Abstract
The relationship between the structure and the antioxidant activity of 21 hindered phenolic compounds was investigated by Rancimat and DPPH· tests. 3- tert -butyl-5-methylbenzene-1,2-diol is the strongest antioxidant in the Rancimat test but not in the DPPH· test because its two hydroxyl groups have very strong steric synergy. 2,6-Di tert -butyl-4-hydroxy-methylphenol exhibits a strong antioxidant activity as 2,6-di tert butyl- 4-methoxyphenol does in lard. 2,6-Di tert -butyl-4- hydroxy-methylphenol also exhibits stronger activity than 2- tert -butyl-4- methoxyphenol. The methylene of 2,6-di tert -butyl-4-hydroxy-methylphenol can provide a hydrogen atom to active free radicals like a phenolic hydroxyl group does because it is greatly activated by both the aromatic ring and hydroxyl group. Five factors affect the antioxidant activities of the phenolic compounds: how stable the phenolic compound free radicals are after providing hydrogen atoms; how many hy drogen atoms each of the phenolic compounds can provide; how fast the phenolic compounds provide hydrogen atoms; how easily the phenolic compound free radicals can combine with more active free radicals, and whether or not a new antioxidant can form after the phenolic compound provides hydrogen atoms.
Highlights
Autoxidation is the main process of fat, oil and lipid-based food deterioration, which results in a loss in nutrition, and the production of an offflavor and other harmful substances (Pokorny et al, 2001)
Our study focused on the relationship between antioxidant structure and activity of these phenolic compounds by using the Rancimat test in lard and the DPPH assay
Other hindered phenolic antioxidants were purchased from Tokyo Kase Kogyo Co, Ltd. 2-tert-butyl-benzene1,4-diol was purchased from Shanghai Chemical Reagent Co. (Shanghai, China)
Summary
Autoxidation is the main process of fat, oil and lipid-based food deterioration, which results in a loss in nutrition, and the production of an offflavor and other harmful substances (Pokorny et al, 2001). Many hindered phenolic antioxidants such as 2,6-ditert-butyl-4-methylphenol (BHT), 4-hydroxy3-tert-butylanisole (BHA), tert-butylated hydroquinone (TBHQ) are widely used as antioxidants in the food industry, especially for bulky oils and fatty foods. These synthetic antioxidants are highly active and cheap. The addition of antioxidants is the most effective, convenient and economical way to retard lipid autoxidation (Li et al, 2006). The antioxidant activity of natural and synthetic phenolic compounds attracts the attention many researchers
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