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| Medicinal plant |
Because plants are so biochemically diverse, they produce thousands of substances commonly referred to as secondary metabolites. Many of these secondary metabolites have medicinal properties that have proven to be beneficial to humankind.
The use of plants for medicinal purposes predates recorded history. Primitive people’s use of trial and error in their constant search for edible plants led them to discover plants containing substances that cause appetite suppression, stimulation, hallucinations, or other effects. Written records show that drugs such as opium have been in use for more than five thousand years.
From antiquity until fairly recent times, most physicianswere also botanists or at least herbalists. Because modern commercial medicines are marketed in neat packages, most people do not realize that many of these drugs were first extracted from plants.
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Chemists have learned how to synthesize many natural products that were initially identified in a plant. However, in many cases a plant is still the only economically feasible source of the drug.
Antibacterial and Anti-inflammatory Agents
The first effective antibacterial substance was carbolic acid, but the first truly plant-derived antibacterial drug was penicillin, which was extracted from a very primitive plant, the fungus Penicillium, in 1928. The success of penicillin led to the discovery of other fungal and bacterial compounds that have antibacterial activity. The most notable of these are cephalosporin and griseofulvin.
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| wintergreen (Gaultheria procumbens) |
Inflammation can be caused by mechanical or chemical damage, radiation, or foreign organisms. For centuries poultices of leaves from coriander (Coriandrum sativum), thornapple (Datura stramonium), wintergreen (Gaultheria procumbens), witch hazel (Hamamelis virginiana), and willow (Salix niger) were used to treat localized inflammation. In the seventeenth and eighteenth centuries, cinchona bark was used as a source of quinine, which could be taken internally.
In 1876 salicylic acid was obtained from the salicin produced by willow (Salix) leaves. Today, salicylic acid, also known as aspirin, and its derivatives, such as ibuprofen, are the most widely used anti-inflammatory drugs in the world.
Drugs Affecting the Reproductive System
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| Mexican plant zoapatle (Montana tomentosa) |
Other plant compounds that affect the reproductive system include diosgenin, extracted from Dioscorea species and used as a precursor for the progesterone used in birth control pills; gossypol from cotton (Gossypium species), which has been shown to be an effective birth control agent for males; ergometrine, extracted from the ergot fungus (Claviceps) and used to control postpartum bleeding; and yohimbine, from the African tree Corynanthe yohimbe, which apparently has some effect as an aphrodisiac. Circulatory, Analgesic, and Cancer-Fighting
Drugs
Opiate alkaloids such as opium, extracted from a poppy (Papaver sonniferum), and its derivatives, such as morphine as well as cocaine, from Erythroxylum coca and Erythroxylum truxillense, have long been known for their analgesic (pain-relieving) properties through their extremely dangerous and addictive effects on the central nervous system.
The primary plant-derived anticancer agents are vincristine and vinblastine, extracted from Catheranthus roseus, maytansinoids from Maytentus serrata, ellipticine and related compounds from Ochrosia elliptica, and paclitaxel (commonly known as taxol) from the yew tree Taxus baccata.
Fighting Asthma, Gastrointestinal Disorders, Parasites
The major anti-asthma drugs come from ephedrine, extracted from the ma huang plant (Ephedra sinaica), and its structural derivatives. Plant-derived drugs that affect the gastrointestinal tract include castor oil, senna, and aloes as laxatives, opiate alkaloids as anti diarrheals, and ipecac from Cephaelis acuminata as an emetic.
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The most useful plant-derived antiparasitic agent is quinine, derived from the bark of the chincona plant (Chincona succirubra). Quinine has been used to control malaria, a disease that has plagued humankind for centuries.
The Future
More plant-derived medicines await discovery, many from tropical rain-forest vegetation. Biotechnology has provided methods by which plants can be genetically modified to produce novel pharmaceuticals.
Progress toward the production of specific proteins in transgenic plants provides opportunities to produce large quantities of complex pharmaceuticals and other valuable products in traditional farm environments rather than in laboratories.
These novel strategies open up routes for production of a broad array of natural or nature-based products, ranging from foodstuffs with enhanced nutritive value to biopharmaceuticals.
