1. Extracts prepared from tea leaves with Polyclar AT (insoluble polyvinylpyrrolidine) contained two methyltransferase activities catalysing the transfer of methyl groups from S-adenosylmethionine to 7-methylxanthine, producing theobromine, and to theobromine, producing caffeine. 2. The methyltransferases exhibited the same pH optimum (8.4) and a similar pattern of effects by metal ions, thiol inhibitors and metal-chelating reagents, both for theobromine and caffeine synthesis. Mg2+, Mn2+ and Ca2+ slightly stimulated enzyme activity but they were not essential. Paraxanthine was shown to be most active among methylxanthines, as the methyl acceptor. However, the formation of paraxanthine from 1-methylxanthine was very low and that from 7-methylxanthine was nil, suggesting that the synthesis of caffeine from paraxanthine is of little importance in intact plants. Xanthine, xanthosine, XMP and hypoxanthine were all inactive as methyl acceptors, whereas [2(-14)C]xanthine and [8(-14)C]hypoxanthine were catabolized to allantoin and urea by tea-leaf extracts. The apparent Km values are as follows: 7-methylxanthine, 1.0 times 10(-14)M; theobromine, 1.0 times 10(-3)M; paraxanthine, 0.2 times 10(-3)M; S-adenosylmethionine, 0.25 times 10(-4)M (with each of the three substrates). 3. The results suggest that the pathway for caffeine biosynthesis is as follows: 7-methylxanthine leads to theobromine leads to caffeine. In contrast, it is suggested that theophylline is synthesized from 1-methylxanthine. The methyl groups of the purine ring of caffeine are all derived directly from the methyl group of S-adenosylmethionine. Little is known about the pathways leading to the formation of 7-methylxanthine. 4. A good correlation between caffeine synthesis and shoot formation or growth of tea seedlings was shown, suggesting that the methylating systems in caffeine synthesis are closely associated with purine nucleotide and nucleic acid metabolism in tea plants.

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On the theobromine and theophylline content of raw coffee and tea

Biosynthesis of caffeine by tea-leaf extracts. Enzymic formation of theobromine from 7-methylxanthine and of caffeine from theobromine.

Researchers have unraveled the nutritive value and other beneficial effects of coffee on human health, especially prevention of lifestyle diseases of the modern world. Therefore, it is being considered as a nutraceutical to prevent and combat diseases of modern society. This chapter describes historical perspectives of green coffee bean, its source, processing, global production scenario, major phytoconstituents, pharmacokinetic attributes, major pharmacological activities, promising potential as a nutraceutical, and some of the possible adverse effects. Its promising antioxidant and weight-reducing potential, ability to check type 2 diabetes and hypertension, ability to prevent cardiovascular and other diseases like cancer and hepatic and neurodegenerative disorders, along with their possible mechanism(s) of action, strongly favor its consideration as a promising nutraceutical and food supplement. However, detailed research work following long-term exposure is warranted to assess the efficacy and safety of coffee.

Green Coffee Bean

1 Caffeine biosynthesis was studied by following the incorporation of 14C into the products of L-[Me-14C]methionine metabolism in tea shoot tips 2 After administration of a 'pulse' of L-[Me-14C]methionine, almost all of the L-[Me-14C]methionine supplied disappeared within 1 h, and 14C-labelled caffeine synthesis increased throughout the experimental periods, whereas the radioactivities of an unknown compound and theobromine were highest at 3 h after the uptake of L-[Me-14C]methionine, followed by a steady decrease There was also slight incorporation of the label into 7-methylxanthine, serine, glutamate and aspartate, disappearing by 36 h after the absorption of L-[Me-14C]methionine 3 The radioactivities of nucleic acids derived from L-[Me-14C]methionine increased rapidly during the first 12 h incubation period and then decreased steadily Sedimentation analysis of nucleic acids by sucrose-gradient centrifugation showed that methylation of nucleic acids in tea shoot tips occurred mainly in the tRNA fraction The main product among the methylated bases in tea shoot tips was identified as 1-methyladenine 4 The results indicated that the purine ring in caffeine is derived from the purine nucleotides in the nucleotide pool rather than in nucleic acids A metabolic scheme to show the production of caffeine and related methylxanthines from the nucleotides in tea plants is discussed

Metabolism of methionine and biosynthesis of caffeine in the tea plant (Camellia sinensis L.).

Es wird eine Arbeitsmethode beschrieben, mit der erstmals der Theophyllingehalt in Kola (5,1–5,3 mg/100 g), Mate (1,0–1,1 mg/100 g) und Kakao (0,20 bis 0,22 mg/100 g) sowie der Theobromingehalt in Mate (71–74 mg/100 g) ermittelt werden konnte. Der fur Kola festgestellte Gehalt an Theobromin (48–52 mg/100 g) stimmt mit den in der Literatur vorliegenden Angaben gut uberein.

On the theobromine and theophylline content of raw coffee and tea

Citations

Biosynthesis of caffeine by tea-leaf extracts. Enzymic formation of theobromine from 7-methylxanthine and of caffeine from theobromine.

Green Coffee Bean

Metabolism of methionine and biosynthesis of caffeine in the tea plant (Camellia sinensis L.).

Über die Bestimmung und den Gehalt von Theobromin und Theophyllin in Mate, Kola und Kakao