Dual inhibitory activities of tannins from Hamamelis virginiana and related polyphenols on 5-lipoxygenase and Lyso-PAF:acetyl-CoA acetyltransferase

In the present study, the effects of tannins obtained from various plant sources on the activity of 5-LOX and AT were examined. With IC50 values ranging from 1.0 to 18.7 mu M, hamamelitannin and the galloylated proanthocyanidins isolated from Hamamelis virginiana L. were found to be most potent inhibitors of 5-LOX. Unlike the 5-LOX study, hamamelitannin proved to be ineffective in the AT assay. Potent candidates are represented by the group of B-type proanthocyanidins. Structure-activity relationships regarding the in vitro inhibitory potency of the polyphenols in the biological assays are discussed.