Isolation and Characterization of Two New Polyphenols from the Anti-Diabetic Fraction of Pod Extract of Caesalpinia pulcherrima Swartz

Abstract

This study was planned and executed to validate the anti-diabetic ethno-medicinal claim of Caesalpinia pulcherrima (Fabaceae) pods and the isolation of potential chemical compounds responsible for the activity.The anti-diabetic activity of the extract was assayed using oral glucose tolerance test and streptozotocin induced hyperglycaemic rats. The partition fractions of the extract were evaluated for their anti-hyperglycaemic activity using oral glucose tolerance test. The most active fraction was subjected to chromatographic separations that led to the isolation and characterisation of two new polyphenolic compounds. The structures of these compounds were elucidated and characterized using IR, 1D- and 2D-NMR and MS techniques.The extract gave comparable (p>0.05) activity to glibenclamide (5 mg/kg) at 100, 200 and 400 mg/kg at 4 h in oral glucose tolerance test and streptozotocin induced diabetic model on day 21. The most active ethyl acetate fraction (200 mg/kg) elicited comparable activity to the positive control at 0.5-4 h with blood glucose reduction of 52.9 % as compared with glibenclamide (5 mg/kg) of 38.9 % at 4 h. The isolated compounds were identified to be 5-(4-hydroxyphenyl)-3-hydroxy-2-methoxyphenol and 3-(4-methanetriol-2,6-dihydroxyphenyl)-3',4',5',5,7-pentahydroxyflavanonol.The significant anti-diabetic property shown by the pods of C. pulcherrima justified its anti-diabetic ethno-medicinal use and the two new polyphenolic compounds isolated from its most active fraction could have contributed to the observed activity.