Safety concern of drugs of herbal origin

World Health Organization defines the drugs of herbal origin as medicinal agents that are mainly composed of the active constituents of plants or other plant material or combination of both of these. Although these agents are considered to be safe or exhibit lesser side effects, however a wide range of plants having medicinal value, the secondary metabolites of these plants have shown various toxic and poisonous effects. In the present review, the various toxic components have been discussed under different classes of herbs such as herbs containing alkaloids, glycosides, terpenoids and phytoestrogens, etc.