Iridoid glycosides from the flower buds of Lonicera japonica and their nitric oxide production and α-glucosidase inhibitory activities

Abstract

The flower buds of Lonicera japonica are commonly used as popular healthy beverages that are also effective in the prevention and cure of a variety of chronic diseases, such as diabetes, and also as an anti-inflammatory treatment for thousands of years. In this study, three new iridoid glycosides along with twenty-five known analogues were isolated from the aqueous extract of L. japonica. Their structures were determined by extensive 1D NMR, 2D NMR and HR-ESIMS spectroscopic data analyses, and all the isolates were investigated with regard to lipopolysaccharide (LPS)-induced nitric oxide (NO) production and α-glucosidase inhibitory effects. Among these compounds, 12 and 13 exhibited strong NO inhibitory activities and no cytotoxic effects. Moreover, most compounds were potent α-glucosidase inhibitors compared with the positive control acarbose. These findings will enhance knowledge about the bioactive components of L. japonica and help promote its potential application in functional foods.