Performance assessment of capsaicin derivatives containing amide groups used as active substances for antifouling coatings

The culprit of biofouling is the formation and reproduction of viable microbial biofilms. For many years, biofouling is a critical issue in marine pollution treatment and has drawn great attention. Herein, eight capsaicin (CAP) derivatives were prepared using aromatic hydrocarbons and amides as raw materials, thereinto, compounds A1, A2, A3, A4, and B1 has not been reported, being considered some new compounds. Meanwhile, the antifouling (AF) property of CAP derivatives were characterized for the first time. The inhibition rates of these CAP derivatives (20 mu g.mL(-1)) against Escherichia coli and Staphylococcus aureus exceed 80% and 92%, respectively. The anti-algal activity of the CAP derivatives is time and concentration dependent. Compounds A3 and A4 exhibit excellent anti-algal activity (> 77.30% against Nitzschia closterium and > 82.50% against C. vulgaris), and their toxicity is lower than that of currently used antifoulants, such as TBT and SeaNine 211. Most importantly, AF coatings with CAP derivatives show excellent AF effects in marine environments for 180 days; moreover, as auxiliary AF agents, CAP derivatives further enhance the AF performance of cuprous oxide-containing coatings, which are widely used as antifoulants. The phenolic hydroxyl group, benzene ring, amide group and chlorine atom in the CAP derivatives are supposed to be the main active groups contributing to the AF performance. This study may provide a promising method to solve marine pollution.

Automated summary

This study synthesized eight capsaicin (CAP) derivatives, some of which were considered new compounds. The antifouling (AF) properties of these compounds were characterized for the first time, showing excellent anti-algal activity and inhibition rates against bacteria. The study suggests that the CAP derivatives have potential applications in marine pollution treatment.