<P> The earliest historical records of herbs are found from the Sumerian civilisation, where hundreds of medicinal plants including opium are listed on clay tablets . The Ebers Papyrus from ancient Egypt describes over 850 plant medicines, while Dioscorides documented over 1000 recipes for medicines using over 600 medicinal plants in De materia medica, forming the basis of pharmacopoeias for some 1500 years . Drug research makes use of ethnobotany to search for pharmacologically active substances in nature, and has in this way discovered hundreds of useful compounds . These include the common drugs aspirin, digoxin, quinine, and opium . The compounds found in plants are of many kinds, but most are in four major biochemical classes, the alkaloids, glycosides, polyphenols, and terpenes . </P> <P> Medicinal plants are widely used in non-industrialized societies, not least because they are far cheaper than modern medicines . The annual global export value of pharmaceutical plants in 2012 was over US $2.2 billion . In many countries there is little regulation of traditional medicine, but the World Health Organization is coordinating a network to encourage safe and rational usage . Medicinal plants face both general threats such as climate change and habitat loss, and the specific threat of over-collection to meet market demand . </P> <P> Plants, including many now used as culinary herbs and spices, have been used as medicines, not necessarily effectively, from prehistoric times . Spices have been used partly to counter food spoilage bacteria, especially in hot climates, and especially in meat dishes which spoil more readily . Angiosperms (flowering plants) were the original source of most plant medicines . Human settlements are often surrounded by weeds used as herbal medicines, such as nettle, dandelion and chickweed . Humans were not alone in using herbs as medicines: some animals such as non-human primates, monarch butterflies and sheep ingest medicinal plants when they are ill . Plant samples from prehistoric burial sites are among the lines of evidence that Paleolithic peoples had knowledge of herbal medicine . For instance, a 60 000 - year - old Neanderthal burial site, "Shanidar IV", in northern Iraq has yielded large amounts of pollen from 8 plant species, 7 of which are used now as herbal remedies . A mushroom was found in the personal effects of Ötzi the Iceman, whose body was frozen in the Ötztal Alps for more than 5,000 years . The mushroom was probably used against whipworm . </P> <P> In ancient Sumeria, hundreds of medicinal plants including myrrh and opium are listed on clay tablets . The ancient Egyptian Ebers Papyrus lists over 800 plant medicines such as aloe, cannabis, castor bean, garlic, juniper, and mandrake . From ancient times to the present, Ayurvedic medicine as documented in the Atharva Veda, the Rig Veda and the Sushruta Samhita has used hundreds of pharmacologically active herbs and spices such as turmeric, which contains curcumin . The Chinese pharmacopoeia, the Shennong Ben Cao Jing records plant medicines such as chaulmoogra for leprosy, ephedra, and hemp . This was expanded in the Tang Dynasty Yaoxing Lun . In the fourth century BC, Aristotle's pupil Theophrastus wrote the first systematic botany text, Historia plantarum . In the first century AD, the Greek physician Pedanius Dioscorides documented over 1000 recipes for medicines using over 600 medicinal plants in De materia medica; it remained the authoritative reference on herbalism for over 1500 years, into the seventeenth century . </P>

Importance of medicinal and aromatic plants in human health