Effect of the Enrichment of Corn Oil With alpha- or gamma-Tocopherol on Its In Vitro Digestion Studied by 1H NMR and SPME-GC/MS; Formation of Hydroperoxy-, Hydroxy-, Keto-Dienes and Keto-E-epoxy-E-Monoenes in the More alpha-Tocopherol Enriched Samples

Abstract

The aim of this study is the analysis of the in vitro digestion of corn oil, and of the effect of its enrichment with three levels of gamma- and alpha-tocopherol, by using, for the first time, 1H nuclear magnetic resonance (1H NMR) and a solid phase microextraction followed by gas chromatography/mass spectrometry (SPME-GC/MS). The attention is focused on the hydrolysis degree, the degradation of oil’s main components, the occurrence of oxidation reactions and main compounds formed, as well as on the bioaccessibility of oil’s main components, of compounds formed in the oxidation, and, of gamma- and alpha-tocopherol. The lipolysis levels reached are high and show a similar pattern in all cases. The oxidation of corn oil components during in vitro digestion is proven, as is the action of gamma-tocopherol as an antioxidant and alpha-tocopherol as a prooxidant. In the more alpha-tocopherol enriched samples, hydroperoxy-, hydroxy-, and keto-dienes, as well as keto-epoxy-monoenes and aldehydes, are generated. The bioaccessibility of the oil’s main components is high. The compounds formed in the oxidation process during in vitro digestion can also be considered bioaccessible. The bioaccessibility of alpha-tocopherol is smaller than that of gamma-tocopherol. The concentration of this latter compound remains unchanged during the in vitro digestion of the more alpha-tocopherol enriched oil samples.

A Global Study by 1H NMR Spectroscopy and SPME-GC/MS of the in Vitro Digestion of Virgin Flaxseed Oil Enriched or not with Mono-, Di- or Tri-Phenolic Derivatives. Antioxidant Efficiency of These Compounds

“…To the best of our knowledge, this is the first time that it has been shown that dodecyl gallate and hydroxytyrosol acetate are not able to inhibit lipase activity. The inability of gamma-tocopherol to inhibit lipase activity has been shown in a previous study and the results here obtained confirm this fact [14]. In contrast to this, and although the differences were not significant, a slightly smaller percentage of triglycerides, and a slightly higher percentage of glycerol in the digestates of the enriched samples than in the nonenriched sample was observed.…”

“…Furthermore, several studies have analyzed the effect that enrichment of certain oils with alpha-tocopherol has on their oxidation when they are submitted to digestion conditions, with controversial results [9,[11][12][13]. Finally, a comparative study of the effect of the enrichment of corn oil with alpha-and gamma-tocopherol showed that the former acts as prooxidant, which is in agreement with some of the aforementioned studies, whereas the second acts as antioxidant [14].…”

Assessing the Impact of Oil Types and Grades on Tocopherol and Tocotrienol Contents in Vegetable Oils with Chemometric Methods

“…Especially when compared with animal-derived foods, edible plant-derived products are the major source of tocols, such as oil seeds; green parts of plants; whole grains; nuts; and vegetable oils of wheat germen, sunflower, corn, as well as olives [2,[13][14][15][16]. Vegetable oils, quintessential lipid foods in the human diet, are considered very suitable for the enrichment of tocopherols due to the lipophilicity of tocopherols [17]. Besides this, the content of tocols in oil is considered an important indicator to reflect the oil quality.…”

Study of the In Vitro Digestion of Olive Oil Enriched or Not with Antioxidant Phenolic Compounds. Relationships between Bioaccessibility of Main Components of Different Oils and Their Composition

“…Both kinds of data are given in Table 1 and Table 2 respectively. As mentioned, data of corn and virgin flaxseed oils were taken from previous studies [ 13 , 14 ]. Regarding data in Table 2 of the molar percentages the different kinds of acyl groups in each oil, it should be mentioned that that although there are four compositional data (%S, %O, %L, %Ln), only three are independent variables.…”

“…In addition to lipolysis, lipid oxidation can also take place during digestion [ 9 , 10 , 11 , 12 , 13 , 14 ], leading to the formation of toxic compounds with detrimental effects on health. It may be expected that the extent of this reaction will not be the same for all kinds of oils and that it will be determined by the oxidative stability of the lipids involved as well as by the presence or absence of minor compounds capable of acting as antioxidants or of prooxidants during digestion.…”