A new compound, (+)-4′- O -acetylsyringaresinol ( 1 ), was isolated from the flowers of Koelreuteria henryi and structurally characterized, together with 14 known compounds. Among the bioactive components, quercetin ( 4 ) showed the highest superoxide anion (O 2 •– ) inhibition (IC 50 = 1.20 ± 0.15 μg/mL). Kaempferol ( 5 ) and luteolin ( 6 ) were most effective against elastase release (IC 50 = 1.32 ± 0.14 and 1.35 ± 0.17 μg/mL, respectively), which were stronger than the positive control phenylmethylsulfonyl fluoride (IC 50 = 34.2 ± 5.1 μg/mL). The NO (nitric oxide) inhibition results showed that luteolin (IC 50 = 0.99 ± 0.09 μg/mL) and quercetin (IC 50 = 2.29 ± 0.21 μg/mL) possessed more potent anti-inflammatory activities than curcumin (IC 50 = 4.53 ± 0.38 μg/mL). Western blot results also indicated that luteolin, quercetin, and kaempferol exhibited a significant inhibitory effect on iNOS expression. Molecular docking simulations further confirmed their interactions with the active site of iNOS (inducible nitric oxide synthase (iNOS), revealing favorable binding energies (−9.0 to −7.7 kcal/mol). These findings highlight the potential of bioactive compounds from K. henryi as anti-inflammatory agents, supporting their traditional medicinal use and suggesting avenues for future therapeutic development. • One new lignan, (+)-4′- O -acetylsyringaresinol ( 1 ), was isolated from flowers of Koelreuteria henryi . • Compounds 4 , 5 , and 6 effectively inhibited superoxide anion generation and elastase release in human neutrophils. • Compounds 4 , 5 , and 6 exhibited inhibitory effects on NO production and iNOS expression. • Molecular docking confirmed the favorable binding affinity to iNOS.
Lu et al. (Sun,) studied this question.