Triterpenoids and triterpenoid saponins from leaves of Bougainvillea spectabilis

Abstract

The genus Bougainvillea with about 18 species belonging to the family Nyctaginaceae is a widespread group throughout the world. Bougainvillea spectabilis was traditionally used in Indian and Mexico for treatment hepatitis, cough, and diarrhea. Ethanolic and methanolic extracts from leaves and stems of this plant showed anti–inflammatory activity. Some pharmacological studies have focused on antidiabetic activity of this species. Some extracts from leaves, bark exhibited hypoglycemic, -glucosidase, and amylase inhibitor activities. Phytochemical investigations have reported the isolation of flavonoids, triterpenoid saponins, and steroids. Leaves of B. spectabilis were collected and extracted with ethanol at room temperature by maceration method to obtain the ethanolic extract. By partitioning with n–hexane, ethyl acetate successively yields n–hexane and ethyl acetate extracts. Column chromatographies on normal phase silica gel, reversed–phase RP–18, and Sephadex LH–20 were used to isolate compounds 1–6. Their chemical structures were elucidated by HRESIMS, 1D, and 2D–NMR and compared with those reported in the literature, including lupeol (1), (20S)–3β–acetoxylupan–29–oic acid (2), maslinic acid (3), 3–O––D–(6'–O–methyl)glucuronopyranosyloleanolic acid (4), 3–O––D–(6'–O–ethyl)glucuronopyranosyloleanolic acid (5), and 3–O––D–glucopyranosyl–(14)––D–(6'–O–methyl)glucuronopyranosyloleanolic acid (6). All these compounds were isolated for the first time from the genus Bougainvillea.