Anti-inflammatory effects and related mechanisms in vitro and in vivo of Hedychium coccineum rhizome essential oil

Hedychium coccineum rhizome is an anti-inflammatory ethnomedicine used to remedy inflammation-related swelling and bronchial asthma. The study aimed to analyze the phytochemical constituents of H. coccineum rhizome essential oil (EO) and evaluate its in vitro and in vivo anti-inflammatory effects and underlying mechanisms. Phytochemical constituents of H. coccineum rhizome EO were analyzed using GC-FID/MS. In RAW264.7 macrophages induced by LPS, blockade of PGE 2, NO, IL-1 β, IL-6, and TNF- α secretion by H. coccineum rhizome EO was measured, and then Western blot, qRT-PCR, and immunofluorescent staining were used to evaluate its underlying mechanisms. Moreover, we used the xylene-induced ear edema model for testing anti-inflammatory potential in vivo and examined auricular swelling as well as tissue and serum contents of IL-1 β, IL-6, and TNF- α. EO ' s main components were E -nerolidol (40.5%), borneol acetate (24.8%), spathulenol (4.5%), linalool (3.8%), elemol (3.5%), and borneol (3.4%). In RAW264.7 cells stimulated by LPS, EO downregulated the expression of pro-inflammatory enzyme (iNOS and COX-2) genes and proteins, thereby suppressing pro-inflammatory mediators (NO and PGE 2 ) secretion. Simultaneously, it reduced TNF- α, IL-1 β, and IL-6 release by downregulating their mRNA expression. Besides, H. coccineum EO attenuated LPS-stimulated activation of NF- κ B (by reducing I κ B α phosphorylation and degradation to inhibit NF- κ B nuclear translocation) and MAPK (by downregulating JNK, p38, and ERK phosphorylation). In xylene-induced mouse ear edema, EO relieved auricular swelling and lowered serum and tissue levels of TNF- α, IL-1 β, and IL-6. H. coccineum EO had powerful in vivo and in vitro anti-inflammatory effects by inhibiting MAPK and NF- κ B activation. Hence, H. coccineum EO should have great potential for application in the pharmaceutical field as a novel anti-inflammatory agent.