Abstract

Objective
To evaluate the antimicrobial activity of different extracts of Hydroclathrus clathratus C. Agardh against human bacterial and fungal pathogens.
Methods
The antimicrobial activities of the extracts against various organisms were tested by using agar well diffusion method. Methanolic extract showed maximum inhibition against Pseudomonas aeruginosa (26.33±1.86mm) while aqueous extract showed no or minimum inihibition.
Results
Maximum activities were recorded by methanolic extract on P. aeruginosa (26.33±1.86mm), S.aureus (21.00±1.78mm), E.coli (19.32±0.89mm), B.subtilis (18.33±1.86mm) and K. Pneumoneae (18.14±1.50 mm). Hexane extract showed maximum antifungal activity against F. oxysporum (18.33±1.86mm) and ethyl acetate showed maximum activity against A.niger (18.33±2.73mm). While, methanolic extract showed more activity against A.flavus (18.00±3.22 mm), C.albicans (18.14±1.50mm) and Penicillium sp. (13.66±1.36mm). However, aqueous extract showed minimum inhibitory effect on the pathogens.
Conclusions
Different solvent extracts of seaweeds used in the present study have shown significant bacterial and fungal action. The study offers opportunities for producing new types of bioactive compounds; however, the mechanism of inhibition and stability of the extracts still are not clear and more studies should be involved.

Key words: Seaweed, Hydroclathrus clathratus, Antibacterial activity, antifungal activity, Gulf of Mannar.