Flavanones from aerial parts of Cordia globosa (Jacq.) Kunth, Boraginaceae

Flavanonas isoladas das partes aéreas de Cordia globosa (Jacq.) Kunth (Boraginaceae)

ARTICLE

Flavanones from aerial parts of Cordia globosa (Jacq.) Kunth, Boraginaceae

Flavanonas isoladas das partes aéreas de Cordia globosa (Jacq.) Kunth (Boraginaceae

Sâmia Andricia S. da Silva^I,*; Maria de Fátima Agra^II; Josean F. Tavares^II; Emídio V. L. da-Cunha^II,III; José Maria Barbosa-Filho^II; Marcelo S. da Silva^II

^IEscola de Enfermagem e Farmácia, Universidade Federal de Alagoas, Cidade Universitária, 57072-970 Maceió-AL, Brazil

^IILaboratório de Tecnologia Farmacêutica, Universidade Federal da Paraíba, 58051-970 João Pessoa-PB, Brazil

^IIIDepartamento de Farmácia e Biologia, Universidade Estadual da Paraíba, 58100-000 Campina Grande-PB, Brazil

ABSTRACT

The phytochemical analysis of aerial parts of Cordia globosa, collected in the Municipality of Picuí, State of Paraíba, Brazil, resulted in the isolation and structural identification of narigenin-4',7-dimethyl ether (0.025 g) and eriodictyol (0.015 g). These compounds are the first flavanones aglycones isolated from the genus Cordia.

Keywords: Cordia globosa, Boraginaceae, flavanones, narigenin-4',7-dimethyl ether, eriodictyol.

RESUMO

A análise fitoquímica das partes aéreas de Cordia globosa, coletadas no município de Picuí, PB, Brasil, resultou no isolamento e identificação estrutural da 7,4'-dimetilnarigenina (0,025 g) e eriodictiol (0,015 g). Estas duas flavanonas são as primeiras agliconas, desta classe, isoladas no gênero Cordia.

Unitermos: Cordia globosa, Boraginaceae, flavanonas, 7,4'-dimetilnarigenina, eriodictiol.

INTRODUCTION

The Boraginaceae family comprises about 2740 species distributed in 148 genera (Stevens, 2001). The genus Cordia is one of the most representatives of this family and the chemical characteristic in this genus is the presence of quinones known as cordiaquinones. However, flavonoids, terpenoids, carbohydrates, lipids and phenylpropanoids are also well reported for the genus (Silva, 2004).

Cordia globosa (Jacq.) Kunth is a shrub popularly known in Northeastern Brazil as 'maria-preta'. The decoction or infusion of the leaves of C. globosa is used in folk medicine for the treatment of the symptoms of rheumatism, painful menstruation and dyspepsia. In Jamaica, the tea of leaves is used by women against painful menstruation (Asprey & Thornton, 1955). The leaves and the stems have spasmolytic activity on guinea pig ileum as well as on rabbit duodenum, and also was confirmed the vasodilator activity on isolated rats' hindquarter (Feng et al., 1962).

Previous studies reported the isolation of 7-methoxyflavone and 3',4',5,7-tetrahydroxy-3methoxyflavone (Silva et al., 2004) from the aerial parts and (1aS*, 1bS*, 7aS*, 8aS*)-4,5-dimethoxy-1a,7a-dimethyl1,1a,1b,2,7,7a,8,8a-octahydrocyclopropa [3,4] cyclopenta [1.2b] naphthalene-3,6-dione and microphyllaquinone from the roots of C. globosa (Menezes et al., 2005). Twenty three and twenty six volatiles compounds were identified for the essential oils obtained from fresh leaves at the flowering and fructification stages, respectively. The bicyclogermacrene (22.7-13.1%) and β-caryophyllene (11.9-11.6%) were the majority constituents (Menezes et al., 2006). In another study, a total of 38 compounds were indentified from the oils obtained from steam and leaves. The main components in the stem oil were 1-endobourbonanol (20.2%) and lynalyl butyrate (14.7%) and in the leaves oil, the β-caryophyllene (39.0%) and α-humulene (12.1%) were the majority (Oliveira et al., 2007).

MATERIAL AND METHODS

General

¹H and ¹³C NMR (1D and 2D) were obtained on a MERCURY VARIAN spectrometer. ¹H and APT¹³C NMR spectra were recorded in a CDCl₃ (CG-01) or CD₃OD (CG-2) at 200 and 50 MHz, respectively. TMS was used as internal standard. TLC, on Si Gel 60 PF₂₅₄ ART 7749 (Merck) and column chromatography with Si Gel ART 7734 (Merck) or Sephadex-LH 20 (Pharmacia) were used.

Plant Material

The aerial parts of Cordia globosa (Jacq.) Kunth were collected in March 2002 in the Municipality of Picuí, State of Paraíba, Brazil. Avoucher specimen (AGRA5185) has been deposited at the Herbarium Prof. Lauro Pires Xavier (JPB) in the Universidade Federal da Paraíba.

Extraction, isolation and the structure elucidation

The fresh aerial parts were dried at 40 ºC for 72 h and after were grownded in a mechanical mill. Dried and powdered aerial parts (10 kg) from C. globosa were extracted with EtOH at room temperature for three days, five consecutive times. The alcoholic extract was then dried and the crude extract (300 g) obtained was taken up in MeOH:H₂O (7:3) and extracted successively with hexane, chloroform, ethyl acetate and n-buthanol.

The hexane (37 g) fraction was subjected to column chromatography packed with silica gel 60 and eluted with hexane, chloroform and methanol; 286 fractions of 50 mL were collected being analyzed and joined through analytical thin-layer chromatography (TLC). The sub-fraction 102-112 (0,320 g) was submitted to column chromatography packed with silica gel 60 an eluted with hexane, ethyl acetate and methanol gradient, resulting 61 fractions of 25 mL that were analyzed and joined through analytical TLC. The sub-fraction 14-21 after being recrystallized in chloroform showed itself as an incolor solid crystalline, yielding 0.025 g of the substance CG-01.

The fraction chloroformic (31 g) was subjected to column chromatography packed with silica gel 60 and eluted with hexane, ethyl acetate and methanol, from which 185 fractions of 50 mL were collected and the analyzed and joined through analytical TLC. The sub-fraction 159-165 (158 mg) was subjected to column chromatography packed with Sephadex LH 20 and eluted with chloroform:methanol (1:1) from which 22 fractions of 20 mL were collected and then analyzed and joined through analytical TLC. The sub-fraction 16-17 (30 mg) was subjected to column chromatography packed with Sephadex LH 20 and eluted with chloroform:methanol (1:1) from which fifteen fractions of 8 mL were collected and then analyzed and joined through analytical TLC. The sub-fraction 10-11 (0.015 g), washing with acetone gave a yellow solid codified as CG-02 (0.015 g).

RESULTS AND DISCUSSION

The ¹H NMR spectrum of compound 1 showed three protons at δ 2.76 (1H, dd, J = 17.3, 3.2 Hz), 3.09 (1H, dd, J = 17.3, 13.0 Hz) and 5.35 (1H, dd, J = 13.0, 3.2 Hz), typically assignable to H-3 and H-2 of a flavanone skeleton, which was indicated also in the ¹H NMR of CG02 [δ 2.68 (1H, dd, J = 17.0, 3.0 Hz), 3.06 (1H, dd, J = 17.0, 12.5 Hz) and 5.26 (dd, J = 12.5, 3.0 Hz)]. In addition, signals for four protons at δ 6.93 (2H, d, J = 8.7 Hz) and 7.38 (2H, d, J = 8.7 Hz)] assignable to the aromatic protons of a 4-monosubstituted B-ring for 1 as well three protons at δ 6.78 (2H, s) and 6.91 (1H, sl) assignable to the aromatic protons of a 3,4-disubstituted B-ring for 2. A downfield proton at δ 12.01 (CG-01) and δ 12.1 (CG-02, DMSO) assignable to C5-OH chelated to C-4 carbonyl, and two additional aromatic protons at δ 6.93 (1H, d, J =

8.7 Hz) and 7.38 (1H, d, J = 8.7 Hz), δ 5.87 (1H, d, J =

2.2 Hz) and 5.89 (1H, d, J = 2.2 Hz) were observed for 1 and 2, respectively, could be assigned to 6 and 7 aromatics protons of the A-ring. Furthermore, two methoxy signals appeared at δ 3.78 (3H, s), 3.81 (3H, s) of compound 1. These spectroscopic data suggested that compound 1 and 2 were 5-hydroxyflavanones substituted with two methoxy groups and three hydroxyl groups, respectively. The ¹³C NMR spectra analysis of 1 and 2 showed signals for 17 and 15 carbons, comprising two methoxy, one methylene, seven methynes and seven non-protonated carbons to 1 and one methylene, six methynes and eight non-protonated carbons to 2. The analysis of these data sets with the spectra of HMQC, HMBC and NOESY, as well as comparison with literature data (Agrawal, 1989), has identified 1 as 5-hydroxy-4',7-dimethoxyflavanone (narigenin-4',7dimethyl ether) and 2 as 3',4',5,7-tetrahydroxyflavanone (eriodictyol), with yielding of 0.00025% and 0.00015%, respectively

Narigenin-4',7-dimethyl ether (1): NMR ¹H (200 MHz, CDCl₃) 2.76 (H-3a, dd, J = 3.2;17.3), 3.09 (H-3b, dd, J = 13.0; 17.3), 3.78 (OCH₃-7, s), 3.81 (OCH₃-4', s), 5.35 (H-2, dd, J = 3.2, 13.0), 6.02 (H-8, d, J = 2.3), 6.05 (H-6, d, J = 2.3), 6.93 (H-5', d, J = 8.7), 7.38 (H-6', d, J = 8.7), 12.01 (s, OH-5). NMR ¹³C (50 MHz, CDCl₃): 43.2 (C-3), 55.4 (OCH₃), 55.7 (OCH₃), 79.0 (C-2), 94.2 (C-8), 95.1 (C-6), 103.1 (C-10), 114.2 (C-3', 5'), 127.7 (C-2', 6'), 130.4 (C-1'), 160.0 (C-4`), 162.9 (C-9), 164.1 (C-5), 168.0 (C-7), 196.0 (C-4).

Eriodictyol (2): NMR ¹H (200 MHz, MeOD) 2.68 (H-3a, dd, J = 3.0; 17.0), 3.06 (H-3b, dd, J = 12.5, 17.0), 5.26 (H-2, dd, J = 3.0, 12.5), 5.87 (H-8, d, J = 2.2), 5.89 (H-6, d, J = 2.2), 6.78 (H-5', H-6', 2H, s), 6.91 (H-2', 1H, sl). NMR ¹³C: 44.1 (C-3), 80.5 (C-2), 96.2 (C-8), 97.0 (C-6), 103.3 (C-10), 114.7 (C-2'), 116.2 (C-5'), 119.3 (C-6'), 131.8 (C-1'), 146.5 (C-3'), 146.9 (C-4'), 164.9 (C-9), 165.4 (C-5), 168.4 (C-7), 197.8 (C-4).

The literature reports the isolation of only sixteen flavanones from Boraginaceae. The flavanones were isolated previously from genera Heliotropium, Cordia and Echiochilon. The majority of flavanones were obtained from the genus Heliotropium, on six species. In Echiochilon only E. fruticosum showed data from flavanones and in Cordia, two glycosides flavanones were previously isolated. The compounds obtained in this work were reported in Boraginaceae family in only one species H. stenophyllum. The flavanones isolated from genera Cordia and Heliotropium are preferably 3', 4',5, 7, -tetraoxigenated (Chart 1).

CONCLUSION

This paper indicates that in Boraginaceae family the genera Heliotropium, Cordia and Echiochilon, until the present moment, are the only ones producing flavanones as well as reports the first flavanones aglycones from Cordia.

ACKNOWLEDGEMENTS

The authors wish to express their gratitude to Vicente Carlos de Oliveira Costa of the Laboratório de Tecnologia Farmacêutica, Universidade Federal da Paraíba, for providing the NMR spectra and CNPq/ IMSEAR for financial support. A sincere thanks is also due to NAPRALERT.

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Publication Dates

• Publication in this collection
  16 July 2010
• Date of issue
  Nov 2010