In Vitro Antioxidant, Antimicrobial, Anticoccidial, and Anti-Inflammatory Study of Essential Oils of Oregano, Thyme, and Sage from Epirus, Greece

Abstract

Origanum vulgare subsp. hirtum, Thymus vulgaris, and Salvia fructicosa are aromatic plants commonly found in Mediterranean countries and are traditionally used in Greece as a remedy for humans, since they are well known as potent antibacterial, antioxidant, and anti-inflammatory agents. Essential oils (EOs) derived from plants cultivated in the mountainous region of Epirus, Greece, were investigated for their inhibitory activity against key microorganisms with relevance to avian health, while also assessing their antioxidant and anti-inflammatory activity. The total phenolic content (TPC) of the EOs was estimated according to the Folin–Ciocalteu method, while the antioxidant capacity was tested through the EOs’ ability to scavenge free radicals by means of the DPPH, ABTS, and FRAP assays. Antibacterial and anti-inflammatory effects were examined by the agar disc diffusion method and the lipoxygenase (LOX) inhibition test, respectively. Furthermore, the EOs’ ability to inhibit the invasion of sporozoites of Eimeria tenella (Wisconsin strain) along with any toxic effects were assayed in Madin–Darby bovine kidney (MDBK) cells. The antioxidant activity of the EOs was observed in descending order: oregano > thyme > sage. The antimicrobial effects of thyme and oregano were equivalent and higher than that of sage, while the anti-inflammatory effect of thyme was higher compared to both sage and oregano. The intracellular invasion of sporozoites was evaluated by the detection of E. tenella DNA by qPCR from cell monolayers harvested at 2 and 24 h post-infection. Parasite invasion was inhibited by the addition of oregano essential oil at the concentration of 100 μg/mL by 83% or 93% after 2 or 24 h, respectively, and was higher compared to the addition of thyme and sage, which had similar effects, but at a less intensive level. The cytotoxic assessment of all three essential oils revealed that they had no effect on MDBK cells compared to dimethyl sulfoxide (DMSO), used as the control substance. The supplementation of oregano, thyme, and sage essential oils had a potent antioxidant, anti-inflammatory, antimicrobial, and anticoccidial in vitro effect that is comparable to synthetic substances or approved drugs, justifying the need for further evaluation by in vivo studies in broilers reared in the absence of antimicrobial and anticoccidial drugs or synthetic antioxidant and/or anti-inflammatory compounds.

Effects of Dietary Supplementation of Essential Oils, Lysozyme, and Vitamins’ Blend on Layer Hen Performance, Viral Vaccinal Response, and Egg Quality Characteristics

“…It was expected that L + EO + VIT blend supplementation would positively affect lipid oxidation status of the eggs. The main secondary metabolites formulating in the tested blend of additives were carvacrol, thymol, p-cymene, γ-terpinene, and linalool, all proven to exhibit antioxidant effects [ 44 , 45 , 46 , 47 , 48 ]. According to our results, both groups provided with the L + EO + VIT blend showed lower levels of lipid oxidation in the produced eggs.…”

Thyme, Oregano, and Garlic Essential Oils and Their Main Active Compounds Influence Eimeria tenella Intracellular Development

“…Previous research has explored the anticoccidial effects of thyme, oregano, and garlic essential oils, as well as their main bioactive molecules, both in vivo and in vitro, focusing primarily on the inhibition of sporozoite invasion [ 23 , 28 ]. Considering that parasite pathogenesis is related to intracellular stages, more extensive evaluation is required to comprehensively assess the impact of these novel compounds.…”

“…Inhibition of invasion was observed at 24 hpi with essential oils, suggesting that the action on sporozoites is so detrimental that internalized sporozoites struggle to undergo further development after meeting these compounds. The effect of similar essential oils on invasion has been explored previously by Sidiropoulou and colleagues [ 9 , 28 ]. E. tenella sporozoites were pre-treated for 1 h with different concentrations of garlic, oregano, and thyme essential oils from Greece.…”

From the Wild to the Field: Documentation, Propagation, Pilot Cultivation, Fertilization, and Phytochemical Evaluation of the Neglected and Underutilized Amelanchier ovalis Medik. (Rosaceae)

“…The total phenolic content of the individual plant organs was determined using the Folin-Ciocalteu method [79] as follows: 20 µL of the extract was mixed with 2.500 µL of deionized water and 400 µL of Folin-Ciocalteu reagent (F9252, Sigma-Aldrich, Darmstadt, Germany). After an initial incubation in the dark for 8 min at room temperature, 500 µL of Na 2 CO 3 7% (w/v) was added, and the reaction mixture was incubated for 30 min in the dark at 40 • C. The samples' absorbance was measured at 750 nm using a UV-vis spectrophotometer (UV-1700 PharmaSpec, Shimadzu, Kyoto, Japan) and their TPC was calculated using a gallic acid standard curve (0-1.5 mg mL −1 , R 2 = 0.947).…”