Antifungal activity of 3,3'-dimethoxycurcumin (DMC) against dermatophytes and Candida species

Dermatomycosis is an infection with global impacts caused especially by dermatophytes and Candida species. Current antifungal therapies involve drugs that face fungal resistance barriers. This clinical context emphasizes the need to discover new antifungal agents. Herein, the antifungal potential of 10 curcumin analogs was evaluated against four Candida and four dermatophyte species. The most active compound, 3,3'-dimethoxycurcumin, exhibited minimum inhibitory concentration values ranging from 1.9‒62.5 to 15.6‒62.5 µg ml-1 against dermatophytes and Candida species, respectively. According to the checkerboard method, the association between DMC and terbinafine demonstrated a synergistic effect against Trichophyton mentagrophytes and Epidermophyton floccosum. Ergosterol binding test indicated DMC forms a complex with ergosterol of Candida albicans, C. krusei, and C. tropicalis. However, results from the sorbitol protection assay indicated that DMC had no effect on the cell walls of Candida species. The in vivo toxicity, using Galleria mellonella larvae, indicated no toxic effect of DMC. Altogether, curcumin analog DMC was a promising antifungal agent with a promising ability to act against Candida and dermatophyte species.

Antimicrobial Activity of Honey against Oral Microorganisms: Current Reality, Methodological Challenges and Solutions

Honey has been shown to have antimicrobial activity against different microorganisms, but its effects on oral biofilms are largely unknown. In this review, we analyzed the currently available literature on the antimicrobial activity of honey against oral biofilms in order to determine its potential as a functional food in the treatment and/or prevention of oral diseases. Here, we compare studies reporting on the antimicrobial activity of honey against systemic and oral bacteria, discuss methodological strategies, and point out current gaps in the literature. To date, there are no consistent studies supporting the use of honey as a therapy for oral diseases of bacterial origin, but current evidence in the field is promising. The lack of studies examining the antibiofilm activity of honey against oral microorganisms reveals a need for additional research to better define aspects such as chemical composition, the mechanism(s) of action, and antimicrobial action.

A Study on the Anti-NF-кB, Anti-Candida, and Antioxidant Activities of Two Natural Plant Hormones: Gibberellin A4 and A7

Introduction: Gibberellins (GA) are terpenoids that serve as important plant hormones by acting as growth and response modulators against injuries and parasitism. In this study, we investigated the in vitro anti-NF-κB, anti-Candida, and antioxidant activity of gibberellin A4 (GA4) and A7 (GA7) compounds, and further determined their toxicity in vivo. Methods: GA4 and GA7 in vitro toxicity was determined by MTT method, and nontoxic concentrations were then tested to evaluate the GA4 and GA7 anti-NF-κB activity in LPS-activated RAW-luc macrophage cell culture (luminescence assay). GA4 in silico anti-NF-κB activity was evaluated by molecular docking with the software “AutoDock Vina”, “MGLTools”, “Pymol”, and “LigPlot+”, based on data obtained from “The Uniprot database”, “Protein Data Bank”, and “PubChem database”. The GA4 and GA7 in vitro anti-Candida effects against Candida albicans (MYA 2876) were determined (MIC and MFC). GA7 was also evaluated regarding the viability of C. albicans preformed biofilm (microplate assay). In vitro antioxidant activity of GA4 and GA7 was evaluated against peroxyl radicals, superoxide anions, hypochlorous acid, and reactive nitrogen species. GA4 and GA7 in vivo toxicity was determined on the invertebrate Galleria mellonella larvae model. Results: Our data show that GA4 at 30 µM is nontoxic and capable of reducing 32% of the NF-κB activation on RAW-luc macrophages in vitro. In vitro results were confirmed via molecular docking assay (in silico), since GA4 presented binding affinity to NF-κB p65 and p50 subunits. GA7 did not present anti-NF-κB effects, but exhibited anti-Candida activity with low MIC (94 mM) and MFC (188 mM) values. GA7 also presented antibiofilm properties at 940 mM concentration. GA4 did not present anti-Candida effects. Moreover, GA4 and GA7 showed antioxidant activity against peroxyl radicals, but did not show scavenging activity against the other tested radicals. Both compounds did not affect the survival of G. mellonella larvae, even at extremely high doses (10 g/Kg). Conclusion: Our study provides preclinical evidence indicating that GA4 and GA7 have a favorable low toxicity profile. The study also points to GA4 and GA7 interference with the NF-κB via, anti-Candida activity, and a peroxyl radical scavenger, which we argue are relevant biological effects.

Terpinen-4-ol and nystatin co-loaded precursor of liquid crystalline system for topical treatment of oral candidiasis

This study was performed to develop a liquid crystalline system (LCS) incorporated with terpinen-4-ol and nystatin to evaluate its antifungal, antibiofilm, and synergistic/modulatory activity against Candida albicans. The LCS was composed of a dispersion containing 40% propoxylated and ethoxylated cetyl alcohol, 40% oleic acid, and 0.5% chitosan dispersion. According to analysis by polarized light microscopy, rheology, and mucoadhesion studies, the incorporation of 100% artificial saliva increased the pseudoplasticity, consistency index, viscosity, and mucoadhesion of the formulation. The minimum inhibitory concentration, minimum fungicidal concentration, and rate of biofilm development were used to evaluate antifungal activity; the LCS containing terpinen-4-ol and nystatin effectively inhibited C. albicans growth at a lower concentration, displaying a synergistic action. Therefore, LCS incorporated with terpinen-4-ol and nystatin is a promising alternative for preventing and treating infections and shows potential for the development of therapeutic strategies against candidiasis.

Antibiofilm efficacy of tea tree oil and of its main component terpinen-4-ol against Candida albicans

Candida infection is an important cause of morbidity and mortality in immunocompromised patients. The increase in its incidence has been associated with resistance to antimicrobial therapy and biofilm formation. The aim of this study was to evaluate the efficacy of tea tree oil (TTO) and its main component - terpinen-4-ol - against resistant Candida albicans strains (genotypes A and B) identified by molecular typing and against C. albicans ATCC 90028 and SC 5314 reference strains in planktonic and biofilm cultures. The minimum inhibitory concentration, minimum fungicidal concentration, and rate of biofilm development were used to evaluate antifungal activity. Results were obtained from analysis of the biofilm using the cell proliferation assay 2,3-Bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) and confocal laser scanning microscopy (CLSM). Terpinen-4-ol and TTO inhibited C. albicans growth. CLSM confirmed that 17.92 mg/mL of TTO and 8.86 mg/mL of terpinen-4-ol applied for 60 s (rinse simulation) interfered with biofilm formation. Hence, this in vitro study revealed that natural substances such as TTO and terpinen-4-ol present promising results for the treatment of oral candidiasis.

Anti-inflammatory and anti-Candida Effects of Brazilian Organic Propolis, a Promising Source of Bioactive Molecules and Functional Food

Brazilian organic propolis (BOP) is an unexplored Brazilian propolis that is produced organically and certified according to international legislation. Our results showed that BOP has strong anti-inflammatory effects and acts by reducing nuclear factor κB activation, tumor necrosis factor α release, and neutrophil migration. In addition, BOP6 exhibited antifungal activity on planktonic and biofilm cultures of Candida albicans, Candida glabrata, Candida tropicalis, Candida krusei, and Candida parapsisolis and reduced in vitro yeast cell adhesion to human keratinocytes at sub-inhibitory concentrations. BOP demonstrated significantly low toxicity in Galleria melonella larvae at antifungal doses. Lastly, a chemical analysis revealed the presence of caffeoyltartaric acid, 3,4-dicaffeoylquinic acid, quercetin, and gibberellins A7, A9, and A20, which may be responsible for the biological properties observed. Thus, our data indicate that BOP is a promising source of anti-inflammatory and antifungal molecules that may be used as a functional food.

Anadenanthera Colubrina vell Brenan: anti-Candida and antibiofilm activities, toxicity and therapeutical action

We evaluated the antifungal and antibiofilm potential of the hydroalcoholic extract of bark from Anadenanthera colubrina (vell.) Brenan, known as Angico, against Candida spp. Antifungal activity was evaluated using the microdilution technique through the Minimum Inhibitory and Fungicide Concentrations (MIC and MFC). The antibiofilm potential was tested in mature biofilms formed by Candida species and analyzed through the counting of CFU/mL and scanning electron micrograph (SEM). In vivo toxicity and therapeutic action was evaluated in the Galleria mellonella model. The treatment with the extract, in low doses, was able to reduce the growth of planktonic cells of Candida species. MIC values range between 19.5 and 39 µg/mL and MFC values range between 79 and 625 µg/mL. In addition was able to reduce the number of CFU/mL in biofilms and to cause structural alteration and cellular destruction, observed via SEM. A. colubrina showed low toxicity in the in vivo assay, having not affected the viability of the larvae at doses below 100mg/kg and high potential in the treatment of C. albicans infection. Considering its high antifungal potential, its low toxicity and potential to treatment of infections in in vivo model, A. colubrina extract is a strong candidate for development of a new agent for the treatment of oral candidiasis.

Interactions between Terpinen-4-ol and Nystatin on biofilm of Candida albicans and Candida tropicalis

The aim of this study was to evaluate the antifungal activity of Terpinen-4-ol associated with nystatin, on single and mixed species biofilms formed by Candida albicans and Candida tropicalis, as well as the effect of terpinen-4-ol on adhesion in oral cells and the enzymatic activity. The minimum inhibitory concentrations and minimum fungicide concentrations of terpinen-4-ol and nystatin on Candida albicans and Candida tropicalis were determined using the microdilution broth method, along with their synergistic activity ("checkerboard" method). Single and mixed species biofilms were prepared using the static microtiter plate model and quantified by colony forming units (CFU/mL). The effect of Terpinen-4-ol in adhesion of Candida albicans and Candida tropicalis in coculture with oral keratinocytes (NOK Si) was evaluated, as well as the enzymatic activity by measuring the size of the precipitation zone, after the growth agar to phospholipase, protease and hemolysin. Terpinen-4-ol (4.53 mg mL-1) and nystatin (0.008 mg mL-1) were able to inhibit biofilms growth, and a synergistic antifungal effect was showed with the drug association, reducing the inhibitory concentration of nystatin up to 8 times in single biofilm of Candida albicans, and 2 times in mixed species biofilm. A small decrease in the adhesion of Candida tropicalis in NOK Si cells was showed after treatment with terpinen-4-ol, and nystatin had a greater effect for both species. For enzymatic activity, the drugs showed no action. The effect potentiated by the combination of terpinen-4-ol and nystatin and the reduction of adhesion provide evidence of its potential as an anti-fungal agent.

In silico approaches for screening molecular targets in Candida albicans: A proteomic insight into drug discovery and development

Candida species are opportunistic pathogens which can cause conditions ranging from simple mucocutaneous infections to fungemia and death in immunosuppressed and hospitalized patients. Candida albicans is considered to be the species mostly associated with fungal infections in humans and, therefore, the mostly studied yeast. This microorganism has survival and virulence factors which, allied to a decreased host immunity response, make infection more difficult to control. Today, the current limited antifungal arsenal and a dramatic increase in fungal resistance have driven the need for the synthesis of drugs with novel mechanisms of action. However, the development of a new drug from discovery to marketing takes a long time and is highly costly. The objective of this review is to show that with advances in biotechnology and biofinformatics, in silico tools such as molecular docking can optimize such a timeline and reduce costs, while contributing to the design and development of targeted drugs. Here we highlight the most promising protein targets in Candida albicans for the development of drugs with new mechanisms of action.

Anti dermatophytic therapy--prospects for the discovery of new drugs from natural products

Millions of people and animals suffer from superficial infections caused by a group of highly specialized filamentous fungi, the dermatophytes, which only infect keratinized structures. With the appearance of AIDS, the incidence of dermatophytosis has increased. Current drug therapy used for these infections is often toxic, long-term, and expensive and has limited effectiveness; therefore, the discovery of new anti dermatophytic compounds is a necessity. Natural products have been the most productive source for new drug development. This paper provides a brief review of the current literature regarding the presence of dermatophytes in immunocompromised patients, drug resistance to conventional treatments and new anti dermatophytic treatments.