[Assay of Tetramethylpyrazine in Szechwan Lovage Rhizome and Cnidium Rhizome by HPLC-DAD-MS].

Objective: To quantity the amount of tetramethylpyrazine in Szechwan Lovage Rhizome (Chuanxiong, the rhizome of Ligusticum chuanxiong Hort., CX) and Cnidium Rhizome(Japanese Chuanxiong, the rhizome of Cnidium officinale Makino, JCX) for quality assessment.

Methods: An HPLC-DAD-MS technique was employed to detect tetramethylpyrazine in 27 CX and 10 JCX samples. Tetramethylpyrazine was separated on a Waters Symmetry C,, column (250 mm x 4. 6 mm, 5 µm). The mobile phase was methanol-acetonitrile-water(27: 1: 72) at a flow rate of 1. 0 mL/min. The column temperature was 35 °C. DAD detection wavelength was 280 nm, while electrospray ionization detector was set at positive mode to collect MS spectrum.

Results: In the total of 37 herb samples, 11 samples were found to contain tetramethylpyrazine with the mean amount of 2. 19 µg/g(n = 11). 6 of 27 CX samples and 5 of 10 JCX sample were found the existence of tetramethylpyrazine with the amount of 0. 60 - 11. 75 µg and 0. 61 - 3. 05 µg/g,respectively. The correlation was not found between tetramethylpyrazine and the cultivation area, morphological character, processing or storage method for CX and JCX samples. It was possible that tetramethylpyrazine resulted from the microbes in soil.

Conclusion: The developed method is accurate to quantify tetramethylpyrazine in CX and JCX herbs. Both the two herbs indeed contain tetramethylpyrazine, but it is not suitable to be a chemical marker to assess the quality of CX and JCX owing to low content.