J. Chil. Chem. Soc, 54, N° 1 (2009); págs: 55-57

 

MONOTERPENES, SESQUITERPENES AND FATTY ACIDS FROM JULOCROTON TRIQUETER (EUPHORBIACEAE) FROM CEARA - BRAZIL

 

SIDNEY G. DE LIMA¹*, JOSÉ M. M. NETO¹, ANTÔNIA M. G. LOPES CITO¹ JOSÉ G. M. DA COSTA² FRANCISCO A. M. REIS³

¹* Departamento de Química, Universidade Federal do Piauí, Campus Universitario Ministro Petrônio Portella — Bairro Ininga - Teresina-PI. CEP: 64.049-550. ²LPPN- URCA. Crato - CE, Brasil. *e-mail address: sidney@ufpi.edu.br
² Instituto de Química — Unicamp — Campiñas — SP.

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ABSTRACT

In this study the volatile constituents from leaves and fruits of Julocroton triqueter (Lam.) Didr. (Euphorbiaceae), a medicinal plant from northwest Brazil, were investigated by GC/MS. Twenty one compounds, which represent about 96% of the total constituents of the essential oil, were identified. Caryophyllene oxide, humulene epoxide II, trans-caryophyllene, occidentalol, α-humulene in the fruit and CM-carvyl acetate, spathulenol, CM-carveol, trans-caryophyllene, trans-carvyl acetate and α-humulene in the leaves were the principal components. From one fraction of the hexane extract of the fruits a mixture of fatty acids were identified as: dodecanoic, tetradecanoic, hexadecanoic, 9-octadecenoic, eicosanoic, trieicosanoic and tetracosanoic acids. The partial analysis of the non-volatile constituents (hexanic fraction) from fruit allowed the isolation and characterization of tetracosan-1-ol (identify by ¹H and ¹³C NMR, FTIR).

Keywords: Julocroton triqueter, volatile constituents, Euphorbiaceae, fatty acid

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INTRODUCTION

The Euphorbiaceae family presents about 7.500 species distributed mainly in tropical areas with larger dispersion centers in America and Africa^1-2. It has great importance not only for the number of species but also for its economical implications related to medicinal and cosmetic industry as well as for its toxicological aspects^3-6. Many Euphorbiaceae are well known in different parts of the world as toxic and/or medicinal. The high diversity of the described effects is a reflex of the high chemical diversity of this plant group³. The genus Julocroton (Euphorbiaceae) has many representative species in Brazil and some of them are widely used in the folk medicine to treat syphilis and ulcers- J. triqueter and depurative - J. humilis⁵.

The ethanolic and hydroalcoholic extract from J. triqueter has been evaluated and presented potential antileishmanial results, with IC₅₀ 29.5 µg\ triL^7-9. Nakano et al.^10-11 and Anastasi¹² reported the isolation and structural determination of the compound julocrotine in J. subpannosus, J. camporum and J. montevidensis^13,14. Most of the species have not been studied from the chemical and pharmacological point of view, and the activity studied had been applied only to crude fixed extracts. In this work we report the partial chemical composition of essential oil from the leaves and fruit of J. triqueter (Lam.) Didr. The chemical composition of the hexanic extract and its methyl ester fraction were also investigated.

MATERIALS AND METHODS

Plant material:

The botanical material was collected at Sobral - Ceará - Brazil and the vegetable material and voucher specimen were deposited at Prisco Bezerra Herbarium, UFC, under the number 27652, it was identified by L.W. Lima-Verde.

Volatile Constituent:

Fresh leaves and fruit samples (1.0 Kg), harvested at the State of Ceará, of Julocroton triqueter (Lam.) Didr. were subjected to hydrodistilation for 2 hours in a Clevenger-type apparatus. The isolated essential oils were dried over anhydrous sodium sulfate and, after filtration, maintained under refrigeration before analysis.

NMR Spectra:

NMR spectra were recorded on a Bruker 500 spectrometer (11.7 Tesla, 500 MHz for ¹H and 125 MHz for ¹³C), in CDC1₃. Chemical shifts 8 (in ppm) are given from internal TMS. The IR spectra were recorded on a Perkin Elmer - Model Spectrum 1000 FTIR (KBr, 4000 crn¹ to 400 cm^-1).

Gas chromatography/mass spectrometry:

Analysis of the oil was performed on HP (5890 A, II MSD) gas chromatograph, connected with MS system (HP 5971 A): dimethylsiloxane DB-5 fused silica capillary column (30 m x 0.25 mm, 0.1 m film thickness); carrier gas: helium 9 mL/min; injectortemperature 250 °C; detectortemperature 200 °C; column temperature 50 -180 °C at 4 °C/min, then 180-250 °C at 20 °C/min. Mass spectrometer operating conditions 70 eV ionization energy. Identification of individual components was based on their mass spectral fragmentation using two computer library MS searches (Wiley Mass Spectral Database 229), retention Índices and comparison with literature data^15-18. Relative percentage amounts were calculated from the total area under the peaks by the software of the apparatus.

Extraction and Isolation:

Dried and powdered fruits (2,8 Kg) of J. triqueter were extracted two times with hexane (3.5 L), followed by ethanol, at room temperature. After solvent evaporation under vacuum 14.1 of hexane and 22.0 g ethanolic extract were obtained, respectively. The ethanolic extract was then fractionated on a silica gel column with hexane, chloroform, ethyl acetate and methanol, gradient eluition, yielding 7.45, 6.90, 3.29 and 3.70 g of extract, respectively. During the process of eluition with hexane was observed the formation of a precipítate yellow, which was then washed in the cold light petroleum, yielding 80 mg of an amorphous solid white. This solid, soluble in chloroform, showed a single component on TLC and analysis by ¹H and ¹³C RMN indicated the tetracosan-1-ol as constituent.

The hexane fraction (7.45 g) was subjected to saponification followed by methylation reaction^19-21, and the reaction was followed by thin-layer chromatography. The reaction mixture was purified by chromatography column and the solvent was then evaporated in a vacuum (unsaponifiable: 0.5 g; saponifiable: 5.49 g). A small portion (saponifiable) of the crude reaction was analyzed in GC-MS.

RESULTS AND DISCUSSION

The identification of the essential oil components was accomplished by comparison of their GC-MS retention Índices as well as their mass spectra with corresponding data of authentic compounds of components of reference oils. To minimize the standard deviation arising from employing a solé substance as internal standard, we decided to employ a retention Índex, namely, Kovat's índex obtained by use of a mixture of the essential oil with eight n-alkanes as internal standards. This approach greatly improved the identification, especially for those compounds with very similar fragmentation patterns. The oils were analyzed on mono and sesquiterpenes, the main components being caryophyllene oxide (41.8%), humulene epoxide II (8.7%), trans-caryophyllene (8.2%), occidentalol (7.4), α-humulene (4.5%) andpara-cimene (4.2%) in the fruit and CM-carvyl acetate (44.6 %), spathulenol (12.1%), cis-carveol (10.8%), trans-caryophyllene (6.0%), trans -carvyl acetate (5.5%) and α-humulene (2.9%) in the leaf, Table 1.

The partial analysis of the non-volatile constituents (hexane fraction) from J. triqueter fruit allowed the isolation of a compound, obtained in the form of an amorphous solid, soluble in chloroform, with a melting point of 75.8 - 77.3 °C (literature²²: 77-79 °C). The ¹H - NMR (500 MHz, CDC1₃) spectrum of the compound showed signals in: 3.60 ppm (t, 2H, H-l); 1.26 ppm (s, 42H); 0,86 ppm (t, 3H, H-24). The analysis of Gated - Decoupled ¹³C NMR (125 MHz, CDC1₃) and ¹³C NMR- DEPT 135° spectrum allowed us to identify signals in: 32.9 ppm (CH₂, C-2); 31.9 ppm (CH₂, C-22); 29.4 - 29.7 ppm (18 CH₂); 25.8 ppm (CH₂, C-3); 22.7 ppm (CH₂, C-23); 14.2 ppm (CH₃, C-24) and 63,1 ppm (-CH₂-0, C-1). FT-IR spectrum showed important stretching and bending vibrations : 3342 crn¹ (O-H stretch); 2918 crn¹ and 2849 cm^-1 (sp³ C-H absorption); 1465 cm^-1 (methylene groups bending absorptions); 1064 cm^-1(C-O, stretching vibration) and 725 cm^-1 (bending motion associated with four or more CH₂ groups in an open chain). The analysis of spectral data allowed us to identify the compound as the Tetracosan-1-ol.

The methylester analysis , obtained from the fatty material, lead to the identification of dodecanoic (0.85%), tetradecanoic (1.15%), hexadecanoic (26.92%), 9-octadecenoic (19.36%), eicosanoic (6.0 %), trieicosanoic (2.29%) and tetracosanoic acid (0.89 %) as main constituents (Table 2).

The results of this preliminary analysis shall be important from the pharmacological point of view, since components of the essential oil have been found to have powerful anti-inflammatory (α-humulene and caryophylene), anti-bacterial, anti-ulcer and anti-fungal (caryophylene and its oxide) and anti-septic (linalool) properties. It has been identified about 96% of the total constituents and in general the study showed that the essential oils present different chemical compositions in different parts of the plant, yielding ranges from 0.12 to 0.30% (w/w) on fresh weight basis. The compounds trans-carvyl acetate, trans-caryophyllene, α-humulene and humulene epoxide were found in essential oils from both leaves and fruits. Unfortunately, there is no other study on Julocroton oil in the literature for comparison purposes and because there is no available data on the biological activity, variability of the composition of essential oil content with regard to season, climate and age, the effects of these variables will be currently studied in our laboratory.

ACKNOWLEDGMENTS

We are thankful to Prof. Afrânio G. Fernandes from the Institute of Biology (UFC) for identifying the plant material, we are grateful to CAPES for financial support and research fellowships, CENAUREMN - UFC for the NMR usage.

 

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(Received 21 April 2008 - Accepted 28 July 2008)