A distinctive flavonoid chemistry for the anomalous genus Biebersteinia

Leaf surface extracts of Biebersteinia orphanidis have yielded a complex mixture 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 surface are gardenin B, luteolin, apigenin, acacetin and the coumarin umbelliferone. The internal leaf flavonoids include the 7-glucosides of apigenin, luteolin and tricetin, together with the 7-rutinosides of apigenin and luteolin. This profile differs from those of B. heterostemon and B. odora. It appears that B. orphanidis is as highly distinctive in its flavonoid pattern as it is phytogeographically. The data also confirm the conclusion of other studies, including rbcL and atpB gene sequence analysis, that Biebersteinia is completely unrelated to the Geraniaceae, where it was once placed.