphological and ultrastructure response in some selected species.

RESULTS

FTIR and GC/MS revealed the existence of different bioactive chemical groups such as polyphenols, fatty acids, terpenes, terpenoids, steroids, aldehydes, alcohols, and esters, phytol which is a diterpene. DPPH results confirmed the antioxidant activity of all extracts where the methanolic extract was the strongest scavenging substrate. All extracts showed strong inhibitory effects against different species at a concentration of 200 µg/ml (P < 0.001). SEM and TEM showed morphological and ultrastructure changes in C. famata.

CONCLUSION

The current study suggested a reliable antifungal activity of different extracts of Vitex agnus-castus against different Candida species and strains. However, further studies are required to confirm the safety of these extracts to be used in medical applications.

Evaluation of the effect of Jaftex herbal mouthwash on the growth of Candida albicans and Candida tropicalis

Background

Increased resistance of Candida albicans to standard antifungal agents has caused special attention to medicinal plants. The aim of this study was to evaluate the effect of Jaftex mouthwash on the growth of C. albicans and Candida tropicalis.

Methods and Material

In this in vitro study, standard strains of C. albicans and C. tropicalis were used. Jaftex mouthwash was prepared with the active ingredient (10g/100cc) of aqueous extract of oak fruit hull (Jaft), Zataria multiflora, and Satureja bachtiarica. The mouthwash was diluted in half, 8 different concentrations were obtained. 10 μl volume of each dilution was poured on discs mounted linearly on the culture medium inoculated with the target fungus. After 24 h, due to the slow growth rate of these fungi, the Petri dishes were incubated at 37°C and the mean minimum inhibitory concentration (MIC) was determined for each fungus. The modified E. test method was used to measure the MIC of Jaftex mouthwash for the two fungi. The experiment was repeated three times for each fungus and the mean value was measured.

Results

The mean value of MIC for C. albicans and C. tropicalis was 0.0625 (mg/mL) and 0.0833 (mg/mL), respectively. Candida albicans appeared to be more sensitive to Jaftex, but no statistically significant difference was observed.

Conclusion

Jaftex mouthwash inhibits the growth of C. albicans and C. tropicalis. The use of this mouthwash is recommended for treatment of oral candidiasis.

Efficacy of true cinnamon (Cinnamomum verum) leaf essential oil as a therapeutic alternative for Candida biofilm infections

Objective(s):

The essential oil (EO) extracted from Cinnamomum verum leaves has been used as an antimicrobial agent for centuries. But its antifungal and antibiofilm efficacy is still not clearly studied. The objective of this research was to evaluate the in vitro antifungal and antibiofilm efficacy of C. verum leaf EO against C. albicans, C. tropicalis, and C. dubliniensis and the toxicity of EO using an in vitro model.

Materials and Methods:

The effect of EO vapor was evaluated using a microatmosphere technique. CLSI microdilution assay was employed in determining the Minimum Inhibitory (MIC) and Fungicidal Concentrations (MFC). Killing time was determined using a standard protocol. The effect of EO on established biofilms was quantified and visualized using XTT and Scanning Electron Microscopy (SEM), respectively. Post-exposure intracellular changes were visualized using Transmission Electron Microscopy (TEM). The toxicological assessment was carried out with the Human Keratinocyte cell line. The chemical composition of EO was evaluated using Gas Chromatography-Mass Spectrometry (GC-MS).

Results:

All test strains were susceptible to cinnamon oil vapor. EO exhibited MIC value 1.0 mg/ml and MFC value 2.0 mg/ml against test strains. The killing time of cinnamon oil was 6 hr. Minimum Biofilm Inhibitory Concentration (MBIC₅₀) for established biofilms was <0.2 mg/ml for all test strains. SEM images exhibited cell wall damages, cellular shrinkages, and decreased hyphal formation of Candida. TEM indicated intracellular vacuolation, granulation, and cell wall damages. Cinnamon leaf oil caused no inhibition of HaCaT cells at any concentration tested. Eugenol was the abundant compound in cinnamon oil.

Conclusion:

C. verum EO is a potential alternative anti-Candida agent with minimal toxicity on the human host.

Plant Preparations and Compounds with Activities against Biofilms Formed by Candida spp

Fungi from the genus Candida are very important human and animal pathogens. Many strains can produce biofilms, which inhibit the activity of antifungal drugs and increase the tolerance or resistance to them as well. Clinically, this process leads to persistent infections and increased mortality. Today, many Candida species are resistant to drugs, including C. auris, which is a multiresistant pathogen. Natural compounds may potentially be used to combat multiresistant and biofilm-forming strains. The aim of this review was to present plant-derived preparations and compounds that inhibit Candida biofilm formation by at least 50%. A total of 29 essential oils and 16 plant extracts demonstrate activity against Candida biofilms, with the following families predominating: Lamiaceae, Myrtaceae, Asteraceae, Fabaceae, and Apiacae. Lavandula dentata (0.045–0.07 mg/L), Satureja macrosiphon (0.06–8 mg/L), and Ziziphora tenuior (2.5 mg/L) have the best antifungal activity. High efficacy has also been observed with Artemisia judaica, Lawsonia inermis, and Thymus vulgaris. Moreover, 69 plant compounds demonstrate activity against Candida biofilms. Activity in concentrations below 16 mg/L was observed with phenolic compounds (thymol, pterostilbene, and eugenol), sesquiterpene derivatives (warburganal, polygodial, and ivalin), chalconoid (lichochalcone A), steroidal saponin (dioscin), flavonoid (baicalein), alkaloids (waltheriones), macrocyclic bisbibenzyl (riccardin D), and cannabinoid (cannabidiol). The above compounds act on biofilm formation and/or mature biofilms. In summary, plant preparations and compounds exhibit anti-biofilm activity against Candida. Given this, they may be a promising alternative to antifungal drugs.

The Use of Essential Oils and Their Isolated Compounds for the Treatment of Oral Candidiasis: A Literature Review

In this literature review, we present the main scientific findings on the antifungal activity of essential oils (EOs) applicable for a new drug formulation to treat oral candidiasis. Seven literature databases were systematically searched for eligible in vitro and clinical trials. Selected articles were screened for biological activity, botanical species, phytochemical composition, study design, and methodological quality. A total of 26 articles were included in the review, of which 21 were in vitro studies and 5 clinical trials. The most promising EOs were obtained from Allium tubeorosum, Cinnamomum cassia, Cinnamomum zeylanicum, and Coriandrum sativum L. Among the phytochemicals, citral and thymol were the most active. Clinical trials indicated that the EOs from Pelargonium graveolens and Zataria multiflora are potentially effective to treat oral candidiasis. Further nonclinical and clinical studies with these EO are warranted to determine their potential use and safety for the treatment of oral candidiasis.

Licochalcone A, a licorice flavonoid: antioxidant, cytotoxic, genotoxic, and chemopreventive potential

Licochalcone A (LicoA) is a flavonoid derived from Glycyrrhiza spp. plants. The present study aimed to investigate the antioxidant, cytotoxic, genotoxic, and chemopreventive effects of LicoA in in vitro and in vivo systems. The results showed that LicoA (197.1 μM) scavenged 77.92% of free radicals. Concentrations of 147.75 µM or higher LicoA produced cytotoxicity in Chinese hamster ovary (CHO) fibroblasts. LicoA treatments of 4.43 to 10.34 µM did not exert genotoxic activity, but at 11.8 µM significantly lowered nuclear division indexes, compared to negative control, revealing cytotoxicity. Lower concentrations (1.85 to 7.39 µM) exhibited protective activity against chromosomal damage induced by doxorubicin (DXR) or methyl methanesulfonate (MMS) in CHO cells. LicoA exerted no marked influence on DXR-induced genotoxicity in mouse erythrocytes, but reduced pre-neoplastic lesions induced by 1,2-dimethylhydrazine (DMH) in rat colon at 3.12 to 50 mg/kg b.w. Biochemical markers and body weight indicated no apparent toxicity. These findings contribute to better understanding the mechanisms underlying LicoA-initiated activity as a promising chemopreventive compound.

ABBREVIATIONS

AC, aberrant crypts; ACF, aberrant crypt foci; ALT, alanine aminotransferase; AST, aspartate aminotransferase; BOD, biochemical oxygen demand; CHO, Chinese hamster ovary fibroblast; DMH, 1,2-dimethylhydrazine; DMSO, dimethyl sulfoxide; DPPH, 2,2-diphenyl-1-picrylhydrazyl; DXR, doxorubicin hydrochloride; EDTA, ethylenediaminetetraacetic acid; GA, gallic acid; LicoA, licochalcone A; MMS, methyl methanesulfonate; MNBC, micronucleated binucleated cells; MNPCE, micronucleated polychromatic erythrocyte; NCE, normochromatic erythrocyte; NDI, nuclear division index; PBS, phosphate-buffered saline; PCE, polychromatic erythrocyte; XTT, 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide.

Fungal Quorum-Sensing Molecules: A Review of Their Antifungal Effect against Candida Biofilms

The number of effective therapeutic strategies against biofilms is limited; development of novel therapies is urgently needed to treat a variety of biofilm-associated infections. Quorum sensing is a special form of microbial cell-to-cell communication that is responsible for the release of numerous extracellular molecules, whose concentration is proportional with cell density. Candida-secreted quorum-sensing molecules (i.e., farnesol and tyrosol) have a pivotal role in morphogenesis, biofilm formation, and virulence. Farnesol can mediate the hyphae-to-yeast transition, while tyrosol has the opposite effect of inducing transition from the yeast to hyphal form. A number of questions regarding Candida quorum sensing remain to be addressed; nevertheless, the literature shows that farnesol and tyrosol possess remarkable antifungal and anti-biofilm effect at supraphysiological concentration. Furthermore, previous in vitro and in vivo data suggest that they may have a potent adjuvant effect in combination with certain traditional antifungal agents. This review discusses the most promising farnesol- and tyrosol-based in vitro and in vivo results, which may be a foundation for future development of novel therapeutic strategies to combat Candida biofilms.

Essential Oils and Mono/bi/tri-Metallic Nanocomposites as Alternative Sources of Antimicrobial Agents to Combat Multidrug-Resistant Pathogenic Microorganisms: An Overview

Over the past few decades, many pathogenic bacteria have become resistant to existing antibiotics, which has become a threat to infectious disease control worldwide. Hence, there has been an extensive search for new, efficient, and alternative sources of antimicrobial agents to combat multidrug-resistant pathogenic microorganisms. Numerous studies have reported the potential of both essential oils and metal/metal oxide nanocomposites with broad spectra of bioactivities including antioxidant, anticancer, and antimicrobial attributes. However, only monometallic nanoparticles combined with essential oils have been reported on so far with limited data. Bi- and tri-metallic nanoparticles have attracted immense attention because of their diverse sizes, shapes, high surface-to-volume ratios, activities, physical and chemical stability, and greater degree of selectivity. Combination therapy is currently blooming and represents a potential area that requires greater attention and is worthy of future investigations. This review summarizes the synergistic effects of essential oils with other antimicrobial combinations such as mono-, bi-, and tri-metallic nanocomposites. Thus, the various aspects of this comprehensive review may prove useful in the development of new and alternative therapeutics against antibiotic resistant pathogens in the future.

Promising Alternative Therapeutics for Oral Candidiasis

:

Candida is the main human fungal pathogen causing infections (candidiasis), mostly in the elderly and immunocompromised hosts. Even though Candida spp. is a member of the oral microbiota in symbiosis, in some circumstances, it can cause microbial imbalance leading to dysbiosis, resulting in oral diseases. Alternative therapies are urgently needed to treat oral candidiasis (usually associated to biofilms), as several antifungal drugs’ activity has been compromised. This has occurred especially due to an increasing occurrence of drugresistant in Candida spp. strains. The overuse of antifungal medications, systemic toxicity, cross-reactivity with other drugs and a presently low number of drug molecules with antifungal activity, have contributed to important clinical limitations.

:

We undertook a structured search of bibliographic databases (PubMed Central, Elsevier’s ScienceDirect, SCOPUS and Springer’s SpringerLink) for peer-reviewed research literature using a focused review in the areas of alternatives to manage oral candidiasis. The keywords used were “candidiasis”, “oral candidiasis”, “biofilm + candida”, “alternative treatment”, “combination therapy + candida” and the reports from the last 10 to 15 years were considered for this review.

:

This review identified several promising new approaches in the treatment of oral candidiasis: combination anti-Candida therapies, denture cleansers, mouth rinses as alternatives for disrupting candidal biofilms, natural compounds (e.g. honey, probiotics, plant extracts and essential oils) and photodynamic therapy.

:

The findings of this review confirm the importance and the urgency of the development of efficacious therapies for oral candidal infections.

Electrospun essential oil-polycaprolactone nanofibers as antibiofilm surfaces against clinical Candida tropicalis isolates

OBJECTIVE

As an approach to prevent biofilm infections caused by Candida tropicalis on various surfaces, determination of effect of biodegradable polycaprolactone nanofibers (PCLNFs) with different concentrations of two different essential oils were tested in this study.

RESULTS

Both of the tested essential oils exhibited antifungal effect (minimal inhibitory concentration; 0.25-0.49 µL/mL, minimal fungicidal concentration; 0.25-0.49 µL/mL, depending on the C. tropicalis strain) (Zone of inhibition caused by 500 μL/mL concentration of oils; 28-56 mm). 0, 2, 4% clove oil PCLNFs and 0, 2, 4% red thyme oil-PCLNFs were free from bead formation and uniform in diameter. Diameters of all essential oil containing PCLNFs were ranged from 760 to 1100 nm and were significantly different from 0% essential oil-PCLNF (P < 0.05). 0, 2, 4% clove oil-PCLNFs were significantly more hydrophobic compared to 8% clove oil-PCLNF (P < 0.01), whereas 0% and 2% red thyme oil-PCLNFs were significantly more hydrophobic compared to 4% and 8% red thyme oil PCLNFs (P < 0.01). Highest amount of biofilm inhibition was observed by 4% clove oil-PCLNF and by 4% red thyme oil-PCLNF.

CONCLUSIONS

Clove and red thyme oils may be used not only as antifungals but also as biofilm inhibitive agents on surfaces of biomaterials that are frequently contaminated by C. tropicalis, when they are incorporated into PCLNFs.

Geraniol and linalool anticandidal activity, genotoxic potential and embryotoxic effect on zebrafish

Aim: Geraniol and linalool are major constituents of the essential oils of medicinal plants. Materials & methods: Antifungal activity of geraniol and linalool were evaluated against five Candida species. The genotoxicity of these compounds was evaluated by the cytokinesis-block micronucleus test, and the embryotoxic assays use zebrafish model. Results: Geraniol and linalool inhibited Candida growth, but geraniol was more effective. The geraniol at concentration of 800 μg/ml and the linalool at concentration of 125 μg/ml significantly increased chromosome damage. Geraniol was more toxic to zebrafish embryo than linalool: LC50 values were 31.3 and 193.3 μg/ml, respectively. Conclusion: Geraniol and linalool have anticandidal activity, but they also exert genotoxic and embryotoxic effects at the highest tested concentrations.

Antifungal Compounds against Candida Infections from Traditional Chinese Medicine

Infections caused by Candida albicans, often refractory and with high morbidity and mortality, cause a heavy burden on the public health while the current antifungal drugs are limited and are associated with toxicity and resistance. Many plant-derived molecules including compounds isolated from traditional Chinese medicine (TCM) are reported to have antifungal activity through different targets such as cell membrane, cell wall, mitochondria, and virulence factors. Here, we review the recent progress in the anti-Candida compounds from TCM, as well as their antifungal mechanisms. Considering the diverse targets and structures, compounds from TCM might be a potential library for antifungal drug development.

Alizarin and Chrysazin Inhibit Biofilm and Hyphal Formation by Candida albicans

Candida albicans is one of the most common pathogen causes fungal infections. This opportunistic pathogen can form biofilms comprised of yeast, hyphae and pseudo hyphal elements, and the hyphal form C. albicans considered as probable virulence factor. We investigated the antibiofilm activities of 13 quinones and anthraquinones related compounds against C. albicans biofilms by using crystal violet and 2,3-bis (2-Methoxy-4-Nitro-5-Sulfo-phenyl)-2H-Tetrazolium-5-Carboxanilide (XTT) reduction assays to assess inhibitions of biofilm growth. Morphological changes in biofilms and biofilm thicknesses were determined by scanning electron microscopy and confocal laser scanning microscopy, respectively. It was found alizarin (1,2-dihydroxyanthraquinone) and chrysazin (1,8-dihydroxyanthraquinone) suppressed C. albicans biofilm formation. Interestingly, alizarin and chrysazin at only 2 μg/ml effectively inhibited hyphal formation and prolonged the survival of C. albicans infected Caenorhabditis elegans, thus showing a distinct antivirulent potential. A structural activity relationship study of alizarin and 6 other anthraquinones showed the presence of a hydroxyl group at C-1 position which is important for antibiofilm and antifilamentation activities. Transcriptomic analyses revealed that alizarin downregulated the expression of several hypha-specific and biofilm related genes (ALS3, ECE1, ECE2, and RBT1). Furthermore, unlike the commercial antifungal drug fluconazole, no acute toxic effect was observed when uninfected nematodes were exposed to alizarin at concentrations up to 1 mg/ml. The results of this study indicate alizarin suppresses the virulence of C. albicans in vivo which suggests alizarin may be considered as a potential candidate for further investigations to develop antifungal agent against fungal pathogen in vivo.

Chemical Composition and In Vitro Cytotoxic and Antimicrobial Activities of the Essential Oil from Leaves of Zanthoxylum monogynum St. Hill (Rutaceae)

Background: The Zanthoxylum monogynum species belongs to the family Rutaceae and is found in Southeast, Midwest, and Northeast Brazil. For this genus several biological activities have been described. Methods: The essential oil (EO) was obtained from the leaves of Zanthoxylum monogynum by hydro-distillation and was analyzed by gas chromatograph and gas chromatograph/mass spectrometry (GC and GC/MS). Also the EO of Z. monogynum was evaluated for in vitro cytotoxic activity against six tumor cell lines and for antimicrobial activity, performing disk diffusion and MIC assays with yeast and bacterial strains. Results: The chemical analysis afforded the identification of 18 components (99.0% of the EO). The major components were found to be citronellol (43.0%) and farnesol (32.0%). The in vitro cytotoxic activity against tumor cell lines, resulted in IC₅₀ values ranging from 11–65 µg/mL against all tested cell lines. Antimicrobial activity of the essential oil was also tested and oil was effective, especially against Cryptococcus sp. yeast. All the tested yeast strains showed at least 90% growth inhibition. Conclusions: the essential oil from leaves of Z. monogynum has a different qualitative and quantitative composition when compared to the composition previously described. Also this EO has significant cytotoxic activity and moderate activity against Cryptococcus sp. and Saccharomyces cereviseae yeasts.

Inhibitory effects of the essential oils α-longipinene and linalool on biofilm formation and hyphal growth of Candida albicans

Candida albicans is one of the most common fungal pathogens, and causes systemic and invasive infections in humans. C. albicans biofilms are composed of yeast and hyphal and pseudohyphal elements, and the transition of yeast to the hyphal stage could be a virulence factor. In this study, diverse essential oils were initially investigated for anti-biofilm activity against C. albicans strains, and cascarilla bark oil and helichrysum oil and their components α-longipinene (a major constituent of both) and linalool were found to markedly inhibit biofilm formation without affecting planktonic cell growth. Moreover, α-longipinene and linalool were found to synergistically reduce biofilm formation. Notably, treatments with cascarilla bark oil, helichrysum oil, α-longipinene, or linalool clearly inhibited hyphal formation, and this appeared to be largely responsible for their anti-biofilm effect. Furthermore, the two essential oils, α-longipinene and linalool, reduced C. albicans virulence in Caenorhabditis elegans.

Antimicrobial Properties of Plant Essential Oils against Human Pathogens and Their Mode of Action: An Updated Review

A wide range of medicinal and aromatic plants (MAPs) have been explored for their essential oils in the past few decades. Essential oils are complex volatile compounds, synthesized naturally in different plant parts during the process of secondary metabolism. Essential oils have great potential in the field of biomedicine as they effectively destroy several bacterial, fungal, and viral pathogens. The presence of different types of aldehydes, phenolics, terpenes, and other antimicrobial compounds means that the essential oils are effective against a diverse range of pathogens. The reactivity of essential oil depends upon the nature, composition, and orientation of its functional groups. The aim of this article is to review the antimicrobial potential of essential oils secreted from MAPs and their possible mechanisms of action against human pathogens. This comprehensive review will benefit researchers who wish to explore the potential of essential oils in the development of novel broad-spectrum key molecules against a broad range of drug-resistant pathogenic microbes.