Flavonoids from Chionanthus retusus (Oleaceae) Flowers and Their Protective Effects against Glutamate-Induced Cell Toxicity in HT22 Cells.

The dried flowers of Chionanthus retusus were extracted with 80% MeOH, and the concentrate was divided into EtOAc, n-BuOH, and H2O fractions. Repeated SiO2, octadecyl SiO2 (ODS), and Sephadex LH-20 column chromatography of the EtOAc fraction led to the isolation of four flavonols (1-4), three flavones (5-7), four flavanonols (8-11), and one flavanone (12), which were identified based on extensive analysis of various spectroscopic data. Flavonoids 4-6 and 8-11 were isolated from the flowers of C. retusus for the first time in this study. Flavonoids 1, 2, 5, 6, 8, and 10-12 significantly inhibited NO production in RAW 264.7 cells stimulated by lipopolysaccharide (LPS) and glutamate-induced cell toxicity and effectively increased HO-1 protein expression in mouse hippocampal HT22 cells. Flavonoids with significant neuroprotective activity were also found to recover oxidative-stress-induced cell damage by increasing HO-1 protein expression. This article demonstrates that flavonoids from C. retusus flowers have significant potential as therapeutic materials in inflammation and neurodisease.