Photolysis of α-Tocopherol in Olive Oils and Model Systems

Abstract

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 1H and 13C 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. Keywords: α-Tocopherol; photolysis; olive oil

Location Effects on Oxidative Stability of Chétoui Virgin Olive Oil

“…These results are in agreement with those previously found suggesting that tocopherol content is highly variety‐dependent (Angerosa and Di Giovacchino 1996; Pirisi et al . 1998; Deiana et al .…”

Evaluation of Virgin Olive Oil Minor Compounds in Progenies of Controlled Crosses

“…This same level of α‐Tocopherol content was reported by Baccouri et al ., 2007 for this variety. This result is in agreement with those reported by Angerosa and Di Giovacchino 1996; Pirisi et al . 1998; Deiana et al .…”

Effects of Temperature and UV Light on Degradation of α‐Tocopherol in Free and Dissolved Form

“…In addition to extended exposure to certain temperatures, several other factors such as oxygen, alkali, light, minerals, and hydroperoxides degrade a-tocopherol [13]. The photooxidation of a-tocopherol has been studied by different groups [14][15][16][17][18][19]. Pirisi et al [14] showed that a solution of olive oil in hexane irradiated with artificial light (k = 290 nm), or sunlight degraded at a rate constant (k) of 1.86 9 10 -4 s -1 and 1.03 9 10 -4 s -1 , respectively with a halftime t 1/2 values of 112 and 62 min, respectively.…”

“…The photooxidation of a-tocopherol has been studied by different groups [14][15][16][17][18][19]. Pirisi et al [14] showed that a solution of olive oil in hexane irradiated with artificial light (k = 290 nm), or sunlight degraded at a rate constant (k) of 1.86 9 10 -4 s -1 and 1.03 9 10 -4 s -1 , respectively with a halftime t 1/2 values of 112 and 62 min, respectively. After olive oil was exposed for 2,500 min to artificial light, the majority of a-tocopherol was degraded (only 17% of the initial amount remaining).…”