Phytosterols in banana (Musa spp.) flower inhibit α-glucosidase and α-amylase hydrolysations and glycation reaction

Three phytosterols were isolated from Musa spp. flowers for evaluating their capabilities in inhibiting glucosidase and amylase activities and glycation of protein and sugar. The three phytosterols were identified as beta-sitosterol (PS1), 31-norcyclolaudenone (PS2) and (24R)-4 alpha, 14 alpha, 4-trimethyl-5 alpha-cholesta-8, 25(27)-dien-3 beta-ol (PS3). IC50 values (the concentration of inhibiting 50% of enzyme activity) of PS1, PS2 and PS3 against alpha-glucosidase were 283.67, 11.33 and 43.10 mu g mL(-1), respectively. For inhibition of alpha-amylase, the IC50 values of PS1, PS2 and PS3 were 52.55, 76.25 and 532.02 mu g mL(-1), respectively. PS1 was an uncompetitive inhibitor against beta-amylase with K-m at 5.51 mu g mL(-1), while PS2 and PS3 exhibited a mixed-type inhibition with K-m at 52.36 and 2.49 mu g mL(-1), respectively. PS1 and PS2 also significantly inhibited the formation of advanced glycation end products (AGEs) in a BSA-fructose model. The results suggest that banana flower could possess the capability in prevention of the diseases associated with abnormal blood sugar and AGEs levels, such as diabetes.