Anti-inflammatory 5,6,7,8-tetrahydro-2-(2-phenylethyl) chromone derivatives from the stems of Aquilaria sinensis.

Three previously undescribed 5,6,7,8-tetrahydro-2-(2-phenylethyl)chromones, (5S,6R,7S,8S)-8-chloro-5-ethoxy-6,7-dihydroxy-2-[2-(4'-methoxyphenyl)ethyl]-5,6,7,8-tetrahydrochromone (1), (5R,6S,7R,8R)-8-chloro-5-ethoxy-6,7-dihydroxy-2-(2- phenylethyl)-5,6,7,8-tetrahydrochromone (2), (5S,6R,7S,8R)-5,8-dichloro-6,7- dihydroxy-2-[2-(4'-methoxyphenyl)ethyl]-5,6,7,8-tetrahydrochromone (3), and 28 known analogues (4-31) were isolated from the stems of Aquilaria sinensis. Their structures were characterized by the spectroscopic methods, and the absolute configuration was resolved by circular dichroism (CD) spectroscopy. Bioactivity evaluation indicated that compounds 3-8 had significant inhibition effect in the production of NO in an inflammatory cell model with relatively lower IC50 values of 5.54, 11.44, 3.68, 7.15, 10.26 and 13.04 μM, respectively, compared to the positive control indomethacin (IC50 = 23.03 μM).