HPLC‒DAD‒QTOF-MS/MS based comprehensive metabolomic profiling of phenolic compounds in Kalimeris indica anti-inflammatory fractions

Abstract Kalimeris indica is widely used in China as an important healthy leafy vegetable, as well as an important traditional herbal medicine for the treatment of anti-inflammatory related diseases. However, systematic information about the bioactive compounds in K. indica remains unclear. Total phenolic content (TPC) and anti-inflammatory effect of different K. indica fractions were evaluated. Ethyl acetate and n-butanol fractions showed higher TPC, and more active in inhibition of nitric oxide (NO) and tumor necrosis factor-alpha (TNF-α) production on lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. Then, HPLC‒DAD‒QTOF-MS/MS was developed to identify phenolic compounds in ethyl acetate and n-butanol fractions. By systematic analysis of retention times, ultraviolet (UV) spectra and diagnostic fragmentation pathways and rules, 46 phenolic compounds, including 5 cinnamic acids, 28 chlorogenic acids (CGAs) and 13 flavonoids, were rapidly unambiguously identified or tentatively deduced by comparison with standards or literature data. 40 of them were found in K. indica for the first time. Absolute quantification results of four major phenolic compounds were also achieved through a standard addition method with RSD less than 7.3% for intra- and inter-day variations. The abundant phenolic compounds might be responsible for the anti-inflammatory effect of K. indica, which laid a foundation for the study of quality control, daily and clinical applications of K. indica.