New Bis-sesquiterpenoids From the Lindera glauca With Anti-inflammatory Activity by Inhibiting the Lipopolysaccharide-induced Expression of Inducible Nitric Oxide Synthase.

Three new sesquiterpenoid dimers linderasesquiterpenoids A-C (1-3) and three known compounds 4-6 were co-isolated from the Lindera glauca. Their structures were elucidated based on spectroscopic methods and electronic circular dichroism calculations. Among them, linderasesquiterpenoid A (1) featuring the rare [4, 9] ring system was the first example of sesquiterpenoid dimers, and also the sesquiterpenoid dimers components were first found in this plant. Meanwhile, linderasesquiterpenoid A (1) exhibited stronger anti-inflammatory activity against lipopolysaccharide-induced nitric oxide (NO) production in RAW 264.7 cells with a 50% inhibitory concentration (IC₅₀) value of 11.0 µM than positive control (indomethacin, IC₅₀ 24.1 µM). Further studies demonstrated that linderasesquiterpenoids A (1) significantly suppressed the protein expression of the enzyme inducible NO synthase, but did not affect the enzyme cyclooxygenase-2.