Effect of Chain Length on the Micellization,Antibacterial, DPPC Interaction and Antioxidant Activities of l‐3,4‐Dihydroxyphenylalanine (l‐DOPA) Esters

l ‐DOPA (l ‐3,4‐dihydroxyphenylalanine) has been widely used as a drug in the clinical treatment of Parkinson's disease. In this report, the systematic study of the effect of chain length on the critical micelle concentration (CMC), antibacterial and antioxidant activity of esters derived from the aromatic amino acid l ‐3,4‐dihydroxyphenylalanine as surfactants are accounted for the first time. The antibacterial activity displayed a cut‐off effect at C₁₂ with respect to both gram positive and gram negative bacteria (except for Pseudomonas aeruginosa where the cut‐off was displayed at C₁₀). Correlation of the CMC with the minimum inhibitory concentration (MIC) shows that the DOPA esters exist in micellar form at the MIC. An increase in chain length of the DOPA esters induces greater binding with phospholipid vesicles 1,2‐dipalmitoyl‐sn‐glycero‐3‐phosphocholine. The C₁₂ ester possessed highest radical scavenging ability among the esters tested against both 2,2‐diphenyl‐1‐picrylhydrazyl and 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulphonic acid) showing that antioxidant activity of the DOPA esters is also affected by chain length. This study showed that DOPA esters are promising candidates as antibacterial agents as well as good antioxidants.