PerspectivesAre you interested in submitting a Perspective Article? Be sure to read The Science Advisory Board's Editorial Guides for Perspective Articles. Click here. Phytochemicals: Their Role in the Modern Era by Amrit Pal Singh, B.A.M.S, M.D. The word, phytochemical, is derived from phyto or plant. Its study involves understanding the chemical composition of plants used in medicine. Phytochemicals produced in plants are secondary compounds responsible for metabolic activities and defense purpose. Phytochemicals are produced by specific biochemical pathways, which occur inside the plant cells. The phytochemicals can range from medicinally useful agents to deadly poisons. A number of phytochemicals isolated from plant material are used in the pharmaceutical drug industry today. With the history of plant-based medicine in mind, one can conclude that in the early days, physicians were not aware of the chemical constituents in the plants. However, they did have knowledge of the active principles responsible for therapeutic activity. In Charaka–Samhita, the classical treatise on Ayurvedic medicine, the word, virya, is similar to word, potency. Drugs have been classified according to the pharmacological activities, but a comprehensive account of the mechanism of action is missing. Ayurveda, the ancient healing system of India, flourished in the Vedic era in India. According to historical facts, the classical texts of Ayurveda, Charaka Samhita and Sushruta Samhita were written around 1000 B.C. The Ayurvedic Materia Medica includes 600 medicinal plants along with therapeutics. Herbs like turmeric, fenugreek, ginger, garlic and holy basil are an integral part of Ayurvedic formulations. These formulations either incorporate a single herb or more than one herb (i.e., polyherbal formulations). Before the availability of synthetic drugs, humans were completely dependent on medicinal herbs for prevention and treatment of diseases. The use of the medicinal herbs for curing disease has been documented in the history of all civilizations. The drugs were used in crude forms like expressed juice, powder, decoction or infusion. Although formulations mentioned in ancient texts are difficult to understand in terms of scientific parameters, some of them are still reputed for their curative values. Ancient healers who developed formulations based on medicinal herbs were probably not aware of the chemical composition of these herbs. Nevertheless, the advancement they made despite the non-availability of scientific procedures is astonishing. The work on Terminalia chebula (myrobalan) mentioned in Charaka Samhita is quiet authentic and modern studies have revealed that the purgative activity mentioned in Ayurveda is justified by the isolation of chebulic acid, the active constituent of myrobalan. Medicinal plants are a significant source of synthetic and herbal drugs in India and China and have been on the forefront when we talk about history of herbal drugs. The traditional systems of medicines: Ayurveda, Siddha, Unani, Western Herbal Medicine, Traditional Chinese Medicine and Homeopathy have roots in medicinal herbs. Herbal medicine has produced a number of distinguished researchers and due to its accessibility to traditions; it is still practiced even by lay practitioners. Sterneur, who first isolated morphine from Papaver somniferum (opium poppy) showed the medical profession that certain phytochemicals produced in plant cells are responsible for pharmacological activity. Later on, other alkaloids isolated from opium poppy were investigated for their pharmacological activities. Codeine showed antitussive activity and papaverine antispasmodic activity. The opium based extracts have been utilized for various pharmacological activities, and a number of alkaloids distributed in the plant have different pharmacological activities. Scientific validation of herbal drugs always has been questioned, but with recent advances and publications of clinical trials, the researchers and the public are viewing herbal products with more respect. In the commercial market, medicinal herbs are used as raw drugs, extracts or tinctures. Isolated active constituents are used for applied research. There has been a dramatic rise in the sale of herbal products like Allium sativum, Hypericum perforatum, Spirulina, Echinacea angustifolia, Ginkgo biloba and Silybum marianum. Before any herbal medicine is screened for testing, phytochemical investigations are essential because sometimes a critical constituent is missing from the herb due to reasons like storage, geographical distribution or processing. Today standardized extracts are used in herbal drug industry and their standard is based on the presence of marker compounds. The marker compounds may or my not have pharmacological activity. A brief account of type of the phytochemicals distributed in plant flora is given below: 1. Alkaloids are basically nitrogen bases and the most important class of phytochemicals. The amino acids act as building blocks for the biosynthesis of alkaloids. 2. Bitter principles are basically glycosides and are found commonly in plants of Genitiaceae. The bitters act on gustatory nerves, which results in increased flow of saliva and gastric juices and acts as appetizers. 3. Phenolic compounds are widely distributed in plant flora. A variety known as polyphenols is found in fruits of some plants. They occur as natural colour pigments and are responsible for the colour of the fruits. 4. Diarylheptanoids are rare compounds found in the family Zingiberaceae. Recent animal studies have shown diarylheptanoids to be potent anti-inflammatory agents. 5. Flavonoids are important group of polyphenols, widely distributed in plant flora. 4,000 flavonoids are known to exist and some of them are pigments in higher plants. Quercetin, kaempferol and quercitrin are common .Soya flavones have recently gained importance due to variety of pharmacological activities. 6. Furanocoumarins are photosensitizing agents used in the treatment of pigment disorders. Ayurveda, the ancient science of India, has described the use of bawachi (Psoralia corylifolia) for the treatment of leucoderma. 7. Furochromones are group of coumarins, derived from benzopyrone. They are related to furanocoumarins. 8. Hydroxycoumarins represents another group of coumarins. 9. Glycosides are water-soluble constituents, found in the cell sap. They are colourless, crystalline substances containing carbon, hydrogen and oxygen. Some glycosides are peculiar in having nitrogen and sulphur. 10. Napthodianthrones are derivatives of anthracene. 11. Neutral principles are bodies of unidentified character. 12. Acylphloroglucinols are group of phenolic compounds having significant antidepressant activity. 13. Resins are brittle, non-volatile, solid substances. Oleoresins are natural products of resin mixed with volatile oils. Gum- resins are plant exudates and are mixtures of gum and resin and often volatile oils. Balsams are combinations of resins or oleoresins with aromatic acids. 14. Saponins are glycosides found in number of plants. They are poisonous. 15. Sesquiterpene lactones constitute significant group of phytochemicals. They are formed by condensation of three isoprene molecules followed by oxidation. 16. Sterols are derivatives of steroids. Modern clinical studies have supported their role as anti-inflammatory and analgesic agents. 17. Tannins are widely distributed in plant flora. They are phenolic compounds of high molecular weight. According to one estimate, only 20 percent of the plant flora has been screened for drugs. Keeping in view the vast treasure of medicinal herbs, one can expect phytochemicals to play a significant role as modern science has limited options for diseases like diabetes mellitus, rheumatoid arthritis, Alzheimer’s disease and Parkinson’s disease. Work on the identification and isolation of phyochemicals is an ongoing process and herbal medicine is expected to play critical role in the future healthcare system. ### Amrit Pal Singh, B.A.M.S, M.D. (Alternative Medicine) Medical Advisor Tas-Med Pvt. Ltd. A Science Advisory Board Member Since February 2002 Address for correspondence: Dr. Amrit Pal Singh House No: 2101 Phase-7 Mohali-160062 Email: amritpal2101@yahoo. com ### << Previous Next >> [ View All Perspectives ] |
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