Glycosidase inhibitory phenolic compounds from the seed of Psoralea corylifolia

The seeds of Psoralea corylifolia were extracted into five different polar solvents: chloroform, 50% ethanol in water, ethanol, methanol and water. All extracts were evaluated for glycosidase inhibitory activity. The chloroform extract (CE) showed the lowest IC 50 values against α-glucosidase (82.9 μg/ml) and α-mannosidase (132 μg/ml). Chromatography of CE yielded nine phenolic compounds which were identified as isovabachalcone ( 1 ), 4′- O -methylbavachalcone ( 2 ), isobavachromene ( 3 ), corylifolin ( 4 ), bavachinin ( 5 ), psoralidin ( 6 ), neobavaisoflavone ( 7 ), corylifol A ( 8 ), and bakuchiol ( 9 ). All isolated compounds, apart from compound 5 , possessed α-glucosidase inhibitory activities. Among them, compounds 6 – 8 exhibited potent inhibition with IC 50 s of 13.7, 27.7 and 11.3 μM, respectively. Furthermore, compounds 2 and 6 showed α-mannosidase inhibitory activity. Mechanistic analysis of their inhibition modes against α-glucosidase showed that compounds ( 6 and 7 ) were noncompetitive, whereas compound 8 was mixed. Furthermore, the most active glycosidase inhibitors ( 2 , 6 – 8 ) were proven to be present in the native seed in high quantities by an HPLC chromatogram.