Evaluation of the In vitro Anti-hyperglycemic Effect of Cinnamomum cassia Derived Phenolic Phytochemicals,via Carbohydrate Hydrolyzing Enzyme Inhibition

Cinnamomum cassia (cinnamon) proanthocyanidins (PACs) are believed to have anti-hyperglycemic potential via stimulation of insulin sensitivity. The present study investigates the carbohydrate hydrolyzing enzyme inhibition of cinnamon PACs. Five grams of cinnamon bark powder were extracted in 100 mL acetone solution (CAE) (acetone: water: hydrochloric acid, 70:29.9:0.01) for 2 h at room temperature and in 100 mL deionized water for 30 min at 90 °C (CWE). PACs were purified from CAE using LH-20 (CAE-PAC) to be further evaluated. PAC contents were evaluated by 4-Dimethylaminocinnamaldehyde (DMAC) assay and yielded 795, 177 and 123 mg/g, for CAE-PAC, CAE and CWE respectively. The total phenolic contents of CAE and CWE were determined to be 152 and 134 mg/g respectively. All extracts were adjusted to the same PAC content (180, 90, 45 and 20 μg) and the inhibitory activity against rat α-glucosidase was determined. The CAE-PAC fraction had very low rat α-glucosidase inhibitory activity, CAE had the highest (IC₅₀ 0.474 mg/mL total phenolic (TP) basis) followed by CWE (IC₅₀ 0.697 mg/mL TP basis). The specific maltase and sucrase inhibitory activities were determined and CAE (IC₅₀ 0.38 and 0.10 mg/mL TP basis) had higher inhibition than CWE (IC₅₀ 0.74 and 0.37 mg/mL TP basis). Results suggest that the observed bioactivity is not PAC dependent and that CAE has a higher anti-hyperglycemic potential than CWE via inhibition of carbohydrate hydrolyzing enzymes.