Simultaneous isolation of gallotannins and a related phenolic from Mangifera indica kernels and assessment of their anti-Trichomonas vaginalis activities

ABSTRACT

Therapeutic alternatives are being searched for trichomoniasis as a result of the increased prevalence of metronidazoleresistant infections. Mangifera indica L. (Anacardiaceae) is an importanttree with a long history in medicine. Traditionally, ithas been used as an anti-diarrheal and anti-diabetic, and recently, its gallotannin-rich leaves and stem bark extracts have shownantiparasitic activities against various parasites. Aiming at exploring the anti-Trichomonas vaginalis activity of mango’sgallotannins, an aqueous ethanol extract of fresh kernels of M. indica was phytochemically investigated. Based on a simplegel chromatographic procedure, ethyl gallate (2), a group of five isomeric tetragalloyl-glucoses (3–7), and a pentagalloylglucose (8) were simultaneously isolated from a single fraction by a preparative Reversed-phase-high performance liquidchromatography. The isolates were identified based on spectroscopic analyses and comparison with reported data. Theyshowed structural-dependent inhibitory effects on the growth of T. vaginalis trophozoites in an in vitro investigation.Ethyl gallate and 1,2,4,6-tetra-O-galloyl-β-D-glucose (7) exhibited elevated anti-T. vaginalis activity (IC50 = 1.3, 2.4μg/ml, respectively). This is the first report exploring the potential of gallotannins as trichomonacidal agents.