Abietane diterpenoids of Rosmarinus officinalis and their diacylglycerol acyltransferase-inhibitory activity

Inhibition of acyl CoA:diacylglycerol acyltransferase (DGAT) has been proposed as one of the drug targets for treating obesity and type 2 diabetes. Bioassay-guided fractionation of the MeOH-soluble extract of Rosmarinus officinalis yielded two new diacylglycerol acyltransferase (DGAT) inhibitory-abietane diterpenoids, 7β-hydroxy-20-deoxo-rosmaquinone (1) and 7β-methoxy-20-deoxo-rosmanol (2), along with six known components, carnosol (3), 7α-methoxyrosmanol (4), 7β-methoxyrosmanol (5), 12-methoxy-canosic acid (6), rosmanol (7), and rosmadial (8). Compounds 1–8 inhibited DGAT1 activity, with the IC50 values ranging from 39.5 ± 0.6 to 144.2 ± 3.1 μM. In particular, carnosol (3), which is one of the major compounds of MeOH-soluble extract of R. officinalis exhibits inhibition of de novo intracellular triacylglycerol synthesis in human hepatocyte HepG2 cells.