Inhibitory activity of methanol extracts from different colored flowers on aldose reductase and HPLC-UV analysis of quercetin

The methanol extracts of flowers obtained from 67 plant species were screened for their inhibitory activity on aldose reductase (AR). Alnus japonica, Aster spathulifolius, Chionanthus retusus, Morus bombycis, Crysanthemum boreale, Persicaria tinctoria, Platycarya strobilacea, and Serratula coronata var. insularis exhibited potent aldose reductase inhibitory (ARI) activity. HPLC-UV analysis of quercetin, an AR inhibitory flavonoid, was performed on extracts showing strong ARI activity. Quercetin was detected in C. retusus, C. boreale, P. tinctoria, and S. coronata var. insularis at concentrations of 1.33, 1.56, 0.82, and 3.37 mg g−1 extract, respectively, indicating that quercetin contributed to the ARI activity of these extracts. In the samples in which quercetin was absent, other compounds may be responsible for their potent ARI activity. These results serve as a basis for further studies regarding the bioactive components responsible for the inhibitory effects of various flower extracts on AR activity.