New Spiranoid Withanolides From Jaborosa Odonelliana

Abstract

From whole Jaborosa odonelliana plants four new withanolides containing a spi-ranic lactone in the side chain, were isolated and their structures elucidated by spectroscopic methods.

Introduction

As part of our studies of the withanolides of argentine species of the genus Jaborosa we have rein-vestigated Jaborosa odonelliana from which we had isolated several years ago the unusual withanolide jaborosalactone P (1) [1]. J. odonelliana grows in the northwest of Argentina, mainly in arid and sandy soils. From plants collected in the province of Salta we have now isolated, besides jaborosalactone P, four new spiranoid withanolides (2-5), which differ from 1 in the substitution pattern of rings A and B.

Experimental

Plant material and isolation procedure: Whole plants of J. odonelliana A. T. Hunziker were col-lected in El Jardín, Depto la Candelaria, Salta. Dried and pulverized plants, were extracted succesively with ether and ethanol at room temperature and both extracts evaporated. The combined residues were fractionated by flash chromatography, RP-HPLC and prep. TLC rendering 1 and four more polar withanolides.

Results and Discussion

The ¹H and ¹³C NMR spectra of compounds 2-5 showed resonances for rings C, D and the side chain, almost identical to those of jaborosalactone P (1); thus, the main difference among the five withanolides was established to be in the functionalization of rings A and B. Compound 3, differed from the other four in the multiplicity pattern of the olefinic protons H-2 and H-3 which corresponded to a 4-substituted withanolide. The presence of additional resonances asigned to an oxygenated CH in the ¹H and ¹³C NMR spectra (δ 3.76 and 69.3 respectively) confirmed the 4β-hydroxy substitution. The epoxide, diol and clorohydrin substituents of 2, 4 and 5 were identified by comparison of the NMR spectra with similarly substituted withanolides and by MS. To this date, spiranoid withanolides con-taining a C-C bond between (C-12) and the side chain (C-23) have only been found in J. odonelliana, J. araucana and J. runcinata [1,2]. The spiranoid withanolide, jaborosalactone 1 [2], isolated from the latter species, showed antitumor activity in in vitro tests for induction of quinone reductase on mouse hepatoma cells (hepalclc7) [3].