Abstract: The anti-inflammatory and antioxidant activities of luteolin, cynaroside, orientin and homoorientin were explored on THP-1 cells. The expression of cytokines in the cells pretreated with each of the four flavonoids were analyzed by fluorescence quantitative polymerase chain reaction (PCR) and Western Blot, and the expression of IκB kinase β (IKKβ), α inhibitor of κB (IκBα), NF-κB P65, nuclear factor erythroid 2 related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) enzyme were also analyzed. It was found that the expression of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) were extremely significantly inhibited by each of the four flavonoids (P < 0.01). Orientin also inhibited the expression of IL-1β (P < 0.01). These four flavonoids significantly inhibited the phosphorylation of IKKβ and IκBα in inflammatory cells, and the three luteolin glycosides also reduced the content of P65 in the nuclei, thereby exerting their anti-inflammatory effects through the NF-κB signaling pathway. Moreover, orientin extremely significantly promoted the expression and nuclear translocation of Nrf2 in inflammatory cells (P < 0.01), which resulted in a lower expression of HO-1 (P < 0.01) and a lower level of oxidative stress. In conclusion, luteolin and its three derivatives are effective against inflammation. In particular, orientin can down-regulate the expression of the NF-κB signaling pathway-related proteins IKKβ, IκBα and P65, thereby exerting its strong anti-inflammatory activity by significantly reducing the expression of TNF-α, IL-6 and IL-1β. Furthermore, by promoting Nrf2 expression and nuclear translocation, orientin can exert a good antioxidant effect, leading to a low level of HO-1 expression.

Key words: luteolin; orientin; anti-inflammatory; antioxidant