Cryptobuchanosides A–G: seven previously undescribed triterpene glycosides from Cryptolepis buchananii R.Br. ex Roem. and Schult. with nitric oxide production inhibition activity

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-6 β ,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 (IC 50 ) values of 18.8–58.5 µM, compared to the positive control compound, dexamethasone, which exhibited an IC 50 of 14.1 µM. Graphical abstract