Effects of the polyphenol content on the anti-diabetic activity of Cinnamomum zeylanicum extracts
Cinnamomum zeylanicum is a popular kitchen spice widely investigated for insulin potentiating effects. Though a group of water soluble polyphenols belonging to the oligomeric procyanidins has been identified as the bioactive principle, the lack of systematic information on the effect of the polyphenol content on safety and anti-diabetic efficacy remains as a major limitation for the development of optimized and standardized cinnamon extracts for functional use. In the present paper, water soluble extracts of Cinnamomum zeylanicum containing 45 and 75% gallic acid equivalents (GAE) of polyphenol content were prepared by a novel process and characterized by tandem mass spectrometry. The polyphenol enhanced extracts were shown to be safe and offered better antioxidant potential, hypoglycemic effect, hypolipidimic effect, and significant decrease in other biochemical parameters as compared to the standard aqueous extract containing 15% GAE, when administered to streptozotocin-induced diabetic rats at 200 mg per kg b.w. for 30 days. The efficacy of polyphenol extracts in lowering blood glucose levels and ameliorating oxidative stress was further demonstrated in humans by administrating ‘procynZ-45’ containing 45% GAE polyphenols at a relatively low dosage of (125 mg × 2) per day for 30 days to 15 volunteers who had elevated fasting blood glucose levels; but not involved in any medication.