Continuing our search for possible cardioactive single constituents of primary and
refined antiarrhythmic extracts of Leonurus cardiaca L. [1] we focused on the group of furanic labdane type diterpenes and other lipophilic
compounds. The paper attended reports herewith the isolation of five diterpenes besides
known lipophilic substances, like sitosterol, stigmasterol, genkwanin and ursolic
acid. In accordance to Knöss et al. [2, 3] the postulated presence of leocardine [4]
as a major reference substance of Leonurus cardiaca L. could not be confirmed. The structures of leopersine E, isoleosibirine, leopersine
F and 7-epi-leopersine F were determined by 1 d/2 d 1H/13C NMR spectroscopical experiments. These labdane-type diterpenes have been found only
once in other Leonurus species, namely in the related Lamiaceae L. sibiricus and L. persicus [5, 6]. A TLC-comparison of different Leonurus species showed a various range as well as highly different amounts of diterpenes.
Furthermore genkwanin, a lipophilic flavone, typical of different Leonurus species, was isolated which may be useful as a chemotaxonomic marker within the subfamily
Lamioideae.
In view of the above mentioned search for possible cardioactive constituents, the
similarity of these diterpenes to e.g. premarrubeine and marrubenol from the closely
related Marrubium vulgare L. might be an important hint at a possible cardioactive property, particularly since
those have been evaluated as calcium channel blocking agents [7].
References:
[1] Ritter M et al. Planta Med 2010; 76: 572 – 582
[2] Knöss W. Plant Cell Reports 1995; 14: 790 – 793
[3] Knöss W et al. Planta Med 1998; 64: 357 – 361
[4] Malakov P et al. Phytochemistry 1985; 24: 2341 – 2343
[5] Tasdemir D et al. J Nat Prod 1996; 59: 131 – 134
[6] Savona G et al. Phytochemistry 1982; 21: 2699 – 2701
[7] El Bardai S et al. Planta Med 2003; 69: 75 – 77
