HPLC-UV-QDa analysis of Citrus aurantium-labelled pre-workout supplements suggest only a minority contain the plant extract

Bitter orange (Citrus aurantium) is a common ingredient in pre-workout supplements with purported weight-loss and performance-enhancing effects. Supplements listing Citrus aurantium or p-synephrine have been associated with reports of adverse cardiovascular events attributed to the active biogenic amines, p-synephrine, p-octopamine or p-tyramine. Additionally, questions have been raised as to the authenticity of the plant-derived active components listed on the supplement labels. The aim of this study was to determine the quantities of these amines in a sample of pre-workout supplements which specifically listed Citrus aurantium, and assess the authenticity of plant material by comparing the ratios of amines found to that found in Citrus aurantium standardized reference materials (SRM). The quantities of amines in the supplements and SRMs were determined using a validated high-performance liquid chromatography-single quadrupole mass spectrometry (HPLC-UV-QDa) method. In the Citrus aurantium SRMs the quantities of trace amines found ranged from 5.30 to 38.00 mg/g (synephrine) 0.14−0.35 mg/g (octopamine) and 0.15–1.90 mg/g (tyramine) with an average ratio of 100:1:5 (synephrine: octopamine: tyramine). Only 42 % (5/12) of the supplements tested had ratios consistent with that found in the SRMs. The average trace amine ratio in those supplements was 100:1:3 while the quantities of trace amines found ranged from 0.35 to 31.31 mg/g (synephrine); 0.005 – 0.10 mg/g (octopamine) and 0.01–1.51 mg/g (tyramine). For the remaining supplements, some did not contain any detectable levels of trace amines or only synephrine was detected with concentrations ranging from 0.003 – 0.95 mg/g. These results suggest a role for authenticity/quality assurance testing of pre-workout supplements and more stringent regulation of pre-workout supplements.