Paraxanthine

Colorless solid

Fixed

1.36 g · cm -3 ( 25 ° C)

294-296 ° C

Slightly soluble in water and in ethanol: 1 and 0.6 g · l -1 ( 20 ° C)

Attention

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Paraxanthine is a chemical compound selected from the group of the xanthines. It is the dimethyl derivative of xanthine and structurally related to the caffeine. It is isomeric with theobromine and theophylline.

Occurrence

Paraxanthine comes in plants only in trace amounts; there it is caused by slow methylation of 7- methylxanthine by S- adenosylmethionine. It is then isomerized in plants almost immediately to caffeine.

Biological Significance and metabolism

Paraxanthine is an adenosine receptor ligand and a major metabolite of caffeine in animals. In humans, about 80 % of the caffeine taken up by the enzyme cytochrome P450 1A2 are demethylated to paraxanthine, which can be detected in human urine. Major metabolite of directly ingested paraxanthine in humans and mice, the 1- methylxanthine; demethylation happens here in the microsomes of the liver by the enzyme cytochrome 2A6 ( CYP2A6 ). CYP1A2 cytochromes can paraxanthine also implement to 7- methylxanthine. About 60% is excreted unchanged in the urine.