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J.Health Sci., 57(5), 425-431, 2011
-Research Letter-
Cytotoxic Characteristics of Two Isomeric Dimers Produced by Oxidation of Sesamol, an Antioxidant in Sesame Oil
Yoshimi Shingai, Aya Fujimoto,
Asuka Nakajima, Minoru Saito,
Kaori Kanemaru, Toshiya Masuda,
and Yasuo Oyama*
Division of Environmental Symbiosis Studies, Graduate School of Integrated Arts and Sciences, The University of Tokushima, 1-1 Minami-Josanjima, Tokushima 770-8506, Japan
Antioxidants themselves are oxidized to prevent oxidation of other molecules. One may ask if the oxidized antioxidants are safe for humans. However, there is very little information on the toxicity of oxidized antioxidants. We previously identified cytotoxic compounds in the products from oxidation of sesamol, a potent antioxidant in sesame oil. In this study using a flow cytometer with fluorescent probes, we revealed cytotoxic characteristics of two isomeric dimers (dimer A and B) in rat thymocytes. Increase in cell lethality by dimer A was more profound than those by sesamol and dimer B. The incubation of cells with dimer A increased the populations of shrunken cells and the cells with phosphatidylserine exposed on outer surface of cell membranes. Since these phenomena are parameters for early stage of apoptosis, the results indicate that dimer A may promote the process of apoptosis. However, the population of the cells containing hypodiploid DNA, a parameter for late stage of apoptosis, was decreased by the incubation with dimer A. It was not the case for dimer B. Results indicate that dimer A may inhibit the degradation of DNA during apoptosis. Taken together, it is likely that dimer A exerts both proapoptotic action and inhibitory action on late stage of apoptosis in rat thymocytes.
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