A-type proanthocyanidins from peanut skins

Article abstract of DOI:10.1016/S0031-9422(98)00736-5

Six A-type proanthocyanidins were isolated from the water-soluble fraction of peanut skins. On the basis of spectral data, reductive cleavage with sodium cyanoborohydride, and chiral HPLC analysis, three new compounds, epicatechin-(2β → O → 7, 4β → 6)-catechin, epicatechin-(2β → O → 7, 4β → 6)-ent-catechin and epicatechin-(2β → O → 7, 4β → 6)-ent- epicatechin were unambiguously identified, together with the three known compounds, proanthocyanidin A-1, proanthocyanidin A-2 and epicatechin-(2β → O → 7, 4β → 8)-ent-epicatechin. ¹³C NMR chemical shift rules to distinguish between [2 → O → 7, 4 → 8] and [2 → O → 7,4 → 6] double- linked heptamethyl ethers of A-type proanthocyanidins are proposed. Bioassay experiments showed that these six compounds possess substantial activity against hyaluronidase.