Flavonoid derivatives and lignan enantiomers from Phanera championii Benth. and their anti-neuroinflammatory activity

Nine undescribed compounds, including two sesquiterpenoid-substituted flavanols (1 and 2), a flavan glucoside (3), and three pairs of lignan enantiomers (4a/4b‒6a/6b), together with 22 known flavonoid derivatives (7a/7b and 8‒27) were isolated from an EtOH extract of the rattans of Phanera championii Benth. Compounds 1 and 2 are extremely rare, featuring a unique combination of flavan-3-ols linked with sesquiterpenoids. Chiral HPLC analysis with a Daicel Chiralpak AD-H column was applied to the separation of four pairs of lignan enantiomers. The absolute configurations of all the undescribed compounds were identified by alkaline hydrolysis, acid hydrolysis, experimental and calculated ECD methods. The results of anti-neuroinflammatory activity indicated that five compounds (16, 22, and 24‒26) exhibited potent inhibitory effects on nitric oxide release in BV-2 microglial cells induced by LPS, with IC₅₀ values ranging from 0.5 to 12.7 μM. Their preliminary structure-activity relationships were discussed.