Antioxidant properties of 8.O.4′-neolignans

A series of naturally occurring 8.O.4′-neolignans (1a–d, 1g, 2g, 2h) and their analogues (1e–f, 1h, 1i, 2a–f, 2i) have been synthesized in racemic form starting from commercially available phenols, such as eugenol, isoeugenol and 4-allyl-2,6-dimethoxyphenol and from aromatic aldehydes, such as piperonal, veratraldehyde and 3,4,5-trimethoxybenzaldehyde. The inhibitory activity of these compounds on superoxide anion (O₂^.-) release by human polymorphonuclear leukocytes (PMNLs) was tested and the structure-activity relationship was also studied.