Anti-inflammatory effect of Piper longum L. fruit methanolic extract on lipopolysaccharide-treated RAW 264.7 murine macrophages

Context: The Piper species was studied several potential properties such as anti-tumor, anti-inflammatory and antioxidant activity. However, the specific anti-inflammatory activity of the extract from the fruits of P. longum L. has not been investigated. Objectives: Our study want to examine the anti-inflammatory effects of P. longum L. fruit methanolic extracts (PLE) on lipopolysachharide (LPS)-stimulated RAW 264.7 murine macrophages to understand the mechanism of this effect. Method: This study examined the chemical profiling of PLE by LC-HRMS analysis and measured the presence of nitric oxide (NO), interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-alpha) in the supernatant using the Griess reagent assay and enzyme-linked immunosorbent assay (ELISA), respectively. The mRNA expression of IL-6, TNF-alpha, cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS) were evaluated by using real-time quantitative polymerase chain reaction (RT-qPCR). Furthermore, the protein expression of COX-2, iNOS and the phosphorylation of MAPK family, c-Jun N-terminal kinase (JNK), p38 in protein level were observed by western blotting. Result: PLE have detected 66 compounds which belong to different classes such as alkaloids, flavonoids, terpenoids, phenolics, lactones, and organic acids inhibited nitric oxide products with the IC50 = 28.5 +/- 0.91 mu g/mL. Moreover, PLE at 10-100 mu g/mL up-regulate HO-1 protein expression from 3 to 10 folds at 3 h. It also downregulated the mRNA and protein expression of iNOS, COX-2, decreased IL-6 and TNF-alpha secretion by modulating the mitogen-activated protein kinase (MAPK) signaling pathway, specifically by decreasing the phosphorylation of p38 and JNK. Conclusion: These results shown chemical profiling of PLE and demonstrated that PLE exhibits anti-inflammatory effects by regulating the MAPK family and could be a potential candidate for the treatment of inflammatory diseases.