Isolation of Antidiabetic Principle from Bougainvillea spectabilis Willd (Nyctaginaceae) Stem Bark

Purpose: To isolate and identify the constituents of Bougainvillea spectabilis Willd (Nyctaginaceae) stem bark. Methods: The methanol extract of Bougainvillea spectabilis stem bark powder was suspended in water and extracted with dichloromethane (CH2Cl2), ethyl acetate (EtOAc), and butanol (BuOH) successively. The ethyl acetate fraction was loaded in a column packed with silica gel and eluted with a gradient of chloroform (CHCl3): methanol (MeOH), and water yielded five fractions (A - E). Chemical constituents were isolated by repeated column chromatography of these fractions. Results: Column chromatography of fractions B and C afforded four compounds identified as pinitol, β-sitosterol, quercetin and quercetin-3-O-α-L-rhamnopyranoside. For the first time, pinitol, β-sitosterol, quercetin and quercetin-3-O-α-L-rhamnopyranoside were isolated from the stem bark of B. spectabilis Willd. Conclusion: An antidiabetic principle, pinitol, was successfully isolated from the stem bark of B. spectabilis Willd.