J Nat Prod. 2004 Apr;67(4):714-7.

Labdane diterpenes of Leonurus sibiricus.

Boalino DM, McLean S, Reynolds WF, Tinto WF.

Laboratory of Bioorganic Chemistry, Department of Biological and Chemical Sciences, University of the West Indies, Cave Hill Campus, Bridgetown, Barbados.

Seven new labdane diterpenes, sibiricinones A-E (1-4, 6) and 15-epi-sibiricinones D and E (5 and 7), and the flavone genkwanin were isolated from the aerial parts of Leonurus sibiricus. Sibiricinone D (4) and 15-epi-sibiricinone D (5), and sibiricinone E (6) and 15-epi-sibiricinone E (7), respectively, were isolated as C-15 epimeric pairs. These secondary metabolites were identified on the basis of 1D and 2D NMR including (1)H-(1)H COSY, HSQC, and HMBC spectroscopic techniques. The stereochemical configurations of compounds 4-7 were assigned through 2D T-ROESY and selective NOE experiments.