3D model (JSmol)
|Molar mass||180.17 g·mol−1|
|Melting point||351 to 352 °C (664 to 666 °F; 624 to 625 K)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
Paraxanthine, or 1,7-dimethylxanthine, is a dimethyl derivative of xanthine, structurally related to caffeine. Like caffeine, paraxanthine is a psychoactive central nervous system (CNS) stimulant. It possesses a potency roughly equal to that of caffeine and is likely involved in the mediation of the effects of caffeine itself.
Production and metabolism
Paraxanthine is not produced by plants and is only observed in nature as a metabolite of caffeine in animals. After intake, roughly 84% of caffeine is demethylated at the 3-position to yield paraxanthine, making it the chief metabolite of caffeine in the body.
Certain proposed synthetic pathways of caffeine make use of paraxanthine as a bypass intermediate. However, its absence in plant alkaloid assays implies that these are infrequently, if ever, directly produced by plants.
Paraxanthine has a number of physiological effects on animals:
- Paraxanthine is a competitive nonselective phosphodiesterase inhibitor which raises intracellular cAMP, activates PKA, inhibits TNF-alpha and leukotriene synthesis, and reduces inflammation and innate immunity.
- Paraxanthine is a nonselective adenosine receptor antagonist which raises plasma epinephrine and diastolic blood pressure.
- Paraxanthine may be responsible for the lipolytic properties of caffeine, and its presence in the blood causes an increase in serum free fatty acid concentration.
- Paraxanthine, unlike caffeine, acts as an enzymatic effector of Na+/K+ ATPase. As a result, it is responsible for increased transport of potassium ions into skeletal muscle tissue. Similarly, the compound also stimulates increases in calcium ion concentration in muscle.
Paraxanthine is believed to exhibit a lower toxicity than caffeine. While blood levels commensurate with average intake appear to be fairly innocuous, high blood concentrations of paraxanthine have been linked to miscarriage in pregnant mothers.
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- Hetzler RK, Knowlton RG, Somani SM, Brown DD, Perkins RM (January 1990). "Effect of paraxanthine on FFA mobilization after intravenous caffeine administration in humans (Bethesda MD 1985)". Journal of Applied Physiology. 68 (1): 44–47. PMID 2312486.
- Hawke TJ, Willmets RG, Lindinger MI (November 1999). "K+ transport in resting rat hind-limb skeletal muscle in response to paraxanthine, a caffeine metabolite". Canadian Journal of Physiology and Pharmacology. 77 (11): 835–843. doi:10.1139/y99-095. PMID 10593655.
- Hawke TJ, Allen DG, Lindinger MI (December 2000). "Paraxanthine, a caffeine metabolite, dose dependently increases [Ca(2+)](i) in skeletal muscle". Journal of Applied Physiology. 89 (6): 2312–2317. PMID 11090584.
- Neal L. Benowitz; Peyton Jacob; Haim Mayan; Charles Denaro (1995). "Sympathomimetic effects of paraxanthine and caffeine in humans". Clinical Pharmacology & Therapeutics. 58 (58): 684–691. doi:10.1016/0009-9236(95)90025-X.
- Mark A. Klebanoff; Richard J. Levine; Rebecca DerSimonian.; John D. Clemens; Diana G. Wilkins (1999). "Maternal Serum Paraxanthine, a Caffeine Metabolite, and the Risk of Spontaneous Abortion". New England Journal of Medicine. 341 (22): 1639–1644. doi:10.1056/NEJM199911253412202. PMID 10572151.
- Media related to Paraxanthine at Wikimedia Commons