Unusual flavonoids produced by Callus of Hypericum perforatum

6-C-prenyl luteolin, a new naturally occurring compound, together with luteolin 5,3'-dimethyl ether, luteolin 5-glucoside and luteolin 3'-glucoside were isolated from callus of Hypericum perforatum var. angustifolium. These flavonoids were completely different from those previously observed in in vivo plants of the same species. The total flavonoid content of callus, around 0.5--0.7 mg g(-1) dry wt, was much lower than that found in wild growing Hypericum perforatum plants (14-70 mg g(-1) dry wt). (C) 1998 Elsevier Science Ltd. All rights reserved.