To investigate the active components against diabetes, the present study isolated eight hydrolyzable tannins from the ethyl acetate extract of Punica granatum flowers by MCI, reversed-phase chromatography(ODS), Sephadex LH-20 chromatography, and HPLC, and the structures were elucidated as 1-O-galloyl-6-O-feruloyl-β-D-glucose(1), 1,2,3,4,6-penta-O-gally-β-D-glucopyranose(2), punicafolin(3), corilagin(4), telimagrandin Ⅰ(5), 1,2-di-O-galloyl-4,6-O-(S)-hexahydroxydiphenoyl-β-D-glucose(6), heterophylliin A(7), and eugeniin(8) on the basis of spectral data and literature records. Among them, compound 1 is a new compound, and compounds 5-8 were isolated from this species for the first time. All isolated compounds were tested for inhibitory activities against α-glucosidase and DPP-Ⅳ. The results indicated that compounds 2, 3, and 5-8 showed significant inhibitory activities against α-glucosidase, while compounds 1 and 4 exhibited moderate inhibitory activities. Compounds 5, 7, and 8 showed moderate inhibitory effects on DPP-Ⅳ. In addition, the type of enzyme inhibition of compound 5 was determined.
Keywords: DPP-Ⅳ; Punica granatum flowers; anti-diabetes; bioactive components; α-glucosidase.