Procyanidins from the bark of Prunus africana

Abstract

From the aqueous acetone extract of the bark of Prunus africana (Hook.f.) Kalkman (Syn. Pygeum africanum Hook.f.) the flavanols catechin (1) and epicatechin (2), and the procyanidins B-1 (3), B-2 (4), B-3 (5), A-2 (6) and C-1 (7) were isolated and identified. Their structures were established as their peracetate derivatives, on the basis of chemical and spectral evidence. The 13C-NMR spectrum of the higher molecular weight polymer fraction revealed a 3',4'-dihydroxylated B-ring oxidation pattern and the 2,3-cis relative stereochemistry of the constituent flavan-3-ol units. The mean average molecular size of the polymers was estimated to be about 8 to 9 flavan-3-ol-units.

Keywords: Prunus africana; Rosaceae; flavan-3-ols; procyanidins