Planta Med 2006; 72 - S_017
DOI: 10.1055/s-2006-949750

Two new isomeric tropane alkaloids from Schizanthus tricolor identified by capillary NMR

M Humam 1, T Kehrli 1, D Jeannerat 2, O Muñoz 3, P Christen 1, K Hostettmann 1
  • 1Laboratory of Pharmacognosy and Phytochemistry, School of Pharmaceutical Sciences, University of Geneva, University of Lausanne, Quai Ernest-Ansermet 30, CH-1211 Geneva 4, Switzerland
  • 2Department of Organic Chemistry, University of Geneva, Quai Ernest-Ansermet 30, CH-1211 Geneva 4, Switzerland
  • 3Departamento de Química, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago, Chile

The genus Schizanthus (Solanaceae) belongs to the tribe Salpiglossidae and is endemic to Chile. It comprises 12 species growing in the northern part, and down to the Andes. Beside pyrrolidine alkaloids, this genus is characterized by the presence of ester derivatives with isomeric C5 acids, namely angelic, senecioic, tiglic, itaconic and mesaconic acids as well as by dimers and trimers [1]. This esterification leads to the formation of numerous structural and configurational isomers.

Two new isomeric tropane alkaloids of 337 Da were isolated from the aerial parts of Schizanthus tricolor Grau and Gronbach, namely 3α-trans-hydroxysenecioyloxy-7ß-senecioyloxytropane and 3α- trans-hydroxysenecioyloxy -7ß-angeloyloxytropane. These isomers were characterized by IR, HRMS and the structures were established by NMR, CapNMR, GC-MS and LC/UV-APCI-MS3.

3α-trans-hydroxysenecioyloxy-7ß-senecioyloxytropane3α-trans-hydroxysenecioyloxy-7ß-angeloyloxytropane

These two isomers are acetylcholinesterase inhibitors, and atypical to the genus Schizanthus as the alcohol group is attached to the senecioyl moiety and not to the tropane nucleus. In this work, the structure elucidation of the two isomers, as well as their separation and isolation are discussed.

Reference: 1. Lounasmaa, M., Tamminen T. (1993), The Alkaloids, Cordell G. A. Ed, Academic Press, San Diego 44: 1–113.