Table 3.
Examples of terpene compounds in EO with the potential anti-inflammatory effects.
| Classes | Compounds | Plant | Type of inflammation | Anti-inflammatory effects | Assay/method | Reference |
|---|---|---|---|---|---|---|
| Monoterpene hydrocarbons | Myrcene | PC | Renal tissues of rats | Inhibited the activities of inflammatory cytokine, pro-inflammatory signalling | ELISA | (Yang & Liao, 2021) |
| Cyclic monoterpene | R-(+)-limonene | Purity > 99%(Sigma Aldrich, St. Louis, MO, USA) | Gastric ulcer in rats | Decreased the levels of TNF-a, IL-6, and IL-1β and increased the level of IL-10 | ELISA kits | (De Souza et al., 2019) |
| Bicyclic monoterpene | Borneol | PC | Acute pancreatitis mice model | Inhibited TNF-α, IL-1β, IL-6, and modulated Nrf2/NF-κB pathway | ELISA | (Bansod et al., 2021) |
| Tropolone monoterpene | Hinokitiol | PC | Inflammation in primary human keratinocytes | Inhibited LPS-mediated up-regulation of pro-inflammatory factors including tumor necrosis factor alpha, IL-6, and prostaglandin E2 (PGE2), and Sirt1 activity | Quantitative Real-Time PCR | (Lee et al., 2017) |
| Terpenophenol | Bakuchiol | Psoralea corylifolia (Seeds essential oil) | Cerebral ischemic injury in mouse BV-2 microglia | Exhibit its anti-inflammatory property via activating Nrf2 signaling | Immuno-fluorescence staining | (Xu, Gao, Wang, Yang, & Xie, 2021) |
| Bicyclic monoterpene | α-Pinene | PC | Focal cerebral ischemia–reperfusion in rats | Neuroprotective effect during ischemic stroke through attenuating neuroinflammation. | ELISA | (Khoshnazar, Parvardeh, & Bigdeli, 2020) |
| Acyclic monoterpene Alcohol | Linalool | Boswellia carterii | Ear edema model and a formalin-inflamed hind paw model | More potent pharmacological effects on hind paw inflammation and COX-2 overexpression | Immuno-histochemistry | (Li, Yang, Li, Zhang, & Tang, 2016) |
| Acyclic monoterpene Alcohol | Geraniol | PC | Lungs in mice model | Improved the inflammatory changes | ELISA | (Lin et al., 2021) |
| Cyclic monoterpene | α-Phellandrene | PC | Wound healing | Suppressed the overproduction of pro-inflammatory cytokines of IL-6 and TNF-α. | ELISA | (De Christo Scherer et al., 2019) |
| Hydroxylated monoterpene | Perillyl alcohol | Purity 96% | Lung tissue in rats | Inhibited cellular inflammation | ELISA | (Beik et al., 2021) |
| Citral isomer | Citral | Purity ≥ 95% | Hyperalgesia and pleurisy in mice | Anti-inflammatory activities | ELISA | (Campos, Lima, Trindade, Souza, Mota, Heimfarth, & Thangaraj, 2019) |
| Monoterpenoid phenol | Carvacrol | PC | Asthma in rats | Reduced of AEC, IgE, IL-4, IL-5, IL-13, TNF-α, IFN-γ, iNOS and MDA | Colorimetric and Quantitative Real-Time PCR | (Ezz-Eldin, Aboseif, & Khalaf, 2020) |
| Oxygenated monoterpene | 1,8-cineole | PC | Upper Ileum Tissues | Prevented low-grade inflammation | Quantitative Real-Time PCR | (Jiang et al., 2021) |
Note: PC = Pure Compound.