Caffeine inosinic acid

In the case of DNA, a D-2-deoxyribose molecule is combined to each of the bases to form a nucleoside, and the nucleosides are then combined with each other with a phosphoric acid to form a polymer (DNA). On the other hand, in the case of RNA, D-ribose, instead of D-2-deoxyribose, is combined to each of the bases to form a nucleoside, and as in the case of DNA, these nucleosides are combined with each other to form a polymer (RNA). Among the bases within DNA and RNA, adenine and guanine have been described in the preceding section. In this section, cytosine, thymine, and uracil, which are pyrimidine bases, will be described. Purine derivatives exist as a constituent unit of nucleic acids and as many kinds of monomers, and these are also present in natural products, such as caffeine, inosinic acid, and cytokinin. On the other hand, as natural products, pyrimidine derivatives are rather rare. Nucleosides composed of pyrimidine bases cytosine, thymine, and uracil coupled with D-ribose are known as cytidine, thymidine, and uridine, respectively. Among these alkaloids, cytidine was first isolated from the nucleic acid of yeast [1,2], and thymidine was isolated from thymonucleic acid [3,4]. In the meantime, uridine was obtained by the weak alkali hydrolysis [5] of the nucleic acids originating from yeast. 

Fig. 11. Control sample co-injected with a solution containing creatinine (Crt), uric acid (UrcA). tyrosine (Tyr), hypoxanthine (Hyp), uridine (Urd), inosine (Ino), guanosine (Guo), hippuric acid (HipA), tryptophan (Trp). theobromine (Thb), and caffeine (Cat). Conditions same as in Fig. 10. Reprinted with permission from Hartwick et at. (H7). Copyright by Elsevier Scientific Publishing Company, Amsterdam.

Inosine-5 -phosphate can be converted to the nucleotides of adenine and guanine, well-known components of nucleic acids. Here, however, we are concerned with other possible means of utilizing this substance. For when one talks of purine alkaloids, one thinks primarily of caffeine, theophylline, and theobromine (Fig. 131). These methylated purine alkaloids are widely distributed, especially caffeine. Its occurrence in coffee (among others, Coffea arabica), tea Camellia sinensis), and cocoa Theobroma cacao) is well-known. 

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