Anticandidal low molecular compounds from higher plants with special reference to compounds from essential oils

A combinatorial approach of Monarda citriodora essential oil (MEO) and linalool vapors to control fruit rot of Citrus limon caused by a new pathogen, Aspergillus foetidus, and its underlying mode of action

AIMS

Citrus limon (lemon) is a widely cultivated citrus fruit. Significant postharvest losses due to fungi plague its production. Environmental and human health hazards have made the application of synthetic fungicides unsuitable. Despite the previous reports of antifungal activities of essential oil (EO) vapors, their synergistic combinations are understudied. Synergistic vapor combinations are advantageous due to less concentration of active components. This study aimed to isolate and identify postharvest fungal pathogens lemon and to evaluate the antifungal effects of synergistic Monarda citriodora EO (MEO)-constituent vapor combinations in vivo and in vitro.

METHODS AND RESULTS

Postharvest fungal pathogens of lemon (C. limon) were isolated from various infected samples. The most pathogenic isolate was identified through morphology and its ITS-based rRNA gene sequencing as Aspergillus foetidus (O4). This is the first report of A. foetidus as a postharvest pathogen of lemon. The minimum fungicidal concentrations (MFCs) of MEO vapors treatment against O4 were 1346.15 µL/L air. For carvacrol, hexanal, and linalool, MFC was same (96.16 µL/L air). Checkerboard assays demonstrated that 1/4 MFC of MEO (336.54 µL/L air) and 1/4 MFC of linalool (24.04 µL/L air) (M + L) were synergistic against O4. M + L vapors reduced the O4 growth on lemons during storage by 64% ± 1.50% and preserved their quality (low weight loss %, unchanged pH, increased ascorbic acid content). Propidium iodide staining, ergosterol content analysis, calcofluor white staining and chitin content analysis revealed the integrity loss of the O4 plasma membrane and cell wall. 2',7'-Dichlorofluorescin diacetate staining revealed accumulation of intracellular reactive oxygen species (ROS), and scanning electron microscopy (SEM) analysis exposed the M + L treated mycelia with malformations.

CONCLUSIONS

M + L vapors offer protection for lemons from A. foetidus and preserve their quality during storage.

Antifungal Activity of Essential Oil and Plant-Derived Natural Compounds against Aspergillus flavus

Aspergillus flavus is a facultative parasite that contaminates several important food crops at both the pre- and post-harvest stages. Moreover, it is an opportunistic animal and human pathogen that causes aspergillosis diseases. A. flavus also produces the polyketide-derived carcinogenic and mutagenic secondary metabolite aflatoxin, which negatively impacts global food security and threatens human and livestock health. Recently, plant-derived natural compounds and essential oils (EOs) have shown great potential in combatting A. flavus spoilage and aflatoxin contamination. In this review, the in situ antifungal and antiaflatoxigenic properties of EOs are discussed. The mechanisms through which EOs affect A. flavus growth and aflatoxin biosynthesis are then reviewed. Indeed, several involve physical, chemical, or biochemical changes to the cell wall, cell membrane, mitochondria, and related metabolic enzymes and genes. Finally, the future perspectives towards the application of plant-derived natural compounds and EOs in food protection and novel antifungal agent development are discussed. The present review highlights the great potential of plant-derived natural compounds and EOs to protect agricultural commodities and food items from A. flavus spoilage and aflatoxin contamination, along with reducing the threat of aspergillosis diseases.

Rosemary essential oil and its components 1,8-cineole and α-pinene induce ROS-dependent lethality and ROS-independent virulence inhibition in Candida albicans

The essential oil from Rosmarinus officinalis L., a composite mixture of plant-derived secondary metabolites, exhibits antifungal activity against virulent candidal species. Here we report the impact of rosemary oil and two of its components, the monoterpene α-pinene and the monoterpenoid 1,8-cineole, against Candida albicans, which induce ROS-dependent cell death at high concentrations and inhibit hyphal morphogenesis and biofilm formation at lower concentrations. The minimum inhibitory concentrations (100% inhibition) for both rosemary oil and 1,8-cineole were 4500 μg/ml and 3125 μg/ml for α-pinene, with the two components exhibiting partial synergy (FICI = 0.55 ± 0.07). At MIC and 1/2 MIC, rosemary oil and its components induced a generalized cell wall stress response, causing damage to cellular and organelle membranes, along with elevated chitin production and increased cell surface adhesion and elasticity, leading to complete vacuolar segregation, mitochondrial depolarization, elevated reactive oxygen species, microtubule dysfunction, and cell cycle arrest mainly at the G1/S phase, consequently triggering cell death. Interestingly, the same oils at lower fractional MIC (1/8-1/4) inhibited virulence traits, including reduction of mycelium (up to 2-fold) and biofilm (up to 4-fold) formation, through a ROS-independent mechanism.

Organic Antifungal Drugs and Targets of Their Action

In recent decades, there has been a significant increase in the number of fungal diseases. This is due to a wide spectrum of action, immunosuppressants and other group drugs. In terms of frequency, rapid spread and globality, fungal infections are approaching acute respiratory infections. Antimycotics are medicinal substances endorsed with fungicidal or fungistatic properties. For the treatment of fungal diseases, several groups of compounds are used that differ in their origin (natural or synthetic), molecular targets and mechanism of action, antifungal effect (fungicidal or fungistatic), indications for use (local or systemic infections), and methods of administration (parenteral, oral, outdoor). Several efforts have been made by various medicinal chemists around the world for the development of antifungal drugs with high efficacy with the least toxicity and maximum selectivity in the area of antifungal chemotherapy. The pharmacokinetic properties of the new antimycotics are also important: the ability to penetrate biological barriers, be absorbed and distributed in tissues and organs, get accumulated in tissues affected by micromycetes, undergo drug metabolism in the intestinal microflora and human organs, and in the kinetics of excretion from the body. There are several ways to search for new effective antimycotics: - Obtaining new derivatives of the already used classes of antimycotics with improved activity properties. - Screening of new chemical classes of synthetic antimycotic compounds. - Screening of natural compounds. - Identification of new unique molecular targets in the fungal cell. - Development of new compositions and dosage forms with effective delivery vehicles. The methods of informatics, bioinformatics, genomics and proteomics were extensively investigated for the development of new antimycotics. These techniques were employed in finding and identification of new molecular proteins in a fungal cell; in the determination of the selectivity of drugprotein interactions, evaluation of drug-drug interactions and synergism of drugs; determination of the structure-activity relationship (SAR) studies; determination of the molecular design of the most active, selective and safer drugs for the humans, animals and plants. In medical applications, the methods of information analysis and pharmacogenomics allow taking into account the individual phenotype of the patient, the level of expression of the targets of antifungal drugs when choosing antifungal agents and their dosage. This review article incorporates some of the most significant studies covering the basic structures and approaches for the synthesis of antifungal drugs and the directions for their further development.

Antifungal and Antiaging Evaluation of Aerial Part Extracts of Thymelaea hirsuta (L.) Endl

In western Algeria, Thymelaea hirsuta aerial parts are traditionally used topically for the treatment of human skin infections. For a better knowledge of its biological activities, this study aimed at evaluating the in vitro antifungal activity and antiaging properties of several extracts of the aerial parts by in vitro assays. Antifungal activity was investigated by using the reference microbroth dilution method (National Committee for Clinical Laboratory Standards) against the dermatophytes ( Microsporum audouinii, Nannizzia gypsea, Trichophyton interdigitale, and Trichophyton rubrum) and the yeast ( Candida albicans). Antiaging (inhibition of 1,1-diphenyl-2-picrylhyorazyl radical scavenging and tyrosinase, lipoxygenase, elastase, and hyaluronidase activities) assays were performed in 96-well plates. All the extracts of T. hirsuta exhibited antifungal activity against M. audouinii, T. rubrum, and C. albicans, while no activity was found against N. gypsea and T. interdigitale. The highest activity was observed on M. audouinii for the aqueous leaf (minimum inhibitory concentration [MIC] of 8 µg/mL) and stem extracts (MIC = 31 µg/mL) and the methanolic leaf extract (MIC = 8 µg/mL). Additionally, some marked morphological alterations were observed on M. audouinii hyphae with all aqueous extracts. Concerning antiage bioassays, the major activity was found against hyaluronidase for the aqueous and methanolic extracts from leaves and the methanolic extract from flowers. Analysis of this last extract by high-performance liquid chromatography, electrospray ionization-mass spectrometry, and nuclear magnetic resonance, allowed us to identify daphnoretin and daphnetin as major components of this extract, and, therefore, responsible for the antiaging activity. In conclusion, this study provides additional experimental data supporting the traditional use of T. hirsuta extracts on some cutaneous dermatophytosis, as well as new perspectives on the potential use of T. hirsuta to ensure better healing of the skin.

In Vitro Antifungal and Topical Anti-Inflammatory Properties of Essential Oil from Wild-Growing Thymus vulgaris (Lamiaceae) Used for Medicinal Purposes in Algeria: A New Source of Carvacrol

The aim of this study is to investigate the Thymus vulgaris essential oil (TVEO) as an antifungal agent in aromatherapy and/or as an active ingredient in the prevention or management of topical inflammatory diseases. The chemical composition of TVEO was determined with gas chromatography and revealed the presence of 25 compounds. Carvacrol was found to be the major component (56.8%). Antifungal action of TVEO was determined in vitro by using different methods. By the disc diffusion method, TVEO showed more potent antifungal activity against Candida strains than the positive control. The diameter of inhibition zone (DIZ) varied from 34 to 60 mm for Candida yeasts. Significantly higher antifungal activity was observed in the vapor phase at lower quantities. Candida albicans and C. parapsilosis were the most susceptible strains to the oil vapor with DIZ varying from 35 to 90 mm. The minimum inhibitory concentrations (MIC) of yeast were determined with an agar dilution method and revealed that MIC varied from 0.3 to 0.15 µL/mL for yeast species. The topical anti-inflammatory potential of TVEO was also explored in vivo with the croton oil-induced ear edema assay. TVEO exhibited a potent anti-inflammatory effect at all doses (100, 10 and 2 mg/kg), which were statistically similar (p > 0.05) to the positive control. This activity was also confirmed at the cellular level with histopathology analysis. Our results suggest the potential application of this carvacrol-rich TVEO in the prevention and management of fungal infections and topical inflammation and deserve further investigation for clinical applications. Furthermore, while the mode of action remains mainly undetermined and should be studied.

Optimum Inhibition of Amphotericin-B-Resistant Candida albicans Strain in Single- and Mixed-Species Biofilms by Candida and Non-Candida Terpenoids

Candida albicans is one of the most common human fungal pathogens and represents the most important cause of opportunistic mycoses worldwide. Surgical devices including catheters are easily contaminated with C. albicans via its formation of drug-resistant biofilms. In this study, amphotericin-B-resistant C. albicans strains were isolated from surgical devices at an intensive care center. The objective of this study was to develop optimized effective inhibitory treatment of resistant C. albicans by terpenoids, known to be produced naturally as protective signals. Endogenously produced farnesol by C. albicans yeast and plant terpenoids, carvacrol, and cuminaldehyde were tested separately or in combination on amphotericin-B-resistant C. albicans in either single- or mixed-infections. The results showed that farnesol did not inhibit hyphae formation when associated with bacteria. Carvacrol and cuminaldehyde showed variable inhibitory effects on C. albicans yeast compared to hyphae formation. A combination of farnesol with carvacrol showed synergistic inhibitory activities not only on C. albicans yeast and hyphae, but also on biofilms formed from single- and mixed-species and at reduced doses. The combined terpenoids also showed biofilm-penetration capability. The aforementioned terpenoid combination will not only be useful in the treatment of different resistant Candida forms, but also in the safe prevention of biofilm formation.

Anti-Candida activity of beneficial vaginal lactobacilli in in vitro assays and in a murine experimental model

Vulvovaginal candidiasis (VVC) is one of the most frequent infections affecting women worldwide. Healthy vaginal microbiota is dominated by lactobacilli, which form a strong defense line against pathogens. In this work, in vitro antimicrobial properties of thirty vaginal Lactobacillus strains were evaluated against eleven Candida vaginal clinical isolates, employing three different methods. Also, the effect of intravaginal (i.va.) administrations (preventive, therapeutic and preventive-therapeutic) of L. reuteri CRL1324 or L. rhamnosus CRL1332 strains against the i.va. challenge with Candida albicans C2 (C.a.) was evaluated in a murine experimental model. From the results of agar overlay and liquid medium assays the selected lactobacilli strains have shown to inhibit the growth of at least one Candida strain. The inhibition was mainly due to the effect of organic acids. Anti-Candida activity was not evidenced in the agar plate diffusion method. In the experimental murine model, only preventive-therapeutic administration of both lactobacilli was able to significantly reduce viable C.a. numbers recovered in vaginal washes and the leukocyte influx induced by the fungi. In conclusion, lactobacilli exhibited in vitro and in vivo antimicrobial effects on Candida, suggesting that they could be promising candidates for protection against VVC.

Isolation and structural elucidation of antifungal compounds from Ryudai gold (Curcuma longa) against Fusarium solani sensu lato isolated from American manatee

In a previous study, we reported that Curcuma longa strain Ryudai gold (RD) showed antifungal activity against Fusarium solani sensu lato (FSSL) among the different species and varieties of turmeric. The present study focused on isolation, identification and structural elucidation of antifungal compounds in RD. The ethyl acetate (EtOAc) fraction was eluted with n-hexane and EtOAc with gradually increasing the concentration of EtOAc (n-hexane:EtOAc; 100:0; 80:20; 60:40, 40:60, 20:80 and 0:100). The antifungal compounds were isolated from the most effective fraction by using silica gel, TOYOPEARL® HW-40F column, and high-performance liquid chromatography. Structural identification of the antifungal compounds was conducted using ¹H NMR, ¹³C NMR, and liquid chromatography-tandem mass spectrometry. The MeOH extract of the rhizome of RD inhibited the growth of FSSL in a concentration-dependent manner. The EtOAc fraction of the MeOH extract of RD demonstrated the highest antifungal activity against FSSL. The purified antifungal compounds were turmeronol B (1), turmeronol A (2), (E)-α-atlantone (3), dihydrobisdemethoxycurcumin (4), demethoxycurcumin (5) and curcumin (6). These six compounds showed concentration-dependent antifungal activity against FSSL. The concentration required for 50% growth inhibition (IC₅₀) of the four isolates of FSSL ranged from 116 to172, 127 to 185, 88 to 109, 90 to 112, 74 to 80 and 63 to 68 μM/L for turmeronol B, turmeronol A, (E)-α-atlantone, dihydrobisdemethoxycurcumin, demethoxycurcumin and curcumin, respectively. These results suggested that RD contained potential antifungal compounds that could be useful to control FSSL. The isolated compounds of RD can be a good source of natural antifungal agents or the lead compounds for the development of new synthetic drugs.

Antifungal Activity of the Volatile Phase of Essential Oils: A Brief Review

Interest in the antifungal activity of essential oils has increased markedly in recent years. The volatile (vapour) components of several essential oils have been demonstrated to have potent antifungal activity, often in excess of that displayed in direct contact assays. A lack of consistent methodology and reporting, however, hinders direct comparison of publications. A variety of mechanisms have been suggested for the activity of these active volatiles against hyphate fungi. This paper briefly reviews some of the more recent data and identifies areas that require standardization and further study.

Ultrasonic and microwave assisted extraction as rapid and efficient techniques for plant mediated synthesis of quantum dots: green synthesis, characterization of zinc telluride and comparison study of some biological activities

In this study, a simple, rapid, and efficient plant-mediated green approach was presented for the synthesis of stable and ultra-small zinc telluride quantum dots (ZnTe QDs) using the aqueous extract of the Ficus johannis plant.

Peptide Extract from Olivancillaria hiatula Exhibits Broad-Spectrum Antibacterial Activity

Increasing reports of infectious diseases worldwide have become a global concern in recent times. Depleted antibiotic pipelines, rapid and complex cases of antimicrobial resistance, and emergence and re-emergence of infectious disease have necessitated an urgent need for the development of new antimicrobial therapeutics, preferably with novel modes of action. Due to their distinct mode of action, antimicrobial peptides offer an interesting alternative to conventional antibiotics to deal with the problems enumerated. In this study, the antimicrobial potential of the peptide extract from the marine mollusc, Olivancillaria hiatula, was evaluated in vitro. Agar diffusion and broth dilution techniques were used to evaluate microbial susceptibility to the peptide extract. Microplate-based assays were also used to investigate time-dependent growth inhibition profiles of microbes in the presence of peptide and evaluate the peptide's ability to modulate the activities of standard antibiotics. Both Gram-positive and Gram-negative bacteria were inhibited by the peptide extract in the agar diffusion assay. The minimum inhibitory concentration (MIC) of peptide against test microorganisms was between 0.039 and 2.5 mg/mL. At the MIC, the peptide extract was bacteriostatic towards all tested microorganisms but bactericidal to Staphylococcus aureus. In the presence of the peptide extract, a prolonged lag phase was observed for all microbes, similar to standard ciprofloxacin. When administered together, peptide extracts enhanced the activities of ciprofloxacin and cefotaxime and were antagonistic towards erythromycin but indifferent towards metronidazole. Taken together, these results show the broad-spectrum antibacterial activity of peptide extract from Olivancillaria hiatula and demonstrate that antimicrobial peptides can be employed in combination with some conventional antibiotics for improved effects.

New insights on the anti-inflammatory potential and safety profile of Thymus carnosus and Thymus camphoratus essential oils and their main compounds

ETHNOPHARMACOLOGICAL RELEVANCE

Thymus camphoratus and T. carnosus are widely used in Portugal for the treatment of inflammatory-related conditions, such as inflammation of the respiratory tract, being the later also used as an antitussive.

AIM OF THE STUDY

Bearing in mind the lack of scientific studies focused on the pharmacological activity of Thymus camphoratus and T. carnosus, this work was designed to validate the anti-inflammatory properties ascribed to these traditional species and concomitantly to unveil both the putative molecular mechanisms behind their bioactivity as well as the safety profile of their essential oils and major compounds.

MATERIALS AND METHODS

The chemical composition of the essential oils was assessed by gas chromatography (GC) and gas chromatography - mass spectroscopy (GC/MS). The nitric oxide (NO) scavenging potential of the oils was tested using S-nitroso-N-acetyl-D,L-penicillamine (SNAP) as NO donor. The anti-inflammatory potential of the essential oils and their major compounds was evaluated by measuring the nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated macrophages as well as the expression of the pro-inflammatory enzymes, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Importantly, and in an attempt to assess the safety profile of the oils and respective major compounds, their effect on macrophages and hepatocytes viability was also determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay.

RESULTS

T. carnosus essential oil was characterized by high amounts of borneol and camphene whereas T. camphoratus oil was rich in 1,8-cineole and borneol. The later presented higher pharmacological activity showing inhibitory effects towards NO production at lower concentrations (0.16 µL/mL) and concomitantly inhibiting the expression of two crucial pro-inflammatory proteins, iNOS and COX-2 (at 0.32 µL/mL). Since no NO scavenging activity was achieved, it is reasonable to conclude that the anti-inflammatory activity of the essential oils occurs upstream of iNOS expression, probably through inhibition of relevant pro-inflammatory signal transduction pathways. Importantly, at bioactive concentrations, the essential oils were devoid of toxicity towards macrophages and hepatocytes. The activity of the isolated compounds was far from that observed for the essential oils, thus suggesting that the anti-inflammatory activity is due to a synergic effect between several compounds in the mixture.

CONCLUSION

Overall, the results herein presented sustain and strengthen the anti-inflammatory properties traditionally ascribed to T. carnosus and T. camphoratus. Additionally, the molecular mechanisms associated to their pharmacological activity were highlighted, opening new avenues for the development of effective anti-inflammatory herbal medicinal products.

Chemical composition and antimicrobial activity of Myrcianthes fragrans essential oil, a natural aromatizer of the traditional Ecuadorian beverage colada morada

ETHNOBOTANICAL AND ETHNOMEDICINAL RELEVANCE

The importance given in Ecuador to the rescue of traditional knowledge and nutritional value of ancestral foods and drinks, has stimulated our investigation of the chemical composition and some biological activities of M. fragrans ('arrayán') essential oil, a natural aromatic additive used in the preparation of the traditional fruit-juice 'colada morada', which is typically drunk in the Day of the Dead or All Soul´s Day.

MATERIAL AND METHODS

Different essential oils of Myrcianthes fragrans (Sw.) McVaught were obtained by hydrodistillation of the aerial parts of the plant collected in Cerro Villonaco (Loja-Ecuador) at three different phenological growth stages, i.e., during foliation (Fo), flowering (Fl) and fruiting (Fr) stages. The chemical compositions of the essential oils were determined by GC/MS and GC/FID techniques. The antimicrobial activities were determined by the broth microdilution method and reported as minimal inhibitory concentration (MIC, ug/mL).

AIMS OF THE STUDY

i) to investigate the traditional uses of arrayán (M. fragrans) in the South region of Ecuador; ii) to identify the main components of the essential oils isolated at different phenological stages; iiì) to test the antimicrobial activity of the essential oils against bacteria and yeasts causing human ailments and a yeast causing food spoilage.

RESULTS

37, 46 and 38 compounds, representing 96.5%, 96.2%, and 95.6% of the three essential oils (Fo, Fl and Fr), respectively, have been identified. Oxygenated monoterpenes (OM) were the major components with percentages of 63.1 (Fo), 49.4 (Fl), and 61.9% (Fr), respectively. The main constituents of the essential oils were the monoterpene aldehydes geranial (1) and neral (2), the content of which varied, depending on the phenological development stage of the plant, spanning from 31.1% and 23.6% (Fo), to 23.6% and 17.8% (Fl), and 29.7% and 24.3% (Fr), respectively. In vitro antimicrobial tests showed that the essential oils from M. fragrans exhibited good activity against the Gram-negative bacteria, K. pneumoniae, and against the yeasts, C. albicans and S. cerevisiae.

CONCLUSIONS

The oil is characterized by a high concentration of the monoterpene aldehydes geranial and neral (citral), that make the aroma of colada morada prepared in southern Ecuador quite different from the beverage made in other regions of the country, where other types of myrtles (Myrtaceae spp.) are used. Moreover, the oil may become a new rich source of the important industrial chemical citral. The pleasant aromatic properties and the good in vitro antimicrobial activity of arrayán oil suggest a plausible scientific explanation for the traditional uses of the plant not only as a natural aromatizer of a traditional beverage but also as a natural anti-infective and anti-yeast agent.

Lichen Xanthones as Models for New Antifungal Agents

Due to the emergence of multidrug-resistant pathogenic microorganisms, the search for new antimicrobial compounds plays an important role in current medicinal chemistry research. Inspired by lichen antimicrobial xanthones, a series of novel chlorinated xanthones was prepared using five chlorination methods (Methods A⁻E) to obtain different patterns of substitution in the xanthone scaffold. All the synthesized compounds were evaluated for their antimicrobial activity. Among them, 3-chloro-4,6-dimethoxy-1-methyl-9H-xanthen-9-one 15 showed promising antibacterial activity against E. faecalis (ATCC 29212 and 29213) and S. aureus ATCC 29213. 2,7-Dichloro-3,4,6-trimethoxy-1-methyl-9H-xanthen-9-one 18 revealed a potent fungistatic and fungicidal activity against dermatophytes clinical strains (T. rubrum, M. canis, and E. floccosum (MIC = 4⁻8 µg/mL)). Moreover, when evaluated for its synergistic effect for T. rubrum, compound 18 exhibited synergy with fluconazole (ΣFIC = 0.289). These results disclosed new hit xanthones for both antibacterial and antifungal activity.

Evaluation of Lavandula stoechas L. subsp. stoechas L., Mentha spicata L. subsp. spicata L. essential oils and their main components against sinusitis pathogens

Lavandula stoechas subsp. stoechas and Mentha spicata subsp. spicata are used for the treatment of sinusitis in Turkish folk medicine. The components of essential oils obtained by hydrodistillation were determined by gas chromatography-flame ionization detector (GC-FID), gas chromatography/mass spectrometry (GC/MS), and thin layer chromatography (TLC). Major components of L. stoechas and M. spicata oils were determined as camphor (46.7%) and carvone (60.6%), respectively. The antibacterial activity of essential oils and their main components were tested against the common selected sinusitis pathogens Streptococcus pneumoniae, Streptococcus pyogenes, Staphylococcus aureus, Haemophilus influenzae, Moraxella catarrhalis, and Pseudomonas aeruginosa using in vitro agar diffusion, microdilution, and vapor diffusion methods. As a result, the tested plant materials, which are locally and natively used against sinusitis, were relatively mild antibacterial (in vitro MICs 310–1250 μg/mL) in action. To use essential oils and their components safely in sinusitis therapy, further detailed in vivo experiments are needed to support their efficacy.

Vetiver Essential Oil in Cosmetics: What Is New?

Background: Vetiver is a key ingredient for the perfume industry nowadays. However, with the constant and rapid changes of personal tastes, this appeal could vanish and this sector could decline quite quickly. New dissemination paths need to be found to tap this valuable resource. Methods: In this way, its potential use in cosmetics either as an active ingredient per se (with cosmeceutical significance or presenting antimicrobial activity) has hence been explored in vitro. Results: In this contribution, we demonstrated that vetiver essential oil displays no particularly significant and innovative cosmetic potential value in formulations apart from its scent already largely exploited. However, evaluated against twenty bacterial strains and two Candida species using the in vitro microbroth dilution method, vetiver oil demonstrated notably some outstanding activities against Gram-positive strains and against one Candida glabrata strain. Conclusions: Based on these findings, vetiver essential oil appears to be an appropriate aspirant for the development of an antimicrobial agent for medicinal purposes and for the development of a cosmetic ingredient used for its scent and displaying antimicrobial activity as an added value.

Antifungal effects of phytocompounds on Candida species alone and in combination with fluconazole

Invasive fungal infections caused by Candida spp. remain the most predominant nosocomial fungal infections. Owing to the increased use of antifungal agents, resistance of Candida spp. to antimycotics has emerged frequently, especially to fluconazole (FLC). To cope with this issue, new efforts have been dedicated to discovering novel antimycotics or new agents that can enhance the susceptibility of Candida spp. to existing antimycotics. The secondary metabolites of plants represent a large library of compounds that are important sources for new drugs or compounds suitable for further modification. Research on the anti-Candida activities of phytocompounds has been carried out in recent years and the results showed that a series of phytocompounds have anti-Candida properties, such as phenylpropanoids, flavonoids, terpenoids and alkaloids. Among these phytocompounds, some displayed potent antifungal activity, with minimum inhibitory concentrations (MICs) of ≤8 µg/mL, and several compounds were even more effective against drug-resistant Candida spp. than FLC or itraconazole (e.g. honokiol, magnolol and shikonin). Interestingly, quite a few phytocompounds not only displayed anti-Candida activity alone but also synergised with FLC against Candida spp., even leading to a reversal of FLC resistance. This review focuses on summarising the anti-Candida activities of phytocompounds as well as the interactions of phytocompounds with FLC. In addition, we briefly overview the synergistic mechanisms and present the structure of the antimycotic phytocompounds. Hopefully, this analysis will provide insight into antifungal agent discovery and new approaches against antifungal drug resistance.

Chemical Variability and Biological Activities of Eucalyptus spp. Essential Oils

Many plant species produce mixtures of odorous and volatile compounds known as essential oils (EOs). These mixtures play important roles in Nature and have been utilized by mankind for different purposes, such as pharmaceuticals, agrochemicals, aromatherapy, and food flavorants. There are more than 3000 EOs reported in the literature, with approximately 300 in commercial use, including the EOs from Eucalyptus species. Most EOs from Eucalyptus species are rich in monoterpenes and many have found applications in pharmaceuticals, agrochemicals, food flavorants, and perfumes. Such applications are related to their diverse biological and organoleptic properties. In this study, we review the latest information concerning the chemical composition and biological activities of EOs from different species of Eucalyptus. Among the 900 species and subspecies of the Eucalyptus genus, we examined 68 species. The studies associated with these species were conducted in 27 countries. We have focused on the antimicrobial, acaricidal, insecticidal and herbicidal activities, hoping that such information will contribute to the development of research in this field. It is also intended that the information described in this study can be useful in the rationalization of the use of Eucalyptus EOs as components for pharmaceutical and agrochemical applications as well as food preservatives and flavorants.

Liquid and vapour-phase antifungal activities of essential oils against Candida albicans and non-albicans Candida

BACKGROUND

The management of Candida infections faces many problems, such as a limited number of antifungal drugs, toxicity, resistance of Candida to commonly antifungal drugs, relapse of Candida infections, and the high cost of antifungal drugs. Though azole antifungal agents and derivatives continue to dominate as drugs of choice against Candida infections, there are many available data referring to the anticandidal activity of essential oils. Since we have previous observed a good antimicrobial activity of some essential oils against filamentous fungi, the aim of this study was to extend the research to evaluate the activity of the same oils on Candida albicans, C.glabrata and C.tropicalis clinical strains, as well as the effects of related components. Essential oils selection was based both on ethnomedicinal use and on proved antibacterial and/or antifungal activity of some of these oils. Fluconazole and voriconazole were used as reference drugs.

METHODS

The minimum inhibitory concentration (MIC) and the minimal fungicidal concentration (MFC) of essential oils (thyme red, fennel, clove, pine, sage, lemon balm, and lavender) and their major components were investigated by the broth microdilution method (BM) and the vapour contact assay (VC).

RESULTS

Using BM, pine oil showed the best activity against all strains tested, though C.albicans was more susceptible than C.glabrata and C.tropicalis (MIC50-MIC90 = 0.06 %, v/v). On the contrary, sage oil displayed a weak activity (MIC50-MIC90 = 1 %, v/v). Thyme red oil (MIC50-MIC90 ≤ 0.0038 %, v/v for C.albicans and C.tropicalis, and 0.0078- < 0.015 %, v/v for C.glabrata), followed by lemon balm, lavender and sage were the most effective by VC. Carvacrol and thymol showed the highest activity, whereas linalyl acetate showed the lowest activity both by two methods. α-pinene displayed a better activity by BM than VC.

CONCLUSION

Results show a good activity of essential oils, mainly thymus red and pine oils, and their components carvacrol, thymol and α-pinene against Candida spp., including fluconazole/voriconazole resistant strains. These data encourage adequately controlled and randomized clinical investigations. The use in vapour phase could have additional advantages without requiring direct contact, resulting in easy of environmental application such as in hospital, and/or in school.

Chemical Composition, Antioxidant and Cytotoxic Activities of Essential Oil of the Inflorescence of Anacamptis coriophora subsp. fragrans (Orchidaceae) from Tunisia

The chemical composition of the essential oil produced by steam distillation of the inflorescences of naturally growing Anacamptis coriophora (L.) R. M. Bateman, Pridgeon & M. W. Chase subsp. fragrans (Pollini) R. M. Bateman, Pridgeon & M. W. Chase (Orchidaceae) from Kroumiria, north-west Tunisia was studied by GC-MS, which led to the identification of 19 volatile components, representing 97% of the oil. The main constituents were methyl-( E)-p-methoxycinnamate (29.3%), 13-heptadecyn-l-ol (18.6%), 2,5-dimethoxybenzyl alcohol (14.1%) and 4-(1,1,3,3-tetramethylbutyl)-phenol (9.0%). DPPH radical scavenging revealed a weak antioxidant activity. In addition, the antiproliferative effects were evaluated on BxPC3 human pancreatic carcinoma cells and on 2008 human ovarian cancer cells showing significant effect. This is the first report of the chemical composition of essential oils obtained from A coriophora subsp. fragrans inflorescences for North Africa. Further studies are needed to understand fully the possible mechanism of action behind the cytotoxic activity of the essential oil.

Antifungal activity and mode of action of thymol and its synergism with nystatin against Candida species involved with infections in the oral cavity: an in vitro study

BACKGROUND

Limitations of antifungal agents used in the treatment of oral candidiasis, as the development of resistant strains, are known by the scientific community. In this context, the aim of this study was to evaluate the antifungal activity of thymol against Candida albicans, Candida tropicalis and Candida krusei strains and to determine its mode of action and synergistic effect when combined with the synthetic antifungal nystatin.

METHODS

The minimum inhibitory concentration (MIC) was determined using a microdilution technique, and the minimum fungicidal concentration (MFC) was determined via subculture sowing. The mode of action of thymol was established by verifying fungal growth in the presence of sorbitol or ergosterol. The fractional inhibitory concentration index (FIC) was determined using the checkerboard method.

RESULTS

Thymol presented an antifungal effect, with MICs of 39 μg/mL for C. albicans and C. krusei and 78 μg/mL for C. tropicalis. The results of the antifungal test remained unchanged in the presence of sorbitol; however, the MIC value of thymol against C. albicans increased eight times (from 39.0 to 312.5 μg/mL) in presence of exogenous ergosterol. The combination of thymol and nystatin reduced the MIC values of both products by 87.4%, generating an FIC index of 0.25.

CONCLUSIONS

Thymol was found to have a fungicidal effect on Candida species and a synergistic effect when combined with nystatin.

Effects of dietary peppermint (Mentha piperita) on growth performance, chemical body composition and hematological and immune parameters of fry Caspian white fish (Rutilus frisii kutum)

Peppermint (Mentha piperita L.) is a very popular herb. While numerous effects have been described in mammals, its effects on fish have received so far limited attention. The effects of dietary administration of peppermint on fry Caspian white fish (Rutilus frisii kutum) were studied. Fish were divided into 4 groups before being fed diets supplemented with 0% (control), 1%, 2% and 3% of peppermint extracts for 8 weeks. Dose-dependent increases of growth parameters (WG and SGR), mucus skin (protein concentration, alkaline phosphatase and antimicrobial activity) and seric (lysozyme and IgM) and blood leucocyte respiratory burst activities and different hematological parameters (number of red and white cells, seric hemoglobin and hematocrit content) were recorded in fry fish fed supplemented diets. However, the dietary peppermint supplements have different effects on the number of blood leucocytes depending on the leucocyte cell type. While no significant differences were observed in the number of blood monocytes and eosinophils, the number of neutrophils and lymphocytes was increased and decreased, respectively, on fish fed peppermint enriched diets, respect to the values found in control fish. Present results corroborate that dietary administration of peppermint promotes growth performance and increases the main hematological and immune humoral (both mucosal and systemic) parameters of fry Caspian white fish. This study may provide new applications of peppermint and, at the same time, promote rational development and utilization of peppermint resources.

Chemical Compositions and Antimicrobial Activities of Ocimum sanctum L. Essential Oils at Different Harvest Stages

BACKGROUND

Essential Oils (EOs) possess antibacterial properties and represent a natural source to treat infections and prevent food spoilage. Their chemical composition might be affected by the environmental condition and the developmental growth stages of the plant.

OBJECTIVES

The current study aimed to determine the variations in chemical compositions and antimicrobial activities of the EOs of Ocimum sanctum L. at different stages of harvesting.

MATERIALS AND METHODS

The oils constituents were analyzed by gas chromatography/mass spectrometry (GC/MS). The effects of three different harvest stages of O. sanctum EOs against most common causes of food-borne were evaluated by broth micro-dilution method as recommended by the Clinical and Laboratory Standards Institute (CLSI).

RESULTS

The analysis of the EOs indicated that eugenol was the major compound of the EOs at all developmental stages which reached its maximum level at the second stage. The results showed that the tested EOs exhibited antimicrobial activities against all of the examined pathogens at concentrations of 0.125-32 µL/mL, except Pseudomonas aeruginosa which was only inhibited by high concentrations of the floral budding and full flowering EOs. EO distilled from the second developmental growth stage (floral budding) of O. sanctum exhibited the strongest antibacterial activities against the food borne bacteria.

CONCLUSIONS

Considering the wide range of antimicrobial activities of the examined EOs, they might have the potential to be used to manage infectious diseases or extend the shelf life of food products.

Comprehensive approach for the detection of antifungal compounds using a susceptible strain of Candida albicans and confirmation of in vivo activity with the Galleria mellonella model

An efficient screening strategy for the identification of potentially interesting low-abundance antifungal natural products in crude extracts that combines both a sensitive bioautography assay and high performance liquid chromatography (HPLC) microfractionation was developed. This method relies on high performance thin layer chromatography (HPTLC) bioautography with a hypersusceptible engineered strain of Candida albicans (DSY2621) for bioactivity detection, followed by the evaluation of wild type strains in standard microdilution antifungal assays. Active extracts were microfractionated by HPLC in 96-well plates, and the fractions were subsequently submitted to the bioassay. This procedure enabled precise localisation of the antifungal compounds directly in the HPLC chromatograms of the crude extracts. HPLC-PDA-mass spectrometry (MS) data obtained in parallel to the HPLC antifungal profiles provided a first chemical screening about the bioactive constituents. Transposition of the HPLC analytical conditions to medium-pressure liquid chromatography (MPLC) allowed the efficient isolation of the active constituents in mg amounts for structure confirmation and more extensive characterisation of their biological activities. The antifungal properties of the isolated natural products were evaluated by their minimum inhibitory concentration (MIC) in a dilution assay against both wild type and engineered strains of C. albicans. The biological activity of the most promising agents was further evaluated in vitro by electron microscopy and in vivo in a Galleria mellonella model of C. albicans infection. The overall procedure represents a rational and comprehensive means of evaluating antifungal activity from various perspectives for the selection of initial hits that can be explored in more in-depth mode-of-action studies. This strategy is illustrated by the identification and bioactivity evaluation of a series of antifungal compounds from the methanolic extract of a Rubiaceae plant, Morinda tomentosa, which was used as a model in these studies.

Coriandrum sativum L. (Coriander) essential oil: antifungal activity and mode of action on Candida spp., and molecular targets affected in human whole-genome expression

Oral candidiasis is an opportunistic fungal infection of the oral cavity with increasingly worldwide prevalence and incidence rates. Novel specifically-targeted strategies to manage this ailment have been proposed using essential oils (EO) known to have antifungal properties. In this study, we aim to investigate the antifungal activity and mode of action of the EO from Coriandrum sativum L. (coriander) leaves on Candida spp. In addition, we detected the molecular targets affected in whole-genome expression in human cells. The EO phytochemical profile indicates monoterpenes and sesquiterpenes as major components, which are likely to negatively impact the viability of yeast cells. There seems to be a synergistic activity of the EO chemical compounds as their isolation into fractions led to a decreased antimicrobial effect. C. sativum EO may bind to membrane ergosterol, increasing ionic permeability and causing membrane damage leading to cell death, but it does not act on cell wall biosynthesis-related pathways. This mode of action is illustrated by photomicrographs showing disruption in biofilm integrity caused by the EO at varied concentrations. The EO also inhibited Candida biofilm adherence to a polystyrene substrate at low concentrations, and decreased the proteolytic activity of Candida albicans at minimum inhibitory concentration. Finally, the EO and its selected active fraction had low cytotoxicity on human cells, with putative mechanisms affecting gene expression in pathways involving chemokines and MAP-kinase (proliferation/apoptosis), as well as adhesion proteins. These findings highlight the potential antifungal activity of the EO from C. sativum leaves and suggest avenues for future translational toxicological research.

Early state research on antifungal natural products

Nosocomial infections caused by fungi have increased greatly in recent years, mainly due to the rising number of immunocompromised patients. However, the available antifungal therapeutic arsenal is limited, and the development of new drugs has been slow. Therefore, the search for alternative drugs with low resistance rates and fewer side effects remains a major challenge. Plants produce a variety of medicinal components that can inhibit pathogen growth. Studies of plant species have been conducted to evaluate the characteristics of natural drug products, including their sustainability, affordability, and antimicrobial activity. A considerable number of studies of medicinal plants and alternative compounds, such as secondary metabolites, phenolic compounds, essential oils and extracts, have been performed. Thus, this review discusses the history of the antifungal arsenal, surveys natural products with potential antifungal activity, discusses strategies to develop derivatives of natural products, and presents perspectives on the development of novel antifungal drug candidates.

Stereospecific synthesis of highly functionalized benzo[3.1.0]bicycloalkanes via multistep cascade reactions

A facile approach for the synthesis of benzo[3.1.0]bicycloalkanesviaalkylation/cyclopropanation cascade reactions of benzyl bromide with triphenylphosphonium bromide.

Antibacterial activity of the lipopetides produced by Bacillus amyloliquefaciens M1 against multidrug-resistant Vibrio spp. isolated from diseased marine animals

In this work, the antibacterial activity of the lipopeptides produced by Bacillus amyloliquefaciens M1 was examined against multidrug-resistant Vibrio spp. and Shewanella aquimarina isolated from diseased marine animals. A new and cheap medium which contained 1.0 % soybean powder, 1.5 % wheat flour, pH 7.0 was developed. A crude surfactant concentration of 0.28 mg/ml was obtained after 18 h of 10-l fermentation and diameter of the clear zone on the plate seeded with Vibrio anguillarum was 34 mm. A preliminary characterization suggested that the lipopeptide N3 produced by B. amyloliquefaciens M1 was the main product and contained the surfactin isoforms with amino acids (GLLVDLL) and hydroxy fatty acids (of 12-15 carbons in length). The evaluation of the antibacterial activity of the lipopeptide N3 was carried out against S. aquimarina and nine species of Vibrio spp.. It was found that all the Vibrio spp. and S. aquimarina showed resistance to several different antibiotics, suggesting that they were the multidrug resistance. It was also indicated that all the Vibrio spp. strains and S. aquimarina were sensitive to the surfactin N3, in particular V. anguillarum. The results demonstrated that the lipopeptides produced by B. amyloliquefaciens M1 had a broad spectrum of action, including antibacterial activity against the pathogenic Vibrio spp. with multidrug-resistant profiles. After the treatment with the lipopeptide N3, the cell membrane of V. anguillarum was damaged, and the whole cells of the bacterium were disrupted.

Chemical composition and antimicrobial activity of essential oils from Chromolaena laevigata during flowering and fruiting stages

The chemical compositions and antimicrobial activities of essential oils from the leaves, stems, capitula, and cypselas of Chromolaena laevigata were evaluated at two different phenological stages, flowering and fruiting. Thirty-eight compounds were identified in the crude oils by GC/MS. The sesquiterpene laevigatin was the major constituent of the leaf, capitulum, and cypsela oils, while the sesquiterpene spathulenol was the main component in the stem oils. The antimicrobial activities of the oils were evaluated against Candida albicans, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. Stem oil obtained from Chromolaena laevigata during the fruiting stage generally showed the highest activity with minimum inhibitory concentration (MIC) values of 62.5 μg/ml against Candida albicans and S. aureus, and 500 μg/ml against P. aeruginosa and E. coli. Pure laevigatin exhibited MIC values of 500 and 125 μg/ml against C. albicans and S. aureus, respectively, indicating that this constituent could be responsible, at least in part, for the antimicrobial activities detected in the crude oils. More studies concerning the biological activities of isolated derivatives are required to improve our knowledge of the antimicrobial potential of volatile compounds present in native plants.

Evaluation of the cytotoxic effect and antibacterial, antifungal, and antiviral activities of Hypericum triquetrifolium Turra essential oils from Tunisia

Background

A number of bio-active secondary metabolites have been identified and reported for several Hypericum species. Many studies have reported the potential use of the plant extracts against several pathogens. However, Hypericum triquetrifolium is one of the least studied species for its antimicrobial activity. The aim of the present study was to evaluate the cytotoxic effect of the essential oils of Hypericum triquetrifolium as well as their antimicrobial potential against coxsakievirus B3 and a range of bacterial and fungal strains.

Methods

The essential oils of Hypericum triquetrifolium harvested from five different Tunisian localities (Fondouk DJedid, Bou Arada, Bahra, Fernana and Dhrea Ben Jouder) were evaluated for their antimicrobial activities by micro-broth dilution methods against bacterial and fungal strains. In addition, the cytotoxic effect and the antiviral activity of these oils were carried out using Vero cell lines and coxsakievirus B3.

Results

The results showed a good antibacterial activities against a wide range of bacterial strains, MIC values ranging between 0.39-12.50 mg/ml and MBC values between 1.56-25.0 mg/ml. In addition, the essential oils showed promising antifungal activity with MIC values ranging between 0.39 μg/mL and 12.50 μg/mL; MFC values ranged between 3.12 μg/mL and 25.00 μg/mL; a significant anticandidal activity was noted (MIC values comprised between 0.39 μg/mL and 12.50 μg/mL). Although their low cytotoxic effect (CC₅₀ ranged between 0.58 mg/mL and 12.00 mg/mL), the essential oils did not show antiviral activity against coxsakievirus B3.

Conclusion

The essential oils obtained from Hypericum triquetrifolium can be used as antimicrobial agents and could be safe at non cytotoxic doses. As shown for the tested essential oils, comparative analysis need to be undertaken to better characterize also the antimicrobial activities of Hypericum triquetrifolium extracts with different solvents as well as their purified fractions and their pure secondary metabolites.

Terpenoids of plant origin inhibit morphogenesis, adhesion, and biofilm formation by Candida albicans

Biofilm-related infections caused by Candida albicans and associated drug resistant micro-organisms are serious problems for immunocompromised populations. Molecules which can prevent or remove biofilms are needed. Twenty-eight terpenoids of plant origin were analysed for their activity against growth, virulence attributes, and biofilms of C. albicans. Eighteen molecules exhibited minimum inhibitory concentrations of <2 mg ml(-1) for planktonic growth. Selected molecules inhibited yeast to hyphal dimorphism at low concentrations (0.031-0.5 mg ml(-1)), while adhesion to a solid surface was prevented at 0.5-2 mg ml(-1). Treatment with 14 terpenoids resulted in significant (p < 0.05) inhibition of biofilm formation, and of these, linalool, nerol, isopulegol, menthol, carvone, α-thujone, and farnesol exhibited biofilm-specific activity. Eight terpenoids were identified as inhibitors of mature biofilms. This study demonstrated the antibiofilm potential of terpenoids, which need to be further explored as therapeutic strategy against biofilm associated infections of C. albicans.

Anti-Candida albicans activity and pharmacokinetics of pogostone isolated from Pogostemonis Herba

The present work was designed to evaluate the in vitro and in vivo anti-Candida activity of pogostone (PO), a natural product isolated from Pogostemon cablin (Blanco) Benth. PO showed potent in vitro activity against clinical Candida spp. isolates tested in this study. PO and the reference drug voriconazole (VRC) were equally effective against all the fluconazole-resistant Candida albicans strains, with MIC ranging from 3.1 μg/ml to 50 μg/ml. Besides, PO was fungicidal against all Candida isolates with MFC ranging from 50 μg/ml to 400 μg/ml. By contrast, VRC was fungistatic as it failed to elicit a fungicidal effect against the Candida spp. isolates at the highest tested concentration (400 μg/ml). Furthermore, oral and topical PO administration effectively reduced the fungal load in vagina of vulvovaginal candidiasis mouse models. Topical PO administration (1.0-4.0 mg/kg) demonstrated higher activity against the vulvovaginal candidiasis than VRC (4.0 mg/kg). The pharmacokinetics and safety profile of PO were also investigated. The pharmacokinetics assay revealed that PO was easily absorbed after oral administration in mice, which might account for its in vivo anti-Candida effect. The acute toxicity test showed that the median lethal dose of PO in mice was 355 mg/kg, which was much higher than the daily dose used for the therapeutic experiments. This study demonstrated the potential of PO as a promising candidate for the treatment of Candida infections, particularly for vulvovaginal candidiasis.

In vitro anti-Candida activity of lidocaine and nitroglycerin: alone and combined

The aim of this work was to study the anti-Candida activity of lidocaine and nitroglycerin alone and in combination. Ten Candida strains were included, corresponding to 1 collection type strain (ATCC 10231) and 9 clinical isolates: 4 C. albicans, 2 C. glabrata, 1 C. tropicalis, 1 C. krusei, and 1 C. parapsilosis. The CLSI reference M27-A3 micromethod was used to determine the anti-Candida activity of the drugs alone; minimal inhibitory and lethal concentrations were determined. The classic checkboard technique was used to determine the activity of combined drugs. Lidocaine fungicidal effect was dosedependent. Nitroglycerin exhibited a higher effect. The drugs combination resulted in a reduction of the inhibitory concentration, corresponding to an additive effect. In conclusion, both drugs exhibited an interesting anti-Candida activity. The combination of lidocaine with nitroglycerin was shown to have an additive effect against Candida spp., predicting the interest to include, in the future, these drugs in a new delivery system for the treatment of mucocutaneous candidosis.

Poisson parameters of antimicrobial activity: a quantitative structure-activity approach

A contingency of observed antimicrobial activities measured for several compounds vs. a series of bacteria was analyzed. A factor analysis revealed the existence of a certain probability distribution function of the antimicrobial activity. A quantitative structure-activity relationship analysis for the overall antimicrobial ability was conducted using the population statistics associated with identified probability distribution function. The antimicrobial activity proved to follow the Poisson distribution if just one factor varies (such as chemical compound or bacteria). The Poisson parameter estimating antimicrobial effect, giving both mean and variance of the antimicrobial activity, was used to develop structure-activity models describing the effect of compounds on bacteria and fungi species. Two approaches were employed to obtain the models, and for every approach, a model was selected, further investigated and found to be statistically significant. The best predictive model for antimicrobial effect on bacteria and fungi species was identified using graphical representation of observed vs. calculated values as well as several predictive power parameters.

The anti-Candida activity of Thymbra capitata essential oil: effect upon pre-formed biofilm

ETHNOPHARMACOLOGICAL RELEVANCE

[corrected] Thymbra capitata essential oil is traditionally considered to exhibit powerful antiseptic properties, thus being used to treat cutaneous infections. The aim of the present study was to evaluate the effect of Thymbra capitata essential oil upon pre-formed biofilm of different Candida strains while comparing it with the activity against planktonic cells.

MATERIALS AND METHODS

Fifteen Candida isolates were included, corresponding to clinical and collection type strains. Essential oil was obtained by hydrodistillation and its composition analysed by GC/MS. Activity upon planktonic cells was evaluated according to M27-A3 macromethod. Its effect upon 24h preformed biofilm biomass was determined using the crystal violet procedure and the metabolic activity was studied applying the XTT/menadione technique.

RESULTS

Biofilm biomass and metabolic activity of all tested species were reduced up to 50% at MIC values. The effect was more pronounced at double MIC values, achieving >80% reduction, except for Candida albicans that presented a more resistant profile (62%).

CONCLUSION

Thymbra capitata essential oil presented an important effect upon Candida biofilms. It is proposed as a valuable antifungal product to be used in an appropriate pharmaceutical formulation for the management of resistant mucocutaneous candidosis.