Procyanidins from the herb of Hypericum perforatum.

From the aqueous acetone extract of the herb of Hypericum perforatum the flavanols catechin (1) and epicatechin (2), and the procyanidins A2 (9), B1 (3), B2 (4), B3 (5), B5 (6), B7 (7) and C1 (8) were isolated. 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 4 to 5 flavan-3-ol units. The procyanidin pattern in comparison to that of Crataegus spec. is briefly discussed.