Coca is any of the four cultivated plants in the family Erythroxylaceae, native to western South America. The plant is a cash crop in Argentina, Bolivia, Colombia, and Peru. It also plays a role in many traditional Andean cultures as well as the Sierra Nevada de Santa Marta (see Traditional uses). Coca is known throughout the world for its psychoactive alkaloid, cocaine. The alkaloid content of coca leaves is low, between 0.25% and 0.77%. This means that chewing the leaves or drinking coca tea does not produce the intense high (euphoria, megalomania, depression) people experience with cocaine. Coca leaf extract had been used in Coca-Cola products from 1885, with cocaine being completely eliminated from the products in or around 1929. Extraction of cocaine from coca requires several solvents and a chemical process known as an acid/base extraction, which can fairly easily extract the alkaloids from the plant.
- 1 Description
- 2 Species and evolution
- 3 Cultivation
- 4 Pharmacological aspects
- 5 History
- 6 Traditional uses
- 7 Commercial and industrial uses
- 8 Literary references
- 9 International prohibition of coca leaf
- 10 Legal status by country
- 11 See also
- 12 References
- 13 External links
The coca plant resembles a blackthorn bush, and grows to a height of 2-3 m (7–10 ft). The branches are straight, and the leaves are thin, opaque, oval, and taper at the extremities. A marked characteristic of the leaf is an areolated portion bounded by two longitudinal curved lines, one line on each side of the midrib, and more conspicuous on the under face of the leaf.
The flowers are small, and disposed in clusters on short stalks; the corolla is composed of five yellowish-white petals, the anthers are heart-shaped, and the pistil consists of three carpels united to form a three-chambered ovary. The flowers mature into red berries.
Species and evolution
There are two species of cultivated coca, each with two varieties:
- Erythroxylum coca
- Erythroxylum novogranatense
- Erythroxylum novogranatense var. novogranatense (Colombian Coca) - a highland variety that is utilized in lowland areas. It is cultivated in drier regions found in Colombia. However, E. novogranatense is very adaptable to varying ecological conditions. The leaves have parallel lines on either side of the central vein.
- Erythroxylum novogranatense var. truxillense (Trujillo Coca) - grown primarily in Peru and Colombia. the leaves of E. novogranatense var. truxillense does not have parallel lines on either side of the central vein like all other varieties.
All four of the cultivated cocas were domesticated in pre-Columbian times and are more closely related to each other than to any other species.
There are two main theories relating to the evolution of the cultivated cocas. The first (put forth by Plowman and Bohm ) suggests that Erythroxylum coca var. coca is ancestral, while Erythroxylum novogranatense var. truxillense is derived from it to be drought tolerant, and Erythroxylum novogranatense var. novogranatense derived from Erythroxylum novogranatense var. truxillense.
Recent research based on genetic evidence (Johnson et al. in 2005, Emche et al. in 2011, and Islam 2011) does not support this linear evolution and instead suggests a second domestication event as the origin of the Erythroxylum novogranatense varieties. There may be a common, but undiscovered ancestor.
The two subspecies of Erythroxylum coca are almost indistinguishable phenotypically. Erythroxylum novogranatense var. novogranatense and Erythroxylum novogranatense var. truxillense are phenotypically similar, but morphologically distinguishable. Under the older Cronquist system of classifying flowering plants, this was placed in an order Linales; more modern systems place it in the order Malpighiales.
Herbicide resistant varieties
Also known as supercoca or la millionaria, Boliviana negra is a relatively new form of coca that is resistant to a herbicide called glyphosate. Glyphosate is a key ingredient in the multibillion-dollar aerial coca eradication campaign undertaken by the government of Colombia with U.S. financial and military backing known as Plan Colombia.
The herbicide resistance of this strain has at least two possible explanations: that a "peer-to-peer" network of coca farmers used selective breeding to enhance this trait through tireless effort, or the plant was genetically modified in a laboratory. In 1996, a patented glyphosate-resistant soybean was marketed by Monsanto Company, suggesting that it would be possible to genetically modify coca in an analogous manner. Spraying Boliviana negra with glyphosate would serve to strengthen its growth by eliminating the non-resistant weeds surrounding it. Joshua Davis, in the Wired article cited below, found no evidence of CP4 EPSPS, a protein produced by the glyphosate-resistant soybean, suggesting Bolivana negra was either created in a lab by a different technique or bred in the field.
Coca is traditionally cultivated in the lower altitudes of the eastern slopes of the Andes (the Yungas), or the highlands depending on the species grown. Coca production begins in the valleys and upper jungle regions of the Andean region, where the countries of Colombia, Peru and Bolivia are host to more than 98 per cent of the global land area planted with coca.
Fresh samples of the dried leaves are uncurled, are of a deep green on the upper, and a grey-green on the lower surface, and have a strong tea-like odor. When chewed, they produce a pleasurable numbness in the mouth, and have a pleasant, pungent taste. They are traditionally chewed with lime or some other reagent such as bicarbonate soda to increase the release of the active ingredients from the leaf. Older species have a camphoraceous smell and a brownish color, and lack the pungent taste.
The seeds are sown from December to January in small plots (almacigas) sheltered from the sun, and the young plants when at 40 to 60 cm (16 to 24 in) in height are placed in final planting holes (aspi), or if the ground is level, in furrows (uachos) in carefully weeded soil. The plants thrive best in hot, damp and humid locations, such as the clearings of forests; but the leaves most preferred are obtained in drier areas, on the hillsides. The leaves are gathered from plants varying in age from one and a half to upwards of forty years, but only the new fresh growth is harvested. They are considered ready for plucking when they break on being bent. The first and most abundant harvest is in March after the rainy season, the second is at the end of June, and the third in October or November. The green leaves (matu) are spread in thin layers on coarse woollen cloths and dried in the sun; they are then packed in sacks, which must be kept dry in order to preserve the quality of the leaves.
|Morphology of the coca plant|
The pharmacologically active ingredient of coca is the coca alkaloid, which is found in the amount of about 0.3 to 1.5%, averaging 0.8%, in fresh leaves. Besides coca, the coca leaf contains a number of other alkaloids, including methylecgonine cinnamate, benzoylecgonine, truxilline, hydroxytropacocaine, tropacocaine, ecgonine, cuscohygrine, dihydrocuscohygrine, nicotine, and hygrine. When chewed, coca acts as a mild stimulant and suppresses hunger, thirst, pain, and fatigue. Absorption of coca from the leaf is less rapid than nasal application of purified forms of the alkaloid (almost all of the coca alkaloid is absorbed within 20 minutes of nasal application, while it takes 2–12 hours after ingestion of the raw leaf for alkaline concentrations to peak.). When the raw leaf is consumed in tea, between 59 and 90% of the coca alkaloid is absorbed.
The coca leaf, when consumed in its natural form, does not induce a physiological or psychological dependence, nor does abstinence after long-term use produce symptoms typical to substance addiction. Due to its alkaloid content and non-addictive properties, coca has been suggested as a method to help recovering cocaine addicts to wean off the drug.
Traces of coca have been found in mummies dating 3000 years back. Other evidence dates the communal chewing of coca with lime 8000 years back. Extensive archaeological evidence for the chewing of coca leaves dates back at least to the 6th century AD Moche period, and the subsequent Inca period, based on mummies found with a supply of coca leaves, pottery depicting the characteristic cheek bulge of a coca chewer, spatulas for extracting alkali and figured bags for coca leaves and lime made from precious metals, and gold representations of coca in special gardens of the Inca in Cuzco.
Coca chewing may originally have been limited to the eastern Andes before its introduction to the Incas. As the plant was viewed as having a divine origin, its cultivation became subject to a state monopoly and its use restricted to nobles and a few favored classes (court orators, couriers, favored public workers, and the army) by the rule of the Topa Inca (1471–1493). As the Incan empire declined, the leaf became more widely available. After some deliberation, Philip II of Spain issued a decree recognizing the drug as essential to the well-being of the Andean Indians but urging missionaries to end its religious use. The Spanish are believed to have effectively encouraged use of coca by an increasing majority of the population to increase their labor output and tolerance for starvation, but it is not clear that this was planned deliberately.
Coca was first introduced to Europe in the 16th century, but did not become popular until the mid-19th century, with the publication of an influential paper by Dr. Paolo Mantegazza praising its stimulating effects on cognition. This led to invention of coca wine and the first production of pure cocaine. Coca wine (of which Vin Mariani was the best-known brand) and other coca-containing preparations were widely sold as patent medicines and tonics, with claims of a wide variety of health benefits. The original version of Coca-Cola was among these. These products became illegal in most countries outside of South America in the early 20th century, after the addictive nature of cocaine was widely recognized. In 1859, Albert Niemann of the University of Göttingen became the first person to isolate the chief alkaloid of coca, which he named "cocaine".
In the early 20th century, the Dutch colony of Java became a leading exporter of coca leaf. By 1912 shipments to Amsterdam, where the leaves were processed into cocaine, reached 1 million kg, overtaking the Peruvian export market. Apart from the years of the First World War, Java remained a greater exporter of coca than Peru until the end of the 1920s. Other colonial powers also tried to grow coca (including the British in India), but with the exception of the Japanese in Formosa, these were relatively unsuccessful.
In recent times (2006), the governments of several South American countries, such as Peru, Bolivia and Venezuela, have defended and championed the traditional use of coca, as well as the modern uses of the leaf and its extracts in household products such as teas and toothpaste.
Traditional medical uses of coca are foremost as a stimulant to overcome fatigue, hunger, and thirst. It is considered particularly effective against altitude sickness. It also is used as an anesthetic and analgesic to alleviate the pain of headache, rheumatism, wounds and sores, etc. Before stronger anaesthetics were available, it also was used for broken bones, childbirth, and during trepanning operations on the skull. The high calcium content in coca explains why people used it for bone fractures. Because coca constricts blood vessels, it also serves to oppose bleeding, and coca seeds were used for nosebleeds. Indigenous use of coca has also been reported as a treatment for malaria, ulcers, asthma, to improve digestion, to guard against bowel laxity, as an aphrodisiac, and credited with improving longevity. Modern studies have supported a number of these medical applications.
Raw coca leaves, chewed or consumed as tea or mate de coca, are rich in nutritional properties. Specifically, the coca plant contains essential minerals (calcium, potassium, phosphorus), vitamins (B1, B2, C, and E) and nutrients such as protein and fiber.
Coca has also been a vital part of the religious cosmology of the Andean peoples of Peru, Bolivia, Ecuador, Colombia, northern Argentina, and Chile from the pre-Inca period through the present. Coca leaves play a crucial part in offerings to the apus (mountains), Inti (the sun), or Pachamama (the earth). Coca leaves are also often read in a form of divination analogous to reading tea leaves in other cultures. As one example of the many traditional beliefs about coca, it is believed by the miners of Cerro de Pasco to soften the veins of ore, if masticated (chewed) and thrown upon them (see Cocomama in Inca mythology). In addition, coca use in shamanic rituals is well documented wherever local native populations have cultivated the plant. For example, the Tayronas of Colombia's Sierra Nevada de Santa Marta would chew the plant before engaging in extended meditation and prayer.
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In Bolivia bags of coca leaves are sold in local markets and by street vendors. The activity of chewing coca is called mambear, chacchar or acullicar, borrowed from Quechua, coquear (northern Argentina), or in Bolivia, picchar, derived from the Aymara language. The Spanish masticar is also frequently used, along with the slang term "bolear," derived from the word "bola" or ball of coca pouched in the cheek while chewing. Typical coca consumption is about 2 ounces (57 grams) per day, and contemporary methods are believed to be unchanged from ancient times. Coca is kept in a woven pouch (chuspa or huallqui). A few leaves are chosen to form a quid (acullico) held between the mouth and gums. Doing so may cause a tingling and numbing sensation in their mouths. (The formerly used dental anaesthetic Novocaine has a similar effect.) Chewing coca leaves is most common in indigenous communities across the central Andean region, particularly in places like the highlands of Colombia, Bolivia and Peru, where the cultivation and consumption of coca is as much a part of the national culture similar to chicha, like wine is to France or beer is to Germany. It also serves as a powerful symbol of indigenous cultural and religious identity, amongst a diversity of indigenous nations throughout South America.
Coca is still chewed in the traditional way, with a tiny quantity of ilucta (a preparation of the ashes of the quinoa plant) added to the coca leaves[contradiction]; it softens their astringent flavor and activates the alkaloids. Other names for this basifying substance are llipta in Peru and the Spanish word lejía, lye in English. The consumer carefully uses a wooden stick (formerly often a spatula of precious metal) to transfer an alkaline component into the quid without touching his flesh with the corrosive substance. The alkali component, usually kept in a gourd (ishcupuro or poporo), can be made by burning limestone to form unslaked quicklime, burning quinoa stalks, or the bark from certain trees, and may be called ilipta, tocra or mambe depending on its composition. Many of these materials are salty in flavor, but there are variations. The most common base in the La Paz area of Bolivia is a product known as lejía dulce (sweet lye), which is made from quinoa ashes mixed with aniseed and cane sugar, forming a soft black putty with a sweet and pleasing flavor. In some places, baking soda is used under the name bico.
In the Sierra Nevada de Santa Marta, on the Caribbean Coast of Colombia, coca is consumed by the Kogi, Arhuaco and Wiwa by using a special device called poporo. The poporo is the mark of manhood. It represents the womb and the stick is a phallic symbol. The movements of the stick in the poporo symbolize the sexual act. For a man the poporo is a good companion that means "food", "woman", "memory", and "meditation". It is important to stress that poporo is the symbol of manhood. But it is the woman who gives men their manhood. When the boy is ready to be married, his mother will initiate him in the use of the coca. This act of initiation is carefully supervised by the Mamo, a traditional priest-teacher-leader.
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Although coca leaf chewing is common only among the indigenous populations, the consumption of coca tea (Mate de coca) is common among all sectors of society in the Andean countries, especially due to their high elevations from sea level, and is widely held to be beneficial to health, mood, and energy. Coca leaf is sold packaged into teabags in most grocery stores in the region, and establishments that cater to tourists generally feature coca tea.
Commercial and industrial uses
In the Andes commercially manufactured coca teas, granola bars, cookies, hard candies, etc. are available in most stores and supermarkets, including upscale suburban supermarkets.
Coca is used industrially in the cosmetics and food industries. A de-cocainized extract of coca leaf is one of the flavoring ingredients in Coca-Cola. Before the criminalization of cocaine, however, the extract was not de-cocainized. Therefore, Coca-Cola's original formula did include cocaine.
Coca tea is produced industrially from coca leaves in South America by a number of companies, including Enaco S.A. (National Company of the Coca) a government enterprise in Peru. Coca leaves are also found in a brand of herbal liqueur called "Agwa de Bolivia" (grown in Bolivia and de-cocainized in Amsterdam), and a natural flavouring ingredient in Red Bull Cola, that was launched in March 2008.
Beginning in the early 21st century, there has been a movement in Bolivia, Peru, and Venezuela to promote and expand legal markets for the crop. The presidents of these three countries have personally identified with this movement. In particular, Evo Morales of Bolivia (elected in December 2005) was a coca grower's union leader. Morales asserts that "la coca no es cocaína"—the coca leaf is not cocaine. During his speech to the General Assembly of the United Nations on September 19, 2006, he held a coca leaf in his hand to demonstrate its innocuity.
Alan García, president of Peru, has recommended its use in salads and other edible preparations. A Peruvian-based company has announced plans to market a modern version of Vin Mariani, which will be available in both natural and de-cocainized varieties.
In Venezuela, former president Hugo Chávez said in a speech on January 2008 that he chews coca every day, and that his "hook up" is Bolivian president Evo Morales. Chávez reportedly said "I chew coca every day in the morning... and look how I am" before showing his biceps to his audience, the Venezuelan National Assembly.
On the other hand, the Colombian government has recently moved in the opposite direction. For years, Bogotá has allowed indigenous coca farmers to sell coca products, promoting the enterprise as one of the few successful commercial opportunities available to recognized tribes like the Nasa, who have grown it for years and regard it as sacred. In December 2005, the Paeces – a Tierradentro (Cauca) indigenous community – started to produce a carbonated soft drink called "Coca Sek". The production method belongs to the resguardos of Calderas (Inzá) and takes about 150 kg (331 lb) of coca per 3,000 produced bottles. The drink was never sold widely in Colombia and efforts to do so ended in May 2007 when it was abruptly banned by the Colombian government.
Coca Colla is an energy drink which is produced in Bolivia with the use of coca extract as its base. It was launched on the Bolivian market in La Paz, Santa Cruz and Cochabamba in mid-April 2010.
Probably the earliest reference to coca in English literature is Abraham Cowley's poem "A Legend of Coca" in his 1662 collection of poems "Six Books of Plants". An 800-year old oral poem is also known as "The legend of coca".
One of the best known examples of fictional references to coca is via Patrick O'Brian's character, Stephen Maturin. In many of the more than twenty book series, a.k.a. the Aubrey–Maturin series, Maturin expounds the benefits of coca. However, the reader is made aware of the truly addictive effects of the drug when rats, who have found the coca (Erythroxylum coca), become seriously addicted and scour the ship looking for it.
International prohibition of coca leaf
Coca leaf is the raw material for the manufacture of the drug cocaine, a powerful stimulant and anaesthetic extracted chemically from large quantities of coca leaves. Today, since it has mostly been replaced as a medical anaesthetic by synthetic analogues such as procaine, cocaine is best known as an illegal recreational drug. The cultivation, sale, and possession of unprocessed coca leaf (but not of any processed form of cocaine) is generally legal in the countries – such as Bolivia, Peru, Chile and Argentina – where traditional use is established, although cultivation is often restricted in an attempt to prevent the production of cocaine. In the case of Argentina, it is legal only in some northern provinces where the practice is so common that the state has accepted it.
The prohibition of the use of the coca leaf except for medical or scientific purposes was established by the United Nations in the 1961 Single Convention on Narcotic Drugs. The coca leaf is listed on Schedule I of the 1961 Single Convention together with cocaine and heroin. The Convention determined that "The Parties shall so far as possible enforce the uprooting of all coca bushes which grow wild. They shall destroy the coca bushes if illegally cultivated" (Article 26), and that, "Coca leaf chewing must be abolished within twenty-five years from the coming into force of this Convention" (Article 49, 2.e).
The historic rationale for international prohibition of coca leaf in the 1961 Single Convention comes from "The Commission of Enquiry on the Coca Leaf study" published in 1950. It was requested of the United Nations by the permanent representative of Peru, and was prepared by a commission that visited Bolivia and Peru briefly in 1949 to "investigate the effects of chewing the coca leaf and the possibilities of limiting its production and controlling its distribution." It concluded that the effects of chewing coca leaves were negative, even though chewing coca was defined as a habit, not an addiction.
The report was sharply criticised for its arbitrariness, lack of precision and racist connotations. The team members' professional qualifications and parallel interests were also criticised, as were the methodology used and the incomplete selection and use of existing scientific literature on the coca leaf. Questions have been raised as to whether a similar study today would pass the scrutiny and critical review to which scientific studies are routinely subjected.
Despite the legal restriction among countries party to the international treaty, coca chewing and drinking of coca tea is carried out daily by millions of people in the Andes as well as considered sacred within indigenous cultures. Coca consumers claim that most of the information provided about the traditional use of the coca leaf and its modern adaptations are erroneous. This has made it impossible to shed light on the plant's positive aspects and its potential benefits for the physical, mental and social health of the people who consume and cultivate it.
In an attempt to obtain international acceptance for the legal recognition of traditional use of coca in their respective countries, Peru and Bolivia successfully led an amendment, paragraph 2 of Article 14 into the 1988 United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances, stipulating that measures to eradicate illicit cultivation and to eliminate illicit demand "should take due account of traditional licit use, where there is historic evidence of such use." Bolivia also made a formal reservation to the 1988 Convention, which required countries to adopt measures to establish the use, consumption, possession, purchase or cultivation of the coca leaf for personal consumption as a criminal offence. Bolivia stated that "the coca leaf is not, in and of itself, a narcotic drug or psychotropic substance" and stressed that its "legal system recognizes the ancestral nature of the licit use of the coca leaf, which, for much of Bolivia's population, dates back over centuries."
However, the International Narcotics Control Board (INCB) – the independent and quasi-judicial control organ for the implementation of the United Nations drug conventions – denied the validity of article 14 in the 1988 Convention over the requirements of the 1961 Convention, or any reservation made by parties, since it does not "absolve a party of its rights and obligations under the other international drug control treaties."
The INCB stated in its 1994 Annual Report that "mate de coca, which is considered harmless and legal in several countries in South America, is an illegal activity under the provisions of both the 1961 Convention and the 1988 Convention, though that was not the intention of the plenipotentiary conferences that adopted those conventions." It implicitly also dismissed the original report of the Commission of Enquiry on the Coca Leaf by recognizing that "there is a need to undertake a scientific review to assess the coca-chewing habit and the drinking of coca tea."
Nevertheless, the INCB on other occasions did not show signs of an increased sensitivity towards the Bolivian claim on the rights of their indigenous population, and the general public, to consume the coca leaf in a traditional manner by chewing the leaf, and drinking coca tea, as "not in line with the provisions of the 1961 Convention." The Board considered Bolivia, Peru and a few other countries that allow such practises to be in breach with their treaty obligations, and insisted that "each party to the Convention should establish as a criminal offence, when committed intentionally, the possession and purchase of coca leaf for personal consumption."
In reaction to the 2007 Annual Report of the INCB, the Bolivian government announced that it would formally issue a request to the United Nations to unschedule the coca leaf of List 1 of the 1961 UN Single Convention. Bolivia led a diplomatic effort to do so beginning in March 2009, but eighteen countries out of a total of 184,those 18 being listed as followed (chronologically: the United States, Sweden, United Kingdom, Latvia, Japan, Canada, France, Germany, Bulgaria, Slovakia, Denmark, Estonia, Italy, Mexico, Russian Federation, Malaysia, Singapore, and Ukraine) objected to the change before the January 2011 deadline. A single objection would have been sufficient to block the modification. The legally unnecessary step of supporting the change was taken formally by Spain, Ecuador, Venezuela, and Costa Rica. In June 2011, Bolivia moved to denounce the 1961 Convention over the prohibition of the coca leaf.
Since the 1980s, the countries in which coca is grown have come under political and economic pressure from the United States to restrict the cultivation of the crop in order to reduce the supply of cocaine on the international market.
Article 26 of the Single Convention on Narcotic Drugs requires nations that allow the cultivation of coca to designate an agency to regulate said cultivation and take physical possession of the crops as soon as possible after harvest, and to destroy all coca which grows wild or is illegally cultivated. The effort to enforce these provisions, referred to as coca eradication, has involved many strategies, ranging from aerial spraying of herbicides on coca crops to assistance and incentives to encourage farmers to grow alternate crops.
This effort has been politically controversial, with proponents claiming that the production of cocaine is several times the amount needed to satisfy legal demand and inferring that the vast majority of the coca crop is destined for the illegal market. As per the proclaimed view, this would not only contributes to the major social problem of drug abuse but also financially supports insurgent groups that collaborate with drug traffickers in some cocaine-producing territories. Critics of the effort claim that it creates hardship primarily for the coca growers, many of whom are poor and have no viable alternative way to make a living, causes environmental problems, that it is not effective in reducing the supply of cocaine, in part because cultivation can move to other areas, and that any social harm created by drug abuse is only made worse by the War on Drugs. The environmental problems include "ecocide", where vast tracts of land and forest are sprayed with glyphosate or Roundup, with the intention of eradicating the coca plant. However, the incidental environmental damage is severe, because many plant species are wiped out in the process.
Boliviana negra, a genetically engineered type of coca, resists glyphosate herbicides and increases yields.
Legal status by country
Outside of South America, most countries' laws make no distinction between the coca leaf and any other substance containing cocaine, so the possession of coca leaf is prohibited. In South America coca leaf is illegal in both Paraguay and Brazil.
In the Netherlands, coca leaf is legally in the same category as cocaine, both are List I drugs of the Opium Law. The Opium Law specifically mentions the leafs of the plants of the genus Erythroxylon. However, the possession of living plants of the genus Erythroxylon are not actively prosecuted, even though they are legally forbidden.
In the United States, a Stepan Company plant in Maywood, New Jersey is a registered importer of coca leaf. The company manufactures pure cocaine for medical use and also produces a cocaine-free extract of the coca leaf, which is used as a flavoring ingredient in Coca-Cola. Other companies have registrations with the DEA to import coca leaf according to 2011 Federal Register Notices for Importers, including Johnson Matthey, Inc, Pharmaceutical Materials; Mallinckrodt Inc; Penick Corporation; and the Research Triangle Institute. According to the Bolivian press, Coca-Cola imported 204 tons of coca leaf in 1996.
- Plowman, T (1979). "Botanical Perspectives on Coca". Journal of Psychedelic Drugs. 11(1-2): 103–117.
- Plowman, T; Rivier L (1983). "Cocaine and Cinnamoylcocaine content of thirty-one species of Erythroxylum (Erythroxylaceae)". Annals of Botany (London) 51: 641–659.
- May, Clifford D (1988-07-01). "How Coca-Cola Obtains Its Coca". The New York Times.
- Transnational Institute - Coca Myths
- Plowman T. "The Origin, Evolution, and Diffusion of Coca, Erythroxylum spp., in South and Central America." In: Stone D, ed. Pre-Columbian Plant Migration. Papers of the Peabody Museum of Archaeology and Ethnology. Harvard University. Vol 76. Cambridge MA: Harvard University Press; 1984. p. 125-163.
- Bohm, B; Ganders F; Plowman T (1982). "Biosystematics and Evolution of Cultivated Coca (Erythroxylaceae)". Systematic Botany 7(2): 121–133. doi:10.2307/2418321.
- Johnson, E; Zhang D; Emche S (2005). "Inter- and Intra-specific Variation among Five Erythroxylum Taxa Assessed by AFLP". Annals of Botany 95: 601–608.
- Emche, S; Zhang D; Islam M; Bailey B; Meinhardt L (2011). "AFLP Phylogeny of 36 Erythroxylum Species Genetic Relationships Among Erythroxylum Species Inferred by AFLP Analysis". Tropical Plant Biology 4: 126–133. doi:10.1007/s12042-011-9070-9.
- Islam M. Tracing the Evolutionary History of Coca (Erythroxylum) [PhD thesis]. Boulder: University of Colorado, Boulder; 2011
- Evolutionary History: Uniting History and Biology to Understand Life on Earth, Edmund Russell. Cambridge University Press. 2011. ISBN 978-0-521-74509-3. Retrieved 2011-03-12.
- Davis, Joshua (2004), The Mystery of the Coca Plant That Wouldn't Die, WIRED 12 (11)
- Dion, Michelle L; Russler,Catherine (2008). "Eradication Efforts, The State, Displacement And Poverty: Explaining Coca Cultivation In Colombia During Plan Colombia". Journal of Latin American Studies 40.3: 399–421. doi:10.1017/s0022216x08004380.
- "Illicit Production of Cocaine - [www.rhodium.ws]". Erowid.org. Retrieved 2013-03-26.
- Jenkins, Amanda; Llosa, Teobaldo; Montoya, Ivan; Cone, Edward (February 9, 1996). "Identification and quantitation of alkaloids in coca tea". Forensic Sci Int 77 (3): 179–189. doi:10.1016/0379-0738(95)01860-3. PMC 2705900. PMID 8819993. Retrieved August 4, 2014.
- Weil, AT (Mar–May 1981). "The therapeutic value of coca in contemporary medicine". Journal of Ethnopharmacology 3 (2-3): 367–76. doi:10.1016/0378-8741(81)90064-7. PMID 6113306.
- Cocaine: Abuse and Addiction
- BS, Liao; RL, Hilsinger; BM, Rasgon; K, Matsuoka; KK, Adour (Jan 1999). "A preliminary study of cocaine absorption from the nasal mucosa". Laryngoscope 109 (1): 98–102. doi:10.1097/00005537-199901000-00019. PMID 9917048. Retrieved August 4, 2014.
- Mazor, Susan; Mycyk, Mark; Wills, Brandon; Brace, Larry; Gussow, Leon; Erickson, Timothy (Dec 2006). "Coca tea consumption causes positive urine cocaine assay". Eur J Emerg Med 13 (6): 341. Retrieved August 4, 2014.
- Jackson, GF; Saady, JJ; Poklis, A (Jan–Feb 1991). "Urinary excretion of benzoylecgonine following ingestion of Health Inca Tea". Forensic Sci Int. 49 (1): 57–64. doi:10.1016/0379-0738(91)90171-e. PMID 2032667. Retrieved August 4, 2014.
- Hanna JM, Hornick CA., "Use of coca leaf in southern Peru: adaptation or addiction," Bull Narc. 1977 Jan-Mar;29(1):63-74.
- "Report of the Commission of Enquiry on the Coca Leaf". United Nations Economic and Social Council: 31. May 1950. Retrieved August 4, 2014.
- Hurtado-Gumucio, J (Oct 2000). "Coca leaf chewing as therapy for cocaine maintenance". Ann Med Interne. 151 Suppl B: B44–8. PMID 11104945.
- Oswaldo Francisco Ribas Lobos Fernández, doctoral thesis, Federal University of Bahia (UFBA), 2007; "Coca Light?"
- Rivera MA; Aufderheide AC; Cartmell LW; Torres CM; Langsjoen O (December 2005). "Antiquity of coca-leaf chewing in the south central Andes: a 3,000 year archaeological record of coca-leaf chewing from northern Chile". Journal of Psychoactive Drugs. 37(4): 455–458. doi:10.1080/02791072.2005.10399820.
- Dillehay et al (2010). "Early Holocene coca chewing in northern Peru". Antiquity 84 (326): 939–953.
- Robert C. Peterson, Ph.D. (May 1977). "NIDA research monograph #13: Cocaine 1977, Chapter I". Retrieved 2007-05-26.
- Eleanor Carroll, M.A. "Coca: the plant and its use". Retrieved 2007-05-26.
- Inciardi, James A. (1992). The War on Drugs II. Mayfield Publishing Company. p. 6. ISBN 1-55934-016-9.
- Musto, DF (1998). "International traffic in coca through the early 20th century". Drug and Alcohol Dependence. 49 (2): 145–156. doi:10.1016/s0376-8716(97)00157-9.
- Transnational Institute - Coca Myths, 2009
- James, A., Aulick, D., Plowman, T., 1975 "Nutritional Value of Coca", Botanical Museum Leaflets, Harvard University 24 (6): 113-119.
- Harvard Study - Nutritional Value of Coca Leaf (Duke, Aulick, Plowman 1975)
- Museo del Oro, Banco de la Republica. "Museo del Oro, Colombia" (in Spanish). Banrep.gov.co. Retrieved 2012-11-09.
- Transnational Institute - Coca Myths, 2009.
- "Drugs and Democracy | Coca leaf: Myths and Reality". Tni.org. 2011-02-18. Retrieved 2012-11-09.
- May, Clifford D. "How Coca-Cola Obtains Its Coca", The New York Times, July 1, 1998. "A Stepan laboratory in Maywood, N.J., is the nation's only legal commercial importer of coca leaves, which it obtains mainly from Peru and, to a lesser extent, Bolivia. Besides producing the coca flavoring agent for Coca-Cola, Stepan extracts cocaine from the coca leaves, which it sells to Mallinckrodt Inc., a St. Louis pharmaceutical manufacturer that is the only company in the United States licensed to purify the product for medicinal use."
- Benson, Drew. "Coca kick in drinks spurs export fears", The Washington Times, April 20, 2004. "Coke dropped cocaine from its recipe around 1900, but the secret formula still calls for a cocaine-free coca extract produced at a Stepan Co. factory in Maywood, N.J. Stepan buys about 100 metric tons of dried Peruvian coca leaves each year, said Marco Castillo, spokesman for Peru's state-owned National Coca Co."
- Coca Yes, Cocaine No? Legal Options for the Coca Leaf, Transnational Institute, Drugs & Conflict Debate Paper 13, May 2006
- (Spanish) Empresa Nacional de la Coca S.A
- Peruvian Drug Control Agency: Coca Cola Buys Coca Leaves, The Narco News Bulletin, January 28, 2005
- Agwabuzz.com Agwa de Bolivia herbal liqueur official site
- The Cola from Red Bull[dead link]
- Dean, Bartholomew 2013"Cocaine Capitalisms & Social Trauma in Peruvian Amazonia", Panoramas, University of Pittsburgh (July 17) 
- Statement of Evo Morales Aima, President of Bolivia at the 61st session of the United Nations General Assembly, September 19, 2006
- Bolivia and Peru Defend Coca Use March 6, 2008. "The United Nations lacks respect for the indigenous people of Peru and Bolivia who have used the coca leaf since forever," said Peruvian Congresswoman Maria Sumire. "For indigenous people, coca is a sacred leaf that is part of their cultural identity," she said.
- "Evo Morales launches 'Coca Colla'". Telegraph. 10 January 2010. Retrieved 22 January 2010.
- "Bolivia banks on 'Coca Colla,' fizzy coca-leaf drink". AFP. 10 January 2010. Retrieved 22 January 2010.
- Peru. History of coca, "the divine plant" of the Incas; with an introductory account of the Incas, and of the Andean Indians of to-day. W. Golden Mortimer, M.D. Ed. J. H. Vail & Co, 1901. Abraham Cowley's poem "A Legend of Coca" : in chapter I An introduction to the history of coca, pp. 25-27.
- The legend of coca, old oral poem - excerpt.
- Single Convention on Narcotic Drugs
- Commission of Enquiry on the Coca Leaf, UNGASS 10-year review website, Transnational Institute
- The Commission of Enquiry on the Coca Leaf, Bulletin on Narcotics - 1949 Issue 1
- The resolution of ambiguities regarding coca, Transnational Institute, March 2008
- Status of treaty adherence, United Nations Convention against Illicit Traffic in Narcotic Drugs and Psychotropic Substances
- Report of the International Narcotics Control Board for 2007, paragraph 220
- Evaluation of the effectiveness of the international drug control treaties, Supplement to the INCB Annual Report for 1994 (Part 3)
- Evaluation of the effectiveness of the international drug control treaties, Supplement to the INCB Annual Report for 1994 (Part 1)
- Report of the International Narcotics Control Board for 2007, paragraph 217
- Response to the 2007 Annual Report of the International Narcotics Control Board, International Drug Policy Consortium (IDPC), March 2008
- Report of the International Narcotics Control Board for 2007, paragraph 219
- Letter Evo Morales to UN Secretary General Ban Ki-moon, March 8, 2008
- "Objections and support for Bolivia's coca amendment". Transnational Institute.
- "Aprueban denuncia contra la Convención de Viena". Los Tiempos. 2011-06-23. Retrieved 2011-06-23.
- Failed States and failed policies: how to stop the drug wars. The Economist, May 2009
- "Importers Notice of Registration - 2011". deaDiversion.usdoj.gov. Retrieved 2012-11-09.
- Turner C. E., Elsohly M. A., Hanuš L., Elsohly H. N. Isolation of dihydrocuscohygrine from Peruvian coca leaves. Phytochemistry 20 (6), 1403-1405 (1981)
- History of Coca. The Divine Plant of the Incas by W. Golden Mortimer, M.D. 576 pp. And/Or Press San Francisco, 1974. This title has no ISBN.
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- Shared Responsibility
- Coca leaf: Myths and Reality website of the Transnational Institute (TNI)
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- Coca leaf news page