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Ethanol extract of <i>Bletilla striata</i> has remarkable anti-inflammatory and anti-pulmonary fibrosis activities in the rat silicosis model. However, its active substances and molecular mechanism are still unclear. To uncover the active ingredients and potential molecular mechanism of the <i>Bletilla striata</i> extract, the lipopolysaccharide (LPS)-induced macrophage inflammation model and phospho antibody array were used. Coelonin, a dihydrophenanthrene compound was isolated and identified. It significantly inhibited LPS-induced interleukin-1&#946; (IL-1&#946;), interleukin-6 (IL-6) and tumor necrosis factor-&#945; (TNF-&#945;) expression at 2.5 &#956;g/mL. The microarray data indicate that the phosphorylation levels of 32 proteins in the coelonin pre-treated group were significantly down-regulated. In particular, the phosphorylation levels of the key inflammatory regulators factor nuclear factor-kappa B (NF-&#954;B) were significantly reduced, and the negative regulator phosphatase and tensin homologue on chromosome ten (PTEN) was reduced. Moreover, the phosphorylation level of cyclin dependent kinase inhibitor 1B (p27^Kip1), another downstream molecule regulated by PTEN was also reduced significantly. Western blot and confocal microscopy results confirmed that coelonin inhibited LPS-induced PTEN phosphorylation in a dose-dependent manner, then inhibited NF-&#954;B activation and p27^Kip1 degradation by regulating the phosphatidylinositol-3-kinases/ v-akt murine thymoma viral oncogene homolog (PI3K/AKT) pathway negatively. However, PTEN inhibitor co-treatment analysis indicated that the inhibition of IL-1&#946;, IL-6 and TNF-&#945; expression by coelonin was independent of PTEN, whereas the inhibition of p27^Kip1 degradation resulted in cell-cycle arrest in the G1 phase, which was dependent on PTEN. The anti-inflammatory activity of coelonin in vivo, which is one of the main active ingredients of <i>Bletilla striata</i>, deserves further study.