The past and present use of plants for medicines.

Evidence of the use of plants for medicinal purposes dates as far back as 60 000 years ago (1) in both western and eastern cultures; in both developed and undeveloped countries. For example, the pharmacopoeia of Emperor Shen Nung of China, around 2730–3000 BC, describes the medicinal use of plants such as Hemp, Aconite, Opium. The Egyptian Pharmacopoeia of Ebers Papyrus, written about 1500 BC, documents the medicinal use of plant extracts such as the poppy of Opium and oil of Castor beans (2, 3). Some of the plants commonly used today, such as peppermint (Mentha piperita), poppy (Papaver somniferum), mugwort (Artemisia vulgaris), sage (Horminum pyrenaicum), rosemary (Hyssopus officinalis), rue (Ruta graveolens) and verbena (Verbena officinalis) are well documented in the “Materia medica” of the great physician Hippocrates (about 460–370 BC) and in the several manuscripts written (around 160 AD) by Galen, a surgeon from Asia Minor. In early civilizations, illness was usually believed to be due to divine punishment. The Aztecs Indian of South America, for example, believed that particular diseases were linked to specific gods; thus their god Tlaloc was associated with diseases caused by water, such as oedema (4). Similarly, Greek physicians, such as Theoprastus, were generally followers of Asclepius, the god of Medicine. Thus the use of plants for healing became strongly associated with the gods. With the fall of the Roman Empire and the advancement of Christianity in western cultures, the use of plants for healing was discouraged. Ironically, although early Christians also saw disease and illness as divine (heaven-sent) punishment, they believed it could only be cured through repentance and prayer, not through the use of medicinal plants. Additionally, as Christianity only recognizes the power of one God, the strong association of many gods and plant medicines led to the value of plant medicines becoming clouded in myths. By the 1500s AD, the use of plants as medicine in western society became further mystified by the “Doctrine of Signatures”. Supporters of the doctrine believed that the physical attributes of plants were indications of their medicinal value. Thus, the holes in the leaves of St John’s wort (Hypericum perforatum) signified