The Neem Tree Back to Map Page Afghanistan, Pakistan, and NW India The neem tree, a plant used cosmetically and medicinally by many cultures for centuries, now appears to offer an environmentally safe alternative to synthetic pesticides as well.     Azadirachta indica, the neem tree. (© 2000, Shimona Quazi. Reprinted by permission.) Neem, or Azadirachta indica, is in the Meliaceae, a family of dicots mostly represented by trees and shrubs. Members of Meliaceae tend to have high-quality wood; one of the family's economically important genera is Swietenia, the true mahoganies. The family includes about 50 genera and 550 species, both tropical and subtropical, with many of them prized for their wood, edible fruits, and ornamental qualities. A. indica is pinnate-leafed, has unwinged seeds, and can attain heights of 30 meters. Another species of Azadirachta, A. excelsa, is valuable because its young shoots are edible and it offers superior wood at maturity. As long as 4,000-4,500 years ago, various parts of the neem tree were used in beauty and medicinal products by the ancient East Indian Harappa. Evidence of these uses exists in remains excavated in the region where the Harappa formerly lived (present-day Afghanistan, Pakistan, and northwestern India, with some scholars including more of northern India and Burma). India, Sri Lanka, Bangladesh, and other areas of southern Asia currently include this plant extract in soap, toothpaste, and other personal products. Most recently, neem-based products have found their way into the American and European mainstream markets.  Medicinally, all parts of the plant have been used, including the fruits, seeds, oil (extracted from the seeds), leaves, roots, and bark. The bark contains the bitter alkaloid margosine (another common name for A. indica is the margosa tree), and the fruit contains the alkaloid azaridine, both found to have anti-inflammatory and antifungal properties. Alkaloids are a major class of natural products that have a physiological effect in other organisms. They characteristically contain carbon, hydrogen, nitrogen, and in many cases, oxygen. Because of their potent pharmacological effects, alkaloids are the basis for many drugs. Neem products for sale: toothpaste, body soap, and an antiseptic face pack. (© 2000, Erica Kipp.) A. indica extract has been used to treat a wide range of ailments, including wounds, burns, sprains, bruises, earache, headache, fever, sore throat, shingles, fungal infections, acne, skin diseases, ulcers, and periodontal diseases. Extracts from this plant are also currently being investigated for use against retroviruses, such as the AIDS virus; for treating cancer, diabetes, and allergies; and for birth control in both men and women. A. indica's insecticidal properties were recognized by the native Americans, who used it as a tick repellent. Neem was also used as an insecticide by the locals in Sudan, but research on the tree did not take off there until 1959 when Dr. Heinrich Schmutterer, a German scientist trained in entomology and plant pathology, was conducting research during a locust swarm.  It was observed that A. indica was among the only plants not destroyed by the plague. Much of the research done by Dr. Schmutterer and scores of other scientists has indicated that A. indica is effective against a wide range of insects, including those in the following orders: Lepidoptera (moths and butterflies), Diptera (true flies), Coleoptera (beetles), Hymenoptera (bees, ants, and wasps), Homoptera (cicadas, aphids, hoppers, and whiteflies), Orthoptera (grasshoppers, katydids, locusts, and crickets), and Heteroptera (firebug, lace bug, stinkbug, and bedbug). Modern investigations have revealed that neem extract can inhibit egg laying in mites, deter herbivory, inhibit insect growth, and act as an effective astringent, antimicrobial, purifying, and detoxifying agent. Several chemicals have been isolated from neem extract, including azadirachtin, nimbin, salannin, epoxyazadiradione, and deacetylsalannin. Azadirachtin, C35H44O16, is the most interesting from an agricultural standpoint. Found concentrated in the leaves and seed oil, it acts as an insect growth regulator. Azadirachtin is structurally similar to insect hormones called ecdysones, which are steroids that interfere with molting (the periodic shedding and secretion of a new exoskeleton) and metamorphosis. This mode of action is different from that of most insecticides on the market, which act by interfering with the insect's central nervous system. Additionally, azadirachtin has been found to deter insects from feeding on plant material, thus qualifying it as an antifeedant. The Agricultural Research Service (ARS), the main in-house research division of the United States Department of Agriculture (USDA), was instrumental in getting azadirachtin approved for use as a pesticide. Azadirachtin is now registered in the United States as a general-use pesticide with a toxicity classification of IV (relatively nontoxic). As an organic molecule, it falls into the chemical class of compounds called tetranortriterpenoids. Chemical structure of azadirachtin. The importance of the neem tree was further noted when ornithologists reported that twigs taken from it have been incorporated in the nest linings of both Sturnus vulgaris (the European starling) and Passer domesticus (the house sparrow). Since nest sites often breed ticks, mites, and bacteria, these birds are reducing the potential of these pests. This type of activity, involving the ways animals use plants, is referred to as zoopharmacognosy, a term coined in 1992 from the Greek roots: zoo- = animal; pharma- = a drug or poison; and -cognosy = to recognize. [For more information, see "Monkey See, Monkey Do."] Clearly, the neem tree is of vital importance for all its current uses and a source of study for future applications. References, Websites, and Further Reading Heywood, V. H. 1993. Flowering plants of the world. New York: Oxford University Press. Immaraju, J. A. 1998. The commercial use of azadirachtin and its integration into viable pest control programmes. Pesticide Science 54(3):285-89. Klocke, J. A., and Isao Kubo. 1991. Defense of plants through regulation of insect feeding behavior. Florida Entomologist 74(1):18-22. Mabberley, D. J. 1997. The plant-book, 2d ed. New York: Cambridge University Press. Mordue, A. J. 1998. Actions of azadirachtin, a plant allelochemical, against insects. Pesticide Science 54(3):277-84. Neem and birth control from the original neem company http://www.neemaura.com/UsesPages/birthcon.htm Office of Pesticide Science, The United States Environmental Protection Agency http://www.epa.gov/pesticides/science.htm University of New Orleans, Flowering Plant Website: Meliaceae http://www.biodiversity.uno.edu/delta/angio/www/meliacea.htm Related Reading in Stern, Introductory Plant Biology, 8th Edition Chapter 5: Roots and Soils How Roots Develop; Root Structure, pp. 63-68 Chapter 6: Stems Woody Dicotyledonous Stems, including bark, pp. 88-93 Chapter 7: Leaves Leaf Arrangements and Types, including pinnate, pp. 106-8 Diagram of leaf arrangements and types, Figure 7.4, p. 109 Chapter 8: Flowers, Fruits, and Seeds Differences Between Dicots and Monocots, including Table 8.1, pp. 129-30 Fruits, pp. 132-39 Seeds, pp. 143-45 Chapter 11: Growth Nutrients, Vitamins, and Hormones, pp. 188-89 Chapter 19: Kingdom Fungi and Lichens Kingdom Fungi-The True Fungi, pp. 336-37