Antifouling activity of sea cucumber (Stichopus herrmanni) extracts in laboratory and its performance in resin epoxy coats in the sea environment

Development of natural and environmentally friendly antifouling agents is a suitable alternative to solve the global marine fouling problem. In the current study, antibacterial, anti-micro algal, anti-barnacle and antifouling activity of non-polar, semi-polar and polar extracts from three parts of the sea cucumber, Stichopus herrmanni, body (i.e. body wall, digestive tract and respiratory tree) were studied. The inhibitory activity assay of n-hexan, ethyl acetate and methanol extracts were evaluated against five bacterial strains, two microalgae species and barnacle larvae. In order to investigate the antifouling performance, the extracts were added to a resin epoxy coats and exposed in the sea water for the duration of three months. Based on Results, the ethyl acetate extract of the body wall with the lowest MIC against S. aureus (0.500 mg/ml) and I. galbana (0.125 mg/ml), and the lowest LC50 against barnacle larvae (0.061 mg/ml), showed the best inhibitory activity. After three months treatment, the coated panels containing 4% extract of ethyl acetate from body wall had the lowest final weight (189.67 ± 5.51 g) and lowest fouling cover percentage (74.76%) among all the panels (P<0.05). Regarding the high antifouling activity of ethyl acetate extract from the body wall of the sea cucumber S. herrmanni, it is recommended as a potential natural alternative for the antifouling coats.