Prenylated flavonoids from the aerial parts of Dorstenia mannii

Four new prenylated flavanones, dorsmanins I, J and epi-dorsmanins F, G, id entified, respectively, as 6,7-(2,2-dimethylpyrano)-8-prenyl-5,3',4'-trihyd roxyflavanone, 6,7-(2,2-dimethyldihydropyrano)-8-prenyl-5,3'-4'-trihydroxyf lavanone, and 2 " -epimers of dorsmanins F and G were isolated from the aer ial parts of Dorstenia mannii together with 13 known flavonoids: 4-hydroxyl onchocarpin, 4-methoxylonchocarpin, 6-prenylchrysoeriol, 6,8-diprenyleriodi ctyol, gancaonin P and dorsmanins A-H. The structures of these secondary me tabolites were determined by spectroscopic means and by comparison with pub lished data and with authentic specimens for some of the known compounds. ( C) 2000 Elsevier Science Ltd. All rights reserved.