Analysis of the Essential Oil of Oenanthe crocata L. and Its Biological Activity

Journal of Essential Oil Research: JEOR, May/Jun 2004 by Bonsignore, L, Casu, L, Loy, G, Deidda, D, Genco, F

Abstract

The chemical composition of the essential oil of the seeds of Oenanthe crocata, an endemic plant of Sardinia and Corsica, has been studied by analytical and spectroscopic methods. Some terpenes, 1,8-cineole, camphor, 1-octyn3-ol-3-niethyl, 8,10-heptadecadiene-4,6-diyne-1,12-diol have been isolated. The cytotoxic, antiviral and antimicrobic activities of the oil have also been evaluated. The oil did not show a significant antiviral activity, but showed a moderate antibacterial activity against Streptococcus faecalis and Bacillus lentus.

Key Word Index

Oenanthe crocata, Apiaceae (Umbelliferae), hemlock water dropwort, essential oil composition, 1,8-cineole, antimicrobial activity, toxicity assessment.

Introduction

Oenanthe crocnta is an endemic plant of Sardinia and Corsica. It belongs to the Apiaceae (Umbelliferae) family and grows in wet zones, marshes, and swamps at altitudes of between O and 1000 m. The oil of this plant is little studied, but its extracts are well known for their high toxicity (1-23). In fact, this plant produces a toxin of the picrotoxin group called oenanthotoxin, which when ingested is capable of causing convulsions followed by lethal coma. Its morphological characteristics are hemicryptophytic with leaves similar to parsley, roots with more or less ovoid tubers, tubulous and fluted stem, and 3/4 pennatifid lower leaves with cuneate segments; the 2/3 cauline leaves are pinnate with thinner segments that evolve into linear. The umbels have 10/40 radii with a thin 4/6 mm fruit with elongated styli (24-26). The plant was picked in the balsamic period (June-July) along the river Bonorchis, in the territory of Abbasanta (Nuoro), more precisely in the area between 4°83' and 4°84' W longitude and 44°44' and 44°45' N latitude. All the samples have been identified by M. Ballero of the Department of Botanical Sciences of the University of Cagliari, and one sample was catalogued and preserved in the department Herbarium.

Experimental

Materials and methods: The seeds were accurately separated from the plant and dried on a flat surface away from light and humidity taking care not to overlap them. Water distillation was carried out in a Clevenger-type still with a few alterations: in particular, the separator was moved away from the boiler to avoid thermal shock to the distilled oil; moreover, the separator was incorporated in a liebig-type refrigerant so that the distillate could be kept at room temperature for the entire experiment. Three hundred and fifty grams of seeds in 11 of water were placed in a boiler to obtain 3.4 g of oil after about three hours distillation. The oil was then dried with molecular sieves and stored in dark vials at 4°C. The oil, which was amber, with [n]^sup 20^= 1,4334, [[alpha]]^sup D^= + l,4, bp=192°C, was obtained with 0.97-1.0% yield.

GC/FTIR: A Chromatographie analysis was carried out using a gas Chromatograph interfaced with FID and FTIR detectors (Perkin Elmer System 2000). The chromatograph is equipped with a J&W Scientific DB-5 (30 m × 0.25 min, 0.25 µm film thickness) with an injector at 300°C, an FID detector at 280°C and an FTIR detector at 200°C. The starting temperature is programmed at 60°C, and increased by 3°G/niin up to 25O0C. The carrier was helium with a flow of 1 mL/min and a split ratio of 1:20. A 0.5 µL aliquot of a solution of oil was injected in diethyl ether. We obtain a Gram-Schmidt interferogram with which we record the IR absorption spectra of all the highlighted peaks (27). At this phase we could already identify a few components by comparing their respective IR spectra with those obtained with standard samples at the same conditions. Quantitative analysis was carried out on a computer by calculating the peak area normalization with the response factor method (28). The list of identified compounds is reported in Table I.

GC/MS: GC/MS analyses were carried out with a Garlo Erba 5300 Chromatograph interfaced with a Cx)MD 1000 mass (Fisons). The Chromatograph column and the operating conditions were identical to those reported for the GC/FTIR analysis. We obtain the Chromatograph of the components and their related mass spectra. By comparing the fragmentations of the examined compounds with those of the authentic samples, it was possible to confirm the structures assigned by GC/FTIR; moreover it was possible to identify other components through the study of mass fragmentations and their related IR absorptions.

SPME/GC/Mass: We also studied the headspace volatiles of the oil. The sample was prepared in a vial where crystalline sodium chloride was added and kept under magnetic stirring at room temperature. [Lambda] syringe equipped with an 85 [mu][eta][iota] PA fibre (Polyacrylate, Supelco) was introduced and suspended in the headspace for 2 min of extraction and 3 min of thermal deabsorption. Chromatography then proceeds in a DB-5 capillary column, programmed with a starting temperature of 40°C, an increase of 3°C/min up to 120°C, a 15 min isotherm, and then an increase of 10°C/min up to 250°C.