Background
Methods
Essential oil samples
Headspace-solid phase microextraction (sHS-SPME) conditions
GC-MS conditions
Antimicrobial assays and chemicals
Bacterial strains
Broth macrodilution test (BDT)
Vapor phase test (VPT)
Results
Headspace-solid phase microextraction - gas chromatographic mass spectrometry (HS-SPME – GC-MS) analysis
Component | RI | Percentage of compounds (%) | ||||||
---|---|---|---|---|---|---|---|---|
1 | 2 | 3 | 4 | 5 | 6 | 7 | ||
α-Pinene | 939 | 1.1 | – | 1.0 | – | 5.7 | 1.4 | 26.1 |
Camphene | 951 | – | – | 2.2 | – | – | – | 7.9 |
β-Pinene | 978 | – | – | – | – | 1.0 | – | 18.0 |
β-Myrcene | 992 | 1.7 | – | 1.9 | – | – | – | – |
α-Phellandrene | 1007 | – | – | – | – | – | 1.2 | – |
α-Terpinene | 1017 | – | – | 1.9 | – | – | – | – |
p-Cymene | 1026 | – | – | 27.9 | – | 6.1 | – | 3.2 |
δ-3-Carene | 1031 | – | – | – | – | – | – | 14.4 |
Limonene | 1044 | – | 12.8 | – | – | 8.2 | – | 17.0 |
1,8-Cineole | 1046 | 17.4 | – | 3.7 | – | 11.1 | 91.0 | – |
γ-Terpinene | 1060 | – | – | 6.5 | – | – | 4.4 | 3.2 |
Terpinolene | 1093 | 3.3 | ||||||
Linalool | 1104 | – | 1.0 | 3.5 | – | 6.7 | – | – |
Isopulegol | 1150 | 1.1 | 1.0 | – | – | – | – | – |
Citronellal | 1153 | – | 42.3 | – | – | – | – | – |
Menthone | 1156 | 19.8 | – | – | – | – | – | – |
Isomenthone | 1159 | 11.6 | – | – | – | – | – | – |
Anethole | 1171 | – | – | – | – | 3.3 | – | – |
Menthol | 1172 | 27.2 | – | – | – | – | – | – |
Isomenthol | 1183 | 3.7 | – | – | – | – | – | – |
α-Terpineol | 1190 | – | 2.2 | – | 1.3 | |||
Pulegone | 1215 | 1.9 | – | – | – | – | – | – |
Citronellol | 1226 | – | 8.9 | – | – | – | – | – |
Nerol | 1230 | – | 12.9 | – | – | – | – | – |
trans-Cinnamaldehyde | 1266 | – | – | – | – | 45.9 | – | – |
Bornyl acetate | 1289 | – | – | – | – | – | – | 4.2 |
Thymol | 1297 | – | – | 46.1 | – | – | – | – |
Isomenthyl acetate | 1305 | 6.6 | – | – | – | – | – | – |
Citronellyl acetate | 1353 | – | 4.6 | – | – | – | – | – |
Neryl acetate | 1365 | – | 3.5 | – | – | – | – | – |
Eugenol | 1373 | – | – | – | 66.9 | 1.4 | – | – |
β-Elemene | 1394 | – | 3.0 | – | – | – | – | – |
β-Caryophyllene | 1417 | 1.3 | – | 2.3 | 26.5 | 5.0 | – | – |
Cinnamyl acetate | 1446 | – | – | – | – | 1.9 | – | – |
α-Humulene | 1452 | – | – | – | 6.0 | – | – | – |
β-Cadinene | 1473 | – | 2.6 | – | – | – | – | – |
β-Muurolene | 1493 | – | 1.5 | – | – | – | – | – |
Total: | 93.4 | 94.1 | 97.0 | 99.4 | 98.5 | 98.0 | 98.6 |
Broth macrodilution test (BDT)
Essential oil |
S. pyogenes
|
S. pneumoniae
|
S. mutans
| |||
---|---|---|---|---|---|---|
MIC | MBC | MIC | MBC | MIC | MBC | |
Cinnamon bark | 0.41 | 0.81 | 0.06 | 0.13 | 0.20 | 0.41 |
Thyme | 0.43 | 0.87 | 0.11 | 0.22 | 0.04 | 0.09 |
Clove | 0.10 | 0.20 | 0.25 | 0.50 | 0.41 | 0.81 |
Peppermint | 0.35 | 0.70 | 0.35 | 0.70 | 0.70 | 1.39 |
Citronella | 0.17 | 0.34 | 0.09 | 0.17 | 0.17 | 0.34 |
Eucalyptus | 2.82 | 5.64 | 1.41 | 2.81 | 0.70 | 1.41 |
Scots pine | 1.35 | 2.71 | 0.68 | 1.35 | 1.35 | 2.71 |
Essential oil |
H. influenzae
|
H. parainfluenzae
|
M. catarrhalis
| |||
---|---|---|---|---|---|---|
MIC | MBC | MIC | MBC | MIC | MBC | |
Cinnamon bark | 0.06 | 0.13 | 0.06 | 0.13 | 0.10 | 0.20 |
Thyme | 0.11 | 0.22 | 0.11 | 0.22 | 0.09 | 0.18 |
Clove | 0.25 | 0.50 | 0.25 | 0.50 | 0.25 | 0.50 |
Peppermint | 0.21 | 0.43 | 0.21 | 0.43 | 0.35 | 0.70 |
Citronella | 0.21 | 0.42 | 0.11 | 0.21 | 0.11 | 0.21 |
Eucalyptus | 1.41 | 2.81 | 0.70 | 1.41 | 2.81 | 5.64 |
Scots pine | 1.35 | 2.70 | 0.34 | 0.68 | 0.34 | 0.68 |
Antibiotic |
S. pyogenes
|
S. pneumoniae
|
S. mutans
|
H. influenzae
|
H. parainfluenzae
|
M. catarrhalis
|
---|---|---|---|---|---|---|
MIC90 | MIC | MIC90 | MIC | MIC | MIC90 | |
Amoxicillin/clavulanic acid | – | – | 0.8 | – | – | 0.2 |
Imipenem | 0.25 | 0.8 | 3.1 | – | – | 0.2 |
Amikacin | – | – | – | 3.1 | 1.6 | – |
Antibacterial activity in vapor phase (VP)
Essential oil |
S. pyogenes
|
S. pneumoniae
|
S. mutans
|
H. influenzae
|
H. parainfluenzae
|
M. catarrhalis
|
---|---|---|---|---|---|---|
MIC | ||||||
Cinnamon bark | 75 | 75 | 90 | 15.62 | 15.62 | 25 |
Thyme | 125 | 90 | 250 | 25 | 31.25 | 50 |
Clove | 225 | 150 | 500 | 90 | 150 | 125 |
Peppermint | 250 | 90 | 375 | 50 | 75 | 31.25 |
Citronella | 125 | 50 | 250 | 50 | 62.5 | 25 |
Eucalyptus | > 1500 | 1200 | > 1500 | 125 | 200 | 225 |
Scots pine | > 1500 | > 1500 | > 1500 | 500 | > 1500 | > 1500 |
Discussion
Essential oil | Liquid phase | Vapor phase |
---|---|---|
Cinnamon bark | 1, 2, 3, 4, 5, 6 | 1, 2, 3, 4, 5, 6 |
Thyme | 1, 2, 3, 4, 5, 6 | 2, 4, 5, 6 |
Clove | 1, 2, 3, 4, 5, 6 | 4 |
Peppermint | 1, 2, 4, 5, 6 | 2, 4, 5, 6 |
Citronella | 1, 2, 3, 4, 5, 6 | 2, 4, 5, 6 |
Eucalyptus | – | – |
Scots Pine | 5, 6 | – |