Table 2.

In vitro studies involving essential oils, anti-inflammatory and antioxidant activity.

Essential oil and/or majority constituent	Doses	Antioxidant and anti-inflammatory assays	Cell line	General results and proposed mechanism of action	Reference
Essential oils of the aerial part of Eucalyptus bridgesiana, Cymbopogon martinii, Thymus vulgaris, Lindernia anagallis, and Pelargonium fragrans	0.01 μg/mL	β-Carotene linoleic acid bleaching test, DPPH radical, and nitric oxide scavenging assay 5-LOX inhibition assay Measurement of IL-1β, IL-8, TNF-α	THP-1 (human mylomonocytic cell)	Strong antioxidant activity in the tests performed; inhibition of 5-LOX activity and reduction of IL-1β, IL-8, and TNF-α secretion in THP-1 cells	Tsai et al. 2011 [24]
Essential oils of the aerial parts of Oenanthe crocata L., β-ocimene, or sabinene	EO: 0.08, 0.16, and 0.32 μL/mL β-Ocimene and sabinene: 0.32–1.25 μL/mL	Measurement of NO, Western blot analysis for iNOS, and nitric oxide scavenging activity	RAW 264.7 macrophages	Strong NO scavenging activity and inhibition of iNOS expression Sabinene exhibited NO scavenging activity only at higher concentrations	Valente et al. 2013 [28]
Essential oils from leaves and stems of Liquidambar Styraciflua	1, 10, 100 and 500 μg/mL	5-LOX and PGE2 inhibition DPPH radical and superoxide scavenging activity	HepG-2 cells	Reduction of DPPH, (OH•), and (O2•) radicals Inhibition of 5-LOX and PGE2	El-Readi et al. 2013 [27]
Essential oil of Patrinia scabiosaefolia	50, 100, 150, 200, and 250 μg/mL	Measurement of IL-1 and IL-6 DPPH radical scavenging assay	BV-2 cell (microglia)	Inhibition of the production of IL-1 and IL-6; scavenging activity against the DPPH radical	Jing et al. 2014 [29]
Essential oil from leaf and branches of Ocotea quixos, wood, and branches and leaves of Callitris intratropica and Copaifera reticulata/langsdorffii gum-resin	5, 10, an 20 μg/mL	β-Carotene linoleic acid bleaching test and DPPH radical scavenging assay Measurement of NO production Western blotting analyses for the iNOS and COX-2 and measurement of IL-8, IL-6, and IL-1β	RAW 264.7 macrophages	The EO of O. quixos and C. reticulata did not possess an antioxidant activity, while Blue Cypress possessed a moderate antioxidant activity Only Ocotea suppress the LPS-induced PGE2 production, LPS-mediated iNOS, and COX-2 elevation Suppression of LPS-stimulated IL-8 and IL-1β production in the cells	Destryana et al. 2014 [30]
Essential oils of Achillea millefolium L., Anethum graveolens L., and Carum copticum L.		DPPH radical scavenging and FRAP assay β-Carotene bleaching test Determination of NO production.	RAW 264.7 macrophages	A. millefolium had the highest antioxidant activity in all conducted assays and inhibited nitric oxide production	Kazemi 2015, Iran [37]
Essential oil of calyx of Hibiscus sabdariffa L.	25, 50, 100, 200, and 300 μg/mL	Determination of NO production Measurement of cytokines Production (IL-1 and IL-6) RT-PCR assay of IL-1, IL-6, TNF-α, iNOS, and COX-2 mRNA Western blot analyses for the p-JNK, p-ERK1/2, NF-κB, and GAPDH	RAW 264.7 macrophages	Inhibition of NF-κB signaling pathways and MAPK (JNK and ERK1/2), reduction of NO production and IL-1, IL-6, TNF-α, COX-2, and iNOS	Shen et al. 2016 [41]
Essential oil of Chamaecyparis obtusa	In vitro: 1, 10, 50 and 100 μg/mL In vivo: 5 and 10 mg/kg	In vitro: measurement of NO, IL-1β, TNF-α, and IL-6 by levels; Western blot analyses for expression of iNOS and COX-2 In vivo: carrageenan-induced paw edema and thioglycollate-induced peritonitis	RAW 264.7 macrophages	Decreasing in the number of total cells and suppression of TNF-α, IL-1β, and IL-6 levels in peritoneal fluid Suppression of iNOS and COX-2 expression	Park et al. 2016 [42]
Essential oils from roots of Rhaponticum carthamoides	25, 50, and 100 μg/mL	Measurement of cytokines IL-1β, IL-6, IL-8, IL-10, TNF-α, and GM-CSF and RT-PCR. ROS formation assay using H2DCF-DA.	Human astrocytes	Decreasing the expression of IL-1β, IL-6, and TNF-α and the ROS level	Skala et al. 2016 [43]
Essential oil from blossoms of Citrus aurantium	15.625, 31.25, 62.5, 125, and 250 μg/mL	DPPH and ABTS radical scavenging activity Determination of morphology and NO production. Quantification of IL-6, TNF-α, and IL-1β Reverse transcription and PCR-RT for iNOS	RAW 264.7 macrophages	Did not show scavenging effects on DPPH and ABTS radicals Inhibition of NO accumulation and suppression of IL-6, TNF-α, and IL-1β secretion Inhibition of the expression of COX-2 and NF-κB activation Involvement of the inflammation process through MAPK signaling pathways, by inhibiting phosphorylation of JNK (c-Jun N-terminal kinase) and p38	Shen et al. 2017 [48]
l-Carveol, l-carvone, m-cymene, valencene, and guaiene	1, 10, and 100 μM	Protective effect against oxidative damage produced by superoxide anion production (O2·−) and hydrogen peroxide Determination of NO production Quantification of IL-1α, TNF-α, and IL-10 Activity of NF-κB	RAW 264.7 macrophages	Reduction in TNF-α and IL-1α levels and increasing in the production of IL-10 Guaiene and m-cymene inhibited NO production l-Carveol and m-cymene significantly inhibited O2·− production Terpenes suppressed NF-κB activity	Marques et al. 2018 [52]

EO: essential oil; NO: nitric oxide; ROS: reactive oxygen species; iNOS: inducible nitric oxide synthase; IL-1β: interleukin-1 beta; DPPH: 2,2-diphenyl-1-picrylhydrazyl radical; LPS: lipopolysaccharide; M: male; ABTS: 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid); NF-κB: nuclear factor kappa B, COX-2: cyclooxygenase; TNF-α: tumor necrosis factor alpha; IL-6: interleukin-6; IL-8: interleukin-8; IL-10: interleukin-10; FRAP: ferric reducing antioxidant power; MPO: myeloperoxidase; PCR-RT: real-time quantitative polymerase chain reaction; H2DCF-DA: 2′,7′-dichlorodihydrofluorescein diacetate; 5-LOX: 5, lipoxygenase; PGE2: prostaglandin E2; MAPK: mitogen-activated protein kinases; GAPDH: glyceraldehyde 3-phosphate dehydrogenase.