CHEMISTRY OF ANTIDOTAL PLANTS

Notwithstanding the existence of adequate therapies, between 30 and 40 ,000 people all over the world die of snake bites every year These cas ualties occur mostly in rural areas of developing countries where a go od portion of the population very often has to resort to <<alexiterous >>, that is, antidotal plants, which are the only therapeutical resour ce available to them. These are credited to alleviate one or various c omplex symptoms like pain, bleeding, inflammation, infection a,ld even poisoning. This does not mean however, that all these planes are to b e considered antidotal. Scientific investigation over their alleged pr operties is guile incipient, As a contribution to the awakening of the interest in this topic the authors present hele a review of the chemi stry of the antidotal plants studied up to now and also offer an appro ach to various subjects related to their ethnobotany, taxonomy and pha rmacology. Snake poisons are basically proteins and represent a comple x mixture of enzymes mostly of the hydrolytic type. Very often they al so contain pneurotoxic and cardiotoxic peptides. Currently nearly 800 antidotal plants are known in the whole world. The botanical families best represented are Leguminous and Asteraceous, with almost 7% of eac h the of the known species. Followed by, Euphorbiaceae, the Apocinacea e, the Rubiaceae, the Aristolochiaceae, and the Araceae. Only a few an tidotal species have been scientifically studied. However, recent publ ications report that several secondary metabolites isolated from these plants could counteract the lethal and/or the different effects of th e various snake poisons. A first group of compounds consists of four i soflavonoids: cabenegrin A-I, cabenegrin A-II, edunol and wedelolacton e. The first three are pterocarpanes which showed a protecting propert y in mice previously injected (i.p.) with the the Bothrops atrox snake poison. Wedelolactone is an active coumestane against the venom of Cr otalus durissus terrificus. The pterocarpanes prelinated show a very p recise chemotaxonomic distribution, as they are only by cel tain Legum inous families. The second group of antidotal compounds are made up by alkaloids. Among them, the aristolochin acid isolated from varies Ari stolochia species, the shumaniofosid and the atropine. It has been dem onstrated that the aristolochin acid is able to inhibit the lytic acti vity and even the edematose properties of some phospholyopasae of snak e venoms. A third group of alexiteric substances is that of the triter penoids, as that of sitosterol, stigmasterol and derivates of gymnemic acid. The fourth group are the tanines. In addition, the isolation fr om microorganisms and from a marine sponge of active compounds against snake venoms, has recently been made public. Proteins present in the serum of some animals, as in the case of the marsupials Didelphis spp. (zarigueyas), are responsible for their natural immunity against snak e venoms. The studies regarding the way the antidotal substances act a re still at a very Nonetheless, it seems that interact with some enzym es of the venoms, inhibiting them as it runs demonstrated for the aris tolochin acid. The tanines could owe their effect to their capacity of forming protein complexes. It is suggested that the described effect of the antidotal substances, on the secondary effects to poisoning be studied.