Zoochemical Profiling of Meretrix casta (Mollusca: Bivalvia) Extracts and Their Antibacterial Property

Meretrix casta has long been recognised for its nutritional value and traditional medicinal applications. This research explores the bioactive compounds present in methanol, ethyl acetate and aqueous extracts of M. casta, and evaluate their antibacterial and antibiofilm efficacy against Pseudomonas aeruginosa, a clinically significant, biofilm-forming pathogen. The bioactive compounds in the extracts were examined using UV-Vis spectroscopy, FTIR, and GC-MS techniques, and the findings revealed the occurrence of diverse bioactive compounds like fatty acids, phenolics, and cholesterol derivatives. Antibacterial activities were assessed via agar well diffusion method, MIC, and Resazurin-based cell viability assay. Out of the three extracts, methanolic extract recorded the maximum activity (MIC = 6.25 μg/mL; IC₅₀ = 1.59 μg/mL), followed by ethyl acetate and aqueous extracts. Interestingly, the methanolic extract also exhibited biofilm inhibition, disrupting >50% at 25 μg/mL. These results indicate that M. casta extracts have potential as a resource of antibacterial and antibiofilm agents effective against P. aeruginosa.