Despite considerable research the evidence around the antidiabetic properties of cinnamon remains equivocal, and this may be due to varietal differences which is an aspect that is understudied. This study systematically compared the anti-hyperglycaemic properties of the four major commercial cinnamon types used around the world (Chinese; Cinnamomum cassia [CC], Indonesian; C. burmanii [IC], Vietnamese; C. loureirii [VC], and Ceylon; C. zeylanicum [SC]). LC-MS analysis showed distinct diffrences in the phytochemical profiles of cinnamon with SC showing the lowest coumarin concentration. CC and IC had the highest polyphenol levels and antioxidant potential, and all four types differed significantly in their content (P < 0.001). All cinnamon types showed potent species-specific effects on starch digestion enzyme activity inhibition (P < 0.001), CC was most effective against α-amylase and all four strongly inhibited α-glucosidase compared to acarbose. Cinnamon significantly reduced starch breakdown during oral (P = 0.006) and gastric (P = 0.029) phases of gastro-intestinal digestion with IC and SC showing consistent effects. No effects of cinnamon were seen in the intestinal phase. IC, VC and SC showed the greatest potential to inhibit formation of advanced glycation endproducts (AGEs) during digestion. In conclusion, cinnamon demonstrates anti-hyperglycaemic properties, however effects are species-specific with best overall properties seen for Ceylon cinnamon.Electronic supplementary materialThe online version of this article (10.1007/s11130-019-00760-8) contains supplementary material, which is available to authorized users.

Cinnamon has been reported to have anti-diabetic properties, however prevailing evidence is equivocal and precludes firm conclusions (1). The ambiguity of reported findings may be due to the use of different cinnamon species in studies, an aspect that has received little research attention. The aim of the current study was to compare the anti-hyperglycaemic properties of the four principal Cinnamon species used round the world i.e. Chinese (C. cassia [CC]), Indonesian C. burmanii [IC]), Vietnamese (C. loureirii [VC]) and Ceylon (C. zeylanicum [SC]) cinnamon. Water extracts of cinnamon were prepared from bark powders (2) , and characterised for polyphenol content, antioxidant potential (3) , and effects on α-amylase (AA) and α-glucosidase (AG) enzyme inhibition (4). The impact of the extracts on starch digestion was assessed using a standardised in vitro gastro-intestinal digestion model (5) , using white bread as the test substrate. All cinnamon types showed high antioxidant and polyphenol contents, with CC and IC showing the greatest values (p < 0.001) (Fig. 1). Chinese C, IC and VC showed the best effects on AA inhibition (p < 0.001). All species showed potent effects against AG compared to acarbose, particularly CC and IC (p < 0.001). Chinese C, IC and SC reduced glucose release from bread during the oral and gastric phases of digestion compared to the control, (p < 0.05), but were similar to each other (p > 0.05). The best overall effects during digestion was seen with SC (Table 1). The cinnamon extracts did not affect the contents of rapidly digestible, slowly digestive or resistant starches. In conclusion, water extracts of cinnamon demonstrate anti-hyperglycaemic properties that are species-specific. Of the four studied, CC, IC and SC showed greater potential.