Table 2.
Antimicrobial activity of essential oils against Listeria monocytogenes NCTC 11994 and L. monocytogenes S0580 by paper disk diffusion method
| L. monocytogenes NCTC 11994 | L. monocytogenes S0580 | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 11 | 1/21 | 1/101 | 1/201 | 1/401 | 1 | 1/2 | 1/10 | 1/20 | 1/40 | |
| Essential oils | Diameter of inhibition zone (mm)2 | |||||||||
| Cinnamomum cassia | 33.8 ± 0.2a | 30.1 ± 0.5a | 25.4 ± 0.1a | 14.6 ± 0.8a | 8.9 ± 0.3a | 34.1 ± 0.3a | 28.4 ± 0.8a | 23.1 ± 0.4a | 16.6 ± 0.7a | 8.5 ± 0.4a |
| Cymbopogon flexuosus | 34.8 ± 0.3b | 24.3 ± 0.8b | 9.1 ± 0.1b | 8.2 ± 0.2b | 7.1 ± 0.1b | 34.0 ± 0.3a | 26.0 ± 0.4b | 8.3 ± 0.2b | 7.9 ± 0.1b | – |
| Cymbopogon nardus | 11.8 ± 0.6c | 10.5 ± 0.3c | – | – | – | 10.8 ± 0.3b | 8.9 ± 0.3c | – | – | – |
| Coriandrum sativum | 11.7 ± 0.6c | 8.0 ± 0.5d | – | – | – | 10.6 ± 0.4b | 7.3 ± 0.5d | – | – | – |
| Cinnamomum verum | 34.0 ± 0.4a | 28.5 ± 0.2e | 21.9 ± 0.6c | 8.7 ± 1.0c | – | 34.0 ± 0.5a | 27.9 ± 1.0e | 17.6 ± 0.8c | 8.7 ± 0.2c | – |
| Eugenia caryophyllus | 14.9 ± 0.5d | 11.3 ± 0.8f | 8.8 ± 0.5b | 7.0 ± 0.9d | – | 14.4 ± 0.1c | 12.7 ± 0.2f | 7.0 ± 0.1d | – | – |
| Kaempferia galanga | – | – | – | – | – | – | – | – | – | – |
| Origanum compactum | 26.8 ± 0.6e | 22.6 ± 0.3 g | 11.1 ± 0.3d | 8.7 ± 0.1c | 7.5 ± 0.3b | 26.8 ± 0.5d | 24.3 ± 0.7 g | 11.4 ± 0.4e | 8.7 ± 0.2c | 7.8 ± 0.1b |
| Origanum heracleoticum | 31.5 ± 0.3f | 25.9 ± 0.3 h | 18.1 ± 0.2e | 12.7 ± 0.2e | 10.0 ± 0.2c | 31.1 ± 0.5e | 27.4 ± 0.5e | 17.6 ± 0.3c | 12.8 ± 0.1d | 9.9 ± 0.1c |
| Origanum majorana | 10.9 ± 0.2 g | – | – | – | – | 11.0 ± 0.2b | 7.0 ± 0.1d | – | – | – |
| Salvia officinalis | 10.3 ± 0.2 g | 8.4 ± 0.4d | – | – | – | 8.8 ± 0.2f | 7.2 ± 0.3d | – | – | – |
| Salvia sclarea | 10.4 ± 0.9 g | 7.2 ± 0.3i | – | – | – | 9.8 ± 0.3 g | 7.0 ± 0.1d | – | – | – |
| Thymus capitatus | 30.2 ± 0.7 h | 23.6 ± 0.3j | 15.6 ± 0.3f | 11.8 ± 0.2f | 9.9 ± 0.2c | 29.3 ± 0.8 h | 24.6 ± 0.6 g | 16.9 ± 0.4f | 12.5 ± 0.2d | 10.2 ± 0.2c |
| Thymus mastichina | 9.5 ± 0.4i | – | – | – | – | 10.8 ± 1.1b | 7.0 ± 0.1d | – | – | – |
| Thymus vulgaris thymoliferum | 30.3 ± 0.6 h | 27.5 ± 0.7k | 13.0 ± 0.4 g | 9.8 ± 0.4 g | 8.0 ± 0.1d | 32.6 ± 0.4i | 29.0 ± 0.4 h | 13.6 ± 0.5 g | 9.9 ± 0.2e | 8.3 ± 0.1a |
| Ampicillin3 | 33.7 ± 1.2 | ND | ND | ND | ND | 33.4 ± 0.4 | ND | ND | ND | ND |
| Chloramphenicol3 | 27.8 ± 1.0 | ND | ND | ND | ND | 26.7 ± 0.6 | ND | ND | ND | ND |
| Streptomycin3 | 18.9 ± 0.6 | ND | ND | ND | ND | 21.6 ± 0.4 | ND | ND | ND | ND |
| Blank control (ethanol) | – | – | – | – | – | – | – | – | – | – |
(–)
Diameter of inhibitory zone <7 mm considered as no antimicrobial activity. ND, not determined.
1
Concentrations (1, 1/2, 1/10, 1/20, 1/40) used were v/v.
2
Values are mean diameter of inhibitory zone (mm) ±SD of five replicates, followed by different letters in column are significantly different (P < 0.05). The diameter of paper disk (6 mm) is included.
3
Ampicillin (10 μg), chloramphenicol (30 μg), and streptomycin (10 μg) used as positive control.