Antiproliferative activity of Pteleopsis suberosa leaf extracts and its flavonoid components in human prostate carcinoma cells

In this work we describe the chem. compn. of Pteleopsis suberosa (Combretaceae) leaf ext. and its biol. activity against androgen-insensitive human prostate cancer cells (DU-145). The methanol ext. of the plant leaves exhibited activity against tumor cell growth. Fractionation of this active ext. led to the isolation and identification of sixteen flavonoids, including gallocatechin and flavonols having kaempferol, quercetin, and myricetin as aglycons. Among the myricetin derivs., myricetin 3-O-(3''-acetyl)-α-L-arabinopyranoside (1) and myricetin 3-O-(4''-acetyl)-α-L-arabinopyranoside (2) are now reported for the first time. Six compds., myricetin 3-O-α-L-rhamnopyranoside (4), myricetin 3-O-β-D-galactopyranoside (7), myricetin 3-O-(6''-galloyl)-β-D-galactopyranoside (9), myricetin 3-O-β-D-xylopyranoside (10), myricetin 3-O-α-L-arabinofuranoside (12), and gallocatechin (14), exhibited significant activity, reducing cell vitality and inducing apoptosis via the caspase-dependent pathway in DU-145 cells that can be, in part, correlated to modulation of redox-sensitive mechanisms.