5,6,7,8-Tetrahydro-2-(2-phenylethyl)chromones from artificial agarwood of Aquilaria sinensis and their inhibitory activity against acetylcholinesterase.

Thirteen previously undescribed 5,6,7,8-tetrahydro-2-(2-phenylethyl)chromones named tetrahydrochromone A-M, together with nine known ones, were isolated from artificial agarwood (induced by holing) originating from Aquilaria sinensis (Lour.) Gilg. The structures of these compounds were unambiguously determined based on extensive NMR spectroscopic analyses, and the absolute configuration was resolved by CD analyses, X-ray crystallographic, chemical and Mosher's method. Tetrahydrochromone A, B, K-M, and Oxidoagarochromone An exhibited inhibitory activity against AChE with the percentage inhibition range from 17.5% to 47.9% (with Tacrine as the positive control; inhibition ratio: 66.7%) when tested at 50 μg/mL. Tetrahydrochromone A-E, F-J feature one methoxy and three hydroxys linked at the cyclohexene ring rather than usual four hydroxys, and tetrahydrochromone K-M represent the first examples of 7,8-epoxy tetrahydrochromones.