High performance liquid chromatography analysis of canthinone alkaloids from Eurycoma longifolia.

A reversed phase-high performance liquid chromatography method with a photodiode array detector was developed for the simultaneous determination of three major alkaloids, 9-methoxycanthin-6-one (1), 3-methylcanthin-5,6-dione (2) and its 9-methoxy analogue (3) in Eurycoma longifolia Jack. These alkaloids were easily separated by a gradient elution protocol of 20 - 42 % acetonitrile in 0.1 % acetic acid. Compound 1 showed characteristic absorption at 350 nm only whereas its dione analogues, 2 and 3 displayed strong absorptions at both 350 and 451 nm. The linear calibration ranges were 0.7 - 50 microg x mL(-1) for 1, 1.5-50 microg x mL(-1) for 2 and 3.1 -100 microg x mL(-1) for 3. The recoveries of the three alkaloids were 90.8-101.0% with relative standard deviations from 0.35 to 6.31 % (n = 3). The limits of detection for all the alkaloids were within the range of 0.35 - 0.7 microg x mL(-1). This method was successfully applied to the phytochemical analysis of E. longifolia roots obtained from different sources.