Monoterpenoids from the root bark of Acanthopanax gracilistylus and their inhibitory effects on neutrophil elastase, 5-lipoxygenase, andcyclooxygenase-2 in vitro

Twenty-four monoterpenoids , including three previously undescribed compounds ( 1 – 3 ), were isolated from the root bark of Acanthopanax gracilistylus W. W. Smith ( Acanthopanacis Cortex ). Their structures were unambiguously established based on spectroscopic analysis (HR-ESIMS, IR, 1D, and 2D NMR), and the absolute configurations of 1 – 3 were elucidated by comparing their experimental and calculated electronic circular dichroism spectra. In addition, the structure of 8 was confirmed by single-crystal X-ray diffraction. The inhibitory activities of 1 – 24 against neutrophil elastase , 5-lipoxygenase, and cyclooxygenase-2 (COX-2) were studied in vitro for the first time, and the results showed that compound 24 possessed a significant inhibitory effect on COX-2 with an IC 50 value of 1.53 ± 0.10 μ Μ. This research first reported the presence of monoterpenoids in Acanthopanacis Cortex , including one monoterpenoid 2 with an unusual 4/5 bicyclic lactone system, and compounds 4 and 5 have never been reported in nature.