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The anti-tumour activities of many plant phenolics at high concentrations (>100 μmol/L) suggest their potential use as dietary supplements in cancer chemoprevention and cancer chemotherapy. However, it is not clear what impact phenolic compounds have at the physiological concentrations obtained through consumption of high phenolic diets on neoplastic cells. In the present study, 54 naturally occurring phenolics were evaluated at physiologically relevant concentrations for their capacity to alter PC12 cell viability in response to serum deprivation, the chemotherepeutic agent etoposide, and the apoptogen C2-ceramide. Surprisingly, novel mitogenic, cytoprotective, and antiapoptotic activities were detected. Quantitative structure–activity relationship modelling indicated that many of these activities could be predicted by compound lipophilicity, steric bulk, and (or) antioxidant capacity, with the exception of inhibition of ceramide-induced apoptosis. Where quantitative structure–activity relationship analysis was insufficient, biochemical assessment demonstrated that the benzoate orsellinic acid blocked downstream caspase-12 activation following ceramide challenge. These findings demonstrate substantive mitogenic, cytoprotective, and antiapoptotic biological activities of plant phenolics on neoplastic cells at physiologically relevant dietary concentrations that should be considered in chemopreventive and chemotherapeutic strategies.

The phototoxic and photoallergic effects of the once popular UV sunscreen p-aminobanzoic acid are related, in part, to its ability to sensitize the formation of singlet oxygen as well as other reactive oxygen species. In this work we demonstrate that the sunscreen-photoinduced inactivation of a model protein, horseradish peroxidase, is reduced by approximately a factor of three when the sunscreen is encaspsulated in zeolite sodium Y. These results provide evidence that using the technology of zeolite encapsulation to prepare a supramolecular sunscreen that minimizes the skin contact of active ingredients may reduce the adverse effects of "naked" sunscreens on biological systems. These radiation-induced effects, unfortunately, frequently accompany the desirable UV-screening role of these products. These results provide an important benchmark for the use of zeolite encapsulation as a means of improving the safety of UV sunscreens for topical application.