Table 2.
Examples of terpene compounds in essential oils with the potential antimicrobial effects.
| Classes | Compounds | Plant | Microorganism strain | Antimicrobial effects | Type of assay | Reference |
|---|---|---|---|---|---|---|
| Monoterpene hydrocarbons | Myrcene | PC | Enterococcus faecalis (ATCC 29212), Streptococcus mutans (ATCC 25175), S. mutans (ATCC 35668), S. mutans (ATCC UA159), and Lactobacillus rhamnosus (ATCC 53103) | Bacterial growth (MIC > 8 × 102 CFU/ml) | Agar dilution | (Chaves-Quirós et al., 2020) |
| Terpineols Monoterpene | α-Terpineol | PC | Escherichia coli (CICC 21530), Shigella flexneri (CICC 21534), and Salmonella enterica (CICC 21513) | Good inhibitory effects against several gram-negative bacteria (MIC 1.531, 0.766, and 1.531 mg/ml) | Two-fold dilutions | (Huang et al., 2021) |
| Tropolone monoterpene | Hinokitiol | PC | Bacillus subtilis, S. aureus, E. coli, and Pseudomonas aeruginosa | (MIC 80, 160, 80, and 320 mg/ml) | Agar dilution | (Suzuki et al., 2019) |
| Bicyclic monoterpene | Borneol | Purity ≥ 98% | E. coli (ATCC 43894), Listeria monocytogenes (ATCC 19118), S. aureus (ATCC 23235), P. aeruginosa (ATCC 27853) | Bacteriostatic activity (MIC 1.25, 5, 5, 10 mg/ml) | Double microdilution | (Wang et al., 2021) |
| Terpenophenol | Bakuchiol | PC | S. aureus (ATCC29213), MRSA N315, MRSA NCTC10442, E. coli (ATCC25922), P. aeruginosa (ATCC9027), Acinetobacter baumannii (ATCC17978), A. baumannii (R2889), Klebsiella pneumoniae (ATCC10031), K. pneumoniae (ATCC14581) | Antibacterial activity (MIC 6.25, 3.125, 3.125, > 100, >50, >50, >50, 12.5, and > 50 μl/ ml) | Broth dilution method | (Li et al., 2021) |
| Cyclic monoterpene | d-Limonene | PC | E. coli (ATCC 8739), S. aureus (ATCC 6538), B. subtilis (ATCC 6633), Saccharomyces cerevisiae (ATCC 9763) | Exhibit strong synergistic (MIC 1, 1, 1, and 0.5 µg/ml) | Serial Dilution | (Zahi et al., 2017) |
| Acyclic monoterpene Alcohol | Geraniol | PC | B. cereus (MTCC 430), E. coli(MTCC 443) | Antimicrobial effect (MIC 1200 µl/ml all tested) | BHI broth | (Syed & Sarkar, 2018) |
| Oxygenated monoterpene | 1,8-cineole | Purity 99% | S. aureus (ATCC 25923), MRSA clinical isolate, P. aeruginosa (ATCC 27853), E. coli (ATCC 25922), K. pneumoniae (ATCC 700603), Enterococcus faecalis (ATCC 51299) Candida albicans (ATCC 90028) | Effect against microorganisms (MIC 128, 128, 256, 32, 64, 128, and 32 g/l) | Serial double dilutions | (Şimşek & Duman, 2017) |
| Cyclic monoterpene | α-Phellandrene | Purity > 99% | Penicillium cyclopium | Inhibit the mycelia growth (MIC 1.7 ml/L) | Agar dilution | (Zhang, Sun, Chen, Zeng, & Wang, 2017) |
| Bicyclic Monoterpene | (+)-3-carene | Purity ≥ 90.0% | Brochothrix thermosphacta (ACCC 03,870), and Pseudomonas fluorescens (ATCC 13,525) | Had strong antibacterial activity (MIC 20 ml/L) | Agar dilution | (Shu et al., 2020) |
| Alkylbenzene Monoterpene | p-Cymene | Salvia officinalis (Essential oil) | E. coli (ATCC 8739), S. aureus (ATCC 6538), C. albicans (ATCC 10231) | Antibacterial activity (MIC 7.5, >15, and 3.75 μl/ml) | Broth microdilution | (Cutillas, Carrasco, Martinez-Gutierrez, Tomas, & Tudela, 2017) |
| Oxygenated monoterpene | Bornyl acetate | S. officinalis (Essential oil) | E. coli (ATCC 8739), S. aureus (ATCC 6538), C. albicans(ATCC 10231) | Antibacterial activity (MIC > 15, 15, and > 15 μl/ml) | Broth microdilution | (Cutillas et al., 2017) |
| Monoterpenoid phenol | Carvacrol | PC | B. cereus (MTCC 430), E. coli (MTCC 443) | Antimicrobial effect (MIC 400 µl/ml all tested) | BHI broth | (Syed & Sarkar, 2018) |
| Acyclic monoterpene Alcohol | Linalool | PC | P. aeruginosa (ATCC9027) | Antibacterial activity (MIC 431 µg/ml) | Medium dilution | (Liu et al., 2020) |
| Citral isomer | Citral | PC | C. albicans (SC5314), C. tropicalis (ATCC1369), S. aureus (ATCC25923) | Antimicrobial action (MIC 0.0313, 0.0156, and 0.0313 v/v%) | Serial microdilutions | (Gao et al., 2020) |
Note: PC = Pure Compound.