In Vitro and In Vivo Antiglycation Effects of Connarus ruber Extract

Accumulation of advanced glycation end products (AGEs) of the Maillard reaction has been implicated in the pathogenesis of diabetes and its complications. Connarus ruber has been used as a folk remedy for several diseases, including diabetes; however, its underlying mechanism has not yet been investigated. This study investigated the effects of C. ruber extract against glycation on collagen-linked AGEs in vitro and streptozotocin-induced diabetic rats (STZ-DM rats) in vivo. The antiglycation activities of C. ruber extract and aminoguanidine (AG) were examined using a collagen glycation assay kit. Nonfluorescent AGE, N^ε-carboxymethyl lysine (CML), N^ω-carboxymethyl arginine, and N^ε-carboxyethyl lysine levels were measured via electrospray ionization-liquid chromatography-tandem mass spectrometry. The effect of the extract on the cytotoxicity of methylglyoxal (MG), a precursor of AGEs, was examined in HL60 cells. STZ-DM rats were treated with the extract for 4 wk, and the effect was assessed using biochemical markers in the serum and CML-positive cells in renal tissues. C. ruber extract dose-dependently inhibited the glycation of collagen and formation of nonfluorescent AGEs, which was comparable to AG, and it significantly attenuated MG-induced cytotoxicity in HL60 cells. Furthermore, the glycated albumin levels in STZ-DM rats decreased, the increase in serum lipid levels was reversed, and immunohistochemistry demonstrated that CML deposition in the glomerulus of STZ-DM rats significantly decreased. Although further studies are needed, C. ruber could be a potential therapeutic for preventing and progressing many pathological conditions, including diabetes.