Autoxidation of benzaldehyde derivatives (BA derivatives) were investigated in aqueous solutions of a nonionic surfactant. In the micellar systems, partition constants (Km) between the micelle and bulk phase for BA derivatives and antioxidants were calculated. In addition, the binding site of those substrates within the micelles were determined.
The summary of the results is shown below.
1) In the micellar systems, the autoxidation of p-hydroxybenzaldehyde (HBA) was inhibited, but that of benzaldehyde (BA) and p-isopropylbenzaldehyde (PBA) was promoted, especially in PBA.
2) In the micellar systems, n-propyl gallate (PG) for HBA, and dl-α-tocopherol (α-T) for BA and PBA showed strong antioxidative activities.
3) HBA and PG molecules within the micelles penetrated only to a small extent into the mantle layer, BA penetrated deeply the mantle layer, and PBA and α-T were the core.
On the basis of the experimental results, it was suggested that the inhibition of HBA oxidation in the micellar systems was due to the influence of the mantle layer under the unaerobic condition, while the promotion of BA and PBA oxidation was due to the influence of the core under the aerobic condition.
It was found that the antioxidants indicating the binding sites similar to those of the BA derivatives within the micelles showed strong antioxidative activity.