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Abstract

New Withanolides from Two Varieties of Jaborosa Caulescens

1
Dpto. de Química Orgánica e IMBIV, Fac. de Ciencias Químicas, Universidad Nacional de Córdoba, Argentina
2
Dpto. de Química Orgánica, Fac. de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina
*
Author to whom correspondence should be addressed.
Molecules 2000, 5(3), 514-515; https://doi.org/10.3390/50300514
Published: 22 March 2000

Abstract

:
The phytochemical study of two species of Jaborosa caulescens (var. caulescens and var. bipinnatifida) yielded the four new withanolides 1-4. The structures of the new compounds were determined using a combination of spectroscopic techniques (including 1D and 2D NMR) and Molecular Modeling.

Introduction

The tribe Jaboroseae (Solanaceae) is comprised by three genera: Jaborosa and Salpichroa, both Southamerican, and Nectouxia, a monotipic genus endemic of Mexico.
Our research interest is focused on the phytochemical study of the Jaborosa genus. This genus is comprised by 23 species and 22 growth in Argentina [1,2].

Experimental

The aerial parts of Jaborosa caulescens var. caulescens and Jaborosa caulescens var. bipinnati- fida were exhaustively extracted with ethanol. After evaporation of the solvent, the crude dried extract was partitioned with hexane-methanol-water (10:9:1). The methanol-water phase was then extracted with methylene chloride. The withanolides were isolated from this extract using different chromatogra- fic techniques like CC, prep. TLC and prep. HPLC. The structures elucidation was performed by a combination of spectroscopic techniques (1H-NMR, 13C-NMR, DEPT, COSY, NOESY, HETCOR, IR, MS, CD) and Molecular Modeling.

Results and Discussion

J. caulescens var. caulescens yielded the withanolides 1 and 2. These two compounds resemble the structures of Jaborosalactona R, S and T (isolated from J. sativa [3]), with respect to the presence of the hemiketal function between C-21 and C-12, but differ in the substitution pattern of ring A and B. Compound 2, once isolated from the plant extract, rapidily demethylate to give compound 1. These evidences rule out the possibility that the methylation be an extraction artifact.
On the other side, compounds 3 and 4 were isolated from J. caulescens var. bipinnatifida. Both compounds possessed a trechonolide type-structure. Their spectroscopic profiles were very similar and also showed the same molecular weight in the MS spectrum. A detailed analysis of the spectroscopic data led us to propose that both structures only differ in the stereochemistry at C-23. This was con- firmed by Circular Dichroism experiments, in which the respective spectra of compound 3 and 4 showed opposite Cotton effect al 217 nm. The sign of the Cotton effect of compound 3 (-) was the same as trechonolide A, indicating the R stereochemistry.
Molecules 05 00514 i001

References and Notes

  1. Hunziker, A. T.; Barboza, G. E. Flora Fanaerogámica Argentina. Proflora 1998, fasc. 54. [Google Scholar]
  2. Barboza, G. E.; Hunziker, A. T. Estudios sobre Solanaceae XXV. Kurtziana 1987, 19, 77–153. [Google Scholar]
  3. Bonetto, G. M.; Gil, R. R.; Oberti, J. C.; Veleiro, A. S.; Burton, G. Novel wihanolides from Jaborosa sativa. J. Nat. Prod. 1995, 58(5), 705–711. [Google Scholar] [CrossRef]

Share and Cite

MDPI and ACS Style

Nicotra, V.E.; Gil, R.R.; Oberti, J.C.; Burton, G. New Withanolides from Two Varieties of Jaborosa Caulescens. Molecules 2000, 5, 514-515. https://doi.org/10.3390/50300514

AMA Style

Nicotra VE, Gil RR, Oberti JC, Burton G. New Withanolides from Two Varieties of Jaborosa Caulescens. Molecules. 2000; 5(3):514-515. https://doi.org/10.3390/50300514

Chicago/Turabian Style

Nicotra, Viviana E., Roberto R. Gil, Juan C. Oberti, and Gerardo Burton. 2000. "New Withanolides from Two Varieties of Jaborosa Caulescens" Molecules 5, no. 3: 514-515. https://doi.org/10.3390/50300514

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