Polyphenol constituents from Salacia species:: Quantitative analysis of mangiferin with α-glucosidase and aldose reductase inhibitory activities

Mangiferin, three catechins, and two catechin dimers were isolated from the roots of Salacia reticulata (SRE), and examined their inhibitory activities against several carbohydrate metabolize enzymes (sucrase, maltase, isomaltase, (alpha -amylase, and aldose reductase). Among them, mangiferin was found to inhibit sucrase, isomaltase, and aldose reductase from rat with IC50 values of 87, 216 and 1.4 mug/ml, respectively. The inhibitory activities of mangiferin are competitive for sucrase and isomaltase with inhibitor constant (K-i) 55 mug/ml and 70 mug/ml, respectively. In order to determine the mangiferin contents in the water extracts from the roots of S. reticulata, a quantitative analytical method by means of HPLC was developed and the mangiferin contents in SRE were determined to be in the range of 0.9-2.3% by the application of this method. A high linear correlation (r=0.934) was observed between the mangiferin contents and the sucrase inhibitory activity. In addition, this analytical procedure of mangiferin was found to be applicable for other Salacia species (S. oblonga, S. chinensis, and S. prinoides). Thus, the quantitative HPLC analysis of mangiferin was supposed to be suitable for the quality control of Salacia species and its products.