Flavonoid Natural Products as Potential Green Antifoulants for Marine Composite Coatings

Flavonoids, a natural polyphenolic substance, exhibit a wide range of biological activities and outstanding potential for marine antifouling. Inhibition zone tests and analysis of the structure-activity relationship were conducted on 10 flavonoids, after which L-epicatechin, dihydromyricetin, and quercetin were selected as antifoulants to prepare three epoxy resin composite antifouling coatings, and their marine antifouling efficacy was further evaluated. The anti-protein adhesion rates of the three composite coatings are all above 90%, and the anti-algae adhesion rates are also all above 80%. They also exhibited excellent inhibitory adhesion effects on gram-positive bacteria, gram-negative bacteria, and marine bacteria. Especially for S. aureus, the inhibition rate is all higher than 90%. The antifoulants can release continuously for a long period of time, and the results of the sea anchor plate tests show that they still have a certain inhibitory effect on the attachment of marine organisms in seawater, with a duration of up to 105 days. This study aims to evaluate the antifouling potential of commercially available flavonoids in epoxy resin coatings, thereby providing a low-cost and easily industrializable strategy for green marine antifouling.