Antilisterial Properties of Cilantro Essential Oil

Journal of Essential Oil Research: JEOR, Sep/Oct 2004 by Delaquis, Pascal J, Stanich, Kareen

Abstract

The minimum inhibitory concentrations (MIC) of crude essential oil of cilantro (Coriandrum satwum L.) and four fractions recovered by fractional distillation of the crude oil were determined against strains of LiiieHa monocyioggMgs, Liiieria gray!, Listeria (wiocMa and LiiteHa seeZigeri. Crude oil inhibited all the test strains at concentrations

Key Word Index

Coriandrum, saticum Apiaceae, cilantro, Listeria spp., antilisterial activity, essential oil composition, linalool, (E)-2-decenal, (E)-S-decenol, decanol, decanal, carvone.

Introduction

Recurring outbreaks of food borne illness caused by Listeria monocytogenes have sustained the demand for preservation systems that limit the proliferation of this psychrotrophic pathogen in refrigerated foods. The development of suitable control strategies for this pathogen would benefit from the availability of functional, effective antilisterial preservatives. Several spices, herbs, plant extracts and essential oils are known to inhibit species of the genus Listeria (1-6). Unfortunately, attempts to eliminate or control the growth of L. monocytogenes in foods with antimicrobials from plants often yield disappointing results (3,7-9). Several explanations have been put forward to explain the limited efficacy of plant extracts in food systems. These include, but may not be limited to, insufficient or assumed understanding of mode of action, poor solubility in the aqueous phase, partitioning of the antimicrobials in the lipid phase and loss in activity due to reactions with food components. In addition, effective control of L. monocytogenes in foods often requires concentrations that affect sensory quality due to the aromatic nature of most antimicrobial pliytochcinicals. There is clearly a need for more potent antilisterial agents and for better characterization of their mode of action.

An evaluation of the antimicrobial properties of various plant essential oils by Delaquis et al. (10) revealed that steam distillates of cilantro (the immature plant of Coriandrum sativum L., source of coriander seed) are highly effective against L. monocytogenes. Cilantro oil was also far more potent than the oil derived from coriander seed. To our knowledge, the antilisterial properties of cilantro oils has not been described previously, and the mechanisms underlying inhibition are unknown. The purpose of the present investigation was threefold: to verify the spectrum of activity against several strains of the genus Listeria; to determine which component(s) of cilantro oil are responsible for antilisterial activity; and to determine whether the oil exerts bacteriostatic or bactericidal activity against species from this genus.

Experimental

Microorganisms and cultural methods: Listeria strains and their origins are provided in Table I. Stock cultures were maintained at 40C on plates of Trypticase Soy Broth (BBL, Cockeysville, MD) amended with 5 g/L Yeast Extract and 15 g/L Agar (TSAYE). Active cultures were prepared by transferring cells from the stock cultures to 10 m L of Trypticase Soy Broth amended with 5 g/L Yeast Extract (TSBYE), followed by incubation for 24 h at 30�C. Inocula for experiments were prepared by dilution of the cultures with fresh TSBYE and spectrophotometric (620 nm) adjustment to reach the desired cell densities according to standard curves for each strain (data not shown).

Cilantro oil and oil fractions: Crude cilantro oil was obtained from Northern Essentials Ltd. (Prince Albert, SK, Canada). Several fractions of variable chemical composition were recovered by fractional distillation of the crude oil in batch mode under vacuum using a custom built, proprietary column. Four separate fractions were retained for further study. Chemical composition, provided in Table III, was determined by gas chromatography/mass spectroscopy as described in Delaquis et al. (10). Crude and fractionated cilantro oil fractions were diluted in hexane (approximately 25.0 mg/25 mL). Aliquots (1 �L) were injected with an autosampler (model 7673A, Hewlett Packard, Avondale, PA) into a gas Chromatograph (model HP 5890) equipped with a flame ionization detector and an HP 3396A integrator. Components were separated on a Supelcowax 10 fused silica capillary column (60 m x 0.25 mm, 0.25 �m film thickness) with helium as a carrier gas and nitrogen make-up gas. The column pressure was maintained at 207 kPa (30 psi) and the injector split ratio was set at 20:1. Injector and detector temperatures were both set at 25O0C, and the oven was programmed to increase from 35�0 -200�C at a rate of 3�C/min, followed by a hold time of 10 min. Quantitative data were obtained from area percent data without the use of correction factors.

Mass spectral data were obtained from an HP 5890-5970 GC-MSD system. The mass spectrometer operated with an ion source at 250�C, ionizing energy of 70eV, scan range of 25-250 amu, threshold at 400, and a frequency of 2.6 scans/s. Programming of column and temperature for separation was similar to that applied in the analytical GC-FID, as described above. Individual components were identified using HP G1034C MS ChemStation software containing an HP G1035A Wiley (138.1) PBM library. Where possible, identity confirmation was accomplished by comparing retention times with reference standards (Aldrich Chem. Co., Milwaukee, WI).