Aromatin D-J: Seven previously undescribed labdane diterpenoids isolated from Blumea aromatica

Blumea aromatica is a traditional Chinese medicine used for treating various diseases such as rheumatoid arthritis, eczema, and pruritus. Previous studies on B. aromatica used a mass defect-filtering strategy via the ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry and reported the presence of several labdane diterpenoids (LADs). To determine the actual structures of these LADs and investigate their biological activities, seven previously undescribed LADs (aromatin D-J) were isolated from the whole B. aromatica herb. The structures of these isolated compounds were characterized using high-resolution mass spectrometry and extensive 1D and 2D NMR analyses. In addition, the absolute configurations of these compounds were determined by comparing the experimental and calculated electronic circular dichroism (ECD) spectra as well as using X-ray crystallographic analysis. All isolated compounds were evaluated for their ability to activate adenylate cyclase by measuring the levels of cyclic adenosine 3',5'-monophosphate (cAMP) in rat ventricular tissue. Aromatin E, F, and J showed moderate activities with an increase in cAMP levels by 67%, 69%, and 64%, respectively, compared with the control group.