Synthesis and Antibacterial Activity of Vanillic Acid Derivatives Containing Indole Structure

Using indole-2-carboxylic acid and vanillic acid as raw materials, a series of 11 novel compounds (7a–k) were synthesized by chemically linking indole-2-carboxylic acid and vanillic acid through an aminothioureido group. The antibacterial activity of these compounds against Vibrio harveyi and Vibrio parahaemolyticus was evaluated using the agar perforating method. The results indicated that compounds 7g–j exhibited superior antibacterial activity against both strains compared to the positive control, with 7g showing the best performance. Structure-activity relationship analysis suggested that alkylation of the nitrogen atom in the indole ring could enhance the antibacterial effect, and shorter carbon chains were associated with better antibacterial activity.