Quantitative analysis was optimized and validated by ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) for determination of four major flavonoids, namely alpinetin, pinocembrin, cardamonin and pinostrobin, and two major flavonoid precursors, namely phenylalanine and cinnamic acid, in two parts of fingerroot: rhizome and rootlet. The following UHPLC-MS/MS conditions were performed: gradient elution mobile phase of 0.1% v/v formic acid in water:0.1% v/v formic acid in acetonitrile, flow rate of 0.2 mL/min and Zorbax SB-C18 column (2.1 x 50 mm, 1.8 μm) and injection volume of 2 μL. The results showed the limit of detection and limit of quantitation in the ranges of 0.0047-0.042 and 0.014-0.13 mg/L, respectively. Using blank fingerroot samples spiked with flavonoids and their precursors at known concentrations in the ranges of 0.05 – 25 ppm into 1.0 mL of the extract solution obtained from the extraction of 1 gram of fingerroot with 10 mL of 50:50 v/v methanol-water, 52% of the experimental recovery data and 85% of the relative standard deviation data were obtained to be within the acceptable values. For sample analysis of rhizome and rootlet of fingerroot from four cultivated areas, rhizome was found to contain 1.3-6.0 folds higher amounts of flavonoids than rootlet. The amounts of major flavonoids in fingerroot were found in the order pinostrobin > pinocembrin > alpinetin > cardamonin, except for pinocembrin > alpinetin > pinostrobin > cardamonin for the sample from Phetchabun province. In addition, the amounts of flavonoid precursors were found, phenylalanine > cinnamic acid with the total amounts of the flavonoids approximately 30-200 folds the total amounts of their precursors.
