Quality evaluation method of Lepidium meyenii using UPLC-UV-Q-TOF-MS

Abstract

In order to evaluate the quality of different varieties of Maca(Lepidium meyenii), the main chemical components in Maca were investigated and a method for simultaneous determination of the main chemical components in Maca was established. UPLC-UV-Q-TOF-MS technology and reference materials were used to identify the structures of 19 main components in Maca. Seven compounds with UV absorption and high contents were selected to establish a simultaneous concentration determination method. The method was employed with a Waters Acquity I-Class~(TM) liquid chromatographic system coupled with a PDA detector and a Waters Acquity Cortecs C_(18)~+ column(2.1 mm×100 mm, 1.6 μm), and acetonitrile-0.2% phosphoric acid water was used as mobile phase(0.45 mL·min~(-1)). The detection wavelength was 195 nm and the column temperature was maintained at 40 ℃. There was efficient separation of seven compounds, p-hydroxybenzylglucosinolate, benzylglucosinolate, N-benzyl-9Z,12Z,15Z-octadecatrienamid, N-benzyl-9Z,12Z-octadecadienamide, N-(3-methoxybenzyl)-hexadecanamide, N-benzyl-hexadecanamide, and N-benzyl-9Z-octadecenamide. The stan-dard calibration curves were good(R~2>0.999). The precision, stability and repeatability were also good. The linearity ranges were 0.197-4.980 μg·mL~(-1) to 193.67-796.8 μg·mL~(-1), and the average recovery rate was 96.71%-103.9%. The average concentration of glucosinolates and macamides in Maca were 1.20% and 0.20%, respectively. Among four kinds of Maca grown in China, the concentration of glucosinolates in yellow Maca and black Maca were relatively high(1.55%), followed by white Maca(0.93%), and purple Maca(0.76%). The concentration of macamides in yellow, purple and white Maca was similar(0.23%-0.29%), however black Maca had significantly lower concentration(0.15%). Peru Maca tested in this study had the lowest concentration of these compounds. This qua-lity evaluation method was fast, accurate, and comprehensively reflects the concentration of the main chemical components in Maca, which provides a useful reference for the quality control and evaluation of Maca.