Seaweeds - A field manual

Bacterial resistance to pharmaceutical drugs is on rise, which emphasizes the need for screening of new drugs from natural resources. Seaweeds from the marine ecosystem are important source of bioactive compounds making them one of the major subjects for screening of various pharmaceutical drugs. So here, we assessed the bacterial growth inhibitory functions of four seaweeds Sargassum wightii, Gracillaria edulis, G. corticata and Ulva lactuca of Andaman Sea and Bay of Bengal, India respectively against three pathogens Pseudomonas aeruginosa, Eischeira coli and Staphylococcus aureus. Solvent extraction of four seaweeds was performed using 70% methanol, ethanol and ethyl acetate. Agar well diffusion method was used to test the bioactivity of seaweeds against pathogens. S. wightii,G. edulis and U. lactuca were observed with better solvent extracts compared to G. corticata. Methanol extract of S. wightii was observed with the highest (29.0 ± 1.22) zone of inhibition (ZOI) and ethyl acetate extract of U. lactuca was observed with the lowest ZOI (5.0 ± 0.0) against S. aureus. Butanol extract of S. wightii was observed with the highest ZOI (14.0 ± 0.83) against P. aeruginosa, whereas G. edulis methanol extract and U. lactuca ethyl-acetate extract were observed with the lowest ZOI (6.0 ± 0.0). For E. coli, butanol and methanol extracts of G. edulis and U. lactuca showed the highest (12.0 ± 0.54) and the lowest (6.0 ± 0.0). Our preliminary results suggest bioactivity of S. wightii, G. edulis and U. lactuca showed positive results. Further biochemical characterization of S. wightiishould be carried out for potential bioactive compounds against human pathogens. Our results suggest bioactive compounds from seaweeds can be used as pharmaceutical drugs.