Naturally occurring antinociceptive substances from plants.

Despite the progress that has occurred in recent years in the development of therapy, there is still a need for effective and potent analgesics, especially for the treatment of chronic pain. One of the most important analgesic drugs employed in clinical practice today continues to be the alkaloid morphine. In this review, emphasis will be given to the important contribution and the history of Papaver somniferum, Salix species, Capsicum species and Cannabis sativa in the development of new analgesics and their importance in the understanding of the complex pathways related to electrophysiological and molecular mechanisms associated with pain transmission. Recently discovered antinociceptive substances include alkaloids, terpenoids and flavonoid. Plant-derived substances have, and will certainly continue to have, a relevant place in the process of drug discovery, particularly in the development of new analgesic drugs.