Abstracts

SHORT REPORT

Chemical composition and larvicidal activity of the essential oils of Cordia leucomalloides and Cordia curassavica from the Northeast of Brazil

Renata P. Santos^I; Edson P. Nunes^II; Ronaldo F. Nascimento^III; Gilvandete Maria P. Santiago^IV; Gustavo Henrique A. Menezes^IV; Edilberto R. Silveira^I; Otília Deusdênia L. Pessoa^* * e-mail: opessoa@ufc.br ^{, I}

^IDepartamento de Química Orgânica e Inorgânica, Centro de Ciências, Universidade Federal do Ceará, CP 12.200, 60021-970 Fortaleza-CE, Brazil

^IIHerbário Prisco Bezerra, Departamento de Biologia, Centro de Ciências, Universidade Federal do Ceará, 60451-970 Fortaleza-CE, Brazil

^IIIDepartamento de Química Analítica e Físico-Química, Universidade Federal do Ceará, CP 12.110, 60461-970 Fortaleza-CE, Brazil

^IVDepartamento de Farmácia, Universidade Federal do Ceará, 60430-370 Fortaleza-CE, Brazil

ABSTRACT

The essential oils obtained from the leaves of Cordia leucomalloides and Cordia curassavica were obtained by hydrodistillation and their chemical compositions determined by a combination of GC-MS and GC-FID. Twenty-three components were tentatively identified in both oils representing 98.6 and 91.2% of the volatile content. The oil of C. leucomalloides was characterized by a large percentage of sesquiterpenes (90.6%), being d-cadinene (17.4%), (E)-caryophyllene (15.7%), bicyclogermacrene (12.5%) and germacrene D (11.2%) the major ones. On the other hand, the oil of C. curassavica showed similar proportions of monoterpenes (47.3%) and sesquiterpenes (43.9%) among which a-pinene (20.5%), b-pinene (13.1%), (E)-caryophyllene (12.4%) and bicyclogermacrene (13.8%) were the predominant compounds. The larvicidal potential of the two oils were evaluated against the third-instar of Aedes aegypti larvae. The results showed that both oils exhibited significant activity, particularly the oil of C. leucomalloides which was able to kill 98.7% of the larvae in the concentration of 100 ppm.

Keywords:Cordia leucomalloides, Cordia curassavica, essential oil, larvicidal activity, terpenoids

RESUMO

Os óleos essenciais das folhas de Cordia leucomalloides e Cordia curassavica foram obtidos por hidrodestilação e suas composições químicas determinadas por uma combinação de CG-EM e CG-DIC. Como resultado, vinte e três componentes foram identificados em ambos os óleos, representando 98,6 e 91,2% da composição volátil. O óleo essencial de C. leucomalloides foi caracterizado por uma alta percentagem de sesquiterpenos (90,6%), sendo d-cadineno (17,4%), (E)-cariofileno (15,7%), biciclogermacreno (12,5%) e germacreno D (11,2%) os majoritários. Por outro lado, o óleo de C. curassavica mostrou proporções similares de monoterpenos (47,3%) e sesquitepenos (43,9%), entre os quais a-pineno (20,5%), b-pineno (13,1%), (E)-cariofileno (12,4%) e biciclogermacreno (13,8%) foram os compostos predominantes. O potencial larvicida dos dois óleos foi avaliado contra larvas no terceiro estágio do mosquito Aedes aegypti. Os resultados mostraram que ambos os óleos apresentaram atividade biológica significativa, particularmente o óleo essencial de C. leucomalloides, o qual foi capaz de matar 98,7% das larvas numa concentração de 100 ppm.

Introduction

The pantropical genus Cordia, represented by shrubs and trees, is one of the major and most important genus of the family Boraginaceae.¹ Some of its species yield excellent wood naturally resistent to attack of several organisms,^2,3 while others are widely used in traditional medicine in several parts of the world.^4-6 Various phytochemical studies on Cordia species have been published, revealing a great number and diversity of secondary metabolites including triterpenes,⁴ flavonoids,⁷ sesquiterpenes,⁸ saponins,⁹ hydroquinones³ and quinones.¹⁰ Nevertheless, there are few studies published about the chemical composition of the essential oils of those plants. To the best of our knowledge, only the chemical composition of the essential oils of C. curassavica (Jack.) (syn.: C. verbenacea D.C.),^1,11C. nitida Vahl.,¹²C. trichotoma Vell.¹³ and C. globosa (Jacq.) H.B.K.¹⁴ have been described. The two later were recently subject of our studies, including their essential oils.

A literature survey revealed that the oil of C. leucomalloides has not been reported but C. curassavica has been the subject of several studies, probably due its etnobotanical value.^1,5,6,15C. curassavica is a medicinal plant with anti-inflammatory and antimicrobial properties. Indeed, artemetin, a flavonoid with anti-inflammatory activity⁵ was isolated from the leaves and its essential oil has exhibited antimicrobial properties.¹² In addition, naphthoquinones with antifungal and larvicidal activities have been isolated from the roots of this plant.⁶ As part of our research program on Cordia species native to Northeast of Brazil,^{8-10,13,14,16-18} the current paper describes the chemical composition of leaf oils of C. leucomalloides and C. curassavica, as well as their larvicidal effects against the mosquito Aedes aegypti, the vector of the yellow fewer and dengue.

Results and Discussion

The list of volatile components and the percentage composition of both oils are shown in Table 1. In the essential oil of C. leucomalloides twenty-three constituents were identified, which represent 98.6% of the total composition. The sesquiterpenoids constitute the dominant fraction (90.6%), with (E)-caryophyllene (15.7%), germacrene D (11.2%), bicyclogermacrene (12.5%) and d-cadinene (17.4%) as the major ones. Likewise, twenty-three constituents were also identified for C. curassavica accouting for 91.2% of the oil composition. The percentage of monoterpenes (47.3%) and sesquiterpenes (43.9%) were approximately the same. a-pinene (20.5%) and b-pinene (13.1%) were the most significant constituents identified in the monoterpene fraction, while (E)-caryophyllene (12.4%) and bicyclogermacrene (13.8%) were the main sesquiterpenes.

Previous studies on leaf essential oil of C. curassavica, from the southeast region of Brazil, showed that the main compounds were a-pinene (29.7%) and (E)-caryophyllene (25.3%). Other terpenoids were also found in significant amounts including allo-aromadendrene (10.0%), a-humulene (4.6%), b-gurjunene (4.1%), spathulenol (2.8%) and bicyclogermacrene (2.7%).⁶ On the other hand, in the oil of C. curassavica from Panama, the most prominent constituent was b-terpinene (32.0%) followed by (E)-caryophyllene (12.0%), camphene (9.0%), germacrene D (9.0%) and a-pinene (6.0%).¹ Despite the compositional differences detected in the three oils samples of C. curassavica from different geographic sites it is important to emphasize the presence of (E)-caryophyllene and a-pinene among the main constituents of both oils of Brazilian origin compared to the high content of b-terpinene solely for C. curassavica of Panamanian origin. a-pinene, (E)-caryophyllene, b-elemene, a-humulene, bicyclogermacrene and d-cadinene are common constituents for C. curassavica of any origin, while camphene is common just to C. curassavica oils from Panama and Northeastern Brazil. It is also important to point out that (E)-caryophyllene, germacrene D and bicyclogermacrene are the major components common for oils from C. leucomalloides and C. curassavica from Northeast of Brazil, but d-cadinene for C. leucomalloides and a- and b-pinene for C. curassavica can distinguish them.

The leaf oils from both investigated Cordia species exhibited significant activity against the third-instar of A. aegypti larvae, showing LC₅₀ of approximately 63.1 ppm for C. leucomalloides and of approximately 97.7 ppm for C. curassavica. The same order of LC₅₀ have been observed previously for the essential oils from Lippia sidoides (63 ppm), Cymbopogon citratus (69 ppm), Ocimum americanum (67 ppm) and O. gratissimum (60 ppm) all considered of high interest for the control of A. aegypti.^19,20 Taking in consideration the LC₅₀ of the mentioned oils and the almost two fold higher toxicity of the oil from C. leucomalloides, relative to C. curassavica, it can be stated that the oil from the former has potential to become a promising natural agent to threat the mosquito life cycle, thus helping in the prevention of dengue fever.

Experimental

Plant material

The leaves of C. leucomalloides (No. 34725) and C. curassavica (No. 34715) were harvested during the flowering stages in January 2005, from Crato County, Ceará, Brazil. Voucher specimens have been deposited at the Herbário Prisco Bezerra (EAC) of the Departamento de Biologia, Universidade Federal do Ceará.

Extraction of the essential oils

The fresh leaves of C. leucomalloides (780 g) were subjected to hydrodistillation in a Clevenger-type apparatus for 2:00 hours to afford 0.07% of a pale yellow oil: - 16° (c = 0.05, CHCl₃), h²⁵ 1.6705. The same procedure were applied to fresh leaves of C. curassavica (900 g) to yield 0.13% of also a pale yellow oil: - 30° (c = 0.05, CHCl₃); h²⁵ 1.6633. The yields (m/m) were calculated based on the fresh weight of the plant materials. The isolated oils, after drying over anhydrous sodium sulfate and filtered were stored in sealed glass vials and maintained under refrigeration before analysis.

Chemical analysis

GC-FID. The quantitative analysis was performed on a Shimadzu GC-17A gas chromatograph equipped with a flame ionization detector using a non-polar DB-5 fused silica capillary column (30 m ´ 0.25 mm i.d., 0.25 µm film thickness). Hydrogen was used as carrier gas at a flow rate of 1 mL min^-1 and 30 psi inlet pressure; split ratio 1:30; the column temperature was programmed from 35 ºC to 180 ºC at a rate of 4 ºC min^-1, then heated at a rate of 17 ºC min^-1 to 280 ºC and held isothermal for 10 min; both injector temperature and detector temperature were 250 ºC.

GC-MS. The analysis was carried out on a Hewlett-Packard Model 5971 GC/MS using a non-polar DB-5 fused silica capillary column (30 m ´ 0.25 mm i.d., 0.25 mm film thickness); carrier gas helium, flow rate 1 mL min^-1 and with split mode. The injector temperature and detector temperature were 250 ºC and 200 ºC, respectively. The column temperature was programmed from 35 °C to 180 ºC at 4 ºC min^-1 and then 180 °C to 250 ºC at 10 ºC min^-1. Mass spectra were recorded from 30 – 450 m/z. Individual components were identified by matching their 70 eV mass spectra with those of the spectrometer data base using the Wiley L-built library and two other computer libraries MS searches using retention indices as a preselection routine,^21,22 well as by visual comparison of the fragmentation pattern with those reported in the literature.^23,24

Larvicidal bioassay

Portions of essential oils (5 to 500 ppm) dissolved in H₂O:DMSO (98.5:1.5) were placed in a beaker (50 mL). 50 instar III larvae of A. aegypti were delivered to each beaker. After 24 hours, at room temperature, the number of dead larvae was counted and the lethal percentage calculated. A control using DMSO and water was carried out in parallel. For each sample, three independent experiments were run. The bioassays were performed at Laboratório de Entomologia, Núcleo de Endemias da Secretaria de Saúde do Estado do Ceará, Brazil.

At the concentrations of 500 and 250 ppm there was 100% larvae mortality for both oils. At 100 ppm the observed mortality was 98.7±0.9 and 50.7±2.0, while at 50 ppm the figures were 9.3±1.2 and 16.0±2.0, for C. leucomalloides and C. curassavica, respectively. This made possible the calculation of the LC₅₀ as 63.1±0.5 and 97.7±1.0, for C. leucomalloides and C. curassavica, respectively.

Acknowledgments

The authors thank the financial support provided by CAPES, CNPq, FINEP, FUNCAP and PRONEX.

Supplementary Information

GC-MS chromatograms of the essential oils from leaves of C. leucomalloides and C. curassavica are available free of charge at http://jbcs.sbq.org.br, as PDF file.

Received: January 10, 2006

Published on the web: July 13, 2006

Supplementary Information

Figure S1

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