Rare benzonaphthoxanthenones from Chinese folk herbal medicine Polytrichum commune and their anti-neuroinflammatory activities in vitro

Two new (1-2) as well as five known (3-7) compounds were isolated from Polytrichum commune, a folk herbal medicine in China, and three of them (2, 4, 5) belong to benzonaphthoxanthenones that are rarely found in nature. Their structures were elucidated by the approach to 1D and 2D NMR spectra. The absolute configuration of 2 was assigned by comparing its experimental and calculated ECD data. 1-5 were investigated for their anti-neuroinflammatory activity against LPS-induced BV-2 cells. 1 and 3 exhibited well protective effect at a concentration of 2.5 mu mol/mL. Molecular docking studies were adopted to further investigate the possible mechanism, whose results suggested that 1 might exert anti-neuroinflammatory effect by inhibiting activity of p38 alpha, JNK2 and TAK1 to reduce the liberation of pro-inflammatory cytokines.