Bioassay-guided fractionation of ethyl acetate extract from Armillaria mellea attenuates inflammatory response in lipopolysaccharide (LPS) stimulated BV-2 microglia

Background: Armillaria mellea (A. mellea) is a traditional Chinese medicinal and edible mushroom, which is proved to possess a lot of biological activities, including anti-oxidation, immunopotentiation, anti-vertigo and anti-aging activities. However, little information is available in regard to its neuroprotection activity in inflammation-mediated neurodegenerative diseases. Purpose: We have found that A. mellea has an anti-inflammatory activity in LPS-induced RAW264.7 cells in our previous study. The objective of this study is to investigate the anti-neuroinflammatory mechanism of a bioassay-guided fractionation (Fr.2) and its active components/compounds. Methods: Compounds were isolated by preparative high performance liquid chromatography (pre-HPLC) and their structures were established by mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopic analyses. The anti-neuroinflammatory effect of Fr.2 and each compounds were investigated in lipopolysaccharide (LPS)-stimulated murine microglia cell line BV-2. Results: We demonstrated that Fr.2 significantly decreased the production of inflammation mediator nitric oxide (NO) and inflammatory cytokines tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6) and interleukin-1beta (IL-1 beta) in a dose-dependent manner (10, 30, 100 mu g/ml). In addition, Fr.2 markedly down-regulated the phosphorylation levels of nuclear factor kappa B p65 (NF-kappa B p65), inhibitory kappa B-alpha( I kappa B-alpha) and c-Jun N-terminal kinases (JNKs) pathways. Sevens compounds were isolated from Fr.2, among them, three compounds, 5-hydroxymethylfurfural (CP1), vanillic acid (CP4) and syringate (CP5) were reported for the first time in A. mellea. NO and inflammatory cytokines (TNF-alpha, IL-6, IL-1 beta) secretion indicated that daidzein (CP6) and genistein (CP7) showed a more outstanding anti-inflammation potential at non-toxic concentrations (10, 30, 100 mu M) than the other five compounds. Conclusions: In conclusion, Fr.2 may have therapeutic potential for neurodegenerative diseases by inhibiting inflammatory mediators and suppress inflammation pathway in activated microglia. Daidzein and genistein may serve as the effective anti-inflammation compounds of Fr.2. (C) 2017 Elsevier GmbH. All rights reserved.