Photolysis of alpha-tocopherol in olive oils and model systems

摘要

The photolysis of a-tocopherol (I) in olive oil (O) acid in some model systems (n-hexane = H; anhydrous n-hexane = KA, and triolein = T) was studied under sunlight and under artificial light (lambda > 290 nm) by HPLC and GC/MS. In O and T, I disappeared linearly to 50% of the starting concentration, reached a constant value, and finally disappeared rapidly from the medium. In the model system, photolysis followed a pseudo-first-order kinetics. Although no peaks attributable to photoproducts were found in O, a main product identified by H-1 and C-13 NMR and GC/MS as 5-formyltocopherol (II) was found in the model systems. Irradiation of compound II led to species undetectable by HPLC in agreement with a slower consecutive kinetic process than that of I. In the HA and T systems, the formation of II occurred at lower levels than in H. The possible behavior of photodegradation is discussed. [References: 14]