4-Nerolidylcatechol (4-NC) is found in Pothomorphe umbellata
root extracts and is reported to have a topical protective effect against UVB
radiation-induced skin damage, toxicity in melanoma cell lines, and antimalarial
activity. We report a comparative study of the antioxidant activity of 4-NC and
α-tocopherol against lipid peroxidation initiated by two free radical-generating
systems: 2,2′-azobis(2-aminopropane) hydrochloride (AAPH) and
FeSO4/H2O2, in red blood cell ghost
membranes and in egg phosphatidylcholine (PC) vesicles. Lipid peroxidation was
monitored by membrane fluidity changes assessed by electron paramagnetic
resonance spectroscopy of a spin-labeled lipid and by the formation of
thiobarbituric acid-reactive substances. When lipoperoxidation was initiated by
the hydroxyl radical in erythrocyte ghost membranes, both 4-NC and α-tocopherol
acted in a very efficient manner. However, lower activities were observed when
lipoperoxidation was initiated by the peroxyl radical; and, in this case, the
protective effect of α-tocopherol was lower than that of 4-NC. In egg PC
vesicles, malondialdehyde formation indicated that 4-NC was effective against
lipoperoxidation initiated by both AAPH and
FeSO4/H2O2, whereas α-tocopherol was less
efficient in protecting against lipoperoxidation by AAPH, and behaved as a
pro-oxidant for FeSO4/H2O2. The DPPH
(2,2-diphenyl-1-picrylhydrazyl) free-radical assay indicated that two free
radicals were scavenged per 4-NC molecule, and one free radical was scavenged
per α-tocopherol molecule. These data provide new insights into the antioxidant
capacity of 4-NC, which may have therapeutic applications for formulations
designed to protect the skin from sunlight irradiation.