Prenyl-flavonoids from Epimedium koreanum Nakai and their soluble epoxide hydrolase and tyrosinase inhibitory activities

A new 8-prenyl-flavonoid, epimedokoreanoside III, and 11 other flavonoids, were isolated from the aerial parts of Epimedium koreanum Nakai. Their chemical structures were elucidated by nuclear magnetic resonance and mass analyzes. All isolates were evaluated for their soluble epoxide hydrolase and tyrosinase inhibitory activities. Among the isolates, compounds 1 , 5 , 9 , 10 , and 12 exerted soluble epoxide hydrolase inhibitory activity in dose-dependent manner, with IC 50 values ranging from 26.0 ± 1.2 to 37.6 ± 1.0 µM, whereas compounds 4 and 9 showed potent inhibition of tyrosinase in a dose-dependent manner, having IC 50 values of 16.8 ± 2.7 and 8.7 ± 2.7 µM, respectively.