3.3 Tocopherols
The individual tocopherols identified are showed in Table 3; a total of 49.8, 86.9 and 41.2 mg/100g of oil were quantified in F1, F2 and F3, respectively; while a total of 94.8, 87.7 and 77.8 mg/100 g of oil were quantified in C1, C2 and C3, respectively. It is recognized that tocopherols are the most important natural antioxidants because of their free radical scavenge activity, involving a tocopherol-tocopheryl semiquinone redox system (Montserrat-de la Paz et al., 2014). In addition they have shown different beneficial effects on degenerative diseases such as atherosclerosis, cardiovascular disease, Alzheimer’s disease and certain type of cancer (Fromm, Bayha, Kammerer & Carle, 2012).
As expected, considering the literature, in all samples γ-tocopherol was the predominant compound followed by β-tocopherol, α-tocopherol and α-tocotrienol. In Futura 75 γ-tocopherol showed a significative increase (p < 0.05) between first and second harvest (40.8 and 82 mg/100 g of oil in F1 and F2, respectively) and then significantly (p < 0.05) decrease at last maturation time (F3, 37.1 mg/100 g of oil). The other tocopherols were present in very low concentration; in fact, β-tocopherol was present only at the first harvesting stage (9.0 mg/100 g of oil) and α-tocotrienol just in the last one (3.3 mg/100 g of oil). α-tocopherol were not detected at first maturation stage, but only in the other two, with a significative (p < 0.05) decrease between them, 4.9 and 0.8 mg/100 g of oil for F2 and F3, respectively. For this reason, the total tocopherols content had the same trend of γ-tocopherol, increasing significantly (p < 0.05) the total concentration at the second harvest stage (F2) reaching a value about 87 mg/100 g of oil (Table 3). Also in Carmagnola γ-tocopherol was the predominant tocopherol with a significative decrease (p < 0.05) during the maturation, 90.2, 81.8 and 72.9 mg/100 g of oil for F1, F2 and F3, respectively. β-tocopherol, on the contrary, was not detected during the entire maturation. α-tocopherol was present in every maturity stage with a significant increase (p < 0.05) in the middle of maturity; 3.5, 5.9 and 4.9 mg/100 g of oil in C1, C2 and C3, respectively. Finally, α-tocotrienol was present just at the beginning of maturity (C1) with a concentration of 1.1 mg/100 g of oil. Total tocopherol concentration follows γ-tocopherol trend, so a constant significative decrease during maturation was recorded; 94.8, 87.7 and 77.8 mg/100 g of oil in C1, C2 and C3, respectively.
Our results agree with literature where γ-tocopherol represent the 90% of the total tocopherols content (Oomah et al., 2002; Anwar, Latif & Ashraf, 2006; Latif & Anwar, 2009; Montserrat-de la Paz et al., 2014). In a study conducted by Kriese et al. (2004), where hempseed oil was extracted by supercritical fluids, the general tocopherol content was much lower than ours, so, in addition to botanical characteristics, climatic and cultivation conditions, also the extraction method affects the tocopherols content.