Abstract:Polymethoxyflavones (PMFs) in citrus have been of increasing interest due to its extensive biological activities. Nobiletin (NOB),one of the main substances of PMFs,has been reported to exhibit anti-oxidant,anti-inflammatory,anti-cancer,and nerve protection resistance activities. Although the anti-inflammatory activity of PMFs has been already reported,its involvement in lung protection has rarely been reported. This article is aimed to investigate the protective effects of PMFs in Citrus reticulata‘Chachi’ on acute lung injury (ALI) induced by lipopolysaccharide in mice. PMFs were extracted from Citrus reticulata‘Chachi’ and purified. The structure of PMFs in citrus was identified. A mouse model of acute lung injury was established by intranasal instillation of lipopolysaccharide. The effects of PMFs on ALI were explored by measuring the degree of lung tissue damage,the wet/dry mass ratio of lung tissue,the activity of oxidative damage indicators,and the content of pro-inflammatory cytokines. The results showed that the main components of the extracted PMFs were the nobiletin and tangeretin (About 80% in the PMFs). PMFs with the contents of 250 mg/kg and NOB with the contents of 50 mg/kg significantly alleviated ALI. It is indicated that PMFs and NOB have good anti-oxidant and anti-inflammatory effects,and have a certain protective effect on ALI.