Phenolic profiling and quantitative determination of common sage (Salvia plebeia R. Br.) by UPLC-DAD-QTOF/MS

Salvia plebeia R. Br. is a medicinal herb that contains important active compounds such as flavonoid and phenolic acid which are responsible for remarkable biological properties. The phenolic composition of S. plebeia was quantitatively investigated using ultra-performance liquid chromatograph coupled with photodiode array detection and quadrupole time of flight mass spectrometry. A total of 16 flavonoids were classified into 10 flavones and 6 flavanones based on UV-spectra and ion fragmentation patterns. Individual flavonoids, including apigenin, luteolin, hispidulin, nepetin, and some flavanones, were glycosylated with glucose at the 5- or 7-position of flavonoid structure. The three major flavones were determined to be 6-hydroxyluteolin 7-O-glucoside [2,452.7 mg/100 g dry weight (DW)], hispidulin 7-O-glucoside (2,281.0 mg/100 g DW) and nepetin 7-O-glucoside (2,002.6 mg/100 g DW). The six flavanones containing the hydroxyl and methoxy groups were determined and, among them, 5,7,3',4'- tetrahydroxy-6-methoxyflavanone 7-O-glucoside have the highest level (938.3 mg/100 g DW). Two hydroxyl flavanone glycosides, 5,6,7,3',4'- pentahydroxyflavanone 7-O-glucoside and 5,6,7,4'- tetrahydroxyflavanone 7-O-glucoside, were presumed to be newly identified compounds, on the basis of the library data from S. plebeia. In addition, higher concentration of rosmarinic acid was also identified.