Antioxidant Activity of Gallic Acid as Affected by an Extra Carboxyl Group than Pyrogallol in Various Oxidative Environments

Abstract

The antioxidant activity of gallic acid and pyrogallol is studied by the DPPH• scavenging assay and the extent of oxidation inhibition of the triacylglycerols of various unsaturated oils (olive, sunflower, and soybean) and their oil‐in‐water emulsions. The gallic acid molecules with an electron‐donating carboxylate anion are significantly stronger DPPH• scavengers than pyrogallol molecules (IC50 = 11.4 vs. 20.2 μM). Regarding the prevention of the triacylglycerols from oxidation, gallic acid is of higher activity than pyrogallol in the bulk oils (86.1–1244.3 vs. 73.4–331.6) but of lower activity in the O/W emulsions (13.0–74.9 vs. 17.4–207.9), depending on their different antioxidant behaviors arisen from the free radical chain mechanism of action as well as interfacial phenomena. Practical Applications: The present study clarifies the role of the carboxyl group in gallic acid antioxidant activity, antioxidant activity as a function of the free radical chain mechanism as well as interfacial phenomena, critical concentration of reverse lipid hydroperoxide micelles as affected by the antioxidant activity, and the effect of the degree of lipid unsaturation on the antioxidant activity of gallic acid and pyrogallol. Comparative antioxidant performance of gallic acid and pyrogallol to scavenge 1,1‐diphenyl‐ 2‐picrylhydrazyl radical (DPPH•) in a methanolic system and to inhibit peroxyl radical (LOO•) in triacylglycerols of olive, sunflower, and soybean oils and their oil‐in‐water (O/W) emulsions.

A comparative study on the antioxidant activity of <i>Gladiolus dalenii</i> Van Geel and nine commonly used substances to compare the antioxidant activity of foods and medicinal plants

“…The three derivatives do not have the free carboxyl grouping, which leads us to conclude that the reduction in the antioxidant activity of these compounds against the DPPH free radical may be associated with this fact. These findings corroborate the data described by Rafiee et al (2018) in their studies comparing the antioxidant activity of GA with PyG. These authors observed a significant contribution of the carboxyl group of GA in the scavenging of DPPH free radicals.…”

Initiation and propagation kinetics of inhibited lipid peroxidation

“…More unsaturated fatty acids generate LOOH molecules of higher polarity and, therefore, of higher levels of surface activity, facilitating their incorporation into the water–oil interfaces 25 . However, more unsaturated LOOH would be bulkier and occupy more space in the interface, decreasing their compact aggregations 26 . The value of [LOOH] IP decreased considerably when adding the antioxidants (Table 2 ).…”

Allelopathic Potential and Active Substances from Wedelia Chinensis (Osbeck)

“…Gallic acid is present in fruits and vegetables [66]; gallnuts, grapes, and blackberries [67]; eucalyptus species and Picea schrenkiana [68]; tea [69]; chestnuts and several berries [51]; Myriophyllum spicatum, Cynomorium coccineum, and Microcystis aeruginosa [70,71]; and black tea [72]. It has many medicinal uses such as antimicrobial [73], neuroprotection [74], antioxidant [75,76], anticancer [77,78], and antiulcer [79] uses and for cardiovascular diseases (CVDs) [80]. Furthermore, gallic acid has lipid homeostasis [81] and antihyperglycemic effects [82] and acts as a cardioprotective agent [83,84].…”