Screening and Isolating Major Aldose Reductase Inhibitors from the Seeds of Evening Primrose ().

Aldose reductase (AR) is a drug target for therapies to treat complications caused by diabetes mellitus, and the development of effective AR inhibitors (ARIs) of natural origin is considered to be an attractive option for reducing these complications. In this research, the rat lens AR (RLAR) inhibitory activity of evening primrose () seeds was investigated for the first time. In our results, the 50% (/) methanol extract of evening primrose seeds exhibits excellent RLAR inhibitory activity (IC value of 7.53 μg/mL). Moreover, after enrichment of its bioactive components, the ARIs are more likely to be present in the ethyl acetate fraction of 50% () methanol extract (EME) of evening primrose seeds, which exhibits superior RLAR inhibitory activity (IC value of 3.08 µg/mL). Finally, gallic acid (), procyanidin B3 (), catechin (), and methyl gallate () were identified as the major ARIs from the EME by affinity-based ultrafiltration-high-performance liquid chromatography and were isolated by high speed countercurrent chromatography, with gallic acid (11.46 µmol/L) and catechin (14.78 µmol/L) being the more potent inhibitors of the four ARIs identified. The results demonstrated that evening primrose seeds may be a potent ingredient of ARIs.