Antifungal Activity of Essential Oils Against Candida Species Isolated from Clinical Samples

Essential Oils against Candida auris-A Promising Approach for Antifungal Activity

The emergence of Candida auris as a multidrug-resistant fungal pathogen represents a significant global health challenge, especially given the growing issue of antifungal drug resistance. This review aims to illuminate the potential of essential oils (EOs), which are volatile plant secretions containing complex mixtures of chemicals, as alternative antifungal agents to combat C. auris, thus combining traditional insights with contemporary scientific findings to address this critical health issue. A systematic literature review was conducted using the PubMed, Scopus, and Web of Science databases from 2019 to 2024, and using the Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) protocol to identify relevant studies on the antifungal efficacy of EOs or their components against C. auris. Of the 90 articles identified, 16 were selected for detailed review. The findings highlight the diverse mechanisms of action of EOs and their components, such as disrupting fungal cell membranes, inducing the production of reactive oxygen species (ROS), and impeding biofilm formation, suggesting that some of them may be as effective as, or better than, traditional antifungal drugs while potentially limiting the development of resistance. However, issues such as variability in the composition of EOs and a paucity of clinical trials have been identified as significant obstacles. In conclusion, EOs and their active ingredients are emerging as viable candidates for creating effective treatments for C. auris, underscoring their importance as alternative or complementary antifungal agents in the face of increasing drug resistance. The call for future research underscores the need for clinical trials and standardization to unlock the full antifungal potential of EOs against C. auris.

From plants to particles: herbal solutions and nanotechnology combating resistant vulvovaginal candidiasis

Despite having current advanced therapy, vulvovaginal candidiasis (VVC) remains a common yet debated healthcare-associated topic worldwide due to multi-drug resistance Candida species. In our review, we outlined and highlighted upcoming values with scope of existing and emerging information regarding the possibility of using various natural molecules combined with modern technology that shows promising anti-candida activity in VVC. Furthermore, in this review, we compiled herbal drug molecules and their nanocarriers approach for enhancing the efficacy and stability of herbal molecules. We have also summarized the patent literature available on herbal drug molecules and their nanoformulation techniques that could alternatively become a new innovative era to combat resistance VVC.

The Formulation and Evaluation of Melaleuca alternifolia Cheel and Cymbopogon flexuosus Linn Essential Oils Emulgel for the Treatment of Vulvovaginal Candidiasis

The global concern regarding the occurrence of antifungal resistance to synthetic conventional azoles used for treating vulvovaginal candidiasis, along with the associated side effects, is significant. Consequently, the pursuit for substitutes such as natural therapies has ensued. Essential oils, derived from plants, have been extensively researched and found to possess antibacterial and antifungal properties. This study aimed to assess the antifungal efficacy of two essential oils, both alone and in combination, against Candida albicans. Essential oils were formulated into an emulgel separately and as combinations. The essential oils of Melaleuca alternifolia and Cymbopogon flexuosus were used in this study. The resulting emulgel formulations were characterized for their antifungal activity against Candida albicans. Physiochemical properties such as pH, viscosity, and appearance were also determined. The prepared emulgels were thereafter observed for stability over a period of 1 month. The MIC of Melaleuca alternifolia was seen to be 50 µL/mL while Cymbopogon flexuous was seen to be more potent at 25 µL/mL against C. albicans exhibiting strong synergistic effect at 0.4. The emulgel formed was white in color, smooth on skin, and had the odor of the essential oils, which is sweet to the nose. The pH of the formulations with the essential oils were acidic in the range of 3.70-3.83, making them suitable for vagina application. The emulgels had viscosities ranging from 4417.6 to 8968.7 mPas, owing to the thickness of the essential oils contained. The emulgel formulation with the combination of essential oils was more potent that the two with individual essential oils; furthermore, the one with Cymbopogon flexuous was more potent than the one with Melaleuca alternifolia. Based on the properties of the formulated emulgels and their activity against the test organism, the preparations have significant potential in the management of vulvovaginal candidiasis.

Antifungal and Antibiofilm Activity of Colombian Essential Oils against Different Candida Strains

Most Candida species are opportunistic pathogens with the ability to form biofilms, which increases their resistance to antifungal drug therapies and the host immune response. Essential oils (EOs) are an alternative for developing new antimicrobial drugs, due to their broad effect on cellular viability, cell communication, and metabolism. In this work, we evaluated the antifungal and antibiofilm potential of fifty EOs on C. albicans ATCC 10231, C. parapsilosis ATCC 22019, and Candida auris CDC B11903. The EOs’ antifungal activity was measured by means of a broth microdilution technique to determine the minimum inhibitory and fungicidal concentrations (MICs/MFCs) against the different Candida spp. strains. The effects on biofilm formation were determined by a crystal violet assay using 96-well round-bottom microplates incubated for 48 h at 35 °C. The EOs from Lippia alba (Verbenaceae family) carvone-limonene chemotype and L. origanoides exhibited the highest antifungal activity against C. auris. The L. origanoides EOs also presented antifungal and antibiofilm activity against all three Candida spp., thus representing a promising alternative for developing new antifungal products focused on yeast infections, especially those related to biofilm formation, virulence factors, and antimicrobial resistance.

In Vitro Activity of Essential Oils Distilled from Colombian Plants against Candidaauris and Other Candida Species with Different Antifungal Susceptibility Profiles

Multi-drug resistant species such as Candida auris are a global health threat. This scenario has highlighted the need to search for antifungal alternatives. Essential oils (EOs), or some of their major compounds, could be a source of new antifungal molecules. The aim of this study was to evaluate the in vitro activity of EOs and some terpenes against C. auris and other Candida spp. The eleven EOs evaluated were obtained by hydro-distillation from different Colombian plants and the terpenes were purchased. EO chemical compositions were obtained by gas chromatography/mass spectrometry (GC/MS). Antifungal activity was evaluated following the CLSI standard M27, 4th Edition. Cytotoxicity was tested on the HaCaT cell line and fungal growth kinetics were tested by time–kill assays. Candida spp. showed different susceptibility to antifungals and the activity of EOs and terpenes was strain-dependent. The Lippia origanoides (thymol + p-cymene) chemotype EO, thymol, carvacrol, and limonene were the most active, mainly against drug-resistant strains. The most active EOs and terpenes were also slightly cytotoxic on the HaCaT cells. The findings of this study suggest that some EOs and commercial terpenes can be a source for the development of new anti-Candida products and aid the identification of new antifungal targets or action mechanisms.

Meta-analysis of the antifungal activities of three essential oils as alternative therapies in dermatophytosis infections

Aims

This work examines the available scientific evidence about the efficiency of essential oils (EO) as an alternative therapy to traditional treatment of fungal infections, including onychomycosis, assessing the effect of the three EO most frequently studied for their antifungal activity (thyme, cinnamon and tea tree EO) against three causative agents of fungal diseases in humans: Trichophyton rubrum, Trichophyton mentagrophytes complex and Candida albicans.

Methods and Results

The PRISMA statement protocol was followed to conduct a bibliographical search and 54 articles that met all the inclusion criteria were retrieved. Differences were observed in the MIC and MFC values depending on the micro‐organism strain and the EO used. The lowest MIC were observed with Cinnamomum zeylanicum EO (0.013–1120 μl ml⁻¹) against the three micro‐organisms. For MFC, the lowest value was found for Thymus vulgaris EO (4.2 μl ml⁻¹) against Trichophyton rubrum.

Conclusions

The antifungal effects of EO could be a very promising solution to overcome the therapeutic shortcomings of antimycotic medication. More experiments are needed to examine the properties of these oils to devise effective and nonaggressive therapies for treatment of dermatophytosis.

Significance and Impact of Study

The results indicate that EO remain good candidates for future treatments and could provide a solution for failed medications and/or adverse reactions to current pharmacological treatments.

Essential oil characterization of Prunus spinosa L., Salvia officinalis L., Eucalyptus globulus L., Melissa officinalis L. and Mentha x piperita L. by a volatolomic approach

In this study a volatolomic approach is proposed for the characterization of the volatile organic compound (VOC) composition of essential oils (EOs) extracted from common aromatic plants. Five species (Prunus spinosa L., Salvia officinalis L., Eucalyptus globulus L., Melissa officinalis L. and Mentha x piperita L.), particularly widespread in Southern Italy, were selected as recognized sources of natural bioactive compounds with beneficial properties. Hydro distillation and solid-liquid extraction with ethanol at different percentages were used to obtain EOs, and their extraction capabilities were compared analyzing chromatographic profiles obtained by headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography - mass spectrometry (GC-MS). The analytical procedure was optimized in term of SPME fiber, adsorption time and desorption time. GC-MS analyses were performed allowing the profiling of the VOC fingerprint in each plant extract. Experimental data were processed by a statistical multivariate approach (Analysis of Variance and Principal Component Analysis obtained for compounds and chemical classes), confirming that EO aroma profiles were statistically different for each of the selected five plants. The proposed volatolomic approach has proved to be an easy and efficient tool to study the aroma profile, allowing the collection of specific information and opening new perspectives and opportunities for the detection and identification of VOCs in agricultural and ecological applications.

Drug Repurposing in Medical Mycology: Identification of Compounds as Potential Antifungals to Overcome the Emergence of Multidrug-Resistant Fungi

Immunodepression, whether due to HIV infection or organ transplantation, has increased human vulnerability to fungal infections. These conditions have created an optimal environment for the emergence of opportunistic infections, which is concomitant to the increase in antifungal resistance. The use of conventional antifungal drugs as azoles and polyenes can lead to clinical failure, particularly in immunocompromised individuals. Difficulties related to treating fungal infections combined with the time required to develop new drugs, require urgent consideration of other therapeutic alternatives. Drug repurposing is one of the most promising and rapid solutions that the scientific and medical community can turn to, with low costs and safety advantages. To treat life-threatening resistant fungal infections, drug repurposing has led to the consideration of well-known and potential molecules as a last-line therapy. The aim of this review is to provide a summary of current antifungal compounds and their main resistance mechanisms, following by an overview of the antifungal activity of non-traditional antimicrobial drugs. We provide their eventual mechanisms of action and the synergistic combinations that improve the activity of current antifungal treatments. Finally, we discuss drug repurposing for the main emerging multidrug resistant (MDR) fungus, including the Candida auris, Aspergillus or Cryptococcus species.

Reassessing the Use of Undecanoic Acid as a Therapeutic Strategy for Treating Fungal Infections

Treating fungal infections is challenging and frequently requires long-term courses of antifungal drugs. Considering the limited number of existing antifungal drugs, it is crucial to evaluate the possibility of repositioning drugs with antifungal properties and to revisit older antifungals for applications in combined therapy, which could widen the range of therapeutic possibilities. Undecanoic acid is a saturated medium-chain fatty acid with known antifungal effects; however, its antifungal properties have not been extensively explored. Recent advances indicate that the toxic effect of undecanoic acid involves modulation of fungal metabolism through its effects on the expression of fungal genes that are critical for virulence. Additionally, undecanoic acid is suitable for chemical modification and might be useful in synergic therapies. This review highlights the use of undecanoic acid in antifungal treatments, reinforcing its known activity against dermatophytes. Specifically, in Trichophyton rubrum, against which the activity of undecanoic acid has been most widely studied, undecanoic acid elicits profound effects on pivotal processes in the cell wall, membrane assembly, lipid metabolism, pathogenesis, and even mRNA processing. Considering the known antifungal activities and associated mechanisms of undecanoic acid, its potential use in combination therapy, and the ability to modify the parent compound structure, undecanoic acid shows promise as a novel therapeutic against fungal infections.

The Effect of Ten Essential Oils on Several Cutaneous Drug-Resistant Microorganisms and Their Cyto/Genotoxic and Antioxidant Properties

In this study, we determined the antimicrobial activity of ten essential oils (EOs)—oregano, thyme, clove, arborvitae, cassia, lemongrass, melaleuca, eucalyptus, lavender, and clary sage—against drug-resistant microorganisms previously isolated from patients with skin infections. The essential oil compositions were determined using gas chromatography coupled to mass spectrometry (GC/MS). The assayed bacteria included Pseudomonas aeruginosa, Proteus vulgaris, Citrobacter koseri, and Klebsiella pneumoniae. Two drug-resistant yeasts (Candidaalbicans and Candida parapsilosis) were also involved in our survey. Oregano, thyme, cassia, lemongrass and arborvitae showed very strong antibacterial and antifungal activity against all tested strains. These results show that these essential oils may be effective in preventing the growth of the drug-resistant microorganisms responsible for wound infections. In this study, the genotoxic effects of tested essential oils on healthy human keratinocytes HaCaT were evaluated using the comet assay for the first time. These results revealed that none of the essential oils induced significant DNA damage in vitro after 24 h. Moreover, the treatment of HaCaT cells with essential oils increased the total antioxidant status (TAS) level. The obtained results indicate that EOs could be used as a potential source of safe and potent natural antimicrobial and antioxidant agents in the pharmaceutical and food industries.

Enhanced Killing of Candida krusei by Polymorphonuclear Leucocytes in the Presence of Subinhibitory Concentrations of Melaleuca alternifolia and "Mentha of Pancalieri" Essential Oils

The aim of this study was to evaluate the influence of tea tree oil (TTO) and "Mentha of Pancalieri" essential oil (MPP) on intracellular killing of Candida krusei, often resistant to conventional drugs, by polymorphonuclear leucocytes (PMNs). Intracellular killing was investigated by incubating yeasts and PMNs with essential oils (EOs) at 1/4 and 1/8 × MIC (Minimal Inhibitory Concentration), in comparison with anidulafungin, used as a reference drug. Killing values were expressed as Survival Index (SI) values. The cytotoxicity of EOs was evaluated by 3-[4,-5-dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay. Both EOs were more efficaceous at 1/8 × MIC than 1/4 × MIC, with killing values higher than observed in EO-free systems and in presence of anidulafungin, indicating that the decreasing concentrations did not cause lower candidacidal activity. This better activity at 1/8 × MIC is probably due to the EOs' toxicity at 1/4 × MIC, suggesting that at higher concentrations EOs might interfere with PMNs functionality. TTO and MPP at 1/8 × MIC significantly increased intracellular killing by PMNs through their direct action on the yeasts (both EOs) or on phagocytic cells (MPP), suggesting a positive interaction between EOs and PMNs to eradicate intracellular C. krusei. These data showed a promising potential application of TTO and "Mentha of Pancalieri" EO as natural adjuvants in C. krusei infection management.