Isolation and Characterization of a Phenolic Antioxidant from the Pacific Oyster (Crassostrea gigas)

Using an oxygen radical absorbance capacity (ORAC) assay, antioxidant activity was detected in the ethanol extract of the Pacific oyster, which was purified by sequential extraction with organic solvents. The ethyl acetate fraction showed the strongest antioxidant activity and was further purified, yielding a single compound [as assessed by thin-layer chromatography (TLC) reverse-phase high-performance liquid chromatography (HPLC)]. This compound was identified as 3,5-dihydroxy4-metboxybenzyl alcohol on the basis of H-1 and C-13 nuclear magnetic resonance (NMR), heteronuclear multiple-bond correlz.tion (HMBC), and electrospray ionization-mass spectrometry (ESI-MS) spectral analyses, a conclusion that was confirmed bycheinical synthesis. The concentration of the compound was 6.7 mg/100 g of whole oyster meat wet weight. This azaphi'philic gritiosidant retarded the copper mediated oxidation of low density lipoproteins (LDLs) and the generation of,tr.ickarbitonc acid.teactive substances. Furthermore, the compound showed substantial antioxidant activity using the ORAC and 2,2-diphenyl-1-picrythy'drazyl (DPPH) assays compared to natural antioxidants. Although the same compound was previously found in brown algae, its presence in other organisms and antioxidant activity are reported here for the first time.