Quantitative analysis of all types of β-carboline alkaloids in medicinal plants and dried edible plants by high performance liquid chromatography with selective fluorometric detection

A high performance liquid chromatographic method was developed to determine all types of β-carboline alkaloids in medicinal and edible plants. The alkaloids, including internal standards, were purified from plant homogenates by serial extractions after reacting with fluorescamine. The extracts were analysed twice using reversed-phase chromatography with fluorometric detection optimized for each individual analyte. β-Carbolines and tetrahydro-β-carbolines were analysed in the first run, while dihydro-β-carbolines were analysed in the second. The simultaneous separation of harmol, norharman, harman, harmine, harmalol, harmaline, tetrahydronorharman, tetrahydroharman and two internal standards was achieved within 17 min by an isocratic elution. β-Carbolines, dihydro-β-carbolines and tetrahydro-β-carbolines could be quantitatively determined in concentrations of 0.01–50.0 ng/mL. In replicate spiking experiments, the mean recovery was 71–110% and the relative standard deviation was 0.3–10.1% within and between assays. Application of the proposed method has revealed that medicinal plants and dried edible plants contain β-carboline alkaloids at ng/g to µg/g levels. Norharman and harman were distributed in all the tested plants, while harmol and harmalol were found only in some plant species. However, no significant amounts of tetrahydro-β-carbolines were detected in any plant materials tested, suggesting that the oxidation of tetrahydro-β-carbolines to β-carbolines occurs during the drying and/or the storing process. The β-carboline alkaloids may be responsible for the pharmacological effects of certain medicinal plants. Copyright © 1999 John Wiley & Sons, Ltd.