Five new 5,11-epoxyguaiane sesquiterpenes in agarwood "Qi-Nan" from Aquilaria sinensis

Five new 5,11-epoxyguaiane sesquiterpenes (1-5), along with a known one (6) were isolated from high quality agarwood 'Qi-Nan' originating from Aquilaria sinensis. Their structures were established based on spectroscopic methods including IR, HR-ESI-MS, 1D, and 2D NMR. Compounds 1-6 were all 5,11-epoxyguaiane sesquiterpenes, sharing the same tetrahydrofuran ring by etherification of C-5 and C-11, and furthermore, functionalized at C-14 in the guaiane skeleton. All the six 5,11-epoxyguaianes (1-6) possess lasting fragrant smell at room temperature. This type of 5,11-epoxyguaiane sesquiterpenes were found to exist in agarwood 'Qi-Nan' only originating from A. sinensis rather than other species of the genus Aquilaria. These isolated guaiane sesquiterpenes showed acetyl cholinesterase inhibitory activities in different degrees ranged from 15% to 63% at the concentration of 50 mu g/mL. (C) 2016 Elsevier B.V. All rights reserved.