Isopropylnorsynephrine is a stronger lipolytic agent in human adipocytes than synephrine and other amines present in Cit
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ORIGINAL PAPER
Isopropylnorsynephrine is a stronger lipolytic agent in human adipocytes than synephrine and other amines present in Citrus aurantium Josep Mercader & Estelle Wanecq & Jian Chen & Christian Carpéné
Received: 10 December 2010 / Accepted: 27 January 2011 / Published online: 19 February 2011 # University of Navarra 2011
Abstract The weight loss observed in consumers of extracts of Citrus aurantium (bitter orange) has been tentatively attributed to the lipolytic and thermogenic effects of the alkaloids abundant in the unripe fruit. Synephrine, octopamine, tyramine, and other alkaloids have been repeatedly identified and quantified in Citrus members of the Rutaceae family or in their extracts incorporated in dietary supplements for weight management. However, there are only scarce reports on their lipolytic action. This study aimed at comparing the acute lipolytic activity of synephrine, octopamine, tyramine, and N-methyltyramine in rat and human adipocytes. Maximal response to the prototypical βadrenergic agonist isoprenaline was taken as reference in both species. In rat, octopamine was slightly more J. Mercader : E. Wanecq : C. Carpéné Institut National de la Santé et de la Recherche Médicale (INSERM), U1048 Toulouse, France J. Mercader : E. Wanecq : C. Carpéné Université de Toulouse, UPS, Institut de Médecine Moléculaire de Rangueil, IFR BMT Toulouse, France J. Chen Syntech (SSPF) International Inc, Montclair, CA 91763, USA C. Carpéné (*) INSERM U1048, I2MC, CHU Rangueil, 31432 Toulouse, France e-mail: [email protected]
active than synephrine while tyramine and N-methyl tyramine did not stimulate—and even inhibited— lipolysis. In human adipocytes, none of these amines stimulated lipolysis when tested up to 10 μg/ml. At higher doses (≥100 μg/ml), tyramine and N-methyl tyramine induced only 20% of the maximal lipolysis and exhibited antilipolytic properties. Synephrine and octopamine were partially stimulatory at high doses. Since synephrine is more abundant than octopamine in C. aurantium, it should be the main responsible for the putative lipolytic action of the extracts claimed to mitigate obesity. Noteworthy, their common isopropyl derivative, isopropylnorsynephrine (also named isopropyloctopamine or betaphrine), was clearly lipolytic: active at 1 μg/ml and reproducing more than 60% of isoprenaline maximal effect in human adipocytes. This compound, not detected in C. aurantium, and which has few reported adverse effects to date, might be useful for in vivo triglyceride breakdown. Keywords Obesity . Isoprenaline . Tyramine . Octopamine . Rat adipocytes . Dietary supplements
Introduction Citrus aurantium is a plant belonging to the Rutaceae family, the fruit of which (bitter orange) has been used for the preparation of extracts sold worldwide under the form of phytoproducts claimed to promote weight loss. The leaves, the peel, and the edible part
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of the fruits of C. aurantium contain elevated amounts of phenethylamine alkaloids (i.e. synephrine, octopamine, tyra
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