Heterocyclic compounds caffeine

Purines A series of heterocyclic compounds that are variously substituted in nature and are known also as purine bases. They include adenine and guanine, constituents of nucleic acids, as well as many alkaloids such as caffeine and theophylline. Uric add is the metabolic end product of purine metabolism. [NIH]... 

More than 50% of all known organic compounds are heterocyclic compounds. They play important roles in medicine and biological systems. A great majority of important drugs and natural products, e.g. caffeine, nicotine, morphine, penicillins and cephalosporins, are heterocyclic compounds. The purine and pyrimidine bases, two nitrogenous heterocyclic compounds, are structural units of RNA and DNA. Serotonin, a neurotransmitter found in our body, is responsible for various bodily functions. 

Caffeine (1,3,7-triniethylxanthine) is the well-known stimnlant present in tea and coffee. Uric acid, the end product of nucleic acid catabolism in humans, birds and reptiles (nric acid was one of the first heterocyclic compounds to be isolated as a pure substance, by the Swedish chemist Carl Scheele in 1776) is formed by the action of the enzyme xanthine oxidase. In cases of excess uric acid, deposition of crystals of uric acid can occur, leading to the joint pain known as gout, usually initially in the big toe and usually in males. 

Caffeine belongs to the family of heterocyclic compounds known as purines. It has the systematic name 3,7-dihydro-l,3,7-trimethyl-lH-purme-2,6-dione it is also known as 1,3,7-trimethylxanthme, and l,3,7-trimethyl-2,6-dioxopurine. Caffeine can be classified as an alkaloid, a term used for substances produced as end products of nitrogen metabolism in some plants. The chemical formula is C8H10N4O2. Caffeine has a molar mass of... 

The term alkaloid is applied to certain nitrogenous constituents of plants. The alkaloids differ widely in structure some like muscarine (218) are aliphatic compounds, others like caffeine (418) contain a ring of carbon atoms and are related to uric acid. The alkaloids which are described briefly here are related to heterocyclic compounds, chiefly pyridine, quinoline. 

A book dealing with alkaloids in foods contains an account on caffeine and related compounds. The synthesis of caffeine, the conversion of uric acid into xanthine, and various syntheses of related heterocyclic compounds form subject matters in a review of broad scope. The role of purine alkaloids in trace-metal metabolism, disease resistance, mutagenesis, and chemotaxonomic considerations in plants has been reviewed. 

Fischer carried out extensive work on the chemistry of purine and on those compounds containing its nucleus. Purine is one of the two nitrogen base ring systems present in DNA. Fischer synthesized approximately 150 members of this class of heterocyclic compounds (including the first synthesis of the alkaloid caffeine (see Experiment [IIB]), uric add, and the xanthines (also see Experiment [IIB]). He developed a general s)mthesis of another nitrogen heterocyde, indole, which was so effective that it has become one of the classic synthetic methods of organic chemistry and is known today as the "Fischer indole synthesis" ... 

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... 

The alkaloids are basic compounds in which an N atom is typically part of a heterocyclic ring but in some cases is merely a substituent of an alicyclic or aromatic ring system (as for example with colchicine, some peptide alkaloids and some Amaryllidaceae alkaloids). Various N-based heterocyclics such as the purine and pyrimidine bases of DNA and RNA (see Chapter 2) and the methylxanthine purine derivatives variously found in tea and coffee (caffeine, theobromine and theophylline) are sometimes referred to as pseudoalkaloids and for consistency will be included as alkaloids in this classification. Indeed all plant heterocyclics with a ring N will be conveniendy lumped in with the alkaloids in the tables for didactic simplicity and consistency. 

Some derivatives have one or two nitrogen atoms at different positions in bicyclic six-six, six-five, or five-five fused aromatic rings. It is also possible to incorporate three, four, or even more nitrogen atoms into these rings. Most will not be seen in this book, but there is an important six-five heterocyclic ring system that contains four nitrogen atoms. This compound is called purine (88X and derivatives of this fundamental heterocycle include adenine (89) and guanine (90), which are components of DNA and RNA (see Chapter 28, Section 28.6). In addition, both uric acid (91 a component of urine) and caffeine (92 found in coffee and tea) have a purine skeleton. 

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