POTENTIAL USEFULNESS OF PLANT EXTRACTS TO COUNTERACT CNIDARIAN VENOMS

Cnidarians toxins are known to have a high impact on public health in marine coastal zones the world over. Consequently these toxins are now recognised as an important focus for research on their therapeutic potential. To date several therapeutically important activities have been experimentally identified in cnidarian extracts and venoms. However, the chemical composition of these materials is still largely unknown. Therefore, the evaluation of venom activity, the properties of constituents and the methods to alleviate damage induced by jellyfish and other cnidarians requires further study. Taxonomists have to date described approximately 13,000 living cnidarian species. A major rationale for their study in the past, besides scientific curiosity, was to better treat victims of their envenomation. This goal still remains a high priority and focused study on this area has increased in recent years. Cnidaria venoms can be neurotoxic and cardiotoxic, may induce dermonecrosis and produce extensive damage to skin and to cutaneous structures. Notably, neurotoxins affecting ion channels, and in particular those active on voltage-gated Na+ and K+ channels, are common in cnidarian and particularly in sea anemone venoms. In fact, the neurotoxicity of cnidarian venoms derives mainly from the activity on cell ion channels, with cnidarian peptide neurotoxins often possessing high affinity and specificity for particular classes of ion channels. Owing to their immunosuppressive activity, K+ channel blockers can be of great significance for drug development. In the quest for new topical products capable of alleviating human cnidarian injuries and pain, natural products and in particular plants, offer a rich resource to explore for extracts or compounds with neutralizing properties against cnidarian toxins. Some reports exist of natural products that are known to exert protective effects against such toxins. Among them, are plant extracts possessing peptidasic activity, being capable of neutralizing various toxins. This chapter will review the current knowledge base on plant extracts from Australia, Italy (and the Mediterranean) and Mexico (three different climatic zones located in different continents, with different environments) that have reported activity or potential to act as therapeutic agents in the treatment of animal venoms. The reported knowledge about their usefulness in treating cnidarian injury and pain is here reviewed. Such extracts may also provide new insights into understanding the toxicological mechanisms of natural venoms.