What is bitter orange?

Bitter orange, also known as Citrus aurantium, is a citrus fruit originally used in Traditional Chinese medicine for stomach ailments, such as constipation, diarrhea, and indigestion.^[1] Today, bitter orange extract, standardized to p-synephrine content, commonly occurs in multi-ingredient formulations labeled as ephedra-free supplements for weight loss: p-synephrine is an alkaloid compound structurally similar to adrenaline and the banned dietary supplement ephedrine.^[2] The pharmacologic and pharmacokinetic properties of p-synephrine vary from its structural analogues enough to mitigate the risks previously seen with ephedrine-containing supplements. ^[1]. p-synephrine should also not be confused with m-synephrine, a synthetic amine derivative of synephrine. m-synephrine does not meet the FDA dietary supplement definition and is a prohibited ingredient.