A distinctive flavonoid chemistry for the anomalous genus Biebersteinia

Leaf surface extracts of Biebersteinia orphanidis have yielded a complex mi xture of five flavones with the unusual 5.7-dihydroxy-6,8-dimethoxy A ring substitution pattern. They are acerosin, hymenoxin. nevadensin, sudachitin and 5.7.4'-trihydroxy-6.8-dimethoxyflavone. Also present at the leaf surfac e are gardenin B, luteolin, apigenin. acacetin and the coumarin umbellifero ne. The internal leaf flavonoids include the: 7-glucosides of apigenin, lut eolin and tricetin, together with the 7-rutinosides of apigenin and luteoli n. This profile differs From those of B. heterostemon and B. odora. It appe ars that B. orphanidis is as highly distinctive in its flavonoid pattern as it is phytogeographically. The data also confirm the conclusion of other s tudies. including rbcL and atpB gene sequence analysis. that Biebersteinia is completely unrelated to the Geraniaceae. where it was once placed. (C) 2 001 Elsevier Science Ltd. Ail rights reserved.