Antifungal Activities of cis-trans Citral Isomers against Trichophyton rubrum with ERG6 as a Potential Target

Insights into the antifungal mechanism of Bacillus subtilis cyclic lipopeptide iturin A mediated by potassium ion channel

Fungal infections pose severe and potentially lethal threats to plant, animal, and human health. Ergosterol has served as the primary target for developing antifungal medications. However, many antifungal drugs remain highly toxic to humans due to similarity in cell membrane composition between fungal and animal cells. Iturin A, lipopeptide produced by Bacillus subtilis, efficiently inhibit various fungi, but demonstrated safety in oral administration, indicating the existence of targets different from ergosterol. To pinpoint the exact antifungal target of iturin A, we used homologous recombination to knock out and overexpress erg3, a key gene in ergosterol synthesis. Saccharomyces cerevisiae and Aspergillus carbonarius were transformed using the LiAc/SS-DNNPEG and Agrobacterium-mediated transformation (AMT), respectively. Surprisingly, increasing ergosterol content did not augment antifungal activity. Furthermore, iturin A's antifungal activity against S. cerevisiae was reduced while it pre-incubation with voltage-gated potassium (Kv) channel inhibitor, indicating that Kv activation was responsible for cell death. Iturin A was found to activate the Kv protein, stimulating K+ efflux from cell. In vitro tests confirmed interaction between iturin A and Kv protein. This study highlights Kv as one of the precise targets of iturin A in its antifungal activity, offering a novel target for the development of antifungal medications.

Antifungal activity and potential mechanism of action of Huangqin decoction against Trichophyton rubrum

Introduction. Trichophyton rubrum is a major causative agent of superficial dermatomycoses such as onychomycosis and tinea pedis. Huangqin decoction (HQD), as a classical traditional Chinese medicine formula, was found to inhibit the growth of common clinical dermatophytes such as T. rubrum in our previous drug susceptibility experiments.Hypothesis/Gap Statement. The antifungal activity and potential mechanism of HQD against T. rubrum have not yet been investigated.Aim. The aim of this study was to investigate the antifungal activity and explore the potential mechanism of action of HQD against T. rubrum.Methodology. The present study was performed to evaluate the antifungal activity of HQD against T. rubrum by determination of minimal inhibitory concentrations (MICs), minimal fungicidal concentrations (MFCs), mycelial growth, biomass, spore germination and structural damage, and explore its preliminary anti-dermatophyte mechanisms by sorbitol and ergosterol assay, HPLC-based ergosterol test, enzyme-linked immunosorbent assay and mitochondrial enzyme activity test.Results. HQD was able to inhibit the growth of T. rubrum significantly, with an MIC of 3.125 mg ml-1 and an MFC of 12.5 mg ml-1. It also significantly inhibited the hyphal growth, conidia germination and biomass growth of T. rubrum in a dose-dependent manner, and induced structural damage in different degrees for T. rubrum cells. HQD showed no effect on cell wall integrity, but was able to damage the cell membrane of T. rubrum by interfering with ergosterol biosynthesis, involving the reduction of squalene epoxidase (SE) and sterol 14α-demethylase P450 (CYP51) activities, and also affect the malate dehydrogenase (MDH), succinate dehydrogenase (SDH) and ATPase activities of mitochondria.Conclusion. These results revealed that HQD had significant anti-dermatophyte activity, which was associated with destroying the cell membrane and affecting the enzyme activities of mitochondria.

Microfluidizing Technique Application for Algerian Cymbopogon citratus (DC.) Stapf Effects Enhanced Volatile Content, Antimicrobial, and Anti-Mycotoxigenic Properties

Medicinal plant extracts are a promising source of bioactive minor contents. The present study aimed to evaluate the distinguished volatile content of Algerian Cymbopogon citratus (DC.) Stapf before and after the microfluidization process and their related antimicrobial and anti-mycotoxigenic impacts and changes. The GC-MS apparatus was utilized for a comparative examination of Algerian lemongrass essential oil (LGEO) with its microfluidization nanoemulsion (MF-LGEO) volatile content. The MF-LGEO was characterized using Zetasizer and an electron microscope. Cytotoxicity, antibacterial, and antifungal activities were determined for the LGEO and MF-LGEO. The result reflected changes in the content of volatiles for the MF-LGEO. The microfluidizing process enhanced the presence of compounds known for their exceptional antifungal and antibacterial properties in MF-LGEO, namely, neral, geranial, and carvacrol. However, certain terpenes, such as camphor and citronellal, were absent, while decanal, not found in the raw LGEO, was detected. The droplet diameter was 20.76 ± 0.36 nm, and the polydispersity index (PDI) was 0.179 ± 0.03. In cytotoxicity studies, LGEO showed higher activity against the HepG2 cell line than MF-LGEO. Antibacterial LGEO activity against Gram-positive bacteria recorded an inhibitory zone from 41.82 ± 2.84 mm to 58.74 ± 2.64 mm, while the zone ranged from 12.71 ± 1.38 mm to 16.54 ± 1.42 mm for Gram-negative bacteria. Antibacterial activity was enhanced to be up to 71.43 ± 2.54 nm and 31.54 ± 1.01 nm for MF-LGEO impact against Gram-positive and Gram-negative pathogens. The antifungal effect was considerable, particularly against Fusarium fungi. It reached 17.56 ± 1.01 mm and 13.04 ± 1.37 mm for LGEO and MF-LGEO application of a well-diffusion assay, respectively. The MF-LGEO was more promising in reducing mycotoxin production in simulated fungal growth media due to the changes linked to essential compounds content. The reduction ratio was 54.3% and 74.57% for total aflatoxins (AFs) and ochratoxin A (OCA) contents, respectively. These results reflect the microfluidizing improvement impact regarding the LGEO antibacterial, antifungal and anti-mycotoxigenic properties.

Characterization of the Sterol 24-C-Methyltransferase Genes Reveals a Network of Alternative Sterol Biosynthetic Pathways in Mucor lusitanicus

Certain members of the order Mucorales can cause a life-threatening, often-fatal systemic infection called mucormycosis. Mucormycosis has a high mortality rate, which can reach 96 to 100% depending on the underlying condition of the patient. Mucorales species are intrinsically resistant to most antifungal agents, such as most of the azoles, which makes mucormycosis treatment challenging. The main target of azoles is the lanosterol 14α-demethylase (Erg11), which is responsible for an essential step in the biosynthesis of ergosterol, the main sterol component of the fungal membrane. Mutations in the erg11 gene can be associated with azole resistance; however, resistance can also be mediated by loss of function or mutation of other ergosterol biosynthetic enzymes, such as the sterol 24-C-methyltransferase (Erg6). The genome of Mucor lusitanicus encodes three putative erg6 genes (i.e., erg6a, erg6b, and erg6c). In this study, the role of erg6 genes in azole resistance of Mucor was analyzed by generating and analyzing knockout mutants constructed using the CRISPR-Cas9 technique. Susceptibility testing of the mutants suggested that one of the three genes, erg6b, plays a crucial role in the azole resistance of Mucor. The sterol composition of erg6b knockout mutants was significantly altered compared to that of the original strain, and it revealed the presence of at least four alternative sterol biosynthesis pathways leading to formation of ergosterol and other alternative, nontoxic sterol products. Dynamic operation of these pathways and the switching of biosynthesis from one to the other in response to azole treatment could significantly contribute to avoiding the effects of azoles by these fungi. IMPORTANCE The fungal membrane contains ergosterol instead of cholesterol, which offers a specific point of attack for the defense against pathogenic fungi. Indeed, most antifungal agents target ergosterol or its biosynthesis. Mucormycoses-causing fungi are resistant to most antifungal agents, including most of the azoles. For this reason, the drugs of choice to treat such infections are limited. The exploration of ergosterol biosynthesis is therefore of fundamental importance to understand the azole resistance of mucormycosis-causing fungi and to develop possible new control strategies. Characterization of sterol 24-C-methyltransferase demonstrated its role in the azole resistance and virulence of M. lusitanicus. Moreover, our experiments suggest that there are at least four alternative pathways for the biosynthesis of sterols in Mucor. Switching between pathways may contribute to the maintenance of azole resistance.

A Perspective on Missing Aspects in Ongoing Purification Research towards Melissa officinalis

Melissa officinalis L. is a medicinal plant used worldwide for ethno-medical purposes. Today, it is grown everywhere; while it is known to originate from Southern Europe, it is now found around the world, from North America to New Zealand. The biological properties of this medicinal plant are mainly related to its high content of phytochemical (bioactive) compounds, such as flavonoids, polyphenolic compounds, aldehydes, glycosides and terpenes, among many other groups of substances. Among the main biological activities associated with this plant are antimicrobial activity (against fungi and bacteria), and antispasmodic, antioxidant and insomnia properties. Today, this plant is still used by society (as a natural medicine) to alleviate many other illnesses and symptoms. Therefore, in this perspective, we provide an update on the phytochemical profiling analysis of this plant, as well as the relationships of specific biological and pharmacological effects of specific phytochemicals. Currently, among the organic solvents, ethanol reveals the highest effectiveness for the solvent extraction of precious components (mainly rosmarinic acid). Additionally, our attention is devoted to current developments in the extraction and fractionation of the phytochemicals of M. officinalis, highlighting the ongoing progress of the main strategies that the research community has employed. Finally, after analyzing the literature, we suggest potential perspectives in the field of sustainable extraction and purification of the phytochemical present in the plant. For instance, some research gaps concern the application of cavitation-assisted extraction processes, which can effectively enhance mass transfer while reducing the particle size of the extracted material in situ. Meanwhile, membrane-assisted processes could be useful in the fractionation and purification of obtained extracts. On the other hand, further studies should include the application of ionic liquids and deep eutectic solvents (DES), including DESs of natural origin (NADES) and hydrophobic DESs (hDES), as extraction or fractionating solvents, along with new possibilities for effective extraction related to DESs formed in situ, assisted by mechanical mixing (mechanochemistry-based approach).

A comprehensive approach to chitosan-gelatine edible coating with β-cyclodextrin/lemongrass essential oil inclusion complex - Characterization and food application

Biopolymer-based films present an ideal matrix for the incorporation of active substances such as antimicrobial agents, giving active packaging a framework of green chemistry and a step forward in food packaging technology. The chitosan-gelatine active coating has been prepared using lemongrass oil as an antimicrobial compound applying a different approach. Instead of surfactants, to achieve compatibilization of compounds, β-cyclodextrin was used to encapsulate lemongrass oil. The antimicrobial effect was assessed using the dip-coating method on freshly harvested cherry tomatoes artificially contaminated by Penicillium aurantiogriseum during 20 days of cold storage. According to the evaluation of the antimicrobial effect of coating formulation on cherry tomato samples, which was mathematically assessed by predictive kinetic models and digital imaging, the applied coating formulation was found to be very effective since the development of fungal contamination for active-coated samples was observed for 20 days.

Screening of Antifungal Activity of Essential Oils in Controlling Biocontamination of Historical Papers in Archives

The main challenge in controlling the microbiological contamination of historical paper is finding an adequate method that includes the use of cost-effective, harmless, and non-toxic biocides whose effectiveness is maintained over time and without adverse effects on cultural heritage and human health. Therefore, this study demonstrated the possibility of using a non-invasive method of historical paper conservation based on plant essential oils (EOs) application. Evaluation of antimicrobial effects of different EOs (lemongrass, oregano, rosemary, peppermint, and eucalyptus) was conducted against Cladosporium cladosporoides, Aspergillus fumigatus, and Penicillium chrysogenum, which are commonly found on archive papers. Using a mixture of oregano, lemongrass and peppermint in ratio 1:1:1, the lower minimal inhibition concentration (0.78%) and better efficiency during a vapour test at the highest tested distance (5.5 cm) compared with individual EOs was proven. At the final step, this EOs mixture was used in the in situ conservation of historical paper samples obtained from the Archives of Vojvodina. According to the SEM imaging, the applied EOs mixture demonstrates complete efficiency in the inhibition of fungi colonization of archive papers, since fungal growth was not observed on samples, unlike the control samples.

Phytochemical Screening, Antifungal, and Anticancer Activities of Medicinal Plants Thymelaea Hirsuta, Urginea Maritima, and Plantago Albicans

Ethyl acetate, ethanol, and acetone extracts of the medicinal plants Thymelaea hirsuta L., Urginea maritima L., and Plantago albicans L. (aerial parts) were evaluated for their phytochemical compositions, antimycotic activity against dermatophytes, and antiproliferative activity against different human cancer cell lines. Among them, the ethanolic extracts showed the highest phytochemical contents along with hyperactivities and were then selected for gas chromatography-mass spectrometry and Fourier-transform infrared spectroscopy analysis. The Fourier-transform infrared spectroscopy analysis confirmed the presence of different characteristic peak values with various functional chemical groups of the active components. However, U. maritima extracts through Fourier-transform infrared spectroscopy analysis showed distinctive peaks related to phenolic, amines, amides, aromatic, alkanes, alkyne, cyclopentanone, conjugated aldehyde, nitro, methoxy, uronic acids, aromatic esters, tertiary alcohol or ester, secondary and primary alcohols, aliphatic ether, sulfoxide, vinylidene, and halo compounds. Many bioactive main compounds with reported biological activities were detected by GC/MS (%) in the ethanolic extract of T. hirsuta, U. maritima, and P. albicans. All studied dermatophytes included a diverse set of virulence factors, including phospholipase, protease, keratinase, hemolysis, and melanoid production, all of which play vital roles in dermatophytic infection. Ethanolic extract of P. albicans inhibited the growth of Trichophyton soudanense totally and Trichophyton erinacei in addition to all Microsporum species. In contrast, the ethanolic extract of Trichophyton hirsuta at concentrations of 25 g/mL totally prevented the growth of all Trichophyton species. EtOH extract of U. maritima completely prevented the growth (100% inhibition) of all dermatophytic strains under study at the lowest concentration of 12.5 μg/mL. Scanning electron microscope analysis revealed considerable morphological modifications and structural alterations in dermatophyte species exposed to ethanolic extract of these plants. The viability of HCT-116, HepG-2, MCF-7, and HeLa cell lines was reduced after treatment with the ethanolic extracts of T. hirsuta, U. maritima, and P. albicans individually with IC50 values (10.0, 9.97, 48.5, and 56.24 μg/mL), (26.98, 25.0, 17.11, and 9.52 μg/mL), and (9.32, 7.46, 12.50, and 16.32 μg/mL), respectively. Our work revealed the significance of these traditional ethnomedical plants as potent sources for biologically active pharmaceuticals with potential applicability for the treatment of fungal and cancer diseases.

Green natural nail polish modified with essential oils to treat onychomycosis

BACKGROUND

Onychomycosis (OM) accounts for about 50% of nail disorders in industrialised countries. Essential oils (EOs), aromatic natural compounds, are known for their antimicrobial activity.

OBJECTIVE

The aim of this work was to evaluate the antifungal efficacy of seven EOs and a commercial MIX against 10 dermatophytes responsible for OM to select the most effective ones to be included in a preventive or curative formulation based on a green natural nail polish (GNNP).

METHODS

Micro-broth dilution tests in line with EUCAST guidelines and olfactory satisfaction test were performed to select the best natural compounds previously analysed by SPME coupled with GC-MS. The same method was used to evaluate the release over time of the active compounds present in the two modified-GNNPs made by adding the best natural compound selected (the C. citratus EO) and the MIX. Furthermore, to evaluate the preventive and curative activity of modified-GNNPs, ex vivo experiments on healthy or colonised nails were performed.

RESULTS AND CONCLUSIONS

Data showed that MIX-modified-GNNP had preventive activity as it inhibits the fungal growth by releasing its active ingredients for 7 days, while the OE-modified GNNP acts as a natural drug showing cytocidal activity on nails colonised by dermatophytes, but it requires two weekly applications.

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.

Melissa officinalis: Composition, Pharmacological Effects and Derived Release Systems-A Review

Melissa officinalis is a medicinal plant rich in biologically active compounds which is used worldwide for its therapeutic effects. Chemical studies on its composition have shown that it contains mainly flavonoids, terpenoids, phenolic acids, tannins, and essential oil. The main active constituents of Melissa officinalis are volatile compounds (geranial, neral, citronellal and geraniol), triterpenes (ursolic acid and oleanolic acid), phenolic acids (rosmarinic acid, caffeic acid and chlorogenic acid), and flavonoids (quercetin, rhamnocitrin, and luteolin). According to the biological studies, the essential oil and extracts of Melissa officinalis have active compounds that determine many pharmacological effects with potential medical uses. A new field of research has led to the development of controlled release systems with active substances from plants. Therefore, the essential oil or extract of Melissa officinalis has become a major target to be incorporated into various controlled release systems which allow a sustained delivery.