KINETICS AND RATE CONSTANTS OF THE REACTION OF ALPHA-TOCOPHEROL AND CHROMAN C-1 PHENOXYL RADICALS WITH UNSATURATED FATTY-ACIDS AND PHOSPHOLIPIDS

The kinetics of decay of phenoxyl radicals of alpha-tocopherol and its analog, chroman C-1, in the reaction with higher fatty acids (HFA) wi th a different saturation degree and with phospholipids (PL) was studi ed by the method of pulse photolysis. The reaction constant increases with an increase in the number of double bonds in the molecule. For HF A with the number of bonds from 1 to 40 it equals to (0.28 +/- 0.15) x 10(-1); (2.5 +/- 1.5) x 10(-1); (1.00 +/- 0.25) x 10(2); (1.94 +/- 0. 01) x 10(2); (1.0 +/- 0.6) x 10(4) l mol(-1) s(-1), respectively (20 d egrees C). Egg phosphatidylcholine (PC) and cardiolipin (from beef hea rt) reveal the highest activities among PL. The values of the constant for these substances are equal to 300 and 380 l mol(-1) s(-1), respec tively, and for soybean PC and phosphatidylethanolamine they are equal to 2.88 and 36.01 mol(-1) s(-1), respectively. The rate constant for the reaction between chroman C-1 phenoxyl and soybean PC is equal to 5 .05 l mol(-1) s(-1). This value is nearly two times higher than that f or alpha-tocopheroxyl.