RP-HPLC methods with fluorescence detection for the analysis of phenethylamine alkaloids in dietary supplements and phytoextracts

Fruits of Citrus aurantium L. var. amara (Rutaceae; vernacular name: bitter orange) also contain adrenergic amines such as octopamine, synephrine, tyramine. They too function as α- and β-agonists, but do not increase the diastolic blood pressure1. After the recent ban of Ephedra sinica Stapf. (Ephedraceae; vernacular name: Ma Huang) in the US many products for weigh loss and bodybuilding now contain Citrus aurantium extracts instead. Although no direct adverse events have been associated with their ingestion thus far, they also should be used with caution because of suspected cardiovascular side effects and possible interferences with CYP P450 enzymes2. Thus, it can cause an alarming increase in the blood levels of many drugs. The seriousness of these effects shown the necessity of reliable analytical methods applicable to quality control of commercial dietary supplements. In the present study the simultaneous analysis of phenethylamine alkaloids was carried out by two developed RP-HPLC methods with fluorescence detection. Tyrosine, octopamine, synephrine, tyramine, N-methyltyramine and hordenine were analysed directly at λem= 310 nm with λex= 280 nm and octopamine, tyrosine and tyramine were determined also at λem= 455 nm with λex= 340 nm after pre-column derivatization with o-phthaldialdehyde (OPA) reagent (I). The derivatization reaction was carried out at ambient temperature, pH 9.5 for 1 min, in presence of 2-mercaptoethanol.