To focus on Herbal materia medica we have to note that, a large and increasing number of patients in all over the world use medicinal herbs or seek the advice of their physician (Developed world) or Traditional Healers and Hakim's (least developing world), yet patients and(physicians) often lack accurate information about the safety and efficacy of herbal remedies.
Popular use of medicinal herbs makes it necessary for physicians to became aware of their health benefits, risks, and uncertainties so that they can educate their patients and the public in general .
Plants have been used medicinally through out the history, you can not ignore this fact specially if you are located in one of the least developing countries, where uses of plants are intensified in proportion with the increase of certain diseases such as AIDS. Even in the most developed countries , many herbs were considered conventional medicines and as such were included in medical curricula (e.g British Pharmacopoeia and the United States). Also a pharmaceutical industry capable of mass production of purified herbs were developed, but unlike the purified herbs in the developed countries, medicinal herbs are not required to demonstrate either safety or efficacy prior to prescription by the traditional healers in the least developed countries, nor are their preparation, time of harvesting and storage condition be identified.
It is worth to recognize that more than about 25 % of modern pharmaceutical drugs have botanical origins, such as digoxin from foxgloves, morphine from poppies, aspirin from willow bark and tomoxifen from pacific yew tree, and so on…..