Comparison of antioxidant activities of selected phenolic compounds in O/W emulsions and bulk oil

Antioxidant activities of 1-o-galloylglycerol (GG), propyl gallate, rosmarinic acid (RA), tocopherols (TOC), and 1:1 combinations of GG/RA and GG/TOC were evaluated using in vitro assays including 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS⁺), and ferric reducing antioxidant power (FRAP). Soybean oil stripped of TOC was utilized as bulk oil and as the oil phase in O/W emulsions for accelerated oxidation test with the selected phenolic compounds. Efficacies of antioxidants were evaluated by monitoring total oxidation (TOTOX) values and fatty acid profiles of oil and O/W samples during the accelerated oxidation. In bulk oil, GG outperformed other singular antioxidants, preventing 39.04% of oxidation for ω-3 fatty acids with a TOTOX value of 166.68. In emulsions, TOC outperformed other singular antioxidants, preventing 38.04% of oxidation with a TOTOX value of 196.72. Considering the polarities of the antioxidants and our testing systems, these results provide supporting evidence for the polar paradox theory.

Phenolic compounds as antioxidants to improve oxidative stability of menhaden oil-based structured lipid as butterfat analog

Phenolic compounds, including propyl gallate, 1-o-galloylglycerol, ferulic, gallic, caffeic, rosmarinic, and carnosic acids, tocopherols, and butylated hydroxytoluene (BHT), were investigated as antioxidants to improve the oxidative stability of a structured lipid (SL) produced by the enzymatic acidolysis of menhaden oil with caprylic and stearic acids. SL had similar physical properties to butterfat but was more susceptible to oxidation. The above phenolic compounds were each added to SL as antioxidants. SL with 1-o-galloylglycerol, rosmarinic acid, or BHT showed the highest oxidative stability during an accelerated oxidation test with the total oxidation (TOTOX) value around 250 after 18 days. Oxidation induction time (OIT) using differential scanning calorimetry showed a good correlation with the accelerated oxidation test. A mixture of 1-o-galloylglycerol and tocopherols at 50:50 ppm had the strongest protective effect on SL (OIT = 115.1 min) compared to the other tested compounds or combinations at the same concentration (OIT < 100 min).

Antioxidant property and characterization data of 1-o-galloylglycerol synthesized via enzymatic glycerolysis

This article provides comprehensive experimental data characterizing antioxidant activity, as well as chemical and physical properties of 1-o-galloylglycerol (GG), synthesized by enzymatic glycerolysis of propyl gallate (PG) using a food-grade lipase (Lipozyme® 435) [1]. GG was characterized by Fourier-transform infrared spectroscopy (FT-IR), ¹H, ¹³C, ¹H–¹H gradient correlation spectroscopy (gCOSY), ¹H–¹³C gradient heteronuclear single quantum coherence (gHSQC), ¹H–¹³C gradient heteronuclear multiple quantum coherence (gHMQC), and ¹H–¹³C gradient heteronuclear multiple bond correlation (gHMBC) nuclear magnetic resonance spectroscopies (NMR), and ultraviolet–visible spectrophotometry (UV–Vis). The antioxidant property of GG, which was evaluated through 1,1-diphenyl-2-picrylhydrazyl (DPPH^•), 2,2′-azinobis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS^•+), ferric reducing antioxidant power (FRAP), and hydrogen peroxide (H₂O₂) scavenging assays, is also presented.