Antioxidant and antiglycation properties of total saponins extracted from traditional Chinese medicine used to treat diabetes mellitus.

Eleven antidiabetic traditional Chinese medicine (TCM) extracts rich in saponins were examined for their antioxidant and antiglycation activities. The antioxidant activities of these extracts were evaluated by studying the inhibition of lipid peroxidation in rat liver microsomes induced by ascorbate/Fe2+, cumine hydroperoxide (CHP) or CCl4/reduced form of nicotinamide-adenine dinucleotide phosphate (NADPH). The antioxidant capacities were also evaluated by studying the scavenging of 2,2'-diphenyl-1-picrylhydrazyl (DPPH) free radical. The antiglycation activities of these extracts were evaluated by hemoglobin-delta-gluconolactone (delta-Glu) assay, bovine serum albumin (BSA)-glucose assay and N-acetyl-glycyl-lysine methyl ester (GK peptide)-ribose assay. Aralia taibaiensis outperformed other extracts in most of the assays except inhibition of early glycation products formation, where Acanthopanax senticosus showed higher activity. Aralia taibaiensis was particularly potent in inhibiting the late glycation and formation of advanced glycation end products (AGEs) on proteins. The antioxidant and antiglycation activities of most extracts were correlated with the saponin content. The results demonstrate that the antidiabetic activities of most extracts could be explained, at least in part, by their combined antioxidant and antiglycation properties.