Anti-inflammatory effects of lycium barbarum leaf extracts in lipopolysaccharide-induced RAW 264.7 macrophage cells and isolation of secondary metabolites

Abstract

Lycium barbarum possesses many bioactivities such as antidiabetic, antioxidant, antitumor, and immunomodulatory activities. In the present study, the MeOH extract (1 mg/mL) prepared from the leaves of L. barbarum cultivated in Turkey exerted significant anti-inflammatory activity via reducing the release of nitric oxide (NO) in LPS-stimulated RAW 264.7 macrophages comparable to positive control indomethacin. Then, the extract was partitioned against CH2Cl2 and EtOAc to yield CH2Cl2, EtOAc and H2O subextracts which were also submitted to the same tests. Among the tested extracts, EtOAc (0.25 and 0.5 mg/mL), and CH2Cl2 (0.25 mg/mL) subextracts showed significant NO production inhibitory activities. The tested extracts also inhibited the production of PGE2 slightly. Successive chromatographic studies on the EtOAc subextract led to the isolation of three secondary metabolites, including chlorogenic acid, hesperidin and rutin as the potential bioactive compounds that are responsible for the in vitro anti-inflammatory activity of the EtOAc subextract. The structures were elucidated based on 1D and 2D NMR spectra. Although chlorogenic acid and rutin were previously reported from leaves of L. barbarum, this is the first report of hesperidin from L. barbarum to the best of our knowledge.