Comparisons of the anti‐inflammatory activity of dendropanax morbifera lev leaf extract contents based on the collection season and concentration of ethanol as an extraction solvent

This study aimed to compare the anti‐inflammatory activity of 10‐year‐old Dendropanax morbifera LEV (DM) leaf extracts. The leaves were collected during different seasons (May, August, and November), and the extracts were prepared using different methods (hot water, 30% ethanol, or 60% ethanol). Lipopolysaccharide‐stimulated RAW264.7 cells were treated with these extracts for 12 h. The anti‐inflammatory effects were evaluated by measuring the production of nitrite; prostaglandin E2 (PGE2); and inflammatory cytokines such as interleukin (IL)‐6, IL‐1β, and tumor necrosis factor‐alpha, in addition to the mRNA expression levels of inducible nitric oxide synthase (iNOS) and cyclooxygenase‐2 and activation of the nuclear factor κB (NF‐κB)/mitogen‐activated protein kinase (MAPK) pathways. The amyrin and polyphenol compositions of the extracts were analyzed using a triple time‐of‐flight mass spectrometer and high‐performance liquid chromatography. The 30% ethanol extract harvested in May and 60% ethanol extracts collected in August and November displayed the highest inhibitions of nitrite, PGE2, and inflammatory cytokines. The 60% ethanol extract harvested in August suppressed activation of the NF‐κB and MAPK signaling pathways. The contents of amyrin and polyphenol compounds were highly dependent on the ethanol concentration used during each season. These results suggest that ethanol extracts of DM leaves may have the potential to regulate inflammatory responses.