ANTIOXIDIZING COMPONENT, MUSIZIN, IN RUMEX-JAPONICUS HOUTT

A substance with antioxidant properties was obtained from the hexane extract of roots of Rumex japonicus Houtt. The active component of the hexane extract was isolated and characterized as 2-acetyl-1,8-dihydroxy-3-methyl naphthalene, trivially named musizin (MUS). The antioxidant activities of MUS in six types of fats and oils were higher than that of butyl hydroxyanisole (BHA) and delta-tocopherol (delta-TOC). Together, TOC and MUS have a synergistic effect, because comparable amounts of either had lower antioxidant activity than various combinations of the two antioxidants. When we studied the antioxidant properties of a mixture of MUS and delta-TOC with methyl linoleate (MeLH), we found that the rates of destruction of the two antioxidants were comparable, but that their destruction occurred sequentially, with MUS first followed by delta-TOC, after which the oxidation of MeLH quickly occurred. Comparison of the antioxidant activity of MUS and its analogs suggests that only one of the two hydroxyl groups in MUS is involved in its antioxidant activity. Intermolecular hydrogen bonding may be involved.