High‐performance liquid chromatographic analysis of tetrahydro‐β‐carbolines in food plants

A high‐performance liquid Chromatographic method is reported for the unambiguous determination of the amount of tetrahydro‐β‐carbolines in food plants. In the method, plant homogenates, together with an internal standard, were first reacted with fluorescamine, serially extracted, and then subjected to reversed‐phase ion‐pair chromatography with fluorometric detection. The pre‐treatment inhibited the artefactual formation of tetrahydro‐β‐carbolines during analysis by removing the precursor tryptamine from the analytical system. Only the original 1,2,3,4‐tetrahydro‐β‐carboline and 1‐methyl‐1,2,3,4‐tetrahydro‐β‐carboline in food plants could be quantitatively determined in the concentrations of 0.1—50.0 ng/mL of homogenate. The recovery was almost 100% from all the tested plants, and the relative standard deviation was less than 8.4% within and between assays. Application of the proposed method has revealed that tomato, banana, pineapple, kiwi, plum and prune contain both tetrahydro‐β‐carbolines at ng to μg/g levels, and that their contents depend on the ripening process.