New spectral data of some flavonoids from Deguelia hatschbachii A.M.G. Azevedo

Abstracts

Entre os flavonóides isolados de Deguelia hatschbachii¹ encontram-se escandenina (1), robustato de metila (2) e 4',5-diidroxi-6-(3,3-dimetilalila)-7-metoxiflavanona (3) que foram identificados pela comparação dos dados espectroscópicos previamente publicados. A obtenção de novos dados espectroscópicos (RMN, RMN-2D e EM/EM) permitiu a atribuição dos deslocamentos químicos de todos os hidrogênios e carbonos nos espectros de RMN ¹H e 13C destas substâncias, assim como a elucidação dos caminhos de fragmentação de 1-3 no espectrômetro de massas.

SHORT REPORT

New spectral data of some flavonoids from Deguelia hatschbachii A.M.G. Azevedo

Aderbal F. Magalhães^I; Ana M. G. A. Tozzi^II; Eva G. Magalhães^I; Valéria R. de S. Moraes^I

^IInstituto de Química, Universidade Estadual de Campinas, CP 6154, 13084-971 Campinas, SP, Brazil

IIInstituto de Biologia, Universidade Estadual de Campinas, CP 6109, 13083-970 Campinas, SP, Brazil

^{Address to correspondence}

RESUMO

Entre os flavonóides isolados de Deguelia hatschbachii¹ encontram-se escandenina (1), robustato de metila (2) e 4',5-diidroxi-6-(3,3-dimetilalila)-7-metoxiflavanona (3) que foram identificados pela comparação dos dados espectroscópicos previamente publicados. A obtenção de novos dados espectroscópicos (RMN, RMN-2D e EM/EM) permitiu a atribuição dos deslocamentos químicos de todos os hidrogênios e carbonos nos espectros de RMN ¹H e ¹³C destas substâncias, assim como a elucidação dos caminhos de fragmentação de 1-3 no espectrômetro de massas.

ABSTRACT

From the roots of Deguelia hatschbachii, the known flavonoids scandenin (1), methyl robustate (2) and 4',5- dihydroxy-6-(3,3-dimethylalyll)-7-methoxy flavanone (3) were isolated and characterized by comparison of their spectroscopic data with those found in the literature. Now the inclusion of 1D- and 2D-NMR and MS/MS data has allowed the complete assignment of all hydrogen and carbon chemical shifts in their NMR spectra, as well as the elucidation of the fragmentation pathways of 1-3 in the mass spectrometer.

Keywords:Deguelia hatschbachii, Leguminosae, 4-hydroxy-3-phenylcoumarins, flavanone

Introduction

Deguelia hatschbachii A. M. G. Azevedo (Leguminosae-Fabaceae) is a new species native to Brazil. It is a medium sized tree, 3-6 m in height, with pink flowers and can be found in the East-south of Minas Gerais State and in the region of Mata Atlântica along the states of Espírito Santo, Rio de Janeiro and São Paulo.

In a previous report¹ we described the structural determination of five new compounds, which were isolated together with eight known ones from the roots of D. hatschbachii.

Since the ¹H and ¹³C NMR literature data for compounds 1-3 are incomplete (Figure 1), in this paper we report the complete assignment of ¹H and ¹³C NMR spectral data of 1-3 by using 1D- and 2D- NMR techniques as well as the fragmentation pathways of 1 and 3 in the mass spectrometer, based on MS/MS experiments.

Experimental

General experimental procedures

¹H NMR (300 and 500 MHz), ¹³C NMR (75 MHz), ¹H-¹³C HETCOR J¹_CH and ¹H-¹³C COLOC Jⁿ_CH (n=2 and 3) spectra were recorded using BRUKER AC 300/P, GEMINI 2000 (VARIAN), GEMINI 300 BB (VARIAN) and INOVA 500 (VARIAN) spectrometers, with TMS as internal standard and CDCl₃ as solvent. Chemical shifts (d) are in ppm and the coupling constants (J) in Hertz (Hz).

EIMS 70 eV, direct probe, MS/MS experiments were performed in a VG Auto Spec-Fisions Instrument by using electron ionization technique at 70 eV (linked scan at 8KeV collisions with Helium).

Plant material, extraction and isolation ¹

4,4'-dihydroxy-3-phenyl-5-methoxy-6-(3,3- dimethylallyl)-2",2"-dimethylchromene (5",6":8,7)-coumarin (1, Scandenin). ¹H NMR spectral data (300 Mhz, CDCl₃/TMS): Table 1. ¹³C NMR spectral data (75 MHz, CDCl₃): Table 2. EIMS (probe) 70 eV, m/z (rel. int.): 434 [M]⁺ (100), 419 [M-Me]⁺ (70), 391 [M-Me-CO]⁺ (4), 379 [M-55]⁺ (3), 363 [M-Me-56]⁺ (3), 300 [M-134]⁺ (7), 285 [M-134-Me]⁺ (66), 245 [M-189]⁺ (12), 257 [M-134-Me-CO]⁺ (12).

4, 5, 4'-trimethoxy-3-phenyl-2", 2"-dimethylchromene (5", 6": 6,7) coumarin (2,Methyl robustate). ¹H NMR spectral data (300 MHz, CDCl₃/TMS): Table 1. ¹³C NMR spectral data (75 MHz, CDCl₃): Table 2. EIMS (probe) 70 eV, m/z (rel. int.): 394 [M]⁺ (33), 379 [M-Me]⁺ (100), 366 [M-CO]⁺ (1), 351 [M-CO-Me]⁺ (2), 135 [M-CO-Me-216]⁺ (12).

5, 4'-dihydroxy-6-(3,3-dimethylallyl)-7-methoxyflavanone (3). ¹H NMR spectral data (500 MHz, CDCl₃/TMS): Table 1. ¹³C NMR spectral data (75 MHz, CDCl₃): Table 2. EIMS (probe) 70 eV, m/z (rel. int.): 354 [M]⁺ (100), 339 [M-Me]⁺ (29), 311 [M-Me-CO]⁺ (28), 299 [M-55]⁺ (27), 234 [M-120]⁺ (11), 219 [M-120-Me]⁺ (43), 206 [M-120-CO]⁺ (20), 191 [M-120-CO-Me]⁺ (17), 179 [M-175] (56), 120 [M-234]⁺ (18), 119 [(M+H)- 234]⁺ (8), 91 [(M+H)- 234-CO]⁺ (13).

Results and Discussion

Scandenin 1 was previously isolated from Derris spruceana² and Derris scandens.³ We now report, for the first time, its ¹³C NMR spectral data (Table 2). The carbon resonances were identified by extensive 2D- NMR correlation experiments [HETCOR and COLOC] (Table 3).

Based on MS/MS experiments selecting the ions of m/z 419 [391 (6%), 285 (100%)], m/z 300 [285 (100%), 269 (22%), 257 (48%), 245 (65%), 229 (17%)] e m/z 134 [106 (100%)] we can confirm the fragmentation pathway⁴ for this compound (Figure 2).

Methyl robustate 2 was previously isolated from Derris robusta⁵ when only UV, IR and low resolution ¹H NMR (60 MHz) spectral data were reported. We now include ¹H (300 MHz), ¹³C NMR data (Tables 1 and 2) and the fragmentation pathway for this compound (Figure 3).

The ¹H NMR spectrum of compound 3 showed the same absorptions found for the flavanone previously isolated from Lonchocarpus minimiflorus,⁶ when only MS and low resolution ¹H NMR (90 MHz) spectral data were reported. 1D- and 2D- NMR experiments allowed the full assignment of all hydrogen and carbon shift values (Tables 1, 2, ⁴ and ⁵).

Based on MS/MS experiments selecting the ions of m/z 339 [219 (26%)], m/z 206 [191 (27%)] and m/z 234 [219 (41%), 206 (11%), 191 (5%), 179 (24%)] we can suggest a fragmentation pathway for this compound (Figure 4).

Conclusions

The combination of 1D- and 2D-NMR techniques has allowed the complete assignment of the ¹H and ¹³C spectral data of the known flavonoids 1-3, until now not found in the literature.

Our results will fill the gap in literature data for these compounds, which are rarely found in nature and can be used to facilitate further assignments of other analogous flavonoids.

Acknowledgments

The authors are grateful to Brazilian agencies CNPq and CAPES for scholarships awarded to Dr. V. R. S. M. and to FAPESP for financial support.

Received: August 27, 2001

Published on the web: October 29, 2002

FAPESP helped in meeting the publication costs of this article.

• 1. Magalhães, A. F.; Tozzi, A. M. G. A.; Magalhães, E. G.; Moraes, V. R. D.; Phytochemistry 2001, 57, 77.
• 2. Garcia, M.; Kano, M. H. C.; Vieira, D. M.; do Nascimento, M. C.; Mors, W. B.; Phytochemistry 1986, 25, 2425.
• 3. Clark, E.P.; J. Org. Chem. 1943, 8, 489.
• 4. Pelter, A.; Stainton, P.; Johnson, A. P.; Barber, M.; J. Heterocycl. Chem. 2 1965, 256.
• 5. Johnson, A.P.; Pelter, A.; J. Chem. Soc. (C) 1966, 606.
• 6. Mahmoud, E. N.; Waterman, P. G.; J. Nat. Prod 1985, 48, 648.

Publication Dates

• Publication in this collection
  07 Apr 2003
• Date of issue
  Jan 2003

History

• Received
  27 Aug 2001