Cytotoxic Characteristics of Two Isomeric Dimers Produced by Oxidation of Sesamol, an Antioxidant in Sesame Oil

Abstract

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.

Lignans of Sesame (Sesamum indicum L.): A Comprehensive Review

“…At high temperatures, sesamol dimerizes into sesamol dimer ( Figure 5 ), which possesses antioxidative activity [ 127 ], but the concentration of sesamol dimer in refined oil is very low [ 123 ]. In the presence of FeCl 3 , oxidation of sesamol by oxygen lead to a mixture of complex conjugated dimers [ 128 ], which exerted cytotoxic activities [ 128 , 129 ]. However, the reaction conditions used (10 days at 40 °C in the presence of 10 mol % FeCl 3 ) do not occur during processing and storage of sesame oil.…”

The electrochemical reactions of pyridoxine (vitamin B6) and some phenolic compounds in aprotic organic solvents

“…Significant interest has been received on the antioxidant ability of sesamol as demonstrated by the extensive research into the evaluation of its efficiency in scavenging free radicals such as DPPH radicals [60,68,79]. In the context of these ongoing efforts, besides pursuing the radical quenching capability of sesamol, one less well-explored approach is the examination on the toxicity of its oxidative products generated [80][81][82]. In order to mimic oxidative products that can possibly be produced in food and relevant systems, in these reported studies, sesamol was subjected to an iron-catalyzed oxidation reaction where several products were isolated and identified, of which selected examples are displayed in Scheme 1.4 [80].…”