Environmentally benign antifouling activity and toxic properties of bioactive metabolites from mangrove Excoecaria agallocha L.

This study was aimed to investigate the antifouling (AF) potentials and toxic properties of methanol extract from leaves of mangrove Excoecaria agallocha. Antimicrofouling activity results inferred that this extract strongly inhibited fouling bacterial and microalgal growth. This extract had also inhibited the settlement of brown mussel Perna indica and larvae of barnacle Balanus amphitrite. Further, EC50 < LC50 and therapeutic ratio > 1 together propagated non-toxic nature of the extract. Mollusk foot adherence assay result showed complete inhibition of foot spreading and loss of attachment of common rocky fouler Patella vulgata to the substrata. Field assay results affirmed that this extract effectively deterred settlement of biofoulers. Purification and GC-MS analysis of bioassay-guided active spot evidenced presence of three major compounds (> 85%) responsible for the promising AF activity. The identified lead compounds subjected to an estimation (BIOWIN™) program developed by United States Environmental Protection Agency (USEPA) predicts that they are biodegradable in nature. Graphical abstract.