Development of a Quantitative NMR Method for Direct and Simultaneous Determination of Four Flavonoids in Scutellaria baicalensis georgi Extracts

Introduction: Scutellaria Baicalensis Georgi (SBG), a Traditional Chinese Medicine (TCM) used for the treatment of antiviral therapy, contains many flavonoids. Materials and Methods: A simple, fast and accurate ¹H quantitative nuclear magnetic resonance (¹HqNMR) method was established for simultaneously determination of four flavonoids (Baicalin, Baicalein, Wogonin and Wogonoside) in SBG extract by using 3,4,5-trichloropyridine as an internal standard (IS). All the NMR determination work was performed at 308 K on an NMR sample tube inserted with a co-axial tube. The NMR sample tube was added with the sample (SBG extract and IS), the co-axial insert tube was added with D2O. Quantification of four flavonoids was carried out by calculating the relative peak area ratio of the selected proton signals from the target compounds and the IS. Results: The validated ¹H-qNMR method was successfully used to determine the four flavonoids in 9 batches of SBG from different origins and the results were in good accordance with those obtained from HPLC. Conclusion: The established ¹H-qNMR method could be used as a powerful tool for the quality control of SBG from different sources and had potential in the quantification of main components from other TCMs.