p-Synephrine

p-Synephrine is a naturally occurring alkaloid found primarily in the bitter orange (Citrus aurantium) plant. It is widely used as an ingredient in dietary supplements marketed for weight loss and sports performance due to its potential to increase fat oxidation and energy expenditure. The compound exists mainly as the l- or R-(−)-enantiomer in nature, while synthetic forms may be racemic mixtures with reduced pharmacological activity compared to the natural form[1][2]. Mechanistically, p-synephrine acts as an agonist at several receptors: - It is a selective agonist of Neuromedin U2 receptor (NMU2R), which plays roles in regulating food intake, energy balance, stress response, and nociception. - It also activates β-3 adrenergic receptors—contributing to lipolytic effects—and has some activity at α1-adrenoreceptors and serotonergic (5-HT1D/5-HT2A) receptors[1][5]. Additionally, it exhibits anti-inflammatory properties by inhibiting eotaxin-1 expression via STAT6 modulation and shows antioxidant effects in animal models[6]. p-Synephrine is not approved as a pharmaceutical drug for any specific indication but is commonly included in over-the-counter dietary supplements.

Brand names

SimpatholSympatolSynephrin

Other names

synephrinepara-synephrinel-synephrineR-(−)-synephrine