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Porphyrins such as protoporphyrin IX (PP IX) and uroporphyrin I (UP I) can be phototoxic to human cells. To study the protective ability of antioxidants (beta-carotene, lycopene, ascorbic acid and alpha-tocopherol), against such porphyrin phototoxicity, membrane destruction experiments (Jurkat cells) and human cell cultures (fibroblasts) were performed. Both beta-carotene and lycopene and also the combination of beta-carotene, ascorbic acid and alpha-tocopherol offered cell protection against PP IX phototoxicity. Investigations of both cell membrane protection and of cell growth showed differences in terms of the protection afforded by the anti-oxidants. Thus, for PP IX, carotenoids alone, and in combination with ascorbic acid and alpha-tocopherol, showed higher protection factors in general than UP I. However, for membrane protection there was significant protection against UP I by the combination of beta-carotene, ascorbic acid and alpha-tocopherol but not by any of these anti-oxidants alone. The membrane protection against PP IX by beta-carotene, and especially lycopene, is significant presumably because of the high lipophilicity of all these molecules. However, the hydrophilic UP I will cause phototoxicity mainly via H(2)O(2), radical or singlet oxygen production in the aqueous phase, and these reactive species may be generated some distance from the cell membrane. This may lead to the little or no protection observed for UP I by the individual antioxidants. Nevertheless, a combination of beta-carotene, ascorbic acid and alpha-tocopherol offers membrane protection against the phototoxicity of both porphyrins. This is believed to occur as a result of synergistic processes. Our results suggest that the treatment of porphyria cutanea tarda and erythropoietic protoporphyria may be improved by the use of a combination of the antioxidants studied.

Antioxidants like β-carotene, α-tocopherol and ascorbic acid should be able to protect human cells against damage due to ultraviolet light. Cultured human fibroblasts have been irradiated with UVA or UVB light after incubation with the antioxidants or combinations of them. The efficiency of the protection by the antioxidants in dietary concentrations is estimated by cell counting following cell culture. In the case of UVA irradiation we find synergistic effects of combinations with β-carotene as the main protector. On the other hand, only additive effects of the tested combinations are observed in the experiments with UVB light. Our experiments show a protective effect of dietary antioxidants against human tissue cell damage by ultraviolet light.

There is current interest in the health benefits of dietary carotenoids and the possible deleterious effects on certain sub-populations such as smokers. Here we report in vivo protection of human lymphocytes, conferred by dietary supplementation of lycopene rich foods against the reactive oxygen species, NO(2)(*) radical (by electron transfer) and 1(O)(2) (by energy transfer). It was found that a lycopene rich diet, maintained for 14 days, increased the serum lycopene level 10 fold compared to serum obtained after the same period, where a typical western European diet had been consumed. Relative lymphocyte protection factors of 17.6 and 6.3 against NO(2)(*) radical and 1(O)(2), respectively, were obtained, which re-enforce epidemiological data, showing protection against several chronic diseases by tomato lycopene.