Abstract
Coccoloba cowellii Britton (Polygonaceae, order Caryophyllales) is an endemic and critically endangered plant species that only grows in the municipality of Camagüey, a province of Cuba. A preliminary investigation of its total methanolic extract led to the discovery of promising antifungal activity. In this study, a bioassay-guided fractionation allowed the isolation of quercetin and four methoxyflavonoids: 3-O-methylquercetin, myricetin 3,3′,4′-trimethyl ether, 6-methoxymyricetin 3,4′-dimethyl ether, and 6-methoxymyricetin 3,3′,4′-trimethyl ether. The leaf extract, fractions, and compounds were tested against various fungi and showed strong in vitro antifungal activity against Cryptococcus neoformans and various Candida spp. with no cytotoxicity (CC50 > 64.0 µg/mL) on MRC-5 SV2 cells, determined by a resazurin assay. A Candida albicans SC5314 antibiofilm assay indicated that the antifungal activity of C. cowellii extracts and constituents is mainly targeted to planktonic cells. The total methanolic extract showed higher and broader activity compared with the fractions and mixture of compounds.
Highlights
Given the promising results obtained for the total extract [8], the antifungal activity was employed as a guide for the fractionation and isolation of active compounds
Antifungal activity against a secondary panel of fungi (Candida spp. and Aspergillus fumigatus) was only determined when fractions were active against the first panel of fungi (C. neoformans and C. albicans)
The bioassay-guided fractionation performed on C. cowellii leaves led to the isolation and tentative identification of at least 21 new compounds in this species; the isolation of the compounds responsible for high antifungal activity shown by the total extract was not successful
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Fungal infections represent a major health problem, with mortality rates comparable to those of tuberculosis or malaria, estimated at 1.5 million individuals per year [1]. The growing number of immunocompromised individuals due to the increase of organ transplantation, the prevalence of cancer and AIDS patients, and the ageing population have all contributed to this situation [2]. The predominant etiological agents of systemic fungal infections are species of Candida, Aspergillus, and Cryptococcus, representing over
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