Planta Med 2012; 78 - PI117
DOI: 10.1055/s-0032-1320804

New labdane diterpenes from Leonotis leonurus and their biological activities

F He 1, 2, W Harding 1, 2
  • 1Department of Chemistry, Graduate Center- City University of New York, New York, NY 10016
  • 2Department of Chemistry, Hunter College- City University of New York, New York, NY 10065

Leonotis leonurus (Lamiaceae), is native to South Africa and has been reported to cause mild marijuana-like sedative effects when smoked or consumed as a tea. Three new labdanes, leonurenones A-C (1-3) were isolated and characterized from a commercial source of Leonotis leonurus. Genetic methods allowed for identification of the plant material. The new compounds contain an uncommon α,β-unsaturated enone moiety in ring B. Compounds 1 and 2 were evaluated in a competitive inhibition assay at the GABA A neuroreceptor site. The aqueous extract has GABAA activity. However, compounds 1 and 2 isolated herein did not show any activity at this receptor, indicating that these compounds are not by themselves responsible for the activity.

Keywords : labdane; leonurenone; Leonotis leonurus ; isolation