2,4-O-Diacetylquercitrin, a Novel Advanced Glycation End-Product Formation and Aldose Reductase Inhibitor from Melastoma sanguineum

A new flavonoid, 2,'' 4 ''-O-diacetylquercitrin (1), along with six known flavonoids (2-7) were isolated from the aerial parts of Melastoma sanguineunz. The structure of the new flavonoid was established by extensive spectroscopic studies and chemical evidence. The inhibitory effects of isolated compounds (1-7) on advanced glycation end-products (AGEs) formation and rat lens aldose reductase (RLAR) in vitro were examined. Of the tested compounds, compound 1 was the strongest inhibitor of AGEs, with an IC50 of 11.46 +/- 0.44 mu m. In the RLAR assay, all tested compounds exhibited greater inhibitory effects on RLAR than that of a positive control, 3,3-tetramethyleneglutaric acid (10(50)=28.8 +/- 1.5 mu m); compound 1 exhibited the strongest RLAR-inhibitory activity, with an IC50 of 0.077 +/- 0.003 mu m.