In this study, nine triterpene glycosides including seven previously undescribed compounds (1-7), were isolated from leaves of Cryptolepis buchananii R.Br. ex Roem. and Schult. using various chromatographic methods. The chemical structures of the compounds were elucidated to be 3-O-β-D-glucopyranosyl-(1 → 6)-β-D-glucopyranosyluncargenin C 28-O-α-L-rhamnopyranosyl-(1 → 2)-β-D-glucopyranosyl ester (1), 3-O-β-D-glucopyranosyl-(1 → 2)-β-D-glucopyranosyluncargenin C 28-O-α-L-rhamnopyranosyl-(1 → 2)-β-D-glucopyranosyl ester (2), 3-O-β-D-glucopyranosyl-(1 → 2)-β-D-glucopyranosyluncargenin C 28-O-β-D-glucopyranosyl-(1 → 4)-α-L-rhamnopyranosyl-(1 → 2)-β-D-glucopyranosyl ester (3), 3-O-β-D-glucopyranosyl-(1 → 2)-β-D-glucopyranosylhederagenin 28-O-α-L-rhamnopyranosyl-(1 → 2)-β-D-glucopyranosyl ester (4), 3-O-β-D-glucopyranosylarjunolic acid 28-O-α-L-rhamnopyranosyl-(1 → 2)-β-D-glucopyranosyl ester (5), 3-O-β-D-glucopyranosyl-(1 → 2)-β- D-glucopyranosyl-6β,23-dihydroxyursolic acid 28-O-α-L-rhamnopyranosyl-(1 → 2)-β-D-glucopyranosyl ester (6), 3-O-β-D-glucopyranosyl-6β,23-dihydroxyursolic acid 28-O-α-L-rhamnopyranosyl-(1 → 2)-β-D-glucopyranosyl ester (7), asiatic acid 28-O-α-L-rhamnopyranosyl-(1 → 2)-β-D-glucopyranosyl ester (8), and 3-O-β-D-glucopyranosylasiatic acid 28-O-α-L-rhamnopyranosyl-(1 → 2)-β-D-glucopyranosyl ester (9), through infrared, high-resolution electrospray ionization mass spectrometry, one- and two-dimensional nuclear magnetic resonance spectral analyses. The isolates inhibited nitric oxide production in lipopolysaccharide-activated RAW 264.7 cells, with half-maximal inhibitory concentration (IC50) values of 18.8-58.5 µM, compared to the positive control compound, dexamethasone, which exhibited an IC50 of 14.1 µM.
Keywords: Cryptolepis buchananii; Asclepiadaceae; Cryptobuchanoside; Nitric oxide inhibitor; Triterpene glycoside.
© 2024. The Author(s) under exclusive licence to The Japanese Society of Pharmacognosy.