Isolation and Characterization of an α-Glucosidase Inhibitor from Musa spp. (Baxijiao) Flowers

摘要

The use of α-glucosidase inhibitors is considered to be an effective strategy in the treatment of diabetes. Using a bioassay-guided fractionation technique, five Bacillus stearothermophilus α-glucosidase inhibitors were isolated from the flowers of Musa spp. (Baxijiao). Using NMR spectroscopy analysis they were identified as vanillic acid (>1), ferulic acid (>2), β-sitosterol (>3), daucosterol (>4) and 9-(4′-hydroxyphenyl)-2-methoxyphenalen-1-one (>5). The half maximal inhibitory concentration (IC50) values of compounds >1–>5 were 2004.58, 1258.35, 283.67, 247.35 and 3.86 mg/L, respectively. Compared to a known α-glucosidase inhibitor (acarbose, IC50 = 999.31 mg/L), compounds >3, >4 and >5 showed a strong α-glucosidase inhibitory effect. A Lineweaver-Burk plot indicated that compound >5 is a mixed-competitive inhibitor, while compounds >3 and >4 are competitive inhibitors. The inhibition constants (Ki) of compounds >3, >4 and >5 were 20.09, 2.34 and 4.40 mg/L, respectively. Taken together, these data show that the compounds >3, >4 and >5 are potent α-glucosidase inhibitors.