Essential oil of trees of the genus Ocotea ( Lauraceae ) in Costa Rica . I . Ocotea brenesii

The chemical composition of the essential oils from leaves and wood of Ocotea brenesii Standl. growing wild in Costa Rica was determined by capillary GC/FID and GC/MS. From the leaves, 64 compounds were identified, corresponding to 85.9% of the oil, and from the wood 57 compounds were identified corresponding to 69.0% of the oil. The major constituents identified in the leaf oil were α-copaene (21.1%), δ-cadinene (9.2%), spathulenol (7.3%), globulol (5.6%) and β-caryophyllene (5.2%). The major constituents of the wood oil were α-copaene (6.6%), caryophyllene oxide (6.3%), β-caryophyllene (6.1%) and humulene epoxide (4.6%). Rev. Biol. Trop. 53(3-4): 431-436. Epub 2005 Oct 3.

The Lauraceae is a family of about 2000-2200 species of mostly tropical trees.The family is an important component of cloud forests in Costa Rica where they occur in high abundance and diversity (Burger andvan der Werff 1990, Haber 1996).This family is recognized by the simple, alternate, stiff and aromatic elliptic to obovate leaves, and by the fruits often borne in a cup.
Ocotea is a genus of 300-400 species growing mainly in the American tropics.The genus Ocotea belongs to the family Lauraceae and it is the largest genus of this family in Mesoamerica with 102 species (van der Werff 2002).
Ocotea brenesii is a tree of evergreen montane forest formations, from 700 to 2000 m elevation.The geographic distribution in Costa Rica ranges from near the "Alberto M. Brenes" Biological Preserve, San Ramón, to the area between Poás and Barva volcanoes in Alajuela Province (Burger and van der Werff 1990) and also is reported in Panama (van der Werff 2002).O. brenesii is recognized by the relatively broad leaves with a few secondary veins that appear thin in texture and dark in color when dry.Also it is characterized by racemose inflorescences and appressed indumenta on the young twigs (van der Werff 2002).
To the best of our knowledge no previous reports on the chemical composition of the oils of O. brenesii have been published.The leaves and dried wood were subject to hydrodistillation for 3 h using a modified Clevenger-type apparatus.The distilled oils were collected and dried over anhydrous sodium sulphate and stored in a freezer (0-10°C).The yield of the colorless oil from the leaf was 0.06% (v/w) and from the wood 0.02% (v/w).
Identification of the components of the oils were performed using the retention indices on DB-5 type column, and by comparison of their mass spectra with those published in the literature (McLafferty 1993, Adams 1995, 2001) or those of our own database.Integration of the total chromatogram, expressed as area percent, has been used to obtain quantitative compositional data.

RESULTS
The chemical compositions of the leaf and wood oils of O. brenesii are presented in Tables 1 and 2. As it can be observed, 64 components were identified from leaves, representing ca.86% of the oil.Sesquiterpenic hydrocarbons were the main constituents (53.4%) of the oil and contained α-copaene (21.1%), δ-cadinene (9.2%) and β-caryophyllene (5.2%) as the main compounds.The second group in quantity was constituted by oxygenated sesquiterpenes (29.9%); spathulenol (7.3%) and globulol (5.6%) are the main constituents.

DISCUSSION
There are several reports on the composition of the oils of plants of the genus Ocotea from South America (Mors 1959, Gottlieb and Magalhães 1960, Gottlieb et al. 1960a, 1960b, Brooks and Campbell 1969, Gottlieb et al. 1981, de Díaz et al. 1991, Reynolds and Kite 1995, Lorenzo et al. 2001, Bruni et al. 2004) and Africa (Terreaux et al. 1994, Menut et al. 2002).The majority of them are characterized by the presence of phenylpropanoids like safrole and O-methyleugenol, cinnamaldehydes and some other benzenoid derivatives.The results obtained in this study showed that the oils of O. brenesii are characterized by compounds of terpenic chemical nature and are lacking of phenylpropanoids or benzenoid constituents that are typical of the majority of the Ocotea essential oils investigated previously.

ACKNOWLEDGMENTS
The authors are grateful to Vicerrectoría de Investigación (UCR) (Project 809-A4-006) for financial support, to L. J. Poveda (Escuela de Ciencias Ambientales, UNA, Heredia) for the botanical identification, to L. Hernández (CIPRONA) for her technical assistance and to N. R. Farnsworth (College of Pharmacy, University of Illinois, USA at Chicago) for his help to access the NAPRALERT database.

TABLE 1
Percentage composition of the leaf oil of Ocotea brenesii