Photolysis of α-Tocopherol in Olive Oils and Model Systems

The photolysis of α-tocopherol ( I ) in olive oil (O) and in some model systems ( n -hexane = H; anhydrous n -hexane = HA, and triolein = T) was studied under sunlight and under artificial light (λ > 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 1 H and 13 C 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.