α-Glucosidase inhibitory activity by the flower buds of Lonicera japonica Thunb

In the present study, the methanol extract from the flower buds of Lonicera japonica Thunb. was investigated on rat intestinal alpha-glucosidase inhibitory activity. This extract enriched in polyphenols, showed a potent alpha-glucosidase inhibitory activity with maltose as a substrate in enzyme assay. The extract was then applied to MCI-gel column chromatography with a water-methanol gradient to give three fractions: fraction 1 (F-1, water), fraction 2 (F-2, 80% methanol in water), and fraction 3 (F-3, 100% methanol). F-2 showed the highest maltase inhibitory activity compared with F-1 and F-3, and down-regulated alpha-glucosidase activity for the maltose hydrolysis in Caco-2 monolayer. In maltose-loaded SD-rats, F-2 significantly reduced postprandial blood glucose level. 3,5-Dicaffeoylquinic acid was found to be the potent maltase inhibitor, whereas chlorogenic acid and rutin showed a weak inhibitory activity against maltase. This is the first report on the mammalian alpha-glucosdiase inhibition of L. japonica. The result presented here suggests a use of the extract of L. japonica for antidiabetes. (C) 2013 Elsevier Ltd. All rights reserved.