Quantification of major compounds from Ixeris dentata, Ixeris dentata Var. albiflora, and Ixeris sonchifolia and their comparative anti-inflammatory activity in Lipopolysaccharide-Stimulated RAW 264.7 Cells

The aim of the present study was to evaluate the comparative anti-inflammatory activities of Ixeris dentata (ID), Ixeris dentata var. albiflora (IDA), and Ixeris sonchifolia (IS) and to identify the main compounds present in extracts. The anti-inflammatory activity was evaluated through lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW 264.7 murine macrophages. Five main compounds consisting of chlorogenic acid, caffeic acid, luteolin 7-O-glucoside, luteolin 7-O-glucuronide, and luteolin were used for simultaneous high-performance liquid chromatography quantification. The total phenolic content present in ID (30mg/g GAE), IDA (35.33mg/g GAE), and IS (43.79mg/g GAE) was correlated to the corresponding LPS-induced NO production inhibitory effect in RAW 264.7 cells as expressed with IC50 values 26.19, 21.43, and 7.59 μg/mL, respectively. Luteolin 7-O-glucoside was found as the major compound in ID (8.76mg/g dry weight) and IDA (10.35mg/g dry weight) and luteolin 7-O-glucuronide was the major compound in IS (34.66mg/g dry weight). Luteolin 7-O-glucoside and luteolin 7-O-glucuronide inhibited LPS-induced NO production with IC50 values of 30 and 4.5 μM, respectively. Furthermore, luteolin, luteolin 7-O-glucoside, and luteolin 7-O-glucuronide suppressed the expression of iNOS and COX-2, and t-BHP-induced ROS generation in LPS-stimulated RAW 264.7 cells. These results clearly showed that the anti-inflammatory potential of ID, IDA, and IS extract are primarily due to their contents of luteolin 7-O-glucoside and luteolin 7-O-glucuronide, respectively.