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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. Full article

Coccoloba cowellii Britton (Polygonaceae) is an endemic and critically endangered plant that only grows in Camagüey, a province of Cuba. In this study, a total of 13 compounds were identified in a methanolic leaf extract, employing a dereplication of the UHPLC-HRMS data by means of feature-based molecular networking (FBMN) analysis in the Global Natural Products Social Molecular Network (GNPS), together with the interpretation of the MS/MS data and comparison with the literature. The major constituents were glucuronides and glycosides of myricetin and quercetin, as well as epichatechin-3-O-gallate, catechin, epicatechin and gallic acid, all of them being reported for the first time in C. cowellii leaves. The leaf extract was also tested against various microorganisms, and it showed a strong antifungal effect against Candida albicans ATCC B59630 (azole-resistant) (IC₅₀ 2.1 µg/mL) and Cryptococcus neoformans ATCC B66663 (IC₅₀ 4.1 µg/mL) with no cytotoxicity (CC₅₀ > 64.0 µg/mL) on MRC-5 SV2 cells, determined by the resazurin assay. Additionally, the extract strongly inhibited COX-1 and COX-2 enzyme activity using a cell-free experiment in a dose-dependent manner, being significantly more active on COX-1 (IC₅₀ 4.9 µg/mL) than on COX-2 (IC₅₀ 10.4 µg/mL). The constituents identified as well as the pharmacological activities measured highlight the potential of C. cowellii leaves, increasing the interest in the implementation of conservation strategies for this species. Full article

The genus Coccoloba (Polygonaceae) comprises approximately 150 species of flowering plants. It is native to the tropical and subtropical regions of America, in South America, the Caribbean and Central America. A wide variety of biological activities has been studied for Coccoloba species due to great diversity of metabolites (mainly flavonoids, tannins, terpenoids and volatile oils) and popular uses reported for different ailments like fever, diarrhea, menstrual disturbance, uterine hemorrhages, hemorrhoids and gonorrhea. The methanolic extract of the leaves of C. cowellii, endemic of the Camagüey province of Cuba and critically endangered, was subjected to structural analysis. The obtained HPLC-DAD-QTOF-ESI-MS data were analyzed employing the MS-DIAL software. A dereplication of the ESI-MS data was realized using the feature-based molecular networking (FBMN) analysis method in the Global Natural Products Social Molecular Networking (GNPS) infrastructure, leading to 12 compound hits against the GNPS database. A total of 13 compounds were tentatively identified by means of MS data, together with the interpretation of the observed MS/MS spectra in comparison with those found in the literature. The major compounds were myricetin and quercetin glucuronides and glycosides and epichatechin-3-O-gallate. The total extract presented an antifungal effect against Candida albicans ATCC B59630 (azole-resistant) (IC50 = 2.13 µg/mL) and was not cytotoxic (IC50 > 64.00 µg/mL) in the resazurin MRC-5 SV2 cell viability assay employed. This is the first report related to chemical composition of C. cowellii plant. The research is now focused on determining the secondary metabolites responsible for the antifungal activity of the total extract. Full article