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Abstract

Southwest coast of India is a unique marine habitat infested with diverse seaweeds. Therefore, the present study was initiated to explore bioactive potential of major seaweeds. Thirteen seaweeds belonging to three groups were collected from the coast was extracted in methanol:dichloromethane (1:1) and tested for different range of bioactivities including brine shrimp cytotoxicity, larvicidal, ichthyotoxic and nematicidal activities. It was found that out of 13 seaweeds extracts, Dictyota dichotoma and Hypnea pannosa showed lethal effect on root knot nematode Meloidogyne javanica. All 13 tested seaweeds invariably showed varied range of ichthyotoxicity particularly D. dichotoma, Valoniopsis pachynema and Acrosiphonia orientalis showed highest toxicity. Of the 13 seaweed extracts studied, A. orientalis, Padina tetrastromatica and Centeroceras clavulatum were most effective against second instar mosquito larvae but the activity of P. tetrastromatica was not restored in the third instar bioassay. A. orientalis exhibited a wide range of activities including brine shrimp cytotoxicity, antifeedant and larvicidal activity. The finding envisages that crude extracts of all seaweeds contained synergistic bioactivities which can be used for the production of potential biopesticides and novel pharmaceutical leads.

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