Marchantins and related polyphenols from liverwort: physico-chemical studies of their radical-scavenging properties.

Structurally unique macrocyclic phenols from liverwort, i.e., marchantins and related substances, were studied for their antioxidative potential using pulse-radiolytic and EPR-spectroscopic techniques. The generally diffusion-controlled rate constants for scavenging of azide radicals as a model electrophilic species and the sufficiently slow bimolecular decay confirm their antioxidative potential. Transient spectra after pulse radiolysis and the EPR spectra both demonstrate the internal strain of the macrocyclic ring. One compound, Perrottetin D, furthermore gave proof to the hitherto only kinetically verifyable superior radical-scavenging capability of the aroxyl radical derived from a phenolic antioxidant.