Carvacrol Content Research Articles

CFD and experimental microfluidic study of the interaction between a natural compound nanoemulsion and E. coli bacterium considering reaction-diffusion-convection model

Essential oils have recently emerged as potent natural antibacterial agents that are effective against pathogenic bacteria. The antibacterial efficacy of a stabilized nanoemulsion of carvacrol (with a mean droplet size of 123.51 nm ± 4.2 nm) on a Gram-negative Escherichia coli (E. coli ATCC 25922) was experimentally and numerically studied utilizing a continuous-flow microfluidic system. The morphology of the destroyed bacteria was examined visually and, bacteria lysis was confirmed by measuring the release of cellular contents. After establishing the antibacterial capability kinetics of the carvacrol nanoemulsions, the acquired data from the time killing assay was used to characterize the E. coli lysis. Moreover, a computational fluid dynamics (CFD) model was implemented to evaluate the influence of altering key parameters such as the Reynolds number, flow rate ratio and inlet carvacrol concentration on the unlysed bacteria percentage at the outlet (Y1) and the mass flow rate (μg/s) of the lysed bacteria at the outlet (Y2). The maximum lysis reaction rate observed in the device was 0.96s-1 corresponding to an inlet carvacrol nanoemulsion concentration of 160μg/mL. The reaction rate (r) was established based on the carvacrol concentration (Aμg/mL) as r=-0.149A0.373. The results obtained from numerical simulations indicated that the Reynolds number causes the most changes in the average value of Y1, while carvacrol concentration impacted most on the average value of Y2 response. The findings presented in this article provide insight into the probable kinetics of carvacrol nanoemulsion antibacterial activity in the microfluidics system.

The Effect of Preharvest Salicylic Acid Treatment on Quality Characteristics of Fresh Thyme (Origanum onites L.) During Cold Storage

The effect of preharvest salicylic acid (SA) treatments on some oil quality and characteristics of fresh thyme (Origanum onites L.) during storage were investigated. The thyme plants were grouped in three blocks for each SA treatment in an orchard. The first group of plants was treated with 1.5 mM SA 20 days before the bloom stage. The second and third group thymes were treated with 1.5 mM SA and only tap water (control), respectively, 10 days before full bloom. The thyme plants harvested at the full bloom stage were transported immediately to the laboratory. The thyme samples were placed in modified atmosphere packaging (MAP) bags and were stored at 1°C and 90 ± 3% relative humidity (RH) for 25 days. Weight loss, leaf color, respiration rate, gas composition in MAP, ethylene production, essential oil and carvacrol content, and sensory quality of thymes were determined during cold storage. SA-treated thymes gave better visual quality, respiration rate, carvacrol content, and ethylene production than the control. As a result, it was determined that preharvest SA treatment could be a promising tool for delaying quality losses in thyme during storage in MAP.

Intraspecific divergence in essential oil content, composition and genes expression patterns of monoterpene synthesis in Origanum vulgare subsp. vulgare and subsp. gracile under salinity stress

BackgroundOregano (Origanum vulgare L.), one of the important medicinal plants in the world, has valuable pharmacological compounds with antimicrobial, antiviral, antioxidant, anti-inflammatory, antispasmodic, antiurolithic, antiproliferative and neuroprotective activities. Phenolic monoterpenes such as thymol and carvacrol with many medical importance are found in Oregano essential oil. The biosynthesis of these compounds is carried out through the methyl erythritol-4 phosphate (MEP) pathway. Environmental stresses such as salinity might improve the secondary metabolites in medicinal plants. The influence of salinity stress (0 (control), 25, 50 and 100 mM NaCl) on the essential oil content, composition and expression of 1-deoxy-D-xylulose-5-phosphate reductoisomerase (DXR), γ-terpinene synthase (Ovtps2) and cytochrome P450 monooxygenases (CYP71D180) genes involved in thymol and carvacrol biosynthesis, was investigated in two oregano subspecies (vulgare and gracile).ResultsEssential oil content was increased at low NaCl concentration (25 mM) compared with non-stress conditions, whereas it was decreased as salinity stress intensified (50 and 100 mM). Essential oil content was significantly higher in subsp. gracile than subsp. vulgare. The highest (0.20 mL pot−1) and lowest (0.06 mL pot−1) amount of essential oil yield was obtained in subsp. gracile at 25 and 100 mM NaCl, respectively. The content of carvacrol, as the main component of essential oil, decreased with increasing salinity level in subsp. gracile, but increased in subsp. vulgare. The highest expression of DXR, Ovtps2 and CYP71D180 genes was observed at 50 mM NaCl in subsp. vulgare. While, in subsp. gracile, the expression of the mentioned genes decreased with increasing salinity levels. A positive correlation was obtained between the expression of DXR, Ovtps2 and CYP71D180 genes with carvacrol content in both subspecies. On the other hand, a negative correlation was found between the expression of CYP71D180 and carvacrol content in subsp. gracile.ConclusionsThe findings of this study demonstrated that both oregano subspecies can tolerate NaCl salinity up to 50 mM without significant reduction in essential oil yield. Also, moderate salinity stress (50 mM NaCl) in subsp. vulgare might increase the carvacrol content partly via increment the expression levels of DXR, Ovtps2 and CYP71D180 genes.

The Preharvest Application of Essential Oils (Carvacrol, Eugenol, and Thymol) Reduces Fungal Decay in Lemons

Lemon postharvest losses are mainly due to the presence of fungal diseases. Current postharvest decay strategies rely on synthetic chemical fungicides; however, consumers are demanding that fruit is free of any chemical residue. The use of new natural alternatives, including essential oils, is emerging due to their potential antimicrobial activity. Therefore, the aim of this work is the elucidation of the effect of carvacrol, eugenol, and thymol, individually and in combination, applied in preharvest. Three different concentrations (100, 500, and 1000 µL/mL) of carvacrol, eugenol, and thymol were individually applied and in combination in ‘Fino’ and ‘Verna’ lemon cultivars. The fungal incidence (mainly Penicillium digitatum and P. italicum) was evaluated weekly for 35 days. Moreover, the main different quality parameters (weight loss, firmness, colour, total soluble solids, titratable acidity, and total phenolic content) of lemons were evaluated at harvest and after 35 days of cold storage. The results showed that carvacrol at the lowest concentration (100 µL/L) provided the lowest fungal incidence with a non-negative effect on the lemon quality parameters during storage, while the highest concentrations and the combination of essential oils resulted in the opposite effect. Therefore, carvacrol applied at 100 µL/L in preharvest could be an eco-friendly alternative to the current fungicides to control lemon decay, while maintaining their optimal quality.

Volatile compounds of Origanum onites L. herbal tea influenced by brewing durations

The tisanes (herbal teas), which are prepared by steeping various parts containing bioactive ingredients of medicinal plants in hot water, have long been used for the prevention and treatment of human diseases. For the effective transfer of phytochemicals to water, the duration of brewing is one of the basic factors that determine the quality of tisanes. This study was carried out to investigate the volatile compounds of Origanum onites L. tisane influenced by 7 different brewing durations (1, 2, 3, 4, 6, 8, and 10 min) by SPME/GC-MS method. To clearly understand the qualitative changes of the tisanes that bear volatile ingredients, the volatile oil (VO) of the plant was also analyzed. Oxygenated monoterpenes (81.43%) were higher than other chemical groups in the VO. Carvacrol (73.2%) was observed as the predominant constituent of O. onites VO. Other major components of the VO were determined as linalool, γ-terpinene, p-cymene, β-bisabolene, caryophyllene, thymol, borneol, α-thujene, and α-terpinene. As a result of chromatographic analysis, oxygenated monoterpenes (96.05–98.19%) were the most major group in O. onites tisanes exposed to different brewing durations. Carvacrol was predominant constituent (84.34–92.6%) in all tisane treatments.The highest carvacrol contents of tisanes were observed at 4 (92.65%), 3 (92.19%), and 6 (91.61%) min. p-Cymene, γ-terpinene, linalool, and thymol were the other main compounds of O. onites tisanes. Based on the current findings, the greatest compounds group dissolved in water were oxygenated derivatives. As a general result, the most effective brewing duration in terms of volatile compounds diversity was determined in 2, 3, and 4 min. Also, the richest treatments in terms of carvacrol content were seen at 3, 4, and 6 min.

Minimal Inhibitory Concentrations of Thymol and Carvacrol: Toward a Unified Statistical Approach to Find Common Trends.

Thymol and carvacrol are some of the most important and used components of Essential oils (EOs); they are widely studied, and there are much data available in the literature. Their Minimal Inhibitory Concentration (MIC) values found in the literature from 2005 to present were used to assess the bioactivity toward yeasts, molds, Gram-positive bacteria, and Gram-negative bacteria, as well as on some bacterial species/serotypes (Salmonella sp., Escherichia coli, E. coli O157:H7, lactic acid bacteria, Listeria monocytogenes, Staphylococcus aureus, S. epidermidis, etc.) to find possible common trends or differences between the two compounds and among the tested species. The results were quite interesting and pointed out that there is a common range for the MIC of thymol and carvacrol for some bacterial species (150-400 mg/L), with some exceptions to this generalized statement. In addition, the statistics pointed out that bacteria could experience homogeneous (S. epidermidis, E. coli O157:H7) or heterogeneous trends (for example, Salmonella sp.) depending on the existence of possible sub-species or different experimental set-ups. Moreover, this paper suggests that there are some drawbacks and issues that should be solved for the effective use of EOs, which are the strong variability among the microorganisms and the lack of standard protocols and reference strains.

Carvacrol exhibits direct antifungal activity against stem-end rot disease and induces disease resistance to stem-end rot disease in kiwifruit

Kiwifruit stem-end rot is a common post-harvest disease caused by Clonostachys rosea and Fusariam equiseti, which triggers rapid fruit decay and reduces the commodity value of the fruit. This study investigated the antifungal activity and mechanism of carvacrol against pathogens of kiwifruit stem-end rot and its ability to induce disease resistance in kiwifruit. The results showed that the minimum inhibitory concentration and minimum fungus concentration of carvacrol to Clonostachys rosea and Fusariam equiseti were 0.06 and 0.09 mg/mL, respectively. Carvacrol could significantly inhibit mycelial growth and spore germination. With the increase of carvacrol concentration, the release of nucleic acid, electrical conductivity, protein, soluble sugar, and lipid contents gradually increased. Propidium iodide staining showed that the membrane integrity of Clonostachys rosea and Fusariam equiseti mycelia treated with carvacrol was damaged. In addition, carvacrol treatment inhibited the spread of plaque diameter after inoculation with Clonostachys rosea and Fusariam equiseti, effectively improved the activities of disease-resistant enzymes during storage, promoted the accumulation of pathogenesis-related proteins chitinase and glucanase, and increased the content of total phenols and flavonoids. These results show the potential application of carvacrol to control kiwifruit stem-end rot disease.

Antimicrobial pseudolatex zein films with encapsulated carvacrol for sustainable food packaging

Environmental problems caused by food packaging impede the sustainability of packed food. Therefore, efficient and environmentally–friendly solutions need to be urgently implemented. Zein is water–insoluble plant protein which can form biodegradable films that have potential to be used as sustainable food packaging. In this work, zein films (zFc) were prepared from dispersions of zein nanocapsules (zNC) containing carvacrol, using pseudolatex technology. zNC were characterized for zeta potential and size. Influence of carvacrol on zFc water resistance, optical and mechanical properties was tested. Encapsulation efficiency and release curves of carvacrol were determined. Antimicrobial activity of zFc with 20% carvacrol was tested under dynamic conditions. It was shown that continuous zein films can be prepared by coalescence of zNC, using pseudolatex technology. Results showed that tested carvacrol concentrations do not affect zNC and zFc properties. Antimicrobial activity of zFc was found to be sufficient to block the growth of Staphylococcus aureus.

Scalable production of antimicrobial food packaging films containing essential oil-loaded halloysite nanotubes

Antimicrobial food packaging holds great promise in extending foods shelf-life and minimizing the risk from foodborne diseases. Specifically, essential oils (EOs) have emerged as promising natural antimicrobials to be incorporated in polymeric materials. Yet, despite the significant research in the field, commercial use of such packaging systems is still in its infancy, due to major barriers, including safety, regulation, benefit-cost ratio, and production capabilities. This work presents industrially viable scale-up production and characterization of antimicrobial low-density polyethylene (LDPE) EOs-containing films, where halloysite nanotubes (HNTs) are employed as functional nanocarriers for EOs. Carvacrol (as a model EO) was loaded into the HNTs nanocarriers and the latter were processed into a masterbatch of LDPE and ethylene vinyl-acetate. The resulting concentrated masterbatch was further diluted and processed into a multilayer film, using a semi-industrial equipment. Carvacrol content in the film was aimed to be low (0.75 wt%) and the produced films displayed a high residual carvacrol content (90 %) in spite of the multiple high-temperature processing steps. Importantly, the resulting films exhibited excellent antifungal efficacy against Penicillium commune, a major food contaminant, in in-vitro micro-atmosphere assays, even after a prolonged storage of 20 months. The film antifungal activity was further studied in two important food systems, bread and fresh cherries, and demonstrated a significant increase of > 73 % in bread shelf-life and 40 % in cherries salability. These results demonstrate that EOs can be incorporated into plastic food packaging systems via industrially viable melt-compounding and extrusion processes, without losing their antimicrobial efficacy. Moreover, we show no migration of HNTs, embedded in the film, into food simulants and address the future perspectives of use of HNTs in food contact materials.

RELATIONSHIP BETWEEN BIOCHEMICAL INDICATORS AND PHENOTYPICAL FEATURES OF GARDEN SAVORY (Satureja hortensis L.)

Relevance. Garden savory (Satureja hortensis L.) is an annual medicinal plant of interest due to the content of essential oil and phenolic compounds, the content of which varies depending on the variety. Identification of the relationship between morphological and biochemical traits will make the se-lection of productive plants more effective and accelerated. The purpose of the study is to identify the phenotypic characteristics of garden savory plants, indicating a high content of certain pharmacologically significant compounds or their groups. Materials and methods. The 9 samples of garden savory served as the object of the study. The content of essential oil was determined in dry raw materials by hydrodistillation according to Clevenger, the component composition was determined by gas chromatography. The flavonoid content was determined in terms of rutin was carried out in terms of rutin, the amount of phenolic compounds and tannins in terms of gallic acid. Results: Early maturing varieties are characterized by a high content of essential oil (r = 0.685) with a low content of tannins (r = –0.69). There was a relationship between the leaf index and the content of tannins (r = 0.620), with the accumulation of flavonoids (r = –0.522), with the content of γ-terpinene in the essential oil (r = 0.77) and of carvacrol (r = –0.76). The presence of anthocyanin coloration is interconnected with the content of essential oil (r = –0.688) and content of carvacrol in it (r = –0.53), with the content of the sum of flavonoids (r = 0.598), gamma terpinene (r =0.541) and tannins (r = 0.7). Conclusion. The identified phenotypic features of garden savory plants indicate a high content of certain pharmacologically significant compounds or their groups. Thus, is shown the selecting possibility of prospective plants according to external features.

Encapsulation of Origanum onites essential oil with different wall material using spray drying.

Origanum onites has antibacterial, antifungal, and antioxidant properties due to its essential oil. The fact that these oils are sensitive to environmental conditions causes the need for advanced processing technologies. This study was aimed to encapsulate essential oil of O. onites by spray drying to extend its shelf life. Spray drying was used to encapsulate the essential oil of O. onites, which was then mixed with maltodextrin, arabic gum, and β-cyclodextrin using response surface methodology. After 60 days of storage, aroma analysis was performed on the essential oil of O. onites and the essential oil powder that was produced under ideal conditions. O. onites essential oil powder was subjected to GC-MS analysis to identify 72 aroma components. Carvacrol and linalool concentrations varied from 22.66 to 30.11 mg/g and from 32.25 to 53.57 mg/g, respectively. The spray-dried microcapsules' D4.3 values ranged from 40.75 to 48.95μm. For every trial, the drying yield and solubility values were higher than 60% and 90%, respectively. The results of the surface optimization showed that the ideal inlet air temperature was 190°C and the ideal concentration of β-cyclodextrin in the wall material was 1%. The findings indicate that O. onites essential oil was successfully encapsulated via spray drying. The preservation of critical aroma compounds in the resulting capsules is high.

Improvement in Essential Oil Quantity and Quality of Thyme (Thymus vulgaris L.) by Integrative Application of Chitosan Nanoparticles and Arbuscular Mycorrhizal Fungi under Water Stress Conditions.

Water stress is one of the critical abiotic stresses and limiting factors in the productivity of plants, especially in arid and semi-arid regions. In recent years, the application of bio-fertilizer and stress-modulating nanoparticles (NPs) is known as one of the eco-friendly strategies for improving plants quantity and quality under stressful conditions. In order to achieve the desirable essential oil (EO) quality and quantity of thyme in water deficit conditions, a 2-year field experiment was carried out as a split plot based on the randomized complete block design (RCBD), with 12 treatments and three replications. The treatments included different irrigation levels, containing irrigation at 80% field capacity (FC80) as no stress, 60% FC as moderate water stress (FC60) and 40% FC as severe water stress (FC40), as well as four different fertilizer sources, including non-application of fertilizer (control), application of arbuscular mycorrhizal fungi (AMF), chitosan NPs (CHT) and co-application of AMF+CHT NPs. The results demonstrated that the dry yield of thyme decreased by 13% and 40.3% under FC60 and FC40 water stress conditions. However, co-application of AMF+CHT NPs enhanced the dry yield of thyme by 21.7% in comparison to the control (non-application of fertilizer). The maximum EO content (2.03%) and EO yield (10.04 g 7 g m-2) of thyme were obtained under moderate water stress (FC60) fertilized with AMF+CHT NPs. Co-application of AMF+CHT NPs enhanced the EO content and EO yield of thyme by 17.1% and 42.7%, respectively. Based on the GC-MS and GC-FID analysis, 38 constituents were identified in the thyme EO, with the major constituents being thymol (35.64-41.31%), p-cymene (16.35-19.38%), γ-terpinene (12.61-13.98%) and carvacrol (2.78-3.93%) respectively. The highest content of thymol and γ-terpinene was obtained under moderate water stress (FC60) fertilized with AMF+CHT NPs. In addition, the highest content of p-cymene and carvacrol was observed in the severe water stress (FC40) fertilized with AMF+CHT NPs. The present research suggests that the co-application of AMF+CHT NPs represents a sustainable and eco-friendly strategy for improving the EO quantity and quality of thyme under water stress conditions.

Effects of microencapsulated carvacrol and cinnamaldehyde on feed digestibility, intestinal mucosa, and biochemical and antioxidant parameters in broilers

The objective of this study was to evaluate the effects of different levels of microencapsulated carvacrol and cinnamaldehyde on metabolizable energy, feed digestibility, intestinal morphometric analysis, and antioxidant parameters in broilers. A completely randomized design with five treatments and eight replications of eight broilers (Cobb male) was used, and collections were carried out at 20 and 42 days of age. Carvacrol and cinnamaldehyde concentrations (mg/kg) were: 0 (control), 50, 100, 150, and 200. Carvacrol and cinnamaldehyde improved apparent metabolizable [...]

Antibacterial and anti-biofilm properties of carvacrol alone and in combination with cefixime against Escherichia coli

BackgroundPlant-derived compounds can be used as antimicrobial agents in medicines and as food preservatives. These compounds can be applied along with other antimicrobial agents to strengthen the effect and/or reduce the required treatment dose.ResultsIn the present study, the antibacterial, anti-biofilm and quorum sensing inhibitory activity of carvacrol alone and in combination with the antibiotic cefixime against Escherichia coli was investigated. The MIC and MBC values for carvacrol were 250 μg/mL. In the checkerboard test, carvacrol showed a synergistic interaction with cefixime against E. coli (FIC index = 0.5). Carvacrol and cefixime significantly inhibited biofilm formation at MIC/2 (125 and 62.5 μg/mL), MIC/4 (62.5 and 31.25 μg/mL) and MIC/8 (31.25 and 15.625 μg/mL) for carvacrol and cefixime, respectively. The antibacterial and anti-biofilm potential effect of carvacrol confirmed by the scanning electron microscopy. Real-time quantitative reverse transcription PCR revealed significant down-regulation of the luxS and pfs genes following treatment with a MIC/2 (125 μg/mL) concentration of carvacrol alone and of only pfs gene following treatment with MIC/2 of carvacrol in combination with MIC/2 of cefixime (p < 0.05).ConclusionsBecause of the significant antibacterial and anti-biofilm activity of carvacrol, the present study examines this agent as an antibacterial drug of natural origin. The results indicate that in this study the best antibacterial and anti-biofilm properties are for the combined use of cefixime and carvacrol.

Effect of carvacrol antioxidant capacity on oocyte maturation and embryo production in cattle.

Carvacrol (C10H14O), an efficient phenolic antioxidant substance for several cell types, may become a useful antioxidant for female germ cells and embryo culture. This study investigates the effects of carvacrol supplementation on bovine oocytes in in vitro maturation (IVM) and embryo production. In total, 1222 cumulus-oocyte complexes were cultured in TCM-199+ alone (control treatment) or supplemented with carvacrol at the concentrations of 3 µM (Carv-3), 12.5 µM (Carv-12.5), or 25 µM (Carv-25). After IVM, the oocytes were subjected to in vitro fertilization and embryo production, and the spent medium post-IVM was used for evaluating the levels of reactive oxygen species and the antioxidant capacity (2,2-diphenyl-1-picryl-hydrazyl-hydrate and 2,2'-azinobis-3-ethyl-benzothiozoline-6-sulphonic acid quantification). A greater (P < 0.05) antioxidant potential was observed in the spent medium of all carvacrol-treated groups compared with the control medium. Moreover, the addition of carvacrol to the maturation medium did not affect (P > 0.05) blastocyst production on days 7 and 10 of culture; however, the total number of cells per blastocyst was reduced (P < 0.05) in two carvacrol-treated groups (Carv-3 and Carv-25). In conclusion, carvacrol demonstrated a high antioxidant capacity in the spent medium after oocyte maturation; however, although embryo production was not affected, in general, carvacrol addition to IVM medium reduced the total number of cells per blastocyst. Therefore, due to the high antioxidant capacity of carvacrol, new experiments are warranted to investigate the beneficial effects of lower concentrations of carvacrol on embryo production in cattle and other species.

Estimating the optimal efflux inhibitor concentration of carvacrol as a function of the bacterial physiological state.

Our aim was to find the optimal efflux inhibitor concentration of a natural component, carvacrol, as a function of the physiological state of Escherichia coli. Using fluorescence-based measurements with two strains of E. coli, the effect of carvacrol was assessed at 17 sub-inhibitory concentrations, at which the bacterial efflux mechanism was compromised. The efficacy of carvacrol, as an efflux inhibitor, was compared to synthetic inhibitors and we found carvacrol the most efficient one. We considered the accumulation of Ethidium Bromide (EtBr) as a proxy for drugs spreading in the cell, thus measuring the efflux activity indirectly. The change in membrane integrity caused by the exposure to carvacrol was monitored using the LIVE/DEAD BacLight Bacterial Viability kit. To find the optimal inhibitory concentration of carvacrol, we used predictive microbiology methods. This optimum varied with the bacterial physiological state, as non-growing cultures were less susceptible to the effect of carvacrol than growing cultures were. Moreover, we point out, for the first time, that the efflux-mediated resistance of untreated cultures was also stronger in the non-growing than in the growing phase at population level.

Production of sage, oregano and rosemary under shading conditions and the effects of light on growth and essential oil properties

Intercropping and agroforestry systems provide sustainable land and resource use efficiency, however, shading conditions generated by the base crop or tree cover is a restricting factor on the growth of the intercrop and productivity of the system. Hence, a two-year field experiment was carried out to assess the yield, essential oil properties, morphological changes, and anatomical adaptation of the shade-exposed sage (Salvia officinalis L.), oregano (Origanum onites L.) and rosemary (Rosmarinus officinalis L.) plants. Plant height, leaf area, chlorophyll content, herbage yield, essential oil content and biochemical profile of the selected species were comparatively examined under open-field, 40% and 75% shading conditions. Initially, after the seedlings were transplanted to the field, a horizontal growth of shaded plants, resulted in lower plant height, then, after the plants covered the soil surface, vertical growth was observed. Overall drug herbage yield decreased by 65% due to the shading treatments in the first year whereas rosemary, sage and oregano had 20.9%, 25.3% and 40.3% lower yields respectively in the second year. Average essential oil content of low-light exposed plants increased by 23% and 41% first and second year of the experiment, respectively. A negative linear relation between α-thujone content in essential oil of sage and shading level was recorded while in contrast, carvacrol content of oregano essential oil increased by shade treatment. The results concluded that herbage yield and quality properties of shaded plants were promising, especially after the first year, considering their potential in intercropping and agroforestry systems. Since the current study represented the results for artificial shading conditions, the tree-based intercropping studies needed to be performed with these species for the final conclusion.

In vitro toxicity of combination of amitraz and carvacrol on Demodex canis.

Canine generalized demodicosis is an inflammatory skin disease, which usually has time-consuming and frustrating treatments. The present study aimed to evaluate the acaricidal activity of carvacrol as a green drug and a combination of carvacrol and amitraz on Demodex canis mites and investigate mites' survival lifetime. Mite samples were collected from a dog affected by demodicosis and had been diagnosed with deep skin scrapings. The motility of mites was examined by using optical microscopy. Samples were tested with 5% of carvacrol, the combination of Carvacrol 5% + Amitraz 0.05%, Amitraz 0.05% as a positive control, and mineral oil as a negative control. The interval time between the adding the test solutions and the moment the last mite ceased was defined as the survival time in the samples and the killing times of mites in each group were compared with each other. It was determined that after administration of a 5% concentration of carvacrol, lethal effects were faster than the combination solution of Carvacrol 5% + Amitraz 0.05%, and the survival times in the control groups were longer than in both treatment groups. Carvacrol, as one of the most important bioactive terpenes, had the most effective in vitro miticidal activity, and it seems that carvacrol alone or in combination with amitraz can be suggested as a possible therapy in the treatment of canine demodicosis.

Carvacrol inhibits bacterial polysaccharide intracellular adhesin synthesis and biofilm formation of mucoid Staphylococcus aureus: an in vitro and in vivo study.

Staphylococcus aureus (S. aureus) is one of the important human pathogens and causes both superficial and systemic infections. More importantly, the formation of S. aureus biofilms, a main cause of its pathogenicity and drug resistance, has been a critical challenge in clinical treatment. Carvacrol, a plant-based natural product, has gained great interest for therapeutic purposes due to its effective biological activity with low cytotoxicity. The present study aimed to investigate the effect of carvacrol on anti-biofilm activity. Growth curve analysis showed that applying a sub-inhibitory concentration of carvacrol (4 μg mL-1) was not lethal to S. aureus SYN; however, the inhibition rate of biofilm formation was as high as 63.6%, and the clearance rate of mature biofilms was as high as 30.7%. In addition, carvacrol effectively reduced the production of biofilm-associated extracellular polysaccharides and showed no effect on eDNA release. Furthermore, qPCR analysis revealed that carvacrol significantly down-regulated the expression of icaA, icaB, icaC, agrA, and sarA (P < 0.05). The in vivo efficacy of carvacrol against biofilm infection was further verified with a biological model of G. mellonella larvae. The results showed that carvacrol was non-toxic to the larvae and can effectively increase the survival rate of the larvae infected with S. aureus strain SYN.

Sustained-release antibacterial gelatin films: Effects of diatomite/carvacrol complex on their structure, physicochemical and antibacterial properties

Antibacterial diatomite/carvacrol (D/C) complex was prepared by utilizing diatomite as an effective carrier of carvacrol, and further incorporated into gelatin with different amounts (0–30%, w/w based on gelatin) to develop a series of antibacterial gelatin-based films. D/C complex was found to have appropriate interaction and compatibility with gelatin matrix as revealed by FTIR and SEM analysis. With increasing D/C complex content, light transmission, moisture content, water solubility and tensile strength of the films decreased, whereas elongation at break and water vapor permeability increased. More importantly, an apparent antibacterial effect began to be observed for the film-forming solution containing 10% (or more) D/C complex, and the subsequent film exhibited a much slower release rate of carvacrol towards food simulant (60 wt% glycerol solution) than gelatin film with the same content of carvacrol. Therefore, the developed antibacterial gelatin films with desirable physical and sustained-release properties have great potential for active food packaging applications.