Affiliations: Division of Food and Health Sciences, Graduate School
of Human Life Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi,
Osaka 558-8585, Japan
Abstract: Ginger (Zingiber officinale Roscoe) shows an antioxidant activity,
and we have been engaging to determine the structures of more than 50
antioxidants isolated from the rhizomes of ginger. The isolated antioxidants
are divided into two groups; gingerol related compounds and diarylheptanoids.
In this study, structure-activity relationship of gingerol related compounds
was evaluated. Gingerol related compounds substituted with an alkyl group
bearing 10-, 12- or 14-carbon chain length were isolated from the
dichloromethane extract of rhizomes using repeated chromatographic techniques.
The antioxidant activities of these compounds were evaluated by the following
measurements; 1) 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging
activity, 2) inhibitory effect on oxidation of methyl linoleate under aeration
and heating by the Oil Stability Index (OSI) method, and 3) inhibitory effect
on oxidation of liposome induced by
2,2'-azobis(2-amidinopropane)dihydrochloride (AAPH). These results suggested
that the substituents on the alkyl chain might contribute to both radical
scavenging effect and inhibitory effect of autoxidation of oils, while
inhibitory effects against the AAPH-induced peroxidation of liposome was
somewhat influenced by the alkyl chain length; the antioxidant activity might
be due to not only radical scavenging activity of antioxidants but also their
affinity of the antioxidants to the substrates.
