Antifungal mechanism of action of Schinus lentiscifolius Marchand essential oil and its synergistic effect in vitro with terbinafine and ciclopirox against dermatophytes

Screening of alkaloids and withanolides isolated from Solanaceae plants for antifungal properties against non-wild type Sporothrix brasiliensis

Antifungal resistance has often been found in animal sporotrichosis in Southern Brazil. The biological potential of compounds from plants of the Solanaceae family against infectious diseases is known, however, it is still unknown against Sporothrix brasiliensis. This study evaluated the anti-Sporothrix brasiliensis activity, synergism, cytotoxicity, and action mechanism of steroidal lactones (withanolides) and alkaloids isolated from these plants. Pure compounds of withanolide D (WNOD), physalin F (PHYF), withanicandin (WNIC), nicandin B (NICB), solasonine (SSON), and solamargine (SMAR) were tested against 12 Sporothrix brasiliensis isolated from cats (n = 11) and dogs (n = 2) through M38-A2 CLSI. For the compounds with the best activity, a checkerboard assay for synergism, sorbitol protection, and ergosterol effect for action mechanism; and MTT test for cytotoxicity were performed. The withanolides WNOD, PHYF, WNIC, and NICB were not antifungal, but SSON (MIC 0.125-1 mg/mL) and SMAR (MIC 0.5-1 mg/mL) were both fungistatic and fungicidal (MFC 0.5-1 mg/mL for both) against wild-type (WT) and non-WT isolates. The activity of SSON and SMAR was indifferent when combined with itraconazole. In the mechanism of action, cell wall and plasma membrane by complexation with ergosterol seemed to be two target structures of SSON and SMAR. SSON was selected for cytotoxicity, whose cell viability in MDBK cells ranged from 28.85 % to 101.75 %, and was higher than 87.49 % at concentrations ≤0.0015 mg/ml. Only the steroidal alkaloids SSON and SMAR were active against non-WT isolates, being promising antifungal candidates for the treatment of feline and canine sporotrichosis with low susceptibility to itraconazole.

Natural Oils Enhance the Topical Delivery of Ketoconazole by Nanoemulgel for Fungal Infections

Nanoemulgel (NEG) pharmaceutical formulations are gaining popularity because of their ability to serve both as a nanoemulsion and as a gel. These products are well-known for their ease of use, spreadability, controlled release, and ability to hydrate dry skin. Natural essential oils have been shown to promote the cutaneous permeability of topical formulations, enhancing medication safety and efficacy. Herein, we developed NEG for the enhanced permeation of ketoconazole against candidiasis using clove oil (clove-oil-NEG) or eucalyptus oil (eucalyptus-oil-NEG), using the gelling agents carbopol 943 and hydroxypropyl methylcellulose (HPMC). We tested various excipients to increase the solubility of ketoconazole and formulate a nanoemulsion (NE). We measured the NE droplet particle size, shape, entrapment efficiency, and drug release. Furthermore, the physicochemical properties of the optimized nanoemulsion formulation were characterized by techniques such as Fourier transform infrared (FT-IR) spectroscopy and X-ray diffraction (XRD) analysis. The NEs were loaded into gels to form NEGs. NEGs were characterized for drug content, homogeneity, rheology, spreadability, and antifungal activity against Candida albicans, both in vitro and in vivo. Optimized ketoconazole NEG preparations consisted of either 15% clove oil or 20% eucalyptus oil. Droplet sizes in the optimized NEs were <100 nm, and the polydispersity indexes were 0.24 and 0.26. The percentages of ketoconazole released after 24 h from the clove-oil-NEG and eucalyptus-oil-NEGs were 91 ± 4.5 and 89 ± 7%, respectively. Scanning electron microscopy (SEM) showed that the NEGs had a smooth, uniform, and consistent shape and internal structural organization. The drug contents in the clove-oil-NEG and eucalyptus-oil-NEG were 98.5 ± 2.2 and 98.8 ± 3.4%, respectively. Permeation values of ketoconazole from clove-oil-NEG and eucalyptus-oil-NEG were 117 ± 7 and 108.34 ± 6 μg cm-2, respectively. The ketoconazole NEG formulations also had higher levels of fungal growth inhibition than a marketed formulation. Finally, in vivo studies showed that the NEGs do not irritate the skin. Ketoconazole NEG with either 15% clove oil or 20% eucalyptus oil is stable with better efficacy than ketoconazole alone due to excellent dispersion, drug dissolution, and permeability and thus might be recommended for the effective and safe treatment of candidiasis.

Essential Oils: Chemistry and Pharmacological Activities

In this review, we provide an overview of the current understanding of the main mechanisms of pharmacological action of essential oils and their components in various biological systems. A brief introduction on essential oil chemistry is presented to better understand the relationship of chemical aspects with the bioactivity of these products. Next, the antioxidant, anti-inflammatory, antitumor, and antimicrobial activities are discussed. The mechanisms of action against various types of viruses are also addressed. The data show that the multiplicity of pharmacological properties of essential oils occurs due to the chemical diversity in their composition and their ability to interfere with biological processes at cellular and multicellular levels via interaction with various biological targets. Therefore, these natural products can be a promising source for the development of new drugs.

The potential role of plant secondary metabolites on antifungal and immunomodulatory effect

With the widespread use of antibiotic drugs worldwide and the global increase in the number of immunodeficient patients, fungal infections have become a serious threat to global public health security. Moreover, the evolution of fungal resistance to existing antifungal drugs is on the rise. To address these issues, the development of new antifungal drugs or fungal inhibitors needs to be targeted urgently. Plant secondary metabolites are characterized by a wide variety of chemical structures, low price, high availability, high antimicrobial activity, and few side effects. Therefore, plant secondary metabolites may be important resources for the identification and development of novel antifungal drugs. However, there are few studies to summarize those contents. In this review, the antifungal modes of action of plant secondary metabolites toward different types of fungi and fungal infections are covered, as well as highlighting immunomodulatory effects on the human body. This review of the literature should lay the foundation for research into new antifungal drugs and the discovery of new targets. KEY POINTS: • Immunocompromised patients who are infected the drug-resistant fungi are increasing. • Plant secondary metabolites toward various fungal targets are covered. • Plant secondary metabolites with immunomodulatory effect are verified in vivo.

Are γ-terpinene, 1,8-cineole, p-coumaric acid, and quercetin active against wild-type and non-wild-type Sporothrix brasiliensis to itraconazole?

The emergence of itraconazole (ITZ)-resistant Sporothrix brasiliensis in feline and canine cases in southern Brazil has hampered the clinical cure of animal sporotrichosis, encouraging the search for therapeutic alternatives. The promising use of plants extracts from Lamiaceae family is known; however, there are no studies with its major compounds, as γ-terpinene (γTER), 1,8-cineole (1,8CIN), p-coumaric acid (pCOU), and quercetin (QUER). For the first time, we evaluated the antifungal, synergistic, cytotoxic activities and action mechanism of these compounds against S. brasiliensis. For this, 28 S. brasiliensis from cats (n = 24) and dogs (n = 4) and standard strains of S. brasiliensis and S. schenckii (n = 4) were tested by M38-A2 (CLSI), revealing non-wild-type (WT) isolates to ITZ on 54.2% (13/24) and 75% (03/04) of feline and canine isolates, respectively. Of the compounds, γTER stood out against all isolates (MIC/MFC 0.75 to > 3 mg/ml; MIC50 3 mg/ml). However, 1,8CIN, pCOU, and QUER showed little or no activity (MIC50 > 3 mg/ml). Thus, γTER was selected for checkerboard assay, whose combination with ITZ showed synergistic (WT isolates) and indifferent (non-WT isolates) interaction. For action mechanism (sorbitol protection and ergosterol effect), γTER acted in membrane by complexing with fungal ergosterol and at the cell wall level, showing two possible pathways as antifungal target. Finally, cytotoxicity (MTT assay) showed that γTER was the safest compound on MDBK cells, even at a concentration of 3 mg/ml (90.16%). Our findings support that γTER is a potent antifungal candidate for the control of sporotrichosis, including against non-WT S. brasiliensis.

Medical cannabis dimethyl ether, ethanol and butane extracts inhibit the in vitro growth of bacteria and dermatophytes causing common skin diseases

Cannabis preparations are gaining popularity among patients with various skin diseases. Due to the lack of scientific evidence, dermatologists remain cautious about their prescriptions. So far, only a few studies have been published about the effects of high-potency cannabis extracts on microorganisms (especially dermatophytes) causing skin problems that affect more than 25% of the worldwide population. Even though, the high-potency cannabis extracts prepared by cold extraction are mostly composed of non-psychoactive tetrahydrocannabinolic acid (THCA) and only low amount of THC, their use in topical treatment can be stigmatized. The in vitro antimicrobial and antifungal activity of two high potent cannabis strains extracted by three solvents traditionally or currently used by cannabis users (ethanol; EtOH, butane; BUT, dimethyl ether; DME) was investigated by broth dilution method. The chemical profile of cannabis was determined by high-performance liquid chromatography with ultraviolet detection and gas chromatography with mass spectrometer and flame ionization detector. The extraction methods significantly influenced chemical profile of extracts. The yield of EtOH extracts contained less cannabinoids and terpenes compared to BUT and DME ones. Most of the extracts was predominantly (>60%) composed of various cannabinoids, especially THCA. All of them demonstrated activity against 18 of the 19 microorganisms tested. The minimal inhibitory concentrations (MICs) of the extracts ranged from 4 to 256 μg/mL. In general, the bacteria were more susceptible to the extracts than dermatophytes. Due to the lower content of biologically active substances, the EtOH extracts were less effective against microorganisms. Cannabis extracts may be of value to treat dermatophytosis and other skin diseases caused by various microorganisms. Therefore, they could serve as an alternative or supportive treatment to commonly used antibiotics.

Isoflavaspidic Acid PB Extracted from Dryopteris fragrans (L.) Schott Inhibits Trichophyton rubrum Growth via Membrane Permeability Alternation and Ergosterol Biosynthesis Disruption

Isoflavaspidic acid PB (PB), a phloroglucinol derivative extracted from aerial parts of Dryopteris fragrans (L.) Schott, had antifungal activity against several dermatophytes. This study was aimed at exploring the antifungal mechanism of PB against Trichophyton rubrum (T. rubrum). The effectiveness of PB in inhibiting T. rubrum growth was detected by time-kill kinetics study and fungal biomass determination. Studies on the mechanism of action were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), sorbitol and ergosterol assay, nucleotide leakage measurement, and UPLC-based test and enzyme-linked immunosorbent assay. Fungicidal activity of PB was concentration- and time-dependent at 2 × MIC (MIC: 20 μg/mL) after 36 h. The total biomass of T. rubrum was reduced by 64.17%, 77.65%, and 84.71% in the presence of PB at 0.5 × MIC, 1 × MIC, and 2 × MIC, respectively. SEM analysis showed that PB changed mycelial morphology, such as shrinking, twisting, collapsing, and even flattening. TEM images of treated cells exhibited abnormal distributions of polysaccharide particles, plasmolysis, and cytoplasmic content degradation accompanied by plasmalemma disruption. There were no changes in the MIC of PB in the presence of sorbitol. However, the MIC values of PB were increased by 4-fold with exogenous ergosterol. At 4 h and 8 h, PB increased nucleotide leakage. Besides, ergosterol content in T. rubrum membrane treated with PB at 0.5 × MIC, 1 × MIC, and 2 × MIC was decreased by 9.58%, 15.31%, and 76.24%, respectively. There was a dose-dependent decrease in the squalene epoxidase (SE) activity. And the reduction in the sterol 14α-demethylase P450 (CYP51) activity was achieved after PB treatments at 1 × MIC and 2 × MIC. These results suggest that PB displays nonspecific action on the cell wall. The membrane damaging effects of PB were attributed to binding with ergosterol to increase membrane permeability and interfering ergosterol biosynthesis involved with the reduction of SE and CYP51 activities. Further study is needed to develop PB as a natural antifungal candidate for clinical use.

First Report of the Biosynthesis and Characterization of Silver Nanoparticles Using Scabiosa atropurpurea subsp. maritima Fruit Extracts and Their Antioxidant, Antimicrobial and Cytotoxic Properties

Candida and dermatophyte infections are difficult to treat due to increasing antifungal drugs resistance such as fluconazole, as well as the emergence of multi-resistance in clinical bacteria. Here, we first synthesized silver nanoparticles using aqueous fruit extracts from Scabiosa atropurpurea subsp. maritima (L.). The characterization of the AgNPs by means of UV, XRD, FTIR, and TEM showed that the AgNPs had a uniform spherical shape with average sizes of 40–50 nm. The biosynthesized AgNPs showed high antioxidant activity when investigated using 1,1-diphenyl-2-picryl-hydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assays. The AgNPs displayed strong antibacterial potential expressed by the maximum zone inhibition and the lowest MIC and MBC values. The AgNPs revealed a significant antifungal effect against the growth and biofilm of Candida species. In fact, the AgNPs were efficient against Trichophyton rubrum, Trichophyton interdigitale, and Microsporum canis. The antifungal mechanisms of action of the AgNPs seem to be due to the disruption of membrane integrity and a reduction in virulence factors (biofilm and hyphae formation and a reduction in germination). Finally, the silver nanoparticles also showed important cytotoxic activity against the human multiple myeloma U266 cell line and the human breast cancer cell line MDA-MB-231. Therefore, we describe new silver nanoparticles with promising biomedical application in the development of novel antimicrobial and anticancer agents.

Green synthesis of silver nanoparticles using mixed leaves aqueous extract of wild olive and pistachio: characterization, antioxidant, antimicrobial and effect on virulence factors of Candida

In this study, a successfully rapid, simple approach was applied for biosynthesis of silver nanoparticles AgNPs using for the first time the mixed leaves extract of Olea europaea subsp. europaea var. sylvestris and Pistacia lentiscus from natural association aimed to enhance their antimicrobial potential. The plant extract acts both as reducing and capping agents. When the aqueous extract was added to AgNO₃ solution, the color was changed from pale to yellow to brown indicating the reduction of Ag ions and synthesis of silver nanoparticles (AgNPs) without any solvent or hazardous reagents. The green synthesized AgNPs were characterized by UV-Vis spectrophotometer, FTIR spectrum and the X-ray crystallography. The AgNPs showed superior antioxidant activity measured by DPPH, Ferric Antioxidant Reducing Power (FRAP) as well as the total antioxidant activity methods. Moreover, the analysis of phytochemical constituents including flavonoids, tannins, alkaloids and total polyphenols contents mentioned the most richness of the silver nanoparticles compared to plant extract. The new synthesized AgNPs demonstrated the bactericidal and fungicidal effects against all the tested bacterial and fungal strains and found to limit the spore germination of filamentous fungi. AgNPs also gave an anti-biofilm activity and synergistic effect with the conventional antibiotic's drugs. Here we firstly describe the silver nanoparticles effect on virulence factors of Candida species by reduction of enzymes like proteinase and phospholipase, inhibition of morphogenesis of Candida albicans cells. This natural product, acquiring these properties, should be promoted to be used in pharmaceutical and medical industries in future.

Trends in the epidemiology of dermatophytosis in the Middle East and North Africa region

Dermatophytosis corresponds to a broad series of infections, mostly superficial, caused by a group of keratinophilic and keratinolytic filamentous fungi called dermatophytes. These mycoses are currently considered to be a major public health concern worldwide, particularly in developing countries such as those in the Middle East and North Africa (MENA) region. Here we compiled and discussed existing epidemiologic data on these infections in the MENA region. Most of the available studies were based on conventional diagnostic strategies and were published before the last taxonomic revision of dermatophytes. This has led to misidentifications, which might have resulted in the underestimation of the real burden of these infections in the MENA countries. Our analysis of the available literature highlights an urgent need for further studies based on reliable diagnostic tools and standard susceptibility testing methods for dermatophytosis, which represents a major challenge for these countries. This is crucial for guiding appropriate interventions and activating antifungal stewardship programs in the future.

Apiaceae Essential Oils: Boosters of Terbinafine Activity against Dermatophytes and Potent Anti-Inflammatory Effectors

Dermatophyte infections represent an important public health concern, affecting up to 25% of the world's population. Trichophyton rubrum and T. mentagrophytes are the predominant dermatophytes in cutaneous infections, with a prevalence accounting for 70% of dermatophytoses. Although terbinafine represents the preferred treatment, its clinical use is hampered by side effects, drug-drug interactions, and the emergence of resistant clinical isolates. Combination therapy, associating terbinafine and essential oils (EOs), represents a promising strategy in the treatment of dermatophytosis. In this study, we screened the potential of selected Apiaceae EOs (ajowan, coriander, caraway, and anise) to improve the antifungal activity of terbinafine against T. rubrum ATCC 28188 and T. mentagrophytes ATCC 9533. The chemical profile of EOs was analyzed by gas chromatography. The minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC) of EOs/main compounds were determined according to EUCAST-AFST guidelines, with minor modifications. The checkerboard microtiter method was used to identify putative synergistic combinations of EOs/main constituents with terbinafine. The influence of EOs on the viability and pro-inflammatory cytokine production (IL-1β, IL-8 and TNF-α) was determined using an ex vivo human neutrophils model. The binary associations of tested EOs with terbinafine were found to be synergistic against T. rubrum, with FICI values of 0.26-0.31. At the tested concentrations (6.25-25 mg/L), EOs did not exert cytotoxic effects towards human neutrophils. Anise EO was the most potent inhibitor of IL-1β release (46.49% inhibition at 25 mg/L), while coriander EO displayed the highest inhibition towards IL-8 and TNF-α production (54.15% and 54.91%, respectively). In conclusion, the synergistic combinations of terbinafine and investigated Apiaceae EOs could be a starting point in the development of novel topical therapies against T. rubrum-related dermatophytosis.

Antifungal Combinations in Dermatophytes

Dermatophytes are the most common cause of fungal infections worldwide, affecting millions of people annually. The emergence of resistance among dermatophytes along with the availability of antifungal susceptibility procedures suitable for testing antifungal agents against this group of fungi make the combinatorial approach particularly interesting to be investigated. Therefore, we reviewed the scientific literature concerning the antifungal combinations against dermatophytes. A literature search on the subject performed in PubMed yielded 68 publications: 37 articles referring to in vitro studies and 31 articles referring to case reports or clinical studies. In vitro studies involved over 400 clinical isolates of dermatophytes (69% Trichophyton spp., 29% Microsporum spp., and 2% Epidermophyton floccosum). Combinations included two antifungal agents or an antifungal agent plus another chemical compound including plant extracts or essential oils, calcineurin inhibitors, peptides, disinfectant agents, and others. In general, drug combinations yielded variable results spanning from synergism to indifference. Antagonism was rarely seen. In over 700 patients with documented dermatophyte infections, an antifungal combination approach could be evaluated. The most frequent combination included a systemic antifungal agent administered orally (i.e., terbinafine, griseofulvin, or azole-mainly itraconazole) plus a topical medication (i.e., azole, terbinafine, ciclopirox, amorolfine) for several weeks. Clinical results indicate that association of antifungal agents is effective, and it might be useful to accelerate the clinical and microbiological healing of a superficial infection. Antifungal combinations in dermatophytes have gained considerable scientific interest over the years and, in consideration of the interesting results available so far, it is desirable to continue the research in this field.

Do essential oils from plants occurring in the Brazilian Caatinga biome present antifungal potential against dermatophytoses? A systematic review

The Caatinga is an exclusively Brazilian biome where semiarid climatic conditions promote singularities in adaptive biodiversity. Many aromatic species are found in this region possessing antifungal properties, which are attributed to their essential oils. Thus, we questioned whether essential plant oils found in the Caatinga present anti-dermatophytic potential. Dermatophytes are keratinophilic fungi that cause one of the most prevalent mycoses globally, skin infections known as dermatophytoses (tineas). Here, we provide a comprehensive report of the available published information, analyzing the methods used to evaluate the antifungal activity, verifying the quality of the evidence and possible clinical applications, and discussing research trends in this area. The plants studied concentrated in the genera Croton (Euphorbiaceae), Lippia (Verbenaceae), Piper (Piperaceae), and Mentha (Lamiaceae). All of the studies used in vitro tests to analyze antifungal potential, and little evidence was ascertained concerning the mechanism of antifungal action. In addition, the essential oils also evidenced drug modifying activity of conventional antifungal drugs (Ketoconazole and Terbinafine). We believe that the anti-dermatophyte potential of plant essential oils occurring within the Caatinga is underestimated and that this review will encourage future chemical-pharmacological investigations into the plants within this biome.Key points• The essential oils from plants occurring in the Caatinga Biome present unknown anti-dermatophyte potential.• The studies against dermatophyte fungi concentrate on the families Lamiaceae and Verbenaceae.• In vitro assays were used to assess the anti-dermatophyte potential of the essential oils.

Preliminary Study on Antifungal Mechanism of Aqueous Extract of Cnidium monnieri Against Trichophyton rubrum

Trichoderma rubrum (T. rubrum) is one of the important pathogens because it is the cause of most dermatomycosis. The treatment of Trichophyton rubrum infection is time-consuming and very expensive; it is easy for the infections to reoccur, leading to therapeutic failures, persistence, and chronic infection. These issues have inspired researchers to study natural alternative therapies instead. Cnidium monnieri (L.), as a kind of traditional Chinese medicine, has a variety of pharmacological activities and a wide range of applications, so it has a high potential for researching and economic value. We detected the effect of aqueous extract of C. monnieri (L.) on the activity of T. rubrum by Cell Count Kit-8 assay (CCK-8), and we found that 128 and 256 μg/ml of aqueous extracts of C. monnieri (L.) co-cultured with T. rubrum for 24 h showed the inhibitory effect on T. rubrum. The results of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirmed that aqueous extract of C. monnieri (L.) damaged the T. rubrum. At the same time, mass spectrometry screening with T. rubrum before and after the treatment of 256 μg/ml of aqueous extracts of C. monnieri (L.) showed that 966 differentially expressed proteins were detected, including 524 upregulated differentially expressed genes (DEGs) and 442 downregulated DEGs. The most significantly downregulated protein was chitin synthase (CHS); and the results of qRT-PCR and Western blotting demonstrated that the expression level of CHS was downregulated in the 256 μg/ml group compared with the control group. The study showed that the aqueous extract of C. monnieri (L.) could destroy the morphology of mycelia and the internal structure of T. rubrum, and it could inhibit the growth of T. rubrum. The antifungal effect of aqueous extract of C. monnieri (L.) may be related to the downregulation of the expression of CHS in T. rubrum, and CHS may be one of the potential targets of its antifungal mechanism. We concluded that aqueous extract from C. monnieri (L.) may be a potential candidate for antifungal agents.

A Review on Antifungal Efficiency of Plant Extracts Entrenched Polysaccharide-Based Nanohydrogels

Human skin acts as a physical barrier; however, sometimes the skin gets infected by fungi, which becomes more severe if the infection occurs on the third layer of the skin. Azole derivative-based antifungal creams, liquids, or sprays are available to treat fungal infections; however, these formulations show various side effects on the application site. Over the past few years, herbal extracts and various essential oils have shown effective antifungal activity. Additionally, autoxidation and epimerization are significant problems with the direct use of herbal extracts. Hence, to overcome these obstacles, polysaccharide-based nanohydrogels embedded with natural plant extracts and oils have become the primary choice of pharmaceutical scientists. These gels protect plant-based bioactive compounds and are effective delivery agents because they release multiple bioactive compounds in the targeted area. Nanohydrogels can be applied to infected areas, and due to their contagious nature and penetration power, they get directly absorbed through the skin, quickly reaching the skin's third layer and effectively reducing the fungal infection. In this review, we explain various skin fungal infections, possible treatments, and the effective utilization of plant extract and oil-embedded polysaccharide-based nanohydrogels.

Evaluation of activity and toxicity of combining clioquinol with ciclopirox and terbinafine in alternative models of dermatophytosis

Dermatophytosis is a superficial fungal infection that affects humans and is very common in small animals. The treatment using the most commonly used antifungals is failing, and new therapeutic alternatives are required to combat the resistance of these fungal infections. Previous studies by the group have shown that clioquinol is an important therapeutic alternative in the treatment of dermatophytosis. The object was to conduct studies of antidermatophytic activity and the irritant potential from the double and triple combinations of clioquinol, terbinafine and ciclopirox in ex vivo and in vivo alternative models. To evaluate the irritant potential of antifungal combinations, the alternative HET-CAM method (chicken egg test chorioallantoic membrane) was used. Ex vivo models were used to assess the effectiveness of antifungal combinations, using pig hooves and veterinary fur. Any possible tissue damage was to assess through in histopathology of swine ears. HET-CAM results showed that all combinations can be classified as non-irritating, corroborated by the results of the histopathological evaluation of the pig's ear skin. Only the double combinations managed to remove 100% of the colony-forming units (CFU) formed on the pig's hooves. The clioquinol + terbinafine combination and the triple combination were more effective than clioquinol + ciclopirox in eradicating the preformed biofilm in fur of veterinary origin. These results show the potential of formulations of clioquinol in combination with antifungals for use in humans and in the veterinary field to combat dermatophytosis, as an important alternative therapy, for use in the near future.

Antifungal Activity of Melaleuca alternifolia Essential Oil (TTO) and Its Synergy with Itraconazole or Ketoconazole against Trichophyton rubrum

Over the past 20–30 years, Trichophyton rubrum represented the most widespread dermatophyte with a prevalence accounting for 70% of dermatophytosis. The treatment for cutaneous infections caused by Trichophyton spp. are imidazoles (ketoconazole (KTZ)) and triazoles (itraconazole (ITZ)). T. rubrum can develop resistance to azoles after prolonged exposure to subinhibitory concentrations resulting in therapeutic failures and chronic infections. These problems have stimulated the search for therapeutic alternatives, including essential oils, and their potential use in combination with conventional antifungals. The purpose of this study was to evaluate the antifungal activity of tea tree oil (TTO) (Melaleuca alternifolia essential oil) and the main components against T. rubrum and to assess whether TTO in association with KTZ/ITZ as reference drugs improves the antifungal activity of these drugs. We used a terpinen-4-ol chemotype (35.88%) TTO, and its antifungal properties were evaluated by minimum inhibitory and minimum fungicidal concentrations in accordance with the CLSI guidelines. The interaction between TTO and azoles was evaluated through the checkerboard and isobologram methods. The results demonstrated both the fungicide activity of TTO on T. rubrum and the synergism when it was used in combination with azoles. Therefore, this mixture may reduce the minimum effective dose of azole required and minimize the side effects of the therapy. Synergy activity offered a promise for combination topical treatment for superficial mycoses.

A review of the methods used to determine the target site or the mechanism of action of essential oils and their components against fungi

Essential oils (EOs) are complex mixtures of compounds derived from plants that exhibit antimicrobial activity. Several studies have demonstrated their antifungal activity in food matrices or in vitro via vapor phase or direct addition. Recently, researchers are focusing on elucidating the target site or the mechanism of action of various EOs. Past research has suggested evidence of how EOs act in the fungal cells via assays assessed from cell wall alterations or gene expression modifications. However, no previous reports have summarized most methods for finding the target site of the mechanism of action for EOs. Therefore, this review presents the methods and assays used to discover the target site or the mechanism of action of EOs against fungal cells. Researchers commonly analyze the plasma membrane integrity using various techniques as well as the changes in cell morphology. Meanwhile, the quantification of the activity of the mitochondrial enzymes, ROS species, and gene expression are less assayed.

Potentiation of antifungal activity of terbinafine by dihydrojasmone and terpinolene against dermatophytes

Dermatophytoses are infections that affect keratinized tissues. Their main etiologic agents are fungi of the genera Microsporum and Trichophyton. The emergence of resistant fungi and the clinical relevance of dermatophytosis have encouraged studies that aim to increase the arsenal of drugs or act on mechanisms that confer multiple drug resistance. This study investigated the modulating activity of terbinafine promoted by dihydrojasmone and terpinolene against Microsporum canis LM 216, Trichophyton interdigitale H6 and T. interdigitale Δmdr2. The minimum inhibitory concentration (MIC) of test drugs was determined by broth microdilution. The effect of the drugs tested on plasma membrane functionality was analysed. Terbinafine MIC was determined in sub-inhibitory concentrations of monoterpenes. Finally, it was performed an association study with terbinafine and monoterpenes. Dihydrojasmone presented lower MIC values than terpinolene. All fungi were sensitive to terbinafine, starting at 1 μg ml^-1 . All tested drugs increased K⁺ release (P < 0·05), affecting the functionality of the plasma membrane. Dihydrojasmone modulated the sensitivity of all strains against terbinafine, and terpinolene modulated the sensitivity of M. canis LM 216 and T. interdigitale Δmdr2. The monoterpenes and terbinafine drug associations presented synergism. In conclusion, the results suggest that the dihydrojasmone and terpinolene are promising antifungal agents that potentiate the antifungal activity of terbinafine against dermatophytes.

8-Hydroxyquinoline 1,2,3-triazole derivatives with promising and selective antifungal activity

Fungal infections that affect humans and plants have increased significantly in recent decades. However, these pathogens are still neglected when compared to other infectious agents. Due to the high prevalence of these infections, the need for new molecules with antifungal potential is recognized, as pathogenic species are developing resistance to the main drugs available. This work reports the design and synthesis of 1,2,3-triazole derivatives of 8-hydroxyquinoline, as well as the determination of their activities against a panel of fungal species: Candida spp., Trichosporon asahii, Magnusiomyces capitatus, Microsporum spp., Trichophyton spp. and Fusarium spp. The triazoles 5-(4-phenyl-1H-1,2,3-triazol-1-yl)quinolin-8-ol (12) and 5-(4-(cyclohex-1-en-1-yl)-1H-1,2,3-triazol-1-yl)quinolin-8-ol (16) were more promising, presenting minimum inhibitory concentration (MIC) values between 1-16 µg/ml for yeast and 2-4 µg/ml for dermatophytes. However, no relevant anti-Fusarium spp. activity was observed. In the time-kill assays with Microsporum canis, 12 and 16 presented time-dependent fungicide profile at 96 h and 120 h in all evaluated concentrations, respectively. For Candida guilliermondii, 12 was fungicidal at all concentrations at 6 h and 16 exhibited a predominantly fungistatic profile. Both 12 and 16 presented low leukocyte toxicity at 4 µg/ml and the cell viability was close to 100% after the treatment with 12 at all tested concentrations. The sorbitol assay combined with SEM suggest that damages on the fungal cell wall could be involved in the activity of these derivatives. Given the good results obtained with this series, scaffold 4-(cycloalkenyl or phenyl)-5-triazol-8-hydroxyquinoline appears to be a potential pharmacophore for exploration in the development of new antifungal agents.

Antichemotactic and Antifungal Action of the Essential Oils from Cryptocarya aschersoniana, Schinus terebinthifolia, and Cinnamomum amoenum

The purpose of this work was to determine the chemical composition and evaluate the antichemotactic, antioxidant, and antifungal activities of the essential oil obtained from the species Cryptocarya aschersoniana Mez, Cinnamomum amoenum (Ness & Mart.) Kosterm., and Schinus terebinthifolia Raddi, as well as the combination of C. aschersoniana essential oil and terbinafine against isolates of dermatophytes. Allo-aromadendrene, bicyclogermacrene, and germacrene B were identified as major compounds in essential oils. The essential oil of C. aschersoniana shown 100 % inhibitory effect on leukocyte migration at the concentration of 10 μg/mL while S. terebinthifolia oil presented 80.1 % inhibitory effect at the same concentration. Only S. terebinthifolia oil possessed free-radical-scavenging activity which indicates its antioxidant capacity. The essential oils were also tested against fungal isolates of dermatophyte species (Trichophyton rubrum, Trichophyton mentagrophytes, Microsporum canis and Microsporum gypseum), resulting in MIC ranging from 125 μg/mL to over 500 μg/mL. C. aschersoniana oil combined with terbinafine resulted in an additive interaction effect. In this case, the essential oil may act as a complement to conventional therapy for the topical treatment of superficial fungal infections, mainly because it is associated with an anti-inflammatory effect.

Influence of Monoterpenes in Biological Activities of Nectandra megapotamica (Spreng.) Mez Essential Oils

Investigating the influence of seasonal variations on biological activities is important for pharmacological studies and metabolic engineering. Therefore, this study was conducted to determine the variation of the chemical composition of essential oils obtained from Nectandra megapotamica leaves, collected at different stages of plant development, as well as its influence on the biological activities. A total of 38 compounds were identified that accounted for 97–99.2% of the chemical composition of the oils. Major differences were observed in the monoterpenic fraction, representing 5.1% of the compounds identified in the productive rest phase to 37.1% in the blooming phase. Bicyclogermacrene and germacrene D were the predominant compounds identified in the oil of all collections. Furthermore, limonene, β-pinene, and spathulenol were identified predominantly in the samples of blooming and fruiting phases. The oils exhibited significant antichemotactic activity and different effects in scavenging the radical 2,2-diphenyl-1-picrylhydrazyl. Variations were also observed in the antifungal activity, with the minimum inhibitory concentrations ranging from 125 to 500 μg/mL. These results demonstrate the influence of monoterpenes, primarily limonene, α-pinene, and β-pinene, on the bioactivities of the oil. Studies investigating the variations in the chemical composition of essential oil may offer a strategy to produce a compound or a group of compounds of interest to industries with a specific pharmacological focus.