A theoretical study on autoxidation of unsaturated fatty acids and antioxidant activity of Pnenovic compounds
2007
Zhang, W. | Shi, B. | Shi, J.
The purpose of this research is to assess oxidative stability of unsaturated fatty acids and their derivatives in leather fatliquors, and to predict effective antioxidants suitable to be used for the systems. The B3LYP/6-31G(d,p) method was employed to obtain C-H and O-H bond dissociation energies of unsaturated fatty acids and phenolic compounds. Using palmitoleic, oleic, ricinoleic, erucic, linoleic, linolenic, and α-eleostearic as models, the autoxidation of unsaturated fatty acids was theoretically clarified based on free-radical chain reaction mechanism and structure-oxidative stability relationships. Calculated results showed that the allylic hydrogens of unsaturated fatty acids are easily abstracted. Unsaturated fatty acid stability is dependent on the number of double bonds and the existence of the substituent group in the carbon chain. Unsaturated fatty acids that contain more double bonds, particularly conjugated double bonds, would be easier to oxidize. Theoretical calculations suggest that the esters are more stable than the free fatty acids. The electron-donating substituent group also favors oxidative stability of unsaturated fatty acids. However, the carbon chain length doesn't significantly affect autoxidation of unsaturated fatty acids. The antioxidative activity of phenolic compounds in unsaturated fatty acids was also studied. Calculated results showed that gallic acid, epigallocatechin, tocopherol and caffeic acid are effective antioxidants in unsaturated fatty acid systems. Epicatechin, ellagic acid and ferulic acid might be suitable to be used as antioxidants for unsaturated fatty acids containing one double bond.
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