Abstract
In this study, the antioxidant activities of 15 flavonoids against lard oil oxidation were determined by using the Rancimat test. Quercetin, dihydromyricetin, luteolin and kaempferol showed the strongest antioxidant activity, with protection factor values (PF) of 11.50, 11.29, 4.24 and 2.49, respectively. The role of conjugated hydroxyl groups of the B and C ring is discussed. By using the following descriptors: ΔHf (the difference in heat of formation between flavonoids and their free radicals resulted after hydrogen atom donation) and HBC (the number of conjugated hydroxyl groups of the B and C ring), the result obtained in the antioxidant Rancimat test could be successfully explained.
Highlights
A number of studies have shown that natural antioxidants from plant sources can effectively inhibit oxidation in food and reduce the risk of age-dependent diseases
It is necessary to determine whether the theoretical methods are still effective to characterize the antioxidant activity of flavonoids in a complex and hydrophobic system, e.g., in the experiments that show how antioxidants protect lipid
The goal of this paper is to measure the antioxidant activity of 15 natural flavonoids in lard oil by a Rancimat test and to present the relationships between molecular structure-derived parameters and the antioxidant activity of flavonoids
Summary
A number of studies have shown that natural antioxidants from plant sources can effectively inhibit oxidation in food and reduce the risk of age-dependent diseases. Structure-activity relationship of flavonoids as antioxidants has been explained successfully by theoretical calculations [3,4]. Hydrogen-donation was thought to be the main mechanism of acton of phenolic antioxidants in oil, and the difference in heat of formation between the phenolic antioxidant and its free radical produced after H-abstraction (ΔHf), appeared to be a good index for measuring the scavenging activity of antioxidants [7].
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