The objective of this study is to investigate the chemical composition of the leaves of Terminalia myriocarpa and to evaluate their α-glucosidase inhibitory activity aiming to be used as a safe antidiabetic. Consequently, 10 compounds were isolated using column and preparative thin-layer chromatographic techniques and identified as alphitolic acid, isovitexin, flavogallonic acid, nigaichigoside F1, quercetin, quadranoside IV, rosamultin, 19α-hydroxyasiatic acid, asiatic acid, and arjunic acid. Structure elucidation was based on chemical (acid hydrolysis) and spectroscopic (UV, 1H, and 13C-NMR) analyses and findings were confirmed through comparison with published data. The α-glucosidase inhibitory activity of the methanol extract fractions and compounds isolated therefrom was evaluated in-vitro alongside that of acarbose (positive control). Results revealed that quercetin and flavogallonic acid were significantly active with half-maximal inhibitory concentrations (IC50) equal to 7.5 ± 0.09 and 21.0 ± 1.4 μM, respectively. Furthermore, the interaction of flavogallonic acid with α-glucosidase enzyme was verified by docking experiment. Accordingly, quercetin and flavogallonic acid could be considered safer natural alternatives to the currently available α-glucosidase inhibitors.
Key words: Terminalia myriocarpa, triterpenoids, tannins, flavonoids, α-glucosidase inhibitory activity, docking study.
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