Anti-inflammatory 5,6,7,8-tetrahydro-2-(2-phenylethyl)chromones from agarwood of Aquilaria sinensis.

Four new 5,6,7,8-tetrahydro-2-(2-phenylethyl)chromones, aqulisinone A (1), (5S, 6R,7S,8S)-8-chloro-5,6,7-trihydroxy-2-[2-(4'-methoxyphenylethyl)]-5,6,7,8-tetrahydrochromone (2), (5S,6R,7S,8S)-8-chloro-5,6,7-trihydroxy-2-(2-phenylethyl)-5,6,7,8-tetrahydrochromone (3), (5S*,6R*,7R*,8S*)-8-chloro-5-ethoxy-6,7-dihydroxy-2-[2-(3'-hydroxy-4'-methoxy-phenylethyl)-5,6,7,8-tetrahydrochromone (4), and seven known analogues (5-11) were isolated from agarwood produced of Aquilaria sinensis. Among the new compounds, 4 is an artifact. The structures were elucidated using spectroscopic methods and by comparison with published NMR spectroscopic data. The absolute configurations of 1-3 were defined based on single-crystal X-ray diffraction and electronic circular dichroism (ECD) data. Compound 1 features a (5,5'')-carbon-carbon bond linkage connecting two 2-(2-phenylethyl)chromone monomeric units. All the new compounds were evaluated for their anti-inflammatory activities by inhibiting the lipopolysaccharide (LPS)-induced nitric oxide (NO) release in RAW264.7 cells, 2 with an IC₅₀ value of 3.46 μM.