Chemical Composition of Leaf and Inflorescence Essential Oils of Eupatorium cannabinum L. from Eastern Lithuania

Abstract

Content and composition of the essential oils of Eupatorium cannabinum L. have been studied. The plants were collected on Neris riverbank in Vilnius district at full flowering stage; oils were prepared by hydrodistillation and analyzed by GC and GC/MS. Germacrene D has been found as a first principal component in five out of six investigated oils (9.1-12.3%) and in one flower oil as third main compound (7.7%). Neryl acetate was a second major constituent in all leaf oils (average mean: 9.4%) and in two samples of inflorescence oils (7.9% and 8.2%), while another ester neryl isobutyrate was the third dominant component in one flower oil. Methyl thymol was the first main compound in one flower oil and the fourth in all investigated leaf oils (average mean: 5.7%). β-Bisabolene comprising 7.1% and 5.6% was second or fourth constituent in two inflorescence, and as third compound (6.7% and 8.6%) in two leaf oils. Seventy-nine identified compounds formed up 71.9-83.8% of total oil content. Monoterpenes and oxygenated monoterpenes dominated both in the inflorescence and leaf oils (36.9-59.3% and 36.5-44.3%, respectively), while the amount of sesquiterpenoids was 22.7-31.8% in the flower and 31.7-38.3% in leaf oils.

Key Word Index

Asteraceae, Eupatorium cannabinum, essential oil composition, germacrene D, neryl acetate, methyl thymol.

Introduction

The genus Eupatorium (tribe Eupatorieae) comprises of about 600 species and spreads worldwide (1), many of which can be found in the American tropical regions (2). The type species, Eupatorium cannabinum, populates wide regions in North America, Europe, Eastern Asia, Taiwan and Philippines (3).

Eupatorium cannabinum L. is the only species, which grows in Lithuania (1). The plant is perennial, of 50-170 cm height, grows in wet, limey and fertile soil near the water, and is common over the entire country.

For decades, the plant was used in Lithuanian folk medicine as aremedyfortreatmentliverdiseases and diarrhea. Nowadays, the plant is widely used in homeopathy. Pharmacological activity (immunological, antibacterial, cytostatic etc.) of E. cannabinum is mainly determinated by flavonoids (4), polysaccharides (5), nontoxic alkaloids and sesquiterpene lactones (eupatoriopicrin is one the most investigated) (6,7).

Essential oils make a major contribution into the biological activity of the plant as well. The chemical composition of E. cannabinum oils and their antibacterial activity were investigated by Italian scientists (8) . In this study, 59 compounds were identified, germacrene D (33.5%) was the majorconstituent and appreciable amounts of α-farnesene (12.9%) and δ-2-carene (6.5%) were detennined in the oils. Among the oxygenated compounds elemol (2.8%) and α-cadinol (2.7%) were the most abundant. The oils showed antibacterial activity against gram-positive bacteria.

In another study, the fungistatic and bacteriostatic activities of E. cannabinum oil, which was rich in lactones, were investigated (9). The authors determined that cyperone (16.9%), (E, E)-α-farnesene (12.3%) and spathulenol (6.1%) were the principal constituents in their oil.

The fungitoxic and cytotoxic properties of E. cannabinum oils have been reported in other studies (10,11,12).

The chemical composition of the inflorescence and leaf oils of E. cannabinum collected in Lithuania was reported earlier (13). Amongthe most abundant constituents were germacrene D (11.7-25.6%), neryl acetate (tr.-8.9%), β-bisabolene (0-8.0%) and β-ylangene (0.6-6.2%) in the oils.

The oils of E. cannabinum fresh leaves collected from North India were investigated (14). Caryophyllene oxide has been found as a main component (28.5%) among the 14 identified compounds in this study.

Hendriks et al. (15) have analyzed oil of the flowering tops of E. cannabinum and they reported more than 60 constituents (without indicating relative percentage composition), among which various mono- and sesquiterpene esters were determined.

The composition of oils of E. cannabinum collected from Corsica and Tuscany were investigated (16,17). Eighty-three constituents were identified in leaves and flowers/fruits oils of the plants collected in south Tuscany (17). Germacrene D was reported as a principal constituent (29.2% and 20.3% in leaf and flower oil, respectively). The main oxygenated compounds in leaf and flower oil were methyl thymol (7.8% and 12.2%) and spathulenol (7.3% and 10.8%). Other constituents in appreciable amounts were bornyl acetate, thymol hydroquinone methyl ether, β-caryophyllene, caryophyllene oxide, bicyclogermacrene, β-bisabolene etc.

α-Terpinene (17.8%), germacrene D (9.1%) and methyl thymol (5.2%) were indicated as the major components in the study of the oil of aerial parts of E. cannabinum from Iran (18).

The aim of the present work is to study chemical composition of the oils of E. cannabinum growing in Eastern Lithuania.

Experimental

The aerial parts (up to -50 cm) of E. cannabinum plants (0.1-0.3 kg) grown on Neris riverbank in Eastern Lithuania, Vilnius district (Mikailiskes) were collected in August 1999-2001.