Antipromastigote and cytotoxic activities of flavonoids from Fridericia speciosa leaves

Fridericia speciosa (Bignoniaceae) is a liana that occurs in humid to dry vegetation in eastern and southeastern Brazil. Species belonging to the genus Fridericia are employed as medicinal plants. This study evaluates the antipromastigote and cytotoxic activities of the crude extract, fractions, and compounds isolated from F. speciosa, and an HPLC (High-Performance Liquid Chromatography) analytical method was used to quantify the bioactive flavonoids. The flavonoids alpinetin (1), luteolin (2), diosmetin (3), and apigenin (4) were isolated from the active EtOAc-soluble fraction (EAF) of the crude ethanol extract (LCE) obtained from F. speciosa leaves. Both LCE and EAF were active against the normal human lung fibroblast cell line GM07492A (IC₅₀ of 460.7 μg mL^-1 and 381.4 μg mL^-1, respectively). Only EAF showed activity against Leishmania amazonensis (80.4% at 50 μg mL^-1). Compounds 1 and 2 were quantified by HPLC-DAD in both LCE (1: 6.21%; 2: 1.11%) and EAF (1: 45.32%; 2: 2.00%). At 100 μM, compounds 1-4 inhibited L. amazonensis flagellar motility by 40.2%, 26.8%, 1.0%, and 24.8%, respectively, while their toxicities (IC₅₀) to the normal cell were > 1000, 353.0, 766.2, and >1000 μg mL^-1, respectively. Therefore, F. speciosa leaves are a prolific source of bioactive flavonoids. (author)