Essential Oils from Bolivia. I. Asteraceae: Baccharis tricuneata (L.f.) Pers. var. ruiziana Cuatrecassas

Journal of Essential Oil Research: JEOR, Sep/Oct 2004 by Arze, Javier Bernardo Lopez, Garneau, Fran�ois-Xavier, Collin, Guy, Jean, France-Ida, Gagnon, H�l�ne

Abstract

The essential oil of the aerial parts of Baccharis tricuneata var. ruiziana (Asteraceae) from Bolivia was analyzed by GC and GC/MS. The oil is characterized by a high percentage of (E)-nerolidol (~68%) and the presence of several minor constituents composed mainly of monoterpenes (~16%), followed by sesquiterpene hydrocarbons (~5%) and oxygenated sesquiterpenes (~3%).

Key Word Index

Baccharis tricuneata, Asteraceae, essential oil composition, (E)-nerolidol.

Introduction

The Bolivian flora has a rich biodiversity and a major part of it is relatively unknown. This series of papers aims to shed light on a small part of its potential: the essential oils. To the author's knowledge very little information is available on Baccharis tricuneata, at least on a chemical basis.

The chemical composition of essential oils from various Baccharis species have been studied. For example Loayza et al. published a paper on the oils of B. dracunculifolia, B. salicifolia and B. latifolia from Bolivia (1). Several other Baccharis oils from Brazil are also known (2-5) as well as from Argentina (6). One of them, the vassoura oil, seems to be available on the market (7,8).

Recently, several papers have been published from various laboratories. Several oils from various Baccharis were mainly constituted of monoterpenes. The main constituents of the oil of B. uncinella DC. were [alpha]-pinene (16%), [beta]-pinene (15%), limonene (13%), and spathulenol (10%) (9). Those of B. notosergila were similar and they were [alpha]-pinene (25.9%), limonene (19.7%), [beta]-caryophyllene (16.9%), and spathulenol (6.7%) (10). In the case of B. rufescens, limonene (14.4%) and (E)-nerolidol (14.5%) were the main compounds of the oil (11).

Other oils showed predominantly the presence of sesquiterpenes. Thus, the oil obtained from B. coridifolia contained: isocaryophyllene (34.3%), [beta]-caryophyllene (10.8%), caryophyllene oxide (9.8%) and [beta]-selinene (8.2%) (12). The major compounds observed in the oil of the aerial parts of B. cordobensis were (E)-nerolidol (15.8%), T-cadinol (14.7%) andcubenol (8.8%) (13). The major constituents for B. articulata [[beta]-caryophyllene (16.9%) and (E)-nerolidol (15.6%)], B. myrtilloides [germacrene D (9.5%)], B. crispa [(E)-nerolidol (27.0%)], and B. salicifolia [[alpha]-cadinol (9.4%) and germacrene D (8.8%)] belong to the same group (12,14).

In this field, it is difficult not to quote the long list of Bohlmann's publications appearing in the 1980s and 1990s (15-27). All these papers deal with solvent extracts. Various types of molecules such as esters, the diterpenes germacrene, labdane, cadinene, kovalane, clerodane in addition to glycosides and furanoid derivatives were identified. Solvent extracts from B. tricuneata were also analyzed (28,29). Particularly, root extracts obtained from Baccharis tricuneata var. ruiziana showed the presence of tremetone and 6-hydroxytremetone (15). These molecules were not observed in the present study (see below). On the other hand, to the best of our knowledge, the chemical composition of the oil of B. tricuneata has not been reported until now.

Experimental

Plant material: Baccharis tricuneata var. ruiziana Cuatrecasas (local name: T'ola enana) is an erect shrub until one meter tall, dioic, deeply branched, with glandular, resinous, aromatic leaves. Altern leaves, ovate-oblong blades or ovate linear blades, three to five margen dentate, small peciol, capitulum with narrow involucre. Occurs in cloud forests between 3200-4500 m above sea level, it grows in hill hangs, plaine grounds, open and humid places. Plant material (1,120 g) was collected in Salto B, in the tropical zone (Chapare) of the Province of Cochabamba (altitude: 3,200 m above sea level). Voucher specimens have been deposited in the National Forestal Herbarium Martin Cardenas of the Universidad Mayor de San Simon.

Oil isolation: The oil was obtained by steam distillation from the aerial parts (leaves and stems), at atmospheric pressure, during 1.5 h, obtaining 6 mL of the oil.

GC and GCMS: GC analyses were done on an HP5890 gas chromatograph equipped with a polar Supelcowax 10 column (30 m x 0.25 mm, film thickness 0.25 �m) and a nonpolar DB-5 column (30 m x 0.25 mm, film thickness 0.25 �m). The temperature program was 40�C for 2 min, then 2�C/min to 210�C, and held constant for 33 min. The compounds were identified by their retention indices on both columns and by GC/MS. GC/MS analyses were done on an HP5972 MSD mass spectrometer at 70 eV coupled to an HP 5890 gas chromatograph. The GC/MS analyses were performed on both columns, polar and nonpolar with the same oven operating conditions. Retention indices and mass spectra were compared to those of the literature (30) and to our own databases.

Results and Discussion

The yield of oil was 0.54% (vol/weight), in fresh material. Its relative density was 0.8834 (20/20), its refractive index was 1.4815 and its optical rotation was 11.40 (pure oil at 20�C).

The oil of B. tricuneata var. ruiziana was characterized by a high percentage of (E)-nerolidol (~68%). Such alarge amount is not uncommon in an essential oil. Thus, Cabreuva oil contains up to 80% nerolidol (31). Nevertheless, for nerolidol, this is a rather rare situation although its presence in lower concentration is very common. For example, the oil of B. dracunculifolia from central Brazil contained up to 21% of this compound (2) and B. crispa oil from Argentina (7) or B. myrtylloides (11) may have even more nerolidol (~27%). The commercially available vassoura oil was reported to contain 15% of the same sesquiterpene (6). In our previous study of three Baccharis species, B. salicifolia, B. latifolia and B. dracunculifolia from Bolivia, the nerolidol percentage was of lesser importance (0-3.5%) (1).