Identification of flavonoids in the stems and leaves of Scutellaria baicalensis Georgi

Scutellaria baicalensis Georgi (S. baicalensis), a perennial herb of the Labiatae family, is a well-known traditional Chinese medicine. In the present study, a comprehensive qualitative analysis of flavonoids in the stems and leaves of S. baicalensis was performed. Under the optimized experimental conditions, 21 flavonoids were clearly detected. 17 of them were successfully identified based on the on-line UV and MS(n) data and were sequentially confirmed by the literature search. The rest 4 flavonones, which were not on-line identified, were successfully isolated and were identified by 1D and 2D NMR. One of them, 5,6,7,3',4'-pentahydroxy flavanone-7-O-glucuronide (2) is a new compound.