Investigación

 

Phytochemical Investigation of Four Teucrium Species

 

Maurizio Bruno,¹ Franco Piozzi,¹* Sergio Rosselli,¹ Antonella Maggio,¹ Meri Alania,² Kaddour Lamara,³ Malik R.Y.Al-Hillo,³ and Orietta Servettaz⁴

 

¹Dipartimento di Chimica Organica, Università di Palermo, Viale delle Scienze, Parco d'Orleans II, 90128 Palermo, Italy. Tel +39-091-596905; Fax +39-091-596825. E-mail bruno@dicpm.unipa.it

²Georgian Academy of Sciences, Institute of Pharmacochemistry, 36 P.Sarajishvili, Tbilisi, Georgia.

³Chemistry Department, Science Exact Institute, Oum El Bouaghi University, Oum El Bouaghi 04000, Algeria.

⁴Dipartimento di Biologia, Università di Milano, Milano, Italy.

 

Recibido el 27 de abril del 2004.
Aceptado el 28 de mayo del 2004.

 

Abstract

Aerial parts of four species of Teucrium were investigated. Three of them contain some already known neoclerodane diterpenoids, occurring in other species of Teucrium. Singularly, the fourth species is devoid of such products.

Keywords: Teucrium, Lamiaceae, diterpenes, neoclerodanes.

 

Resumen

Las partes aéreas de cuatro especies Teucrium fueron estudiadas. Tres de ellas contienen algunos diterpenoides neoclerodánicos ya conocidos, que se encuentran en otras especies de Teucrium. Sorprendentemente, en la cuarta especie no se encuentran dichos productos.

Palabras clave: Teucrium, Lamiaceae, diterpenos, neoclerodanos.

 

The aerial parts of species of the genus Teucrium, Lamiaceae (Labiatae), are known to contain neoclerodane diterpenoids showing interesting antifeedant activity. The chemistry of the diterpenoids isolated from this genus was reviewed in previous papers [1-4]. Continuing our chemotaxonomic studies on the genus, we report here on the results obtained on four more species: T. dunense Sennen (from Majorca island, Spain), T. nuchense C. Koch (from Georgia, Caucasus), T. cylindraceum Greuter et Burdet (from Algeria), T. thymoides Pomel (from Algeria).

From T. dunense we isolated three already known neo-clerodanes: 19-acetyl-gnaphalin [5] 1, isoeriocephalin [6] 2, 6-acetyl-picropolin [7] 3.

Only one known product occurred in T. nuchense, teucrin A [8-10] 4.

Two known diterpenoids were identified in T. cylindraceum: auropolin [11] 5 and 20-epi-auropolin [12] 6.

No diterpenoid was found in T. thymoides. This absence is rather unusual: including this case, the species of Teucrium devoid of neoclerodanes are only 14 out of the almost 120 taxa examined until now. From the taxonomic point of view, it is remarkable that 7 of them grow in the Iberian Peninsula (T. algarbiense, T. compactum, T. lusitanicum, T. pseudochamaepytis, T. rotundifolium, T. scordioides, T. subtrifidum), 5 in Northern Africa (T. apollinis, T. cyrenaicum, T. davaeanum, T. decipiens, T. thymoides), and only two in the extreme Eastern Mediterranean area (T. cyprium, T. montbretii subsp. pamphilicum).

 

Experimental section

General experimental procedures. Column chromatography was performed using Merck Si gel (No. 7734). NMR spectra were run on a Bruker AC 250 E apparatus. MS were recorded on a Finnigan TSQ70 instrument (70 eV, direct inlet).

Plant material. Aerial parts of T. dunense were collected on 4-6-1989 in the island of Majorca (Spain) on the dunes of Alcudia (east coast). A specimen is deposited in the Herbarium of the Dipartimento di Biologia, Università di Milano. T. nuchense was cultivated in the Botanic Garden of Tbilisi, Georgia, and harvested on 5-11-1998. A specimen is deposited in the Herbarium of the Botanic Garden. T. cylindraceum was collected on 28-4-2000 at Elmegiar, 120 km southeast of Biskra, Algeria. A specimen is deposited in the Herbarium of the Institut National de Agronomie (INA) at El-Harrach, Algeria. T. thymoides was harvested on 5-5-2000 at Jebel Boukadra, 30 km North of Tebessa, Algeria. A specimen is deposited in the same Herbarium.

Extraction and isolation. Dried and finely powdered aerial parts of each species (about 200 g) were extracted three times with Me₂CO at room temperature for 1 week. After filtration, the solvents were evaporated under reduced pressure and the residues chromatographed with a solvent gradient from 100% petroleum ether (bp 50-70°C) to 100% EtOAc, and finally with EtOAc-MeOH (9:1). Previous known compounds were identified by NMR and mass spectra, in comparison with authentic specimens.

 

References

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