Transients and cooperative action of β-carotene, vitamin E and C in biological systems in vitro under irradiation
Using N ∙3 species as specific electron acceptor a defined ascorbate radical: AH ∙↔A ∙-+H + (λ max=360 nm, ∊=3400 dm 3 mol -1 cm -1) is observed. The attack of DMSO ∙+ on vit.E results in a vit.E ∙ radical ( k=1×10 9 dm 3 mol -1 s -1; λ max=425 nm, ∊=2400 dm 3 mol -1 cm -1; 2 k=4.7×10 8 dm 3 mol -1 s -1). Vit.E-acetate leads to the formation of a radical cation (vit.E-ac ∙+). β-carotene reacts also with DMSO ∙+ forming a radical cation, β-car ∙+ ( k=1.75×10 8 dm 3 mol -1 s -1; λ max=942 nm, ∊=14 600 dm 3 mol -1 cm -1), which probably leads to the formation of a dimer radical cation, (β-car) ∙+2 ( k=2.5×10 7 dm 3 mol -1 s -1). Using E.coli bacteria (AB1157) as a model system in vitro it was found that all three vitamins are rather efficient radiation protecting agents. They can also increase the activity of cytostatica, e.g., mitomycin C (MMC), by electron transfer process. The mixture of vit.E-ac and β-car acts contradictory, but adding vit.C to it a strong cooperative enhancement of the MMC activity is observed once again. A relationship between the pulse radiolysis and the radiation biological data is found and discussed. A possible explanation of the previously reported trials concerning the role of vit.E and β-car on the increased occurence of lung and other types of cancer in smokers and drinkers is presented.