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Research Article

A series of cinnamic acid derivatives and their inhibitory activity on intestinal α-glucosidase

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Pages 1194-1200 | Received 27 Sep 2008, Accepted 21 Jan 2009, Published online: 23 Sep 2009
 

Abstract

Inhibition of α-glucosidase and α-amylase delays the digestion of starch and disaccharides to absorbable monosaccharides, resulting in a reduction of postprandial hyperglycemia. Finding effective mammalian α-glucosidase inhibitors from natural sources can be beneficial in the prevention and treatment of diabetes mellitus. We investigated the inhibitory activity of cinnamic acid derivatives against rat intestinal α-glucosidase and porcine pancreatic α-amylase in vitro. Among 11 cinnamic acid derivatives, caffeic acid, ferulic acid, and isoferulic acid were the most potent inhibitors against intestinal maltase with IC50 values of 0.74 ± 0.01, 0.79 ± 0.04, and 0.76 ± 0.03 mM, respectively, whereas ferulic acid (IC50 = 0.45 ± 0.01 mM) and isoferulic acid (IC50 = 0.45 ± 0.01 mM) were effective intestinal sucrase inhibitors. However, all cinnamic acid derivatives were found to be inactive in pancreatic α-amylase inhibition. Kinetic analysis revealed that intestinal maltase was inhibited by caffeic acid, ferulic acid, and isoferulic acid in a mixed-inhibition manner. In addition, ferulic acid and isoferulic acid inhibited intestinal sucrase in a mixed type manner, whereas caffeic acid was a non-competitive inhibitor. The combination of isoferulic acid and acarbose showed an additive inhibition on intestinal sucrase. This study could provide a new insight into naturally occurring intestinal α-glucosidase inhibitors that could be useful for treatment of diabetes and its complications.

Acknowledgements

This research was financially supported by the Faculty of Allied Health Sciences, Chulalongkorn University.

Declaration of interest: The authors report no conflicts of interest.

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