Synthesis and evaluation of phenolic capsaicin-derived self-polymers for antibacterial activity

Abstract

Capsaicin, as a low-toxic antibacterial bioactive substance, is recognized as an environmentally friendly antifouling agent. To obtain a naturally derived antifouling agent with stronger antibacterial ability, capsaicin-derived self-polymers (labeled POHABA, PPHABA, PAHMA, and PAMTHBA) containing phenols (catechol, hydroquinone, resorcinol, phloroglucinol) and N-hydroxymethyl acrylamide were synthesized by precipitation polymerization, which was uniform spheroids with folded surfaces (diameter 0.6–1.6 µm, except PAMTHBA diameter 200–400 nm). The antibacterial activity assay showed that they had a significant inhibitory effect on E. coli and S. aureus (MIC: 0.4 mg/mL against E. coli and 0.8 mg/mL against S. aureus; antibacterial rate: 99.99 % for E. coli and 98.18 % for S. aureus), which was related to the content of phenolic hydroxyl on the surface of the microspheres by comparison with the semi-quantitative analysis of EDS and XPS spectra. The antibacterial activity of self-polymers was significantly higher than that of the monomers, mainly because there were more and more uniform hydroxyl groups on the surface of polymer microspheres. These results provide a theoretical basis for capsaicin-derived self-polymers to be applied to environmentally friendly antifouling agents.