Resveratrol,
sesamol,
sesame oil and
sunflower oil are known natural dietary components with intrinsic
cancer chemopreventive potentials. As a part of our study of dietary constituents as potential
cancer chemopreventive agents, we have assessed the anti-
cancer potentials of these products in the promotion stage of
cancer development employing the in vitro
Epstein-Barr virus early antigen activation assay induced by the
tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA). Further, we studied the activities of these compounds in the brine shrimp cytotoxicity assay as well as on the stable
1,1-diphenyl-2-picrylhydrazyl (DPPH)
free radical scavenging bioassay with a view to comparing some of the mechanisms of their anti-
cancer activity. Finally, we compared the observed chemoprotective capabilities of the four products in the in vivo 7,12 dimethylbenz(a)
anthracene initiated and TPA-promoted mouse skin two-stage
carcinogenesis protocols. All the products tested showed a profound inhibitory effect on the
Epstein-Barr virus early antigen induction using Raji cells. Comparatively,
sesame oil was the most potent followed by
sesamol and then
resveratrol. Only
sesamol and
resveratrol showed a remarkable cytotoxic activity in the brine shrimp lethality assays as well as profound
free radical scavenging activity in the DPPH bioassay. In both test systems,
sesamol exhibited a more remarkable activity than
resveratrol while
sesame oil and
sunflower oil did not exhibit any appreciable activity even at the highest concentrations tested (4000 microg ml(-1) ). In our in vivo assay at a 50-fold molar ratio to TPA,
sesamol offered 50% reduction in mouse skin
papillomas at 20 weeks after promotion with TPA. Under an identical molar ratio to TPA,
resveratrol offered a 60% reduction in the
papillomas in mouse at 20 weeks. Thus
sesamol seems to be an almost equally potent chemopreventive agent.
Sesame oil and
sunflower oil offered 20 and 40% protection, respectively, in the mouse skin
tumor model. The
anti-oxidant capabilities of these compounds could not solely explain the observed anti-
cancer characteristics.
Resveratrol is present in grapes.
Sesamol, a constituent of
sesame oil and
sunflower oil are regularly consumed dietary natural products. The observed chemopreventive effect of these products particularly warrants more attention since they already exist in the population with no known adverse effects.