Guaianolide

 SL guaianolide (11,13-dehydrocompressanolide). 





DEPT spectrum (CDCl 3 , 75.5 MHz) of the guaianolide. 


 Mass spectra recorded in the positive MS E mode for guaianolide and parthenolide (500.0 μg mL -1 ) of the dichloromethane fraction of the





COSY spectrum (CDCl 3 , 300 MHz) of the guaianolide







HMBC correlation spectrum (CDCl 3 , 300 MHz) of the guaianolide. 






HMQC correlation spectrum (CDCl 3 , 300 MHz) of the guaianolide.





 13 C NMR spectrum (75.5 MHz, CDCl 3 ) of the guaianolide. 





1 H NMR spectrum (CDCl 3 , 300 MHz) of the guaianolide.

Journal of the Brazilian Chemical Society

Print version ISSN 0103-5053
On-line version ISSN 1678-4790

J. Braz. Chem. Soc. vol.14 no.5 São Paulo Sept./Oct. 2003

http://dx.doi.org/10.1590/S0103-50532003000500006 

Sesquiterpene lactones and other chemical constituents of Mikania hoehnei R.

Juliana S. Chaves; Dionéia C. R. de Oliveira^*

Departamento de Física e Química. Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Via do Café s/n, 14040 903, Ribeirão Preto-SP, Brazil

http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532003000500006

8b-hydroxyzaluzanin D (1). Colorless gum; C₁₇H₂₀O₅; IR n_max/cm^-1 (NaCl film): 3494 (OH alcohol), 1750 (g-lactone), 1730 (acetyl group), 1664 and 1641 (c=c double bonds); EI-MS, m/z (relative intensity in %): 262 [M⁺- ketene] (14), 91 (24), 43 [CH₃CO]⁺ (100); ¹H NMR (300 MHz, CDCl₃), see Table 1. ¹³C NMR, DEPT 135⁰ and HMQC (75 MHz, CDCl₃): 45.0 (d, C-1), 36.5 (t, C-2), 74.5 (d, C-3), 147.7 (s, C-4), 50.4 (d, C-5), 77.6 (d, C-6), 50.1 (d, C-7), 65.7 (d, C-8), 41.8 (t, C-9), 142.8 (s, C-10), 136.0 (s, C-11), 170.8 (s, C-12), 121.6 (t, C-13), 117.4 (t, C-14), 114.2 (t, C-15), 169.4 (s, C-1'), 21.2 (q, C-2').

Results and Discussion

The chromatographic fractionation of hexane, ethyl acetate and ethanol extracts yielded stigmasterol, b-sitosterol and campesterol, lupeyl acetate,²¹ b-sitosteryl and stigmasteryl glucopyranosides,²² benzil 2,6-dimethoxybenzoate,²³ luteolin,²⁴ kaempferol²⁴ and dehydrocostuslactone.^13,14 The structures were established by comparison of their spectroscopic properties (mainly IR, ¹H and ¹³C NMR) with those reported in the literature and in some cases by direct comparison with authentic samples.

Structure of the guaianolide 1 was deduced from the IR, MS, ¹³C and ¹H NMR spectra data and the stereochemistry was defined from the coupling constants' value J and nOe difference correlations. This lactone has been previously reported as a synthetic compound obtained in the controlled acetylation of the natural guaianolide Integrifolin (8-epi-desacylcynaropicrin).¹² The IR spectrum displayed bands at 1750 cm^–1 (g-lactone), at 1730 cm^–1 (acetyl group), at 3494 cm^-1 (hydroxyl group) and weak bands at 1664, 1641 cm^–1 (c=c double bonds).

Inspection of the ¹H NMR spectrum of compound 1 indicated several signals very close to those observed in Zaluzanin D¹⁵. The position and the stereochemistry (b-orientation) of hydroxyl group at C-8 were determined by nOe correlation (Figure 1). nOe's were observed between the H-8 (d 4.37) and H-13a (d 5.62), H-7 (d 2.98) and H-9b (d 2.61). In the same way, correlation of the H-3 (d 5.50) with H-2b (d 2.45) and H-15a (d 5.32) in the nOe spectrum confirmed the a-orientation of H-3 which was attached to the carbon atom which is linked to the acetate group, as previously defined as Zaluzanin D (compound 2).

Just as the NMR spectrum of 2, the NMR spectrum of guaianolide 1 exhibited two characteristic doublets at d 6.42 and 5.62 (J 3.8 and 3.2 Hz respectively) corresponding to hydrogens of H - 13a and H - 13b of an exocyclic methylene group conjugated with a g-lactone. The exocyclic methylene groups attached to C-10 and C-4 were characterized by two singlets at d 4.99 (H-14a), 5.10 (H-14b) and a pair of triplets (J 2.0 Hz) at d 5.32 (H-15a) and 5.52 (H-15b), respectively.

The stereochemistry cis of the ring junction at C-1 and C-5 was established by the coupling constant (J 8.3 Hz) between H-1 and H-5. In the case of 1b, 5a-trans- guaianolide, a value of 10.0 Hz or greater is expected according to that reported in the literature.^25,26 The lactone ring junction was confirmed to be trans (6b H, 7aH) by the large coupling constant (J ~ 3.0 Hz) of the H -13-a-methylene protons this is due to H-6/H-7 (J 8.9 Hz) coupling constant.¹⁶

All other signals were in agreement with the proposed structure of the guaianolide 1 (Table 1). Heteronuclear multiple quantum correlation ¹H – ¹³C (HMQC) allowed us to assign unambiguously the signals of all carbons.

Besides the importance chemosystematic,²⁷ sesquiterpene lactone posseses a wide spectrum of biological activity.²⁸ Zaluzanin C, Zaluzanin D and its derivatives have shown several biological activities, such as activity against the P 388 lymphocytic leukemia in vitro,^29,30 antifungal activity,^31,32 inhibitory activity on nitric oxide production and nuclear fator KB,³³ inhibitory activity on ethanol absorption.³⁴

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