Antifungal mode of action of macrocarpal C extracted from Eucalyptus globulus Labill (Lan An) towards the dermatophyte Trichophyton mentagrophytes

Antifungal activity of synthetic xanthenone against fluconazole-resistant Candida auris and its mechanism of action

Candida auris, an emerging multidrug-resistant fungal pathogen discovered in Japan in 2009, poses a significant global health threat, with infections reported in about 25 countries. The escalation of drug-resistant strains underscores the urgent need for new treatment options. This study aimed to investigate the antifungal potential of 2,3,4,4a-tetrahydro-1H-xanthen-1-one (XA1) against C. auris, as well as its mechanism of action and toxic profile. The antifungal activity of XA1 was first evaluated by determining the minimum inhibitory concentration (MIC), time-kill kinetics and biofilm inhibition. In addition, structural changes, membrane permeability, reactive oxygen species (ROS) production, and in vitro and in vivo toxicity of C. auris after exposure to XA1 were investigated. The results indicated that XA1 exhibited an MIC of 50 μg/mL against C. auris, with time-kill kinetics highlighting its efficacy. Field emission scanning electron microscopy (FE-SEM) showed structural damage in XA1-treated cells, supported by increased membrane permeability leading to cell death. Furthermore, XA1 induced ROS production and significantly inhibited biofilm formation. Importantly, XA1 exhibited low cytotoxicity in human epidermal keratinocytes (HaCaT), with a cell viability of over 90 % at 6.25 μg/mL. In addition, an LD50 of 17.68 μg/mL was determined in zebrafish embryos 24 h post fertilization (hpf), with developmental delay observed at prolonged exposure at 6.25 μg/mL (48-96 hpf). These findings position XA1 as a promising candidate for further research and development of an effective antifungal agent.

Tinea pedis: an updated review

Background

Tinea pedis is one of the most common superficial fungal infections of the skin, with various clinical manifestations. This review aims to familiarize physicians with the clinical features, diagnosis and management of tinea pedis.

Methods

A search was conducted in April 2023 in PubMed Clinical Queries using the key terms 'tinea pedis' OR 'athlete's foot'. The search strategy included all clinical trials, observational studies and reviews published in English within the past 10 years.

Results

Tinea pedis is most often caused by Trichophyton rubrum and Trichophyton interdigitale. It is estimated that approximately 3% of the world population have tinea pedis. The prevalence is higher in adolescents and adults than in children. The peak age incidence is between 16 and 45 years of age. Tinea pedis is more common amongst males than females. Transmission amongst family members is the most common route, and transmission can also occur through indirect contact with contaminated belongings of the affected patient. Three main clinical forms of tinea pedis are recognized: interdigital, hyperkeratotic (moccasin-type) and vesiculobullous (inflammatory). The accuracy of clinical diagnosis of tinea pedis is low. A KOH wet-mount examination of skin scrapings of the active border of the lesion is recommended as a point-of-care testing. The diagnosis can be confirmed, if necessary, by fungal culture or culture-independent molecular tools of skin scrapings. Superficial or localized tinea pedis usually responds to topical antifungal therapy. Oral antifungal therapy should be reserved for severe disease, failed topical antifungal therapy, concomitant presence of onychomycosis or in immunocompromised patients.

Conclusion

Topical antifungal therapy (once to twice daily for 1-6 weeks) is the mainstay of treatment for superficial or localized tinea pedis. Examples of topical antifungal agents include allylamines (e.g. terbinafine), azoles (e.g. ketoconazole), benzylamine, ciclopirox, tolnaftate and amorolfine. Oral antifungal agents used for the treatment of tinea pedis include terbinafine, itraconazole and fluconazole. Combined therapy with topical and oral antifungals may increase the cure rate. The prognosis is good with appropriate antifungal treatment. Untreated, the lesions may persist and progress.

Antifungal and Immunomodulatory Ingredients from Traditional Chinese Medicine

Fungal infections have become a growing public health challenge due to the clinical transmission of pathogenic fungi. The currently available antifungal drugs leave very limited choices for clinical physicians to deal with such situation, not to mention the long-standing problems of emerging drug resistance, side effects and heavy economic burdens imposed to patients. Therefore, new antifungal drugs are urgently needed. Screening drugs from natural products and using synthetic biology strategies are very promising for antifungal drug development. Chinese medicine is a vast library of natural products of biologically active molecules. According to traditional Chinese medicine (TCM) theory, preparations used to treat fungal diseases usually have antifungal and immunomodulatory functions. This suggests that if antifungal drugs are used in combination with immunomodulatory drugs, better results may be achieved. Studies have shown that the active components of TCM have strong antifungal or immunomodulatory effects and have broad application prospects. In this paper, the latest research progress of antifungal and immunomodulatory components of TCM is reviewed and discussed, hoping to provide inspiration for the design of novel antifungal compounds and to open up new horizons for antifungal treatment strategies.

Moroccan medicinal plants traditionally used for the treatment of skin diseases: From ethnobotany to clinical trials

ETHNOPHARMACOLOGICAL RELEVANCE

Skin diseases are among the most common human health affections. A healthy skin promotes a healthy body that can be achieved through modern, allopathic and natural medicines. Therefore, medicinal plants can be a reliable therapy in treating skin diseases in humans through a diverse range of bioactive molecules they contain.

AIM OF THE STUDY

This review aims to provide for the first-time scientific evidence related to the dermatological properties of Morocco's medicinal plants and it aims to provide a baseline for the discovery of new drugs having activities against skin issues.

METHODS

This review involved an investigation with different search engines for Moroccan ethnobotanical surveys published between 1991 and 2021. The plants used to treat skin diseases have been determined. Information regarding pharmacological effects, phytochemical, and clinical trials related to the plants listed in this review was collected from different scientific databases like PubMed, Science Direct, Google Scholar, Web of Science and Scopus. The data were analyzed and summarized in the review.

RESULTS

A total of 401 plants belonging to 86 families mainly represented by Asteraceae, Lamiaceae, Fabaceae, and Apiaceae which have been documented to be in common use by Moroccans for managing skin diseases. Among those plants recorded, the most commonly used are Allium cepa L, Chamaeleon gummifer (L.) Cass and Salvia rosmarinus Schleid. Mill. Leaves were the most commonly used plant part, while powder and decoction were the most common method of traditional drug preparation. 107 of the 401 plants (27%) have undergone pharmacological validation. A total of 44 compounds isolated from 27 plants were investigated to treat different types of skin diseases, and 25 plants have been clinically studied for their activities against skin diseases.

CONCLUSION

The beneficial effects of using Moroccan medicinal plants to treat skin diseases, according to traditional practices, have been proven in numerous scientific studies. Therefore, other studies should focus on isolating and identifying specific bioactive compounds from plant extracts, revealing more valuable therapeutic properties. Furthermore, additional reliable clinical trials are needed to confirm their beneficial effect on patients with skin diseases.

An Insight into Biomolecules for the Treatment of Skin Infectious Diseases

In assigning priorities, skin infectious diseases are frequently classified as minor when compared to infectious diseases of high mortality rates, such as tuberculosis or HIV. However, skin infections are amongst the most common and prevalent diseases worldwide. Elderly individuals present an increased susceptibility to skin infections, which may develop atypical signs and symptoms or even complicate pre-existing chronic disorders. When the skin fails to correct or inhibit the action of certain pathogenic microorganisms, biomolecules endowed with antimicrobial features are frequently administered topically or systemically to assist or treat such conditions. (1) Antibiotics, (2) antimicrobial peptides, or (3) natural extracts display important features that can actively inhibit the propagation of these pathogens and prevent the evolution of infectious diseases. This review highlights the properties and mechanisms of action of these biomolecules, emphasizing their effects on the most prevalent and difficult to treat skin infections caused by pathogenic bacteria, fungi, and viruses. The versatility of biomolecules’ actions, their symbiotic effects with skin cells and other inherent antimicrobial components, and their target-directed signatures are also explored here.

Study on the Biocontrol Potential of Antifungal Peptides Produced by Bacillus velezensis against Fusarium solani That Infects the Passion Fruit Passiflora edulis

A bacterium identified as Bacillus velezensis with a growth inhibitory effect against Fusarium solani, a pathogen that caused basal stem rot in the passion fruit Passiflora edulis, was isolated in this study. From the fermentation broth of B. velezensis, a type of antifungal peptide (named BVAP) with a molecular weight of ca. 1.5 kDa was purified and found to be fengycin. BVAP suppressed mycelial growth in F. solani with an IC₅₀ of 5.58 μg/mL, which was superior to those of the chemical fungicides thiram (41.24 μg/mL) and hymexazol (343.31 μg/mL). The antifungal activity remained stable after exposure to 50-100 °C or following incubation with solutions at pH 1-3. Further research revealed that BVAP increased the permeability of the F. solani mycelial membrane, brought about swelling at the tips of hyphae, and elicited abnormal accumulation of nucleic acids and chitin at the sites of swelling. These findings indicate that BVAP possessed a remarkable biocontrol potential toward F. solani.

Biofilm Eradication Activity of Herb and Spice Extracts Alone and in Combination Against Oral and Food-Borne Pathogenic Bacteria

The purpose of this study was to select herbs and spices with potent biofilm eradication activities. Further, the combined effects of herb and spice extracts against pathogenic biofilms were evaluated. The biofilm eradication activities of ethanol extracts of 104 herbs and spices were measured by combining a colorimetric microbial viability assay with a biofilm formation technique. Ethanol extract of clove had potent biofilm eradication activities against Escherichia coli, Porphyromonas gingivalis, and Streptococcus mutans. Ethanol extracts of eucalyptus and rosemary had potent biofilm eradication activities against P. gingivalis, Staphylococcus aureus and S. mutans. The combination of extracts of clove with eucalyptus or rosemary showed synergistic or additive effects, or both, on biofilm eradication activities. The main biofilm inhibitors in the ethanol extracts of clove, eucalyptus and rosemary were eugenol, macrocarpals and carnosic acid, respectively. The combinations of extracts of clove with eucalyptus or rosemary had potent biofilm eradication activities against oral and food-borne pathogenic bacteria. The findings of the present study reveal that specific combinations of herb and spice extracts may prevent and control biofilm-related oral diseases, food spoilage, and food poisoning.

Eucalyptal D Enhances the Antifungal Effect of Fluconazole on Fluconazole-Resistant Candida albicans by Competitively Inhibiting Efflux Pump

The frequent emergence of azole-resistant strains has increasingly led azoles to fail in treating candidiasis. Combination with other drugs is a good option to effectively reduce or retard its incidence of resistance. Natural products are a promising synergist source to assist azoles in treating resistant candidiasis. Eucalyptal D (ED), a formyl-phloroglucinol meroterpenoid, is one of the natural synergists, which could significantly enhance the anticandidal activity of fluconazole (FLC) in treating FLC resistant C. albicans. The checkerboard microdilution assay showed their synergistic effect. The agar disk diffusion test illustrated the key role of ED in synergy. The rhodamine 6G (R6G) efflux assay reflected ED could reduce drug efflux, but quantitative reverse transcription PCR analysis revealed the upregulation of CDR1 and CDR2 genes in ED treating group. Efflux pump-deficient strains were hyper-susceptible to ED, thus ED was speculated to be the substrate of efflux pump Cdr1p and Cdr2p to competitively inhibit the excretion of FLC or R6G, which mainly contributed to its synergistic effect.

Buckwheat Antifungal Protein with Biocontrol Potential To Inhibit Fungal ( Botrytis cinerea) Infection of Cherry Tomato

A 11 kDa antifungal protein FEAP was purified from buckwheat ( Fagopyrum esculentum) seed extract with a procedure involving (NH₄)₂SO₄ precipitation and chromatography on SP-Sepharose, Affi-gel blue gel, Mono S, and Superdex peptide. Its N-terminal sequence was AQXGAQGGGAT, resembling those of buckwheat peptides Fα-AMP1 and Fα-AMP2. FEAP exhibited thermostability (20-100 °C) and acid resistance (pH 1-5). Its antifungal activity was retained in the presence of 10-150 mmol/L of K⁺, Mn²⁺, or Fe³⁺ ions, 10-50 mmol/L of Ca²⁺ or Mg²⁺ ions, and 50% methanol, 50% ethanol, 50% isopropanol, or 50% chloroform. Its half-maximal inhibitory concentrations toward spore germination and mycelial growth in Botrytis cinerea were 79.9 and 236.7 μg/mL, respectively. Its antifungal activity was superior to the fungicide cymoxanil mancozeb (248.1 μg/mL). FEAP prevented B. cinerea from infecting excised leaves, intact leaves, and isolated fruits of cherry tomato. Its mechanism involved induction of an increase in cell membrane permeability and a decrease in mitochondrial membrane potential.

Purification of an Antifungal Peptide from Seeds of Brassica oleracea var. gongylodes and Investigation of Its Antifungal Activity and Mechanism of Action

In this study, a 8.5-kDa antifungal peptide designated as BGAP was purified from the crude extract of the seeds of Brassica oleracea var. gongylodes by employing a protocol that comprised cation exchange chromatography on SP-Sepharose, cation exchange chromatography on Mono S and gel filtration chromatography on Superdex peptide. BGAP showed the highest amino acid sequence similarity to defensin peptides by mass spectrometric analysis. BGAP showed a broad spectrum of antifungal activity with a half maximal inhibitory concentration at 17.33 μg/mL, 12.37 μg/mL, 16.81 μg/mL, and 5.60 μg/mL toward Colletotrichum higginsianum, Exserohilum turcicum, Magnaporthe oryzae and Mycosphaerella arachidicola, respectively. The antifungal activity of BGAP remained stable (i) after heat treatment at 40–100 °C for 15 min; (ii) after exposure to solutions of pH 1–3 and 11–13 for 15 min; (iii) after incubation with solutions containing K⁺, Ca²⁺, Mg²⁺, Mn²⁺ or Fe³⁺ ions at the concentrations of 20–150 mmol/L for 2 h; and (iv) following treatment with 10% methyl alcohol, 10% ethanol, 10% isopropanol or 10% chloroform for 2 h. Fluorescence staining experiments showed that BGAP brought about an increase in cell membrane permeability, a rise in reactive oxygen species production, a decrease in mitochondrial membrane potential, and an accumulation of chitin at the hyphal tips of Mycosphaerella arachidicola.

In Vitro Antibiofilm Activity of Eucarobustol E against Candida albicans

Formyl-phloroglucinol meroterpenoids (FPMs) are important types of natural products with various bioactivities. Our antifungal susceptibility assay showed that one of the Eucalyptus robusta-derived FPMs, eucarobustol E (EE), exerted a strong inhibitory effect against Candida albicans biofilms at a concentration of 16 μg/ml. EE was found to block the yeast-to-hypha transition and reduce the cellular surface hydrophobicity of the biofilm cells. RNA sequencing and real-time reverse transcription-PCR analysis showed that exposure to 16 μg/ml of EE resulted in marked reductions in the levels of expressions of genes involved in hyphal growth (EFG1, CPH1, TEC1, EED1, UME6, and HGC1) and cell surface protein genes (ALS3, HWP1, and SAP5). Interestingly, in response to EE, genes involved in ergosterol biosynthesis were downregulated, while the farnesol-encoding gene (DPP3) was upregulated, and these findings were in agreement with those from the quantification of ergosterol and farnesol. Combined with the obvious elevation of negative regulator genes (TUP1, NRG1), we speculated that EE's inhibition of carbon flow to ergosterol triggered the mechanisms of the negative regulation of hyphal growth and eventually led to biofilm inhibition.

Management of tinea corporis, tinea cruris, and tinea pedis: A comprehensive review

The prevalence of superficial mycotic infection worldwide is 20–25% of which dermatophytes are the most common agents. Recent developments in understanding the pathophysiology of dermatophytosis have confirmed the central role of cell-mediated immunity in countering these infections. Hence, a lack of delayed hypersensitivity reaction in presence of a positive immediate hypersensitivity (IH) response to trichophytin antigen points toward the chronicity of disease. Diagnosis, though essentially clinical should be confirmed by laboratory-based investigations. Several new techniques such as polymerase chain reaction (PCR) and mass spectroscopy can help to identify the different dermatophyte strains. Management involves the use of topical antifungals in limited disease, and oral therapy is usually reserved for more extensive cases. The last few years have seen a significant rise in the incidence of chronic dermatophyte infections of skin which have proven difficult to treat. However, due to the lack of updated national or international guidelines on the management of tinea corporis, cruris, and pedis, treatment with systemic antifungals is often empirical. The present review aims to revisit this important topic and will detail the recent advances in the pathophysiology and management of tinea corporis, tinea cruris, and tinea pedia while highlighting the lack of clarity of certain management issues.