Chalcone tetramers, lophirachalcone and alatachalcone, from Lophira alata as possible anti-tumor promoters

Two chalcone tetramers were isolated as inhibitors of Epstein-Barr virus (EBV)-activation induced by a tumor promoter, teleocidin B-4, from a medicinal plant in tropical west Africa, Lophira alata (Ochnaceae). One of them was identified as lophirachalcone. The other, named alatachalcone, was new, and the structure was determined by spectral properties. Both compounds also showed potent inhibitory activities against teleocidin B-4-induced inflammation on mouse ear. In an initiation-promotion experiment on mouse skin, alatachalcone (16 nmol) significantly inhibited tumor promotion caused by 12-O-tetradecanoylphorbol-13-acetate (TPA, 1.6 nmol).