Alkaloids, cocoa bean

Foods derived from cocoa beans have been consumed by humans since at least 460 to 480 AD. The source of cocoa beans, the species Theobroma, contains a variety of biologically active components. These include the purine alkaloids theobromine, caffeine, and theophylline. Structurally, they are methylated xanthines and, thus, are often referred to as methylxanthines. Theobromine (3, 7-dimethylxanthine) is the predominant purine alkaloid in cocoa and chocolate. Caffeine (1, 3, 7-trimethylxanthine), the major purine alkaloid found in coffee and tea, is found in cocoa and chocolate at about one eighth the concentration of theobromine. Only trace amounts of theophylline (1, 3-dimethylxanthine) are detected in cocoa and chocolate products. 

With the death of the bean, cellular structure is lost, allowing the mixing of water-soluble components that normally would not come into contact with each other. The complex chemistry that occurs during fermentation is not fully understood, but certain cocoa enzymes such as glycosidase, protease, and polyphenol oxidase are active. In general, proteins are hydrolyzed to smaller proteins and amino acids, complex glycosides are split, polyphenols are partially transformed, sugars are hydrolyzed, volatile acids are formed, and purine alkaloids diffuse into the bean shell. The chemical composition of both unfermented and fermented cocoa beans is compared in Table 1. 

Although low levels of methylxanthines have been detected in the leaves and flowers of T. cacao, the primary storage location is within the seed or bean.16 The cocoa bean is the major natural source of the methylxanthine theobromine, but contains only small amounts of caffeine. Theophylline has been detected in cacao beans, but at such low concentrations that its presence generally is ignored. Together, theobromine and caffeine account for up to 99% of the alkaloid content of T. cacao beans. Alkaloid content is affected by genetic makeup, maturity of beans at harvest, and fermentation process. Analytical methodology also is partially responsible for some of the disparity in methylxanthine values since many early methods were unable to separate theobromine and caffeine. 

Timbie, D., Studies on the protein and purine alkaloids of cocoa beans, Ph.D. thesis, The Pennsylvania State University, 1977. 

Alkaloids are compounds that contain nitrogen in a heterocyclic ring and are commonly found in about 15-20% of all vascular plants. Alkaloids are subclassified on the basis of the chemical type of their nitrogen-containing ring. They are formed as secondary metabolites from amino acids and usually present a bitter taste accompanied by toxicity that should help to repel insects and herbivores. Alkaloids are found in seeds, leaves, and roots of plants such as coffee beans, guarana seeds, cocoa beans, mate tea leaves, peppermint leaves, coca leaves, and many other plant sources. The most common alkaloids are caffeine, theophylline, nicotine, codeine, and indole... 

Alkaloids such as caffeine and theobromine were obtained from cocoa beans and guarana seeds (Saldana and others 2002a,b). 

Caffeine, 1,3,7-trimethylxanthine, is the major alkaloid, occms in teaplants, coffee, guarana, cola nuts, cocoa beans, mate and other plants. It is a powerful stimirlant of the central nervous system and also stimirlates the cardiac muscle. However, high... 

The two alkaloids theobromine and theophylline are isomeric, theobromine being the 3-7-di-methyl xanthine and theophylline the I-3-di-methyl xanthine. Theobromine is the principal alkaloid of the cocoa bean. Cacao theohroma. It occurs also in small amounts in kola nuts and tea leaves. Theophylline is present in small amounts in tea. They both resemble caffeine in being crystalline, weak bases. 

Triacanthine (17) has been isolated from Holarrhena mitis Details on the structure and total synthesis of eritadenine (18), a hypocholesterolemic alkaloid from Lentinus edodes, have been reported.An unsuccessful attempt to improve the imidazole ring-closure reaction in a total synthesis of eritadenine, which has been previously discussed, was also reported in this study. Concentrations of both caffeine and theobromine in the cocoa bean were shown to increase most markedly in the time period from flowering to harvest. ... 

Caffeine is also found in tea leaves from Camellia sinensis (up to 5 %) and in the seeds of cola nuts (Cola nitida, up to 2 %). Mat6 (Paraguay tea. Ilex para-guariensis, with 0.3-1.5%) and the seeds of the cocoa plant (Theobroma cacao, with 0.05%) show a significantly lower content. The main alkaloid in cocoa beans is theobromine. 

These three alkaloids are well-known compounds, as they are present in everyday foods and beverages, such as cocoa, drinking chocolate, tea, and cola, as well as in pharmaceutical products. In cocoa products, theobromine is the major alkaloid, followed by caffeine, which is found in small quantities. Slight traces of theophylline have been identified therefore, it is not considered relevant and is not reviewed in the cocoa products [22,23], The range of methylxanthines also depends on variables such as the origin of the cocoa beans, the fermentation process, and the cocoa production process. Thus, for instance, defatted cocoa beans may contain about 4% and 0.2% of theobromine and caffeine, respectively [24], Regarding their physiological effects in humans, methylxanthines have been related to various body systems, mainly the central nervous system, but also the cardiovascular, renal, and respiratory systems [25,26],... 

The active ingredient that makes tea and coffee valuable to humans is caffeine. Caffeine is an alkaloid, a class of naturally occurring compounds containing nitrogen and having the properties of an organic amine base (alkaline, hence, alkaloid). Tea and coffee are not the only plant sources of caffeine. Others include kola nuts, mate leaves, guarana seeds, and, in small amount, cocoa beans. The pure alkaloid was first isolated from coffee in 1821 by the French chemist Pierre Jean Robiquet. 

The amount of flavonoids and flavanols in cocoa and chocolate might be highly variable and this variability is multifactorial. For example, plant s genetic predisposition dictates the biosynthesis of the primary (sugars, amino acids, etc.) and secondary metabolites (proanthocyanidins, saponins, alkaloids, etc.) while genetics can cause as much as a fourfold difference in flavan-3-ol content of fresh cocoa beans [22, 23]. Variability with respect to secondary metabolites exists between varieties (or cultivars) of the same species. However, various environmental factors determine the extent to which genetic potentialities are... 

Fresh cocoa beans, the seeds of cacao tree (Theobroma cacao, StercuUaceae), have a sour odour and a sour, bitter and astringent taste. The main contributors to the bitter taste are purine alkaloids. The astringent taste of cocoa products is mainly influenced by oligomeric procyanidins, flavan-3-ol-C-glycopyranosides (see Section 8.3.6.2.2) and N-phenylpropenoyl amino acids (see Section 2.2.1.2.1). 

The total alkaloid content of cocoa beans Theobroma cacao, Sterculiaceae) is in the range of from 0.7 to 3.2% of dry matter. The main alkaloid is theobromine, the content of which is 0.6-3.1% and the content of caffeine ranges from 0.02 to 0.5%. Dark chocolate contains 0.3-0.7% of theobromine and 0.02-0.03%... 

Belonging to the same chemical group as atropine is the important alkaloid cocaine, C17H21O4N. It is obtained from the leaves of the coca plant, Erythroxylon coca, which grows in South America (Bolivia and Peru) and in Java and Ceylon. Distinction should be made between the coca plant and the cacao bean from which cocoa and chocolate are made. 

For the analysis of cocoa samples, the beans were ground using a mortar and pestle [27] or a laboratory mill [28,29] to obtain a homogeneous material. Then, to analyze procyanidins and alkaloids, these were first defatted between three and four times with n-hexane to remove the fat from the cocoa matrix. Second, an off-line liquid-liquid extraction (LLE) was performed to extract the procyanidins and alkaloids from this matrix. Various solutions formed by acetone were used as the extraction solutions. These were acetone/water (70/30, v/v) [27], acetone/water/acetic acid (70/28/2, v/v/v) [18], and acetone/water/acetic acid (70/29.5/0.5, v/v/v) [28,29] (see Table 14.1). Afterwards, the extracts were sonicated [18] or vortexed [28,29] and centrifuged. The supernatants were combined from the centrifuged tubes and filtered with glass wool [28,27]. Finally, the organic solvent of these extracts was removed by rotary evaporation at a temperature between 30°C and 40°C. 

With regard to alkaloids analysis, theobromine was the main compound found in cocoa extracts. This is in agreement with this compound being the most important methylxanthine found in products from the cocoa tree, Theobroma cocao [22], Theobromine was also detected at higher concentrations than caffeine. These were around 42 and 3.5 mg/g lyophilized cocoa extracts (beans, nibs, liquor, and powder) [28],... 

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