Essential Oils from Ocotea austinii C. K. Allen (Lauraceae) from Costa Rica

Abstract

The composition of the essential oil from leaves and twig wood of Ocotea austinii growing wild in Costa Rica was determined by capillary GC/FID and GC/MS. Seventy-six and seventy-seven compounds were identified in the leaf and twig wood oils corresponding to about 99.8% and 98.3% of the total amount of the oils, respectively. The leaf oil consists mainly of terpene hydrocarbons (87.5%) and oxygenated terpenes (11.8%). The major components of the leaf oil were α-pinene (33.2%), β-pinene (13.0%) and δ-cadinene (5.7%). The wood oil also consisted mainly of terpene hydrocarbons (67.4%) and oxygenated terpenes (29.9%). The major components of the wood oil were α-pinene (14.9%), β-pinene (8.2%), β-eudesmol (9.1%), α-eudesmol (8.8%) and viridiflorene (5.0%)

Key Word Index

Ocotea austinii, Lauraceae, essential oil composition, α-pinene, β-pinene.

Introduction

The genus Ocotea (Lauraceae) is widely represented in the American tropics with 300-400 species and it is the largest genus of diis family in Mesoamerica with 102 species (1). 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 the individuals occur in high abundance and diversity (2,3). 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 austinii C. K. Allen (Syn. Ocotea irazuensis Lundell) is a tree endemic to central Costa Rica. It is popularly known as ira, ira colorado and ira rosa (4). The geographic distribution of the species includes the central volcanic mountain range from Palmira (Province of Alajuela) in the north, tiiroughout the western part of the Talamanca mountain range (near Santa María de Dota and Empalme, Province of San José) (1). Ocotea austinii is a canopy species, and frequendy emergent. The greatest abundance of the species is found in the higher montane, wet evergreen forests formations, characterized by the presence of Quercus spp. This tree (O. austinii) grows in well-drained plateaus or flatlands of volcanic origin, with small slopes in an elevation range of 1700 to 3000 m, temperatures between 6°-20°C, and an annual rainfall between 3500 and 8000 mm (5). As happens widi otiier Ocotea species (6) the timber of this tree is excellent for making furniture and general construction.

Previous Work

Many phytochemical investigations have been performed on plants of the genus Ocotea. These plants are well known as a source of benzylisoquinoline alkaloids, lignans, neolignans and phenylpropanoids (7-14). The chemical composition of the volatile oils of some Ocotea species have been the subject of several studies (15-28).

To the best of our knowledge no previous reports on the composition of the oils of Ocotea austinii have been published.

Experimental

Plant material: Fresh leaves and twigs of Ocotea austinii C.K. Allen (Syn. Ocotea irazuensis Lundell), Lauraceae, growing wdd in Costa Rica were collected in March 2001, in the Turrialba volcano slopes, Province of Cartago, Costa Rica, in an ecological life zone called Lower Montane Moist Forest (29). A voucher specimen was deposited at the Herbarium of the University of Costa Rica at the School of Biology (herbarium number USJ-77418).

Oil isolation: The leaves and dried twig wood were subjected to hydrodistiUation for 3 h using a modified Clevengertype apparatus. The distilled ods were collected and dried over anhydrous sodium sulfate and stored in a freezer (0°-10°C). The yield of the colorless oil from the leaf was 0.1% (v/w) and from the wood 0.2% (v/w).

General analytical procedures: GC analysis. The oils of O. austinii were analyzed by GC/FID using a Shimadzu GC-17 gas Chromatograph. The data were obtained on a 5% phenyl- 95% mediylpolysiloxane fused silica capillary column (30 m x 0.25 mm; film thickness 0.20 pm), Hefiflex (Adtech) AT-5, with a Shimadzu Class-VP, version 4.3 software. Operating conditions were: carrier gas N^sub 2^, flow 1.0 mL/min; oven temperature program: 60°-220°C at 3°C/min, 220°C (10 min); sample injection port temperature 250°C; detector temperature 275°C; split 1:50.

GC/MS analysis: The analysis by GC/MS was performed using a Shimadzu GC-17A gas Chromatograph coupled with GCMS-QP5050 apparatus and CLASS 5000 software with Wiley 138 computer database. The data were obtained on a 5% phenyl- 95% methylpolysdoxane fused silica capillary column (30 m x 0.25 mm; film thickness 0.25 µm). Operating conditions were: carrier gas He, flow 1.0 mL/min; oven temperature program: 60°-240°C at 3°C/min; sample injection port temperature 250°C; detector temperature 260°C; ionization voltage: 7OeV; ionization current 60 µA; scanning speed 0.5 s over 38-400 amu range; split 1:70.

Identification: Identification of the components of the oils was performed using the retention indices on DB-5 type column, and by comparison of tiieir mass spectra with tiiose published in the literature (30-32) or those of our own database. Integration of the total chromatogram, expressed as area percent, has been used to obtain quantitative compositional data.