Unusual dimeric flavonoids from Fridericia prancei (Bignoniaceae) and their taxonomic significance

Fridericia Mart. emend L.G. Lohmann is one of the largest and most complex genera of neotropical lianas comprising species that are morphologically variable and taxonomically complicated. Phytochemical investigation of leaves of Fridericia prancei (A.H.Gentry) L.G. Lohmann led to the isolation and identification of one alkaloid, trigonelline (1), and five unusual dimeric flavonoids, i.e., brachydin D (2), brachydin E (3), brachydin A (4), brachydin J (5), and brachydin C (6). We describe these rare dimeric flavonoids in F. prancei for the first time and show that they represent chemical synapomorphies of the Acrodromous venation clade.