Development and application of a UPLC method for studying influence of phenological stage on chemical composition of...

The influence of phenological stages on chemical composition of Scutellariae Radix (SR), the root of Scutellaria baicalensis Georgi, was investigated. In order to deal with a large quantity of samples, a rapid ultra-performance liquid chromatographic (UPLC) was first developed and validated for the simultaneous quantification of five flavonoids, namely baicalin (baicalein-7-O-β-D-glucuronide, BG), wogonoside (wogonin-7-O-β-D-glucuronide, WG), baicalein (BA), wogonin (WO), oroxylin A (OA) in the samples. Good linearity was obtained in the range of 0.742-389 ng (r ²  > 0.9999) and satisfactory recoveries were obtained (101.72-104.56 %) with the RSD value below 5.0 %, for all analytes. Also, extraction conditions were optimized to obtain maximum extractive contents of the five flavonoids. Content variations of the five active ingredients in 225 samples from three different origins were investigated in five major phenological periods. It was found that the effect of phenology on the contents of the tested five flavonoids was similar in the three origins. The contents of flavone O-glycosides, i.e., BG and WG accumulated to the highest level in leaf expansion period, while flavonoid aglycones, i.e., BA, WO and OA appeared a maximum concentration in flowering period. The UPLC method established in this study was rapid and of good accuracy, repeatability and resolution, and hence can assist in the quality control of SR.