Rapid isolation of geraniin from Nephelium lappaceum rind waste and its anti-hyperglycemic activity

Recently we confirmed the ability of ethanolic Nephelium lappaceum L rind extract to act as anti-hyperglycemic agent. Geraniin. an ellagitannin, was identified as the major bioactive compound isolated from the ethanolic Nephelium lappaceum L rind extract. In this study, we describe the rapid isolation of geraniin from the above plant. In addition to its extremely high anti-oxidant activity and low pro-oxidant capability, geraniin is seen to possess in vitro hypoglycemic activity (alpha-glucosidase inhibition: IC50 = 0.92 mu g/ml and alpha-amylase inhibition: IC50 = 0.93 mu g/ml), aldol reductase inhibition activity (IC50 = 7 mu g/ml) and has the ability to prevent the formation of advanced glycation end-products (AGE). Geraniin was observed to exhibit these properties at more significant levels compared to the positive controls acarbose (carbohydrate hydrolysis inhibitor), quercetin (aldol reductase inhibitor) and green tea (AGE inhibitor). Geraniin therefore, has the potential to be developed into an anti-hyperglycemic agent. Our findings also strongly support the use of a geraniin-standardised N. lappaceum extract in the management of hyperglycemia. (C) 2010 Elsevier Ltd. All rights reserved.