Natural antifoulants from the marine cyanobacterium Lyngbya majuscula

Abstract

Filamentous benthic marine cyanobacteria are a prolific source of structurally unique bioactive secondary metabolites. A total of 12 secondary metabolites, belonging to the mixed polyketide–polypeptide structural class, were isolated from the marine cyanobacterium, Lyngbya majuscula, and were tested to determine if they showed activity against barnacle larval settlement. The assays revealed four compounds, dolastatin 16 (1), hantupeptin C (4), majusculamide A (10), and isomalyngamide A (12), that showed moderate to potent anti-larval settlement activities, with EC₅₀ values ranging from 0.003 to 10.6 μg ml⁻¹. In addition, field testing conducted over a period of 28 days (using the modified Phytagel™ method) based on the cyanobacterial compound, dolastatin 16, showed significantly reduced barnacle settlement as compared to controls at all the concentrations tested. The results of this study highlight the importance of marine cyanobacteria as an underexplored source of potential environmentally friendly antifoulants.

Keywords:

• marine cyanobacterium
• secondary metabolites
• natural antifoulants
• barnacles
• cyprid settlement

Acknowledgements

The authors acknowledge NIE AcRF (RI 8/05 TLT and RP 5/02 GPL) for financial support. In addition, the authors thank A.L. Ang (NSSE, NIE) and S.G.Y. Lee (NSSE, NIE) for providing valuable technical assistance as well as the Raffles Marina Ltd, Singapore, for the use of the research berth for the field experiments.