Abstract
The emergence of fungal resistance to commercial drugs has been a major problem for the WHO. In this context, research with natural products is promising in the discovery of new active substances. Thus, this work evaluated the antifungal effect of a medicinal plant (i.e., Mesosphaerum suaveolens) against strains of the genus Candida, tested the combined effect with the drug fluconazole, and, finally, determined the phenolic constituents present in the species. Initially, aqueous extracts of leaves (AELMs) and aerial parts (AEAPMs) of the species were prepared. For microbiological assays, the minimum fungicidal concentration was determined by broth microdilution, and the combined effect of fluconazole extracts were verified by sub-inhibitory microdilution concentrations (CFM/8) followed by spectrophotometric readings which were used to determine the IC50. HPLC detected the presence of flavonoids and phenolic acids, detecting eight compounds present in the samples of which caffeic acid and quercetin were major components. The AELMs modulated fluconazole activity since it decreased fluconazole’s IC50 from 7.8 µg/mL to an IC50 of 4.7 µg/mL (CA LM 77) and from 28.8 µg/mL to 18.26 µg/mL (CA INCQS 40006) for the C. albicans strains. The AEAPMs were able to potentiate the effect of fluconazole more effectively than the AELMs. Such an effect was significant for the 16 µg/mL concentration for CA LM 77 and 32 µg/mL for CA INCQS 40006. The AEAPMs as well as the AELMs presented clinically relevant activities for C. tropicalis strains. For the C. tropicalis LM 23 strain, the AEPMs obtained an IC50 of 25 µg/mL and the AELMs an IC50 of 359.9 µg/mL.
Highlights
Candida yeasts reside in humans as commensals and are part of the normal microbiota in healthy subjects
IC50 antibiotic of 64.5 μg/mL, parameter by more than 100% (Figure 5b)
Mbatchou et al [39], evaluating the action of the aqueous extract of the M. suaveolens aerial parts, showed that the species presents antifungal action by halo inhibition against C. albicans strains when compared with the antibiotic griseofulvin
Summary
Candida yeasts reside in humans as commensals and are part of the normal microbiota in healthy subjects. When an imbalance between the microbiota and the host’s immune system occurs, these fungi can become pathogenic, causing candidiasis and presenting different clinical forms depending on the type of infection and the degree of immunosuppression. Mucosal, systemic, and allergic skin reactions are the common clinical presentation [1,2,3,4]. Infections caused by Candida yeasts are related to a high morbidity and mortality rate in which these species are caused by superficial and systemic candidiasis, and the latter represents a serious problem for health systems and patients [5]. Lumpy, odorless, and non-purulent vaginal discharge [7]; other symptoms include itching, burning, redness, odorless discharge, injury, pain, edema, erythema, interdigital erosion, folliculitis, exudate, purulence, onychomycosis, and paronychia [8,9,10,11]
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