Inhibitory effect of the red seaweed Plocamium brasiliense against the toxic effects of Lachesis muta snake venom

The ability of extracts and fractions of the red seaweed Plocamium brasiliense to inhibit hemorrhagic, edematogenic, hemolytic, clotting and proteolytic activities of Lachesis muta snake venom was analyzed. In Brazil, snakebites by L. muta are low (2 %) when compared to Bothrops genus (90 %); however, their lethality indexes are three times higher than Bothrops .E nvenomation byL. muta venom results in hemorrhage, pain, necrosis, hemolysis, myotoxicity, and death. Since antivenom does not efficiently neutralize local effects, a large number of researchers have attempted to identify molecule(s) from natural sources to inhibit such activities to use them as an alternative treatment for snakebite. We tested four extracts of seaweed P. brasiliense obtained with solvents of increasing polarities: n-hexane (HEX), dichloromethane (DCM), ethyl acetate (ACE), and hydroalcohol (HYD). Extracts of alga or fractions were incubated with L. muta venom, and then, biological assays were performed. The extracts, except the HYD, inhibited all the assays but with different potencies. The DCM extract fully inhibited all activities. Moreover, DCM and HEX extracts inhibited hemolysis induced by a phospho- lipase A2 isolated from L. muta venom (LM-PLA2-I). A fraction from HEX enriched in cholesterol isolated from HEX extract inhibited proteolysis by L. muta venom and hemolysis by LM-PLA2-I; in contrast, monoterpenes isolated from DCM extract did not inhibit both activities. Seaweeds may be a promising source of natural inhibitors of the toxic effects caused by snakebite by L. muta venom, and they may be used to develop new strategies for antivenom treatment.