Cashew

Anacardium occidentale, the cashew, is an evergreen tree in the Anacardiaceae (cashew or sumac family) that originated in Central and South America and is now cultivated commercially in semi-arid tropical areas in Africa, India, Sri Lanka, and southeastern Asia for the production of cashew nuts. The tree, which is up to 12 meters (40 feet) tall, has leathery alternate leaves, and flowers with 5 petals and 5 sepals. The fruits take an unusual form, with a kidney-shaped nut (drupe) borne on the end of an receptacle (the stem that holds the flower and fruit), which becomes enlarged and fleshy so that it appears as a fruit (with the nut like a comma dangling at its end), and is referred to as a “cashew apple.” The cashew apple is edible, with an astringent flavor, and is used in jams, jellies, chutneys, and beverages (including a cashew wine); it is a good source of vitamin A and contains up to five times as much vitamin C as citrus juice. Cashew apples are also used as animal fodder. Cashew nuts, which are important in the cuisine of India, are often roasted and salted and eaten as a snack, and are high in protein, vitamins (A, D, K, and E) and minerals (including calcium, phosphorus, and iron). Other products from the plant include cashew nutshell liquid (CNSL), which is an irritant to human skin (it causes blisters similar to those of poison ivy, Toxcicodendron radicans, which is in the same genus) but is used as a lubricant and insecticide; and acajou gum, from the plant’s stem, which can be used as a substitute for gum arabic or in similar applications, such as varnish. Total 2010 world production of cashew nuts was 3.6 million tons, harvested from 4.4 million hectares. India was long the leading producer of cashew nuts. However, Nigeria was the largest producer in 2001, and Vietnam’s production surpassed them both in 2002; Vietnam has been the leading producer since. Brazil is the leading producer of commercially sold cashew apples. (Bailey et al. 1976, Encyclopedia Brittanica 1993, Morton 1987, van Wyk 2005)

The cashew tree Anacardium occidentale can provide many traditional and industrial byproducts. In terms of culinary uses, cashews appear in the cuisine of many countries and are featured prominently in the cusine of Thailand, China, India, Malaysia, Brazil, Panama and Indonesia. They have also become popular as snacks and appetizers in Western Societies and also appear as ingredients in Western confections (Nair et. al. 1979). Cashew trees produce: cashew nuts, kernels, cashew apples, edible oil from the nuts (not usually extracted because of the high price the nuts themselves fetch), indelible ink deived form the bark and, yellow dye extracted from leaves (Nair et. al. 1979). Tannins extracted from the testa (seed coat) are used in the leather industry, and gum from the bark is used for bookbinding, while sap its is used for wood preservative (Asogawa et. al. 2007). Senegalese fishermen use the the extract from it's leaves to dye their fishnets yellow (Asogawa et. al. 2007). Recent studies have found that although the cashew apple is often not valued as highly as the nut by cultivators it has the potential to gross significantly more than it costs to gross because clarified cashew apple juice can be used to grow Leuconostoc mesenteroids which can be used to produce high added value products such as dextran, lactic acid, mannitol and oligosaccharides (Horato, Rabelo and Gonclaves 2007). Another byproduct that has proven to be useful in industrial manufacturing is cashew nut shell liquid (CNSL). It is composed of anacardic acid, cardarol, and cardol (EPA 2009). While it does not seriously effect rates, it is an acute hazard to fish, aquatic invertebrates, and aquatic plants based on toxicity estimates for cardol at .001 mg/L, .004mg/L, and .010mg/L respectively (EPA 2009). CNSL is an intermediate used in the manufacturing of other basic organic chemicals which are found in automotive car products, antioxidants, rubber compounds, and is a modifier for plastics (EPA 2009). CNSL is used in wood and fabric preservatives, paints, plastics, printing ink, germicides, insecticides, waterproofing compounds, synthetic resins, dyes, anti-fade agents in brake lining and clutch facing (Asogawa et. al. 2007) As an insecticide or pest repellant, CNSL has been shown to be effective against Aedes aegypti larvae and Biomphalaria glabrata snails (Laurens et. al. 1998). Cashew nut shells are also highly toxic to Callosobruchus subinnotatus , a pest of the bambarra-groundnut crop, however they also stunt the seed development bambarra-groundnuts (Oparaeke and Bunmi 2006). CNSL is also a very effective termite killer, killing 100% of soldiers and worker termites exposed to it by the 90th minute, which means it is of comparable effectiveness to currently marketed products (Asogawa et. al. 2007). It has been posited that wood treatment products to ward off termite attack created from CNSL are more environmentally friendly than other alternatives (Mwalongo et. al. 1999). Medicinally, cashew nutshell oil (CNO) has proven to be effective at killing off the human intestinal worm ancylostomiasis and has additionally been observed to be highly effective against Trichuris and Ascaris, though the asserting study only observed three cases of each (Eichbaum, Koch-Wesser and Leoo 1950). In Brazil it has traditionally been used to treat ulcers, hypertension and diarrhea (Konan et. al. 2007). A study investigating whether such application may be potentially harmful tested for acute toxicity, 30-day subacute toxicity and genotoxicity in rats and found that rats showed no symptoms from exposure to crude extract but did exhibit induced frame-shift base pair substitution and damage to chromosomes (Konan et. al. 2007).