Chiral Gas Chromatographic Determination of Ephedrine-Type Alkaloids in Dietary Supplements Containing Má Huáng

Abstract

Má Huáng is a traditional Chinese medicine derived from the aerial parts of several Ephedra species (Ephedraceae). These plants produce (-)-ephedrine, (+)-pseudoephedrine, (-)-norephedrine, (+)-norpseudoephedrine, (-)-N-methylephedrine, and (+)-N-methylpseudoephedrine. Racemic and (-)-epnedrine, (+)-pseudoephedrine, and (±)-norephedrine (phenylpropanolamine) are used clinically in the United States and are largely synthetic in origin. Current interest in Má Huáng is spurred by reports describing a "thermogenic" (calorie burning) effect provided by mixtures of ephedrine, caffeine, and aspirin. Products providing the key thermogenic compounds from natural sources are available as dietary supplements in retail outlets. Reports of potentially unsafe levels of the alkaloids, as well as possible fortification of Má Huáng-containing products with synthetic Ephedra alkaloids, prompted the development of a chiral gas chromatographic (GC) method that allows determination of alkaloid patterns and identification of isomerically impure synthetic alkaloids. Nine products were analyzed on a γ-cyclodextrin capillary GC column. Identity of the alkaloids was verified by GC/mass spectrometry (MS) and GC/matrix isolation/Fourier transform infrared spectroscopy. No synthetic isomers were found in the dietary supplements analyzed. Three products contained only one of the ephedrine-type alkaloids. One product that listed Má Huáng as an ingredient contained no detectable ephedrine-type alkaloid. In products containing measurable quantities of these compounds, total alkaloid levels ranged from 0.3 to 56 mg/g.