Determination of chemical composition, antioxidant properties and antimicrobial activity of coriander seed essential oil on a number of pathogenic microorganisms

Essential oils and secondary metabolites of plants have too many uses in medicine as well as food and hygiene industries. The herbal essential oils include different health features including antioxidant and antibacterial activities. Several forms of the activated oxygen, also known as reactive oxygen species (ROS), include free radicals and non-free radical species. In traditional Iranian medicine, coriander seeds are widely used to treat the disease. The objectives of this paper were to identify the chemical compounds and to measure the phenol content and the antioxidant potential of coriander seed essential oil in addition to its free radical scavenging activity. The other aim of this work was to investigate the antimicrobial of coriander seed essential oil on Bacillus cereus, Salmonella typhi, Escherichia coli and Pseudomonas aeruginosa “in vitro”.

In this research, the coriander seed essential oil (100 g) was extraction using water-distillation method with clevenger apparatus. Afterwards, coriander seed essential oil was collected in vials which had already been weighed by a 0.0001 balance and stored at 4 °C until testing. Chemical composition of coriander seed essential oil was determined using gas chromatography. The antioxidant activity was determined by 2,2’-azinobis (3-ethylbenzothiazoline-6-sulphonic acid) di-ammonium salt (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicles, respectively. The method of Folin-Ciocalteu was performed through determination of TPC. The result was reported as mg of gallic acid/g of the dried coriander seed essential oil. The antioxidant potential of the essential oil was compared with BHA synthetic antioxidant at a concentration of 100 μg/ml. Antibacterial activity of coriander essential oil was determined by disc diffusion agar (Kirby-Bauer test), minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) methods.

Based on the results of chemical analysis, the coriander seed essential oil was rich in oxygenated monoterpenes (89.94%). The main compound of coriander seed essential oil was Linalool (76.75%). The highest percentage of free radical scavenging for DPPH was 53.5% and for ABTS 66.6% at 900 ppm concentration. The total phenol content essential oil was 38.04 ± 0.02 mg GAE/g. The result show that, the most sensitive and the most resistant bacteria with diameter inhibition zone 30.30 mm and 23.15 mm were Bacillus cereus and Salmonella typhi respectively. MIC of coriander seed essential oil for Bacillus cereus, Salmonella typhi, Escherichia coli and Pseudomonas aeruginosa was 2, 4, 4 and 4 mg/ml respectively. MBC of coriander seed essential oil for Bacillus cereus, Salmonella typhi, Escherichia coli and Pseudomonas aeruginosa was 512, > 512, > 512 and 512 mg/ml respectively. In general, the results indicated that the coriander seed essential oil was effective on microorganisms; nevertheless, the extent of its effectiveness varied depending on the type of microorganism. The gram-positive bacteria are more sensitive to essential oil rather than gram-negative ones. The higher resistance of gram-negative bacteria to the essential oils of medicinal plants could be attributed to the more complex structure of the cell membrane of these bacteria compared with the single layer structure of the gram-positive ones. The results of this study revealed that coriander seed essential oil had less antioxidant activity than synthetic antioxidant BHA. Antibacterial activity of the essential oil was higher than the gentamicin antibiotic. Regarding the chemical compositions identified in the coriander seed essential oil, these compositions could be employed as an important economical source uses in medicine as we as food and hygiene industries.