Inhibitory Activities of Stauntonia hexaphylla Leaf Constituents on Rat Lens Aldose Reductase and Formation of Advanced Glycation End Products and Antioxidant

Stauntonia hexaphylla (Thunb.) Decne. (Lardizabalaceae) leaves (SHL) have been used traditionally as analgesics, sedatives, diuretics, and so on, in China. To date, no data have been reported on the inhibitory effect of SHL and its constituents on rat lens Aldose Reductase (RLAR) and advanced glycation end products (AGEs). Therefore, the inhibitory effect of compounds isolated from SHL extract on RLAR and AGEs was investigated to evaluate potential treatments of diabetic complications. The ethyl acetate (EtOAC) fraction of SHL extract showed strong inhibitory activity on RLAR and AGEs; therefore, EtOAc fraction (3.0 g) was subjected to Sephadex LH-20 column chromatography, for further fractionation, with 100% MeOH solvent system to investigate its effect on RLAR and AGEs. Phytochemical investigation of SHL led to the isolation of seven compounds. Among the isolated compounds, chlorogenic acid, calceolarioside B, luteolin-3'-O-β-D-glucopyranoside, quercetin-3-O-β-D-glucopyranoside, and luteolin-7-O-β-D-glucopyranoside exhibited significant inhibitory activity against RLAR with IC₅₀ in the range of 7.34-23.99 μM. In addition, 3-(3,4-dihydroxyphenyl) propionic acid, neochlorogenic acid, and luteolin-3'-O-β-D-glucopyranoside exhibited the most potent inhibitory activity against formation of AGEs, with an IC₅₀ value of 115.07-184.06 μM, compared to the positive control aminoguanidine (820.44 μM). Based on these findings, SHL dietary supplements could be considered for the prevention and/or treatment of diabetes complication.