Inhibitory effects of Luobuma tea and its components against glucose-mediated protein damage

Luobuma tea, prepared from the leaves of Apocynum venetum L., is a popular beverage in China. In this study, the activity of Luobuma leaf extract and its components against the formation of advanced glycation endproducts (AGEs), which are largely involved in the pathogenesis of diabetic vascular complications, was examined using the in vitro glycation reaction. Strong inhibitory activity against the formation of AGEs was shown by Luobuma aqueous extract. Following further fractionation of this extract, seven polyphenolic compounds, i.e. (+/-)-gallocatechin, (-)-epigallocatechin, (+/-)-catechin, (-)-epicatechin, epicatechin-(4beta-8)-gallocatechin, epigallocatechin-(4beta-8)-epicatechin and procyanidin B-2, were isolated by Sephadex LH-20 column chromatography. These purified compounds also exerted inhibitory activities that were more potent than the positive control, aminoguanidine. Our findings may help to explain the beneficial effects of this plant against atherosclerosis.