Bis-spirolabdane Diterpenoids from Leonotis nepetaefolia

Jun Li†, Frank R. Fronczek‡, Daneel Ferreira†, Charles L. Burandt, Jr.§, Vincent Setola, Bryan L. Roth, and Jordan K. Zjawiony†*

†Department of Pharmacognosy and Research Institute of Pharmaceutical Sciences, School of Pharmacy, §National Center for Natural Products Research, University of Mississippi, University, Mississippi 38677-1848, United States

‡ Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803-1804, United States

Department of Pharmacology, School of Medicine and NIMH Psychoactive Drug Screening Program, University of North Carolina, Chapel Hill, North Carolina 27599, United States

J. Nat. Prod., Article ASAP

DOI: 10.1021/np3000156

Publication Date (Web): April 4, 2012

Copyright © 2012 The American Chemical Society and American Society of Pharmacognosy

Ten new bis-spirolabdane diterpenoids, leonepetaefolins A–E (1, 3, 5, 7, 9) and 15-epi-leonepetaefolins A–E (2, 4, 6, 8, 10), together with eight known labdane diterpenoids (11–18) as well as two known flavonoids, apigenin and cirsiliol, were isolated from the leaves of Leonotis nepetaefolia. The structures of the new compounds were determined on the basis of 1D- and 2D-NMR experiments including ¹H, ¹³C, DEPT, ¹H–¹H COSY, HSQC, HMBC, and NOESY. The absolute configuration of an epimeric mixture of 1 and 2 was determined by X-ray crystallographic analysis. The compounds isolated were evaluated for their binding propensity in several CNS G-protein-coupled receptor assays in vitro.

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