Kaempferol Rhamnosides from Geranium Sibiricum as Aldose Reductase Inhibitors and Their Content by HPLC Analysis

The study investigated the aldose reductase (AR) inhibitory activity of Geranium sibiricum, which showed significant inhibition with an IC50 value of 2.4 µg/mL. The ethyl acetate fraction exhibited even stronger inhibition (IC50 value, 0.41 µg/mL) due to kaempferol rhamnosides, specifically kaempferol-7-O-rhamnoside and kaempferol-3,7-O-dirhamnoside. Kaempferol-3,7-O-dirhamnoside was more potent than kaempferol-7-O-rhamnoside with IC50 values of 0.55 µM and 1.23 µM, respectively. High-performance liquid chromatography (HPLC) analysis showed high concentrations of these compounds in the methanol extract. These findings suggested that G. sibiricum could be a promising natural source for developing therapies to manage diabetic complications by inhibiting AR, a key enzyme in the polyol pathway linked to such complications. This was the first study to report on the AR inhibitory efficacies of these compounds.