Taste alkaloids

Theobromine was isolated from the seeds of the cacao tree and then shortly afterward was synthesized from xanthine by Fischer.132 Theobromine is the primary bitter-tasting alkaloid found in cocoa and chocolate chocolate contains 0.5—2.7% theobromine. Theobromine is water insoluble and is an isomer of theophylline as well as paraxanthine. Theobromine is categorized as 3,7-dimethylxanthine while theophylline is 1,3-dimethyl-7f/-purine-2,6-dione and paraxanthine is 1,7-dimethylxanthine. Theophylline is known to be a bitter-tasting principle of green tea. Theobromine is used as a vasodilator (a blood vessel widener), as an aid in urination, and... 

Main components 5-15% bitter tasting alkaloids, mainly chinine, chinidine, cinchonine, cinchonidine, as well as 3-5% tannins, up to 2% chinovin (a bitter tasting triterpene glycoside), resins, starch. 

The free bases are soluble in lipophilic organic solvents, like chloroform. The different solubility for bases and salts is used for isolation and purification. Alkaloids are generally colourless solid materials. Some alkaloids that do not contain oxygen, like coniine, nicotine and sparteine, are liquid, and berberine and chelidonine are intensely yellow. Several alkaloids, e.g. strychnine and quinine, have a very bitter taste. Alkaloids give precipitates with heavy metals like mercury and bismuth. DragendorfPs reagent is used to show the presence of alkaloids. 

C8H10N4O2. An alkaloid occurring in tea, coffee and guarana, from which it may be prepared by extraction, It is also manufactured by the methylation of theobromine and by the condensation of cyanoacetic acid with urea. Crystallizes with H2O or anhydrous from organic solvents. M.p. (anhydrous) 235"C, sublimes at 176 C. Odourless, and with a very bitter taste. Caffeine acts as a stimulant and diuretic, and is a constituent of cola drinks, tea and coffee. 

Organic aromatic molecules are usually sweet, bitter, a combination of these, or tasteless, probably owing to lack of water solubiUty. Most characteristic taste substances, especially salty and sweet, are nonvolatile compounds. Many different types of molecules produce the bitter taste, eg, divalent cations, alkaloids, some amino acids, and denatoirium (14,15). 

Simple Bases. In addition to the alkaloids proper, 1 4-TETRAMETHYLDiAMiNoBUTANE, MCjN. (CHj) . NMCj, has been found in Hyoscyamus muticus by Merck and in H. reticulatus by Konovalova and Magidson. It was described by Willstatter and Heubner as a colourless liquid, 0-7941, b.p. 169°, with a pungent, acrid taste. The... 

Bitter taste, like sweet taste, is exhibited by a very diverse group of chemical compounds. Because the bitter taste is generally regarded as unpleasant, and because it is often associated with such compounds as those alkaloids and glycosides that are harmful to man, detailed studies have been minimal. There is thus very little information available from which to deduce the chemical grouping common to those compounds eliciting the bitter response. 

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... 

True alkaloids derive from amino acid and they share a heterocyclic ring with nitrogen. These alkaloids are highly reactive substances with biological activity even in low doses. All true alkaloids have a bitter taste and appear as a white solid, with the exception of nicotine which has a brown liquid. True alkaloids form water-soluble salts. Moreover, most of them are well-defined crystalline substances which unite with acids to form salts. True alkaloids may occur in plants (1) in the free state, (2) as salts and (3) as N-oxides. These alkaloids occur in a limited number of species and families, and are those compounds in which decarboxylated amino acids are condensed with a non-nitrogenous structural moiety. The primary precursors of true alkaloids are such amino acids as L-ornithine, L-lysine, L-phenylalanine/L-tyrosine, L-tryptophan and L-histidine . Examples of true alkaloids include such biologically active alkaloids as cocaine, quinine, dopamine, morphine and usambarensine (Figure 4). A fuller list of examples appears in Table 1. 

This is a non-chemical, and probably the first biological, method of determining the presence of alkaloids. It was first used particularly with quinolizidine alkaloids in lupine plants. The tasters were men or animals, even in ancient times. It is based on the fact that quinolizidine alkaloid has a bitter taste. This method is qualitative. Taste is a subjective and individual category, especially in the... 

Quinolizidine alkaloids are non-toxic to the legumes which produce them. On the other hand, the quinolizidine alkaloids can be toxic and in some cases very toxic to other organisms. The biotoxicity of alkaloids has for some time been considered to be connected with their bitter taste" ° ". The quinolizidine alkaloids are certainly bitter in taste to humans. However, not all alkaloids are. Literature states that some pyrrolizidine and indolizidine alkaloids are not bitter in their pure forms" Furthermore, there are many non-alkaloid compounds, such as flavonoids, that are bitter in taste but non-toxic. Therefore, although quinolizidine alkaloids are bitter, the connection between biotoxicity and bitter taste is not absolute. 

Animal sequestration of alkaloids is connected not only with taste but also with the toxicity of these compounds. It has been stated that the toxicity of alkaloids is very selective. Aniszewski has published data with some LDjq coefficients for some alkaloids and some pesticides and compared their toxicity from a selectivity point of view. There was clear evidence that alkaloids (sparteine and lupanine) are much more toxic for vertebrates than are some pesticides (e.g. malafione, phenitrothione, etc.). For invertebrates, pesticides were clearly more toxic than alkaloids. Selective toxicity coefficients (STC) were counted by dividing the LDjg for vertebrates by the LDjg for invertebrates. When the STC is 1.0 there is no selectivity when STC is >1 there is invertebrate selectivity and when <1 there is vertebrate selectivity. Selectivity simply means there exists more ability to toxify the organism. 

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