Discovery of markers for discriminating the age of cultivated ginseng by using UHPLC-QTOF/MS coupled with OPLS-DA

Abstract

Background: Ginseng (Ginseng Radix et Rhizoma, Panax ginseng C.A. Meyer) is gaining more publicity in modern society due to its health benefit and huge value in market. In the practice of grading and pricing of ginseng, the age is one of the major factor influencing the price and grade of ginseng. Therefore, the age discrimination is an important task for the quality control of ginseng. However, the traditional morphological methods are too subjective to be reproductive in discrimination.

Purpose: To establish a method that can discriminate the ginseng samples with different cultivation years.

Study design: To analyze the correlation between chemical compositions and cultivation years of cultivated ginseng samples of different age and thus discover potential quality marker (Q-marker) for discriminating the age of cultivated ginseng.

Methods: In the present study, the ultra-high performance liquid chromatography coupled with the quadrupole-time of flight mass spectrometry (UHPLC-QTOF/MS) were utilized for the age discrimination and marker discovery. A statistical data processing procedure was established to screen markers and reduce the false positive rate.

Results: The results showed that the ginseng samples from 2- to 6-year-old could be well separated in the orthogonal projections on the latent structure - discrimination analysis (OPLS-DA) using the markers screened by the established statistical procedure, which could reduce approximately 20% of the insignificant markers and false positive discoveries. Ultimately, more than 50 compounds contributing to the age discrimination were identified including one new compound (malonylginsenoside). One negative marker (1038.4825@8.98) was discovered for the 2-year-old ginseng, and an equation was established to effectively predict the age of 3- to 6-year-old of ginseng.

Conclusion: The constructed method can discriminate the ginseng samples with different cultivation years and is a complement to the traditional discrimination method of ginseng age.

Keywords: Age discrimination; LC-MS; OPLS-DA; Panax ginseng; Q-marker.