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

Abstract

The effect of enriching virgin flaxseed oil with dodecyl gallate, hydroxytyrosol acetate or gamma-tocopherol on its in vitro digestion is studied by means of proton nuclear magnetic resonance and solid phase microextraction followed by gas chromatography/mass spectrometry. The extent and pattern of the lipolysis reached in each sample is analyzed, as is the bioaccessibility of the main oil components. None of the phenolic compounds provokes inhibition of the lipase activity and all of them reduce the lipid oxidation degree caused by the in vitro digestion and the bioaccessibility of oxidation compounds. The antioxidant efficiency of the three tested phenols is in line with the number of phenolic groups in its molecule, and is dose-dependent. The concentration of some minor oil components such as terpenes, sesquiterpenes, cycloartenol and 24-methylenecycloartenol is not modified by in vitro digestion. Contrarily, gamma-tocopherol shows very low in vitro bioaccessibility, probably due to its antioxidant behavior, although this increases with enrichment of the phenolic compounds. Oxidation is produced during in vitro digestion even in the presence of a high concentration of gamma-tocopherol, which remains bioaccessible after digestion in the enriched samples of this compound.

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

“…It has been reported that certain polyphenolic compounds, polymeric or not, are able to inhibit lipase activity and reduce the lipolysis extent reached during lipid digestion [ 5 , 38 ]. However, this ability has not been observed in the phenolic compounds involved in this study [ 14 ]. Table 1 shows the molar percentages of the different glyceryl species found in the digestates of olive oil enriched with various concentrations of dodecyl gallate (DG), hydroxytyrosol acetate (HTA) and gamma -tocopherol (γT).…”

“…The data of lipolysis yields of other edible oils such as corn oil C and virgin flaxseed oil F, obtained in previous studies [ 13 , 14 ] under the same digestive conditions as in this study, are given in Table 1 . It can be observed that the extent and pattern of lipolysis is very different to that of olive oils O 1 and O 2 .…”

“…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 previous studies on the in vitro digestion of edible oils of different unsaturation degree it was proved that lipid oxidation takes place during this process [ 9 , 10 , 11 , 12 , 13 , 14 ]. This is a subject of great importance due to the toxicity of some of the oxidation compounds that can be formed, because they can be absorbed through the intestinal wall.…”

“…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.…”