In vitro antimicrobial activity of common species of seaweeds native to Trinidadian coasts

Marine macrophytes have been recently recognized as promising sources of bioactive molecules and as such many drugs leads have arisen from them. We investigated the antibacterial activity of methanol extracts of seaweeds against several human pathogens. Among the seaweeds screened, three species showed inhibitory effects against at least one pathogen, with Ulva fasciata and Amphiroa rigida exhibiting bacteriostatic activity and Chaetomorpha crassa showing bactericidal action against pathogenic Gram-positive cocci. Further testing revealed that the extracts of Chaetomorpha crassa displayed the ability to inhibit biofilm formation and virulence gene expression in Methicillin resistant Staphylococcus aureus (MRSA). Isolation and identification of the bioactive molecules of Chaetomorpha crassa revealed the two free fatty acids stearic acid and linolenic acid. This research shows that several species of marine plants found in Trinidad comprise bioactive compounds and may be good candidates for further investigations aimed at isolating and evaluating these compounds for potential medical applications.