Spirodela polyrhiza (L.) Sch. ethanolic extract inhibits LPS-induced inflammation in RAW264.7 cells

Spirodela polyrhiza (L.) Sch. is widely used in Korean traditional medicine. No previous work has investigated in detail the anti-inflammatory activities of S. polyrhiza or assessed in vitro their potential underlying mechanism(s). We assessed the effects of S. polyrhiza ethanolic extract (SPEE) on the production of inflammatory mediators in lipopolysaccharide (LPS)-stimulated RAW264.7 cells and investigated some potential underlying mechanisms. Additionally, we performed simultaneous determination of seven flavonoids in S. polyrhiza by high-performance liquid chromatography (HPLC)-photodiode array (PDA).

RAW264.7 cells were subjected to 5, 10, 20, and 50 μg/mL of SPEE for 1 h then treated with LPS for 24 h. Production of namely nitric oxide (NO), prostaglandin E(2) and cytokine levels were measured by the Griess reagent and ELISA, respectively. To investigate the underlying mechanisms of the anti-inflammatory activities of SPEE, expression of NO synthase (iNOS), cyclooxygenase-2 (COX-2), and nuclear factor-kappa B (NF-κB) proteins were evaluated by western blot analysis. HPLC analysis was performed using a Gemini C(18) column at 40°C and PDA detection at 340 nm.

SPEE treatment significantly inhibited the LPS-induced production of NO, prostaglandin E(2), interleukin-6, and tumor necrosis factor-α and inhibited the expression of iNOS and COX-2 via attenuation of NF-κB p65 expression. The contents of the seven flavonoids in S. polyrhiza range from 0.25 to 8.77 mg/g.

These results indicate that the anti-inflammatory activity of SPEE may be NF-κB p65 signaling. Also, the method will help to improve quality control of S. polyrhiza.