OMAHA, Neb.–The naturally occurring form of p-synephrine, derived from bitter orange (Citrus aurantium), exhibited at least twice the physiological activity as synthetic p-synephrine, according to a paper by Sidney J. Stohs, Ph.D., dean emeritus of the School of Pharmacy and Health Professions at Creighton University Health Sciences Center, Omaha, NE.
In “Stereochemical and Physiological Differences Between Naturally Occurring p-Synephrine and Synthetic p Synephrine," Stohs, FACN, CNS, ATS, FASAHP, found p-synephrine works primarily by stimulating beta-3 receptors, which increase thermogenesis and lipolysis, but do not affect blood pressure. Based on existing receptor binding studies, Stohs reported synthetic p-synephrine binds to only one-half of receptors compared to the natural version.
Further, Stohs said synthetic p-synephrine is a mixture of the l- and d- enantiomeric forms, and while the l-synephrine is the form found in nature (fruits), the d- form does not occur in fruits. The d- form can be produced in small amounts during the extraction and isolation processes the fruits undergo.
Stohs also noted that bitter orange extracts that are derived from the immature bitter orange fruit not only contain natural p-synephrine, but also flavonoids and other protoalkaloids. These compounds provide additional health benefits that are not present in synthetic p-synephrine. He called out the bitter orange extract, Advantra Z (from Nutratech Inc.), as having these extra nutrients.
Stohs has been the author of numerous studies on the safety of bitter orange extract and p-synephrine use.