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

•L. japonica showed a potent maltase inhibitory activity in enzyme assay.•L. japonica down-regulated maltose-hydrolysis activity in Caco-2 monolayer.•L. japonica significantly reduced postprandial blood glucose level in vivo.•3,5-Dicaffeoylquinic acid was found to be the potent maltase inhibitor.