Antimicrobial and antioxidant activities of ethyl acetate and methanol extracts of Littorina littorea and Galatea paradoxa

The aquatic environment is a vital resource for bioprospecting pharmacologically important natural products. Molluscs are known to harbour compounds with antimicrobial, antitumor and antioxidant activities. This study evaluated the antimicrobial and antioxidant properties of ethyl acetate and methanol tissue extracts of two molluscs, Littorina littorea (L. littorea) and Galatea paradoxa (G. paradoxa). Agar diffusion and broth dilution assays were used to test for antimicrobial activity against nine microbes. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) method was used to determine antioxidant activity of the extracts. Extracts of both molluscs showed significant activity against all the bacteria strains tested but were inactive towards the fungus. The best antibacterial activity was recorded by methanol extract of L. littorea towards Pseudomonas aeruginosa. In comparison to ethyl acetate extracts, methanol extracts were more efficient in scavenging the DPPH radical. Methanol extracts of L. littorea had an IC50 of 0.37 mg/mL which was closer to that of the standard ascorbic acid drug (0.0048 mg/mL) than any of the other extracts. The findings of this work indicate that the tissue extracts of L. littorea and G. paradoxa are promising sources of antimicrobial and antioxidant agents that can be utilized for pharmaceutical and nutraceutical purposes.