Antioxidant Capacity of Oat (Avena sativa L.) Extracts. 1. Inhibition of Low-Density Lipoprotein Oxidation and Oxygen Radical Absorbance Capacity

Abstract

Milled oat groat pearlings, trichomes, flour, and bran were extracted with methanol and the fractions tested in vitro for antioxidant capacity against low-density lipoprotein (LDL) oxidation and R-phycoerythrin protein oxidation in the oxygen radical absorbance capacity (ORAC) assay. The oxidative reactions were generated by 2,2'-azobis(2-amidinopropane) HCl (AAPH) or Cu(2+) in the LDL assay and by AAPH or Cu(2+) + H(2)O(2) in the ORAC assay and calibrated against a Trolox standard to calculate Trolox equivalents (1 Trolox equivalent = 1 TE = activity of 1 micromol of Trolox). The antioxidant capacity of the oat fractions was generally consistent with a potency rank of pearlings (2.89-8.58 TE/g) > flour (1.00-3.54 TE/g) > trichome (1.74 TE/g) = bran (1.02-1.62 TE/g) in both LDL and ORAC assays regardless of the free radical generator employed. A portion of the oat antioxidant constituents may be heat labile as the greatest activity was found among non-steam-treated pearlings. The contribution of oat tocols from the fractions accounted for <5% of the measured antioxidant capacity. AAPH-initiated oxidation of LDL was inhibited by the oat fractions in a dose-dependent manner, although complete suppression was not achieved with the highest doses tested. In contrast, Cu(2+)-initiated oxidation of LDL stimulated peroxide formation with low oat concentrations but completely inhibited oxidation with higher doses. Thus, oats possess antioxidant capacity most of which is likely derived from polar phenolic compounds in the aleurone.

Development of a Sustainable Process for the Solid-Liquid Extraction of Antioxidants from Oat

“…That was the case of the interaction between the temperature and time (AC), particle size and time (BC), and particle size and solvent (BC). ORAC results in this study (<0.001-31.10 µmol TE/g oat) were similar to reported values (2.08-28 µmol TE/g oat) from other research [6,14]. These values can be compared to ORAC contained in fruits where values range from 37.42-274 µmol TE/g [28].…”

“…From this distribution it was found that 63% of the distribution was in the size of 0.50 mm. This is important since this is the size used in a great deal of reports regarding extraction of antioxidants from oat [3,8,[13][14][15][16]. Hence, the experiments proposed in this research covered this range, this to evaluate the effect of particle size in the extraction.…”

“…In order to avoid sources of bias experiments were run in a randomly sequence. Maximum and minimum levels of factorial design 1 were obtained from experiments already reported [3,13,14,16]. For solvents, the coded values (1, −1) referred to different polarity levels, the higher level must be the polar solvent.…”

Bioactivity of oats as it relates to cardiovascular disease

“…Minor differences in relative activity were assigned to the reactivity preference of specific phenols towards different radical types. The correlation of activity with phenolic content is consistent with other studies 61 and it appears that most of the antioxidant activity of oats resides with the hydrophilic components and particularly the phenolic fraction in the aleurone 62 . In this study, the contribution of oat tocols accounted for , 5 % of the measured antioxidant capacity although it has been noted 60 that the assumption of equivalent reaction rates between 6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid (Trolox) and tocols on which the calculation was based is not necessarily correct in all cases.…”

The effect of grain polyphenols and the addition of vitamin E to diets enriched with α-linolenic acid on the antioxidant status of pigs

“…Among cereals, oat grain has been extensively investigated and has been shown to contain many compounds that exhibit antioxidant properties, such as tocopherols, tocotrienols, flavonoids, phenolic acids, avenantramides and sterols (Peterson, 2001). A major part of the antioxidant capacity (>95%) of oat is derived from phenolic compounds in the aleurone, and only <5% from tocols (Handelman et al, 1999). In a study on broiler chickens, partial replacement of maize with oats increased the oxidative stability of fat in meat (Lopez-Bote et al, 1998).…”