High Carvacrol Content Research Articles

Essential Oil of Fractionated Oregano as Motility Inhibitor of Bacteria Associated with Urinary Tract Infections.

In this research, several analyses were carried out on concentrated fractions of Mexican oregano essential oil (Poliomintha longiflora Gray) in order to determine its ability to inhibit the growth and the motility of Escherichia coli (swimming), Pseudomonas aeruginosa (swimming), and Proteus vulgaris (swarming); these Gram-negative bacteria associated with urinary tract infections are motile due to the presence of flagella, which is considered an important virulence factor that favors their motility when trying to reach the target organ and cause an infection. Also, the resistance pattern to antibiotics of each strain was determined. The results showed resistance pattern (8 out of 12 antibiotics tested) for P. aureginosa, while E. coli and P. vulgaris were resistant to 4 antibiotics out of the 12 tested. On the other hand, fractionated oregano caused an inhibition of growth and a reduction in motility, varying between fractions and among bacteria. Fraction 4 showed major growth reduction, with MBC values ranging from 0.002 to 23.7 mg/mL. Treatment with fractionated oregano (F1, F2, F3, F4) reduced the motility by 92-81% for P. vulgaris, 90-83% for E. coli, and 100-8.9% for P. aeruginosa. These results demonstrated a higher performance with a lower application dose due to its high content of Carvacrol and Thymol; unlike other concentrated fractions, this synergy of oxygenated monoterpenes may cause greater antimicrobial activity.

Shelf Life of Minced Pork in Vacuum-Adsorbed Carvacrol@Natural Zeolite Nanohybrids and Poly-Lactic Acid/Triethyl Citrate/Carvacrol@Natural Zeolite Self-Healable Active Packaging Films.

Enhancing food preservation and safety using environmentally friendly techniques is urgently needed. The aim of this study was to develop food packaging films using biodegradable poly-L-lactic acid (PLA) as biopolymer and carvacrol (CV) essential oil as an antioxidant/antibacterial agent for the replacement of chemical additives. CV was adsorbed onto natural zeolite (NZ) via a new vacuum adsorption method. The novel nanohybrid CV@NZ with a high CV content contained 61.7%wt. CV. Pure NZ and the CV@NZ nanohybrid were successfully dispersed in a PLA/triethyl citrate (TEC) matrix via a melt extrusion process to obtain PLA/TEC/xCV@NZ and PLA/TEC/xNZ nanocomposite films with 5, 10, and 15%wt CV@NZ or pure NZ content. The optimum resulting film PLA/TEC/10CV@NZ contained 10%wt. CV@NZ and exhibited self-healable properties, 22% higher tensile strength, 40% higher elongation at break, 45% higher water barrier, and 40% higher oxygen barrier than the pure PLA/TEC matrix. This film also had a high CV release content, high CV control release rate as well as 2.15 mg/L half maximal effective concentration (EC50) and 0.27 mm and 0.16 mm inhibition zones against Staphylococcus aureus and Salmonella enterica ssp. enterica serovar Typhimurium, respectively. This film not only succeeded in extending the shelf life of fresh minced pork, as shown by the total viable count measurements in four days but also prevented the lipid oxidation of fresh minced pork and provided higher nutritional values of the minced meat, as revealed by the heme iron content determination. It also had much better and acceptable sensory characteristics than the commercial packaging paper.

Effective Inhibition of Listeria monocytogenes Biofilm Formation by Satureja rechingeri Essential Oil: Mechanisms and Implications.

Biofilm formation by foodborne pathogens, particularly Listeria monocytogenes, poses a significant challenge in food industry facilities. In this study, we investigated the inhibitory potential of Satureja rechingeri essential oil (Sr-EO) against L. monocytogenes growth and biofilm formation. Gas chromatography-mass spectrometry analysis revealed a high carvacrol content in Sr-EO, a compound with known antimicrobial properties. We examined the effects of Sr-EO on initial attachment and preformed biofilms, using crystal violet and MTT assays to quantify attached biomass and metabolic activity, respectively. Our results demonstrated that Sr-EO not only prevented initial attachment but also effectively disrupted preformed biofilms, indicating its potential as a biofilm-control agent. Microscopy analysis revealed alterations in bacterial cell membranes upon Sr-EO treatment, leading to increased permeability and cell death. Additionally, Sr-EO significantly suppressed bacterial motility, with concentrations exceeding 0.25μL/mL completely inhibiting motility. Furthermore, gene expression analysis revealed the down regulation of genes associated with biofilm formation, attachment, and quorum sensing, suggesting that Sr-EO modulates bacterial gene transcription. These findings suggest that Sr-EO can be a promising candidate for controlling biofilm formation and bacterial contamination in food processing environments.

Biologically active substances of new marjoram varieties and prospects for their use

Biologically active substances, essential oils, and plant extracts were studied obtained from new high-yield varieties of Origanum vulgare L. (Raduga, Belaya Ptitsa, Krymchanka) and Origanum tyttanthum Contsch. (Alcina) of the GSBSI “NBG – NSC RAS” breeding. It was found that the O. vulgare variety Belaya Ptitsa was distinguished by the content of essential oil, the main component of which was carvacrol. The maximum total content of phenolic substances and flavonoids was distinguished by an alcoholic extract from the O. tyttanthum variety. Neochlorogenic and rosemary acids, apigenin-6,8-di-C-glucoside, carvacrol, and thymol were identified in extracts of all the studied marjoram varieties. It is shown that the vegetable raw material O. vulgare cv “Belaya Ptica” is promising for the production of essential oil with a high content of carvacrol, and O. tyttanthum cv “ can serve as a raw source of rosemary acid.

High throughput pre-breeding evaluation of Greek oregano (Origanum vulgare L. subsp. hirtum) reveals multi-purpose genotypes for different industrial uses

Origanum vulgare L. subsp. hirtum (commonly known as Greek oregano) is a perennial species of the Lamiaceae family that counts numerous applications in the food and pharmaceutical industry. The exploitation of Greek oregano germplasm lies in its unique diversity in secondary metabolites, which are accumulated in the aerial parts of the plant. For the industrial exploitation of this crop the starting germplasm is of high importance in terms of valorizing well characterized chemotypes with desired and stable agronomic and phytochemical traits. For this reason, a pre-breeding evaluation of twenty-one accessions collected and preserved under the same environmental conditions was performed in order to develop a descriptive database containing: a) morphometric traits, b) the genetic structure, c) the extensive metabolic fingerprint in terms of volatile composition, polyphenolic and triterpenoid content, and d) the ‘bio-activity’ on the embryonic development of Ascaridia galli eggs for highly divergent accessions. This study revealed the existence of essential oil rich chemotypes superior in morphometric characteristics, containing high carvacrol content (> 75%) and traces of thymol (< 5%), according to the requested international standards. Apart from genotypes considered as ‘high yield essential oil-producers’ (> 6%), accessions of highly productivity of ‘green’ raw materials rich in polyphenols and triterpenoids were also identified. According to their rosmarinic acid content, Greek oregano accessions were classified in three groups; 1) those with significantly high concentration (1640–2726 mg 100 g−1 dry weight), 2) those expressing intermediate content (1103–1200 mg 100 g−1 dry weight), and 3) the ones with significantly low content (< 873 mg 100 g−1 dry weight). A total of 118 polymorphic alleles were identified using sequence-related amplified polymorphism (SRAPs) and simple sequence repeat (SSRs) markers, while 2 genetic clusters based on a single data matrix with SRAPs and SSRs alleles, were identified. The presence of private bands in some accessions was also observed, which can be used in future breeding programs for germplasm authentication purposes. As a result this study provides a comprehensive knowledge on metabolic and genetic diversity of Greek oregano accessions native to Greece, as well as powerful tools for the selection of starting genetic materials for subsequent breeding studies to create superior cultivars. The multifaceted approach was developed to exploit the genetic resources of Greek oregano in further breeding programs for subsequent selection of genotypes with desired traits.

Unravelling the Chemotaxonomic Identity of "White" and "Black" Oregano (Origanum vulgare) in Northern Greece.

The two types of oregano used by the inhabitants of the villages of Μount Belles (GR1260001), the "white" oregano with white flowers and "black" oregano with purple flowers, were studied. The two oregano types were collected from five localities along an altitudinal gradient from 217 m up to 1299 m. "White" oregano, was found in the three lowland regions (up to 752 m) where the Pannonian-Balkanic turkey oak-sessile oak forest habitat (code 91M0) dominates. The "black" oregano was collected from the two higher altitudes, at 1177 m and 1299 m, where the Asperulo-Fagetum beech forest habitat (9130) occurs. Measurements of the density and size of peltate glandular hairs (sessile glands) on calyces, bracts, and leaves suggest that "white" oregano is distinguished by its conspicuous - apparently larger - glands. These differences were reflected in the total essential oil content, with the "white" oregano being much richer (up to 4.3 mL/100 g dry weight) than the "black" (up to 0.6%). Striking differences have also been found in the volatile fraction of their essential oil composition. The "white" oregano oils were characterized by the high content of carvacrol (up to 92.6% of identified peaks, by Headspace GC-MS). On the other hand, the two "black" oregano oils have a different aromatic profile, first reported from Greece, with main components including the sesquiterpenes β-caryophyllene, D-germacrene, δ-cadinene and β-bisabolene. The results so far indicate that "white" and "black" oregano, Origanum vulgare subsp. hirtum and subsp. vulgare respectively, can be clearly distinguished either by their morphological (glandular) differences or by chemical (essential oil) composition.

Chemical composition and biological activity of essential oil of the Moroccan endemic Origanum grosii

The aim of this research was to study the chemical composition and biological activity of essential oil of the Moroccan endemic Origanum grosii on biofilm of Staphylococcus aureus strains.Qualitative and quantitative composition of the essential oil was analyzed by gas chromatography and gas chromatography-mass spectrometry. The Minimum Inhibitory Concentration was determined using the broth microdilution method.Phytochemical analyses revealed a high content of carvacrol, p-cymene, γ-terpinene and thymol. The antibiofilm effect of essential oil of Origanum grosii was tested against three staphylococcal strains (Staphylococcus aureus MBLA, Staphylococcus aureus CECT976 and Staphylococcus aureus ATCC25923). Results showed that the Minimum Inhibitory Concentration are lower than the Minimum Bactericidal Concentration (MBC = 2 MIC), hence the bacteriostatic power of this essential oil.In fact, essential oil of Origanum grosii presented a high antibiofilm effect against different staphylococcal strains by the inhibition of the biofilm formation and showed also a significant antibacterial activity (dose-dependent), since it increases with the increase in the concentration of this essential oil.The use of essential oil of Origanum grosii as natural antibacterial agent may effectively inhibit the growth of biofilm of medical relevance. Results indicated also that essential oil of Origanum grosii may be a potential alternative against Staphylococcus resistant strains.For this reason, the essential oil of Origanum grosii can be a promising alternative for both microbial control and therapeutic treatment against pathogenic resistant bacteria. Nevertheless, further studies should be conducted in order to elucidate the mechanisms of action of the essential oil on the bacterial cells under study.

Evaluation of Antimicrobial Activity of Thymbra spicata L. var. spicata Essential Oil as a Potential Source of Herbal Medicine

Background: Since ancient times, human kind has used plants for their flavor and essence and especially for medical purposes; they are also used as food sources. Turkey, due to its geographical location, is home to many varieties of species of medicinal and aromatic plants. Aromatic and medicinal plants produce essential oils in the form of secondary metabolites. These essential oils are being used in the food, cosmetic, and pharmaceutical industries. Due to the various side effects of synthetic agents, the use of essential oils as antimicrobial agents comes to the fore. Objective: The purpose of this study was to determine the essential oil composition of Thymbra spicata L. var. spicata collected from the Gaziantep Region of Turkey and to evaluate its antimicrobial efficacy against microorganism species commonly encountered in food, cosmetic, and pharmaceutical industries. Methods: In this study, the antimicrobial effect of the volatile oil obtained from dried leaves of Thymbra spicata L. var. spicata, traditionally known as Zahter, was investigated. For this purpose, volatile oil was obtained from the leaves of the plant by steam vapor distillation method. Antimicrobial efficacy tests were conducted against microorganisms; Staphylococcus aureus, Enterococcus hirae, Enterococcus faecalis, Listeria monocytogenes, Escherichia coli, Klebsiella pneumoniae, Proteus hauseri, Pseudomonas aeruginosa, Salmonella typhimurium, and Candida albicans. Results: Results of the experiments showed that the volatile oil obtained from Thymbra spicata L. var. spicata had a cidal effect on selected pathogenic microorganisms even at low concentrations. Conclusion: This study showed that the high carvacrol content of the T. spicata L. var. spicata grown in the Gaziantep region of Turkey is a promising source of antimicrobial raw materials in the pharmaceutical, cosmetic, and food industries.

Chemical profile and eco-safety evaluation of essential oils and hydrolates from Cistus ladanifer, Helichrysum italicum, Ocimum basilicum and Thymbra capitata

The demand for natural-based products for industrial applications is increasing sharply and therefore the search for new alternatives to the plants traditionally used is growing. These alternative plants can be an important source of bioactive compounds under a circular economy approach. Considering the potential future use of new plant products by the industry, it is necessary to assess the risk associated with their introduction into the ecosystem. This work aims to provide an insight into the volatile profiles and evaluate the potential (eco)toxic effects of essential oils (EO’s) and hydrolates of four plant species, namely rockrose (Cistus ladanifer), curry plant (Helichrysum italicum), conehead thyme (Thymbra capitata) and basil (Ocimum basilicum). Chemical analysis were performed by GC-MS and acute toxicity tests were performed using the model organism Daphnia magna. The essential oil and the hydrolate from H. italicum, as well as all the other hydrolates caused no immobilization up to the highest concentrations tested, suggesting that all hydrolates present low to no risk towards D. magna. Similarly, the essential oil of H. italicum, presented negligible risk towards D. magna. For C. ladanifer and T. capitata essential oils, the EC50 (the concentration estimated to immobilize 50 per cent of the Daphnia) at 48 h varied between 199.7 mg/L and 12.1 mg/L, respectively. The essential oil from C. ladanifer was mainly characterised by monoterpene hydrocarbons, while the H. italicum was richer in sesquiterpene hydrocarbons. Both essential oil and hydrolate from T. capitata contained exclusively monoterpene hydrocarbons with a particularly high content of carvacrol. The higher acute toxicity of T. capitata essential oil can be attributed to the high amount of carvacrol present in the distillate. Overall, of the essential oils and hydrolates tested, all can be classified as practically non-toxic, except for T. capitata essential oil that, according to the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) of the United Nations, can be classified as moderately toxic.

Effect of carvacrol in the properties of films based on poly (vinyl alcohol) with different molecular characteristics

Poly (vinyl alcohol) (PVA) is a hydrophilic linear polymer obtained from the controlled hydrolysis of poly (vinyl acetate) (PVAc). The molecular weight (Mw) and degree of hydrolysis (DH) of PVA are considered relevant in both the functionality of the polymer and its capacity for film formation. This study analysed the influence of the Mw and DH of PVA on both the film's ability to incorporate carvacrol (CA), for the purposes of obtaining active films for food packaging application, as well as on the film microstructure, thermal behaviour and its functional properties as packaging material. CA was incorporated at 5 and 10 g/100 g polymer by emulsification in the polymer-water solutions, while the films were obtained by casting. The higher Mw polymer provided films with a better mechanical performance but less CA retention and a more heterogeneous structure. In contrast, low Mw, partially acetylated PVA gave rise to homogenous films with a higher CA content that increased the mechanical resistance and stretchability of the films. The melting temperature of this polymer with acetyl groups was lower than the degradation temperature, which makes thermoprocessing feasible.

The Incorporation of Carvacrol into Poly (vinyl alcohol) Films Encapsulated in Lecithin Liposomes.

Lecithin-encapsulated carvacrol has been incorporated into poly (vinyl alcohol) (PVA) for the purpose of obtaining active films for food packaging application. The influence of molecular weight (Mw) and degree of hydrolysis (DH) of the polymer on its ability to retain carvacrol has been analysed, as well as the changes in the film microstructure, thermal behaviour, and functional properties as packaging material provoked by liposome incorporation into PVA matrices. The films were obtained by casting the PVA aqueous solutions where liposomes were incorporated until reaching 0 (non-loaded liposomes), 5 or 10 g carvacrol per 100 g polymer. The non-acetylated, high Mw polymer provided films with a better mechanical performance, but less CA retention and a more heterogeneous structure. In contrast, partially acetylated, low Mw PVA gave rise to more homogenous films with a higher carvacrol content. Lecithin enhanced the thermal stability of both kinds of PVA, but reduced the crystallinity degree of non-acetylated PVA films, although it did not affect this parameter in acetylated PVA when liposomes contained carvacrol. The mechanical and barrier properties of the films were modified by liposome incorporation in line with the induced changes in crystallinity and microstructure of the films.

Anty-microbial, and anty-biofilm-forming properties of Origanum vulgare L. essential oils on Staphylococcus aureus and its antioxidant action

Essential oils (EOs) have been widely used in folk and traditional medicine, cooking, cosmetology and other sectors of the economy. The antimicrobial properties of essential oils determine the relevance of the study of their effectiveness against antibiotic-resistant biofuel clinical isolates. Our research was aimed to determine the antimicrobial and antibiofilm properties of essential oil of Origanum vulgare L. on clinical isolates of bacteria of the genus Staphylococcus and its antioxidant effect. The raw materials of Origanum vulgare L. for large-scale essential oil isolation were donated by established growers in Slovakia (Agrokarpaty, Ltd.). EOs were obtained by the large-scale distillation apparatus specifically designed for the aromatic and medicinal plants. Calendula Co., in Nova Lubovna, Slovakia. The analysis of EOs was carried out using a gas chromatograph Varian 3090. Antimicrobial activity of EOs was determined using well agar diffusion method. Quantification of biofilm formation was carried out using a microtiter plate assay and the spectrophotometric method. Biofilm formation was quantified by measuring optical density at 550 nm. Biochemical analysis of O. vulgare essential oil showed a high content of carvacrol and thymol (72%). All strains of Staphylococcus aureus were sensitive to this essential oil. At the same time, the lowest indicators of growth retardation zones were characteristic of S. aureus MRSA clinic biofilm creation. We have determined the antibio­film effect of O. vulgare essential oil on S. aureus isolates. The study showed the degradation of the biofilm under the influence of essential oil decreased with decreasing concentration. At the same time, even with the action of essential oil, the concentration of 0.01% showed a 42% decrease in the process of biofilm formation. At the highest concentration of 0.10%, a destruction of the biofilm by 78% was found. The study of the influence of essential oils on the formed biofilm showed that 0.1% solution of oil causes degradation of the biofilm by 73.2%; 0.05% – by 58% and 0.01% – by 51.5%. O. vulgare essential oil also showed high antioxidant properties. The neutralization rate of free radicals was 83%. The revealed antimicrobial properties of O. vulgare essential oil make it promising to be used as an antistatic agent, including as a component that contributes to the disintegration of biofilm in the treatment of boils, carbuncles, panari­tiums, phlegmon, wound suppuration, inhalation for respiratory diseases, as a component of rinses in inflammatory periodontal diseases.

Chemical composition, in vitro antibacterial and antioxidant potential of Omani Thyme essential oil along with in silico studies of its major constituent

Thyme is an evergreen shrub that has been utilized in traditional medicine and culinary packages for centuries because of its aroma and medicinal properties. The medicinal properties of thyme leaves are attributed to its volatile constituents. The study aimed to identify the volatile constituents in the oil extracted from the Thyme sp grown in Oman and to evaluate its in vitro antibacterial and antioxidant activity. Fresh Thyme leaves were collected from Muscat, Sultanate of Oman in the month of September 2018. Thyme oil was isolated from leaves by hydro-distillation. The volatile chemical constituents present in the thyme oil were analyzed by Gas Chromatograph coupled with Mass Spectrometer. The ability of isolated oil to scavenge free radicals was evaluated by an in vitro DPPH assay method while antimicrobial activity was tested against S. aureus and E. coli bacterial strains by disc diffusion method. The bioactivity of the major constituent of the oil was predicted with the help of PASS and CLC-pred software. Molecular docking studies were performed by docking server. GC–MS analysis of thyme oil revealed the presence of 11 components. Carvacrol and γ-terpinene were identified as the major volatile constituents in thyme oil. Thyme oil inhibited 71.57% of DPPH radicals at 40 µg/mL concentration. Thyme oil displayed the better antimicrobial activity than the standard drug ampicillin against both the bacteria. Antiseptic, antiinfective, reductant and antimutagenic bioactivities of carvacrol as predicted by PASS support the in vitro experimental results. CLC-pred showed carvacrol to be active against Metastatic melanoma, Oligodendroglioma and Non small cell lung cancer cell lines. The antioxidant and antimicrobial activity of Omani thyme oil could be due to its high content of carvacrol. Omani thyme oil seems to be a viable alternative source of natural antimicrobial agent(s) and warrants further studies to ascertain its therapeutic spectrum of biological studies.

Essential oil composition of summer savory (Satureja hortensis L.) cv. Saturn depending on nitrogen nutrition and plant development phases in raw material cultivated for industrial use

Environmental factors such as mineral nutrition as well as plant ontogeny are the major determinants of the quantity and quality of essential oil (EO) in medicinal and herbal plants. The aim of the present study was to assess the effect of nitrogen and plant development phases on the yield of fresh mass and the yield of essential oil, content and chemical composition of essential oil from summer savory cv. Saturn cultivated for industrial use. The two-factor experiment was carried out in a random-block design with five replications. The nitrogen dose (0; 4; 8; 12; 16 g N m−2) and the plant development phase (the beginning of flowering and full flowering) were the experimental factors. There was a significant effect of the nitrogen dose and plant development phase on the essential oil content of the summer savory. The content of essential oil in the summer savory herb was in the range of 2.52–5.89%. The essential oil was shown to contain four dominant components, i.e. carvacrol, gamma-terpinene, alpha-terpinene, and para-cymene. The highest carvacrol content was noted for the lowest nitrogen dose in the phase of full flowering of plants. Additionally, the highest parameters of the summer savory essential oil were obtained from plants harvested in the initial flowering stage.

Seasonal variation in yield and chemical composition of Moroccan Thymbra capitata (L.) Cav. essential oil and its corresponding hydrolat extracted essential oil

The aim of the present work was to study the variation in yield and chemical composition of the pure essential oil (EO) and essential oil dissolved in its corresponding hydrolat (HEO) of Thymbra capitata (L.) Cav. of Morocco according to its stage of growth. The results obtained revealed that the yield of essential oil increases with the growth of the plant to reach its maximum at post-flowering stage (2.90%). On the other hand, the yield of dissolved essential oil in the corresponding hydrolats peaked at the flowering stage (0.53%) and then dropped. The analysis of these oils was performed by the GC-MS and showed that carvacrol was the major compound of this plant during its growth stage. The highest carvacrol content was noted at the flowering stage for EO (84.26%) and at the pre-flowering stage for HEO (98.54%). However, the evolution of concentration of p -cymene (3.84-6.01%) and g- terpinene (3.45-5.68%) in EO seems to be the opposite of carvacrol. Moreover, these two monoterpene hydrocarbons are absent or almost absent in HEO.

Formulation, characterization and antimicrobial activity of tablets of essential oil prepared by compression of spray-dried powder

Oregano essential oil (EO) was encapsulated by spray drying emulsions stabilized with polysaccharides. Both, emulsions and spray-dried powder (SDP) were characterized physicochemically and SDP was compressed into tablets with low (10% w/w) and high (20% w/w) EO content. Compression behavior, redispersibility and release of EO were studied. Antimicrobial activity of reconstituted emulsions was evaluated by disc diffusion and broth dilution. SDP showed good EO encapsulation efficiency and retained high carvacrol content. SDP with low EO content formed strong tablets, whereas SDP with high EO formed weaker tablets but with acceptable mechanical strength and friability. Oil leakage due to compression was negligible. Reconstitution of original emulsion was faster from the SDP than the tablets and the use of disintegrants did not show improvement. Interestingly, addition of croscarmellose sodium (CCS) greatly increased the release rate of EO from tablets despite lack of effect on redispersibility, possibly due to fast liquid uptake/swelling by the CCS fibres combined with repulsion between negatively charged carboxyl groups on CCS and gum Arabic resulting in opening of the microencapsulating wall. Sodium starch glycolate had small effect on release. The antimicrobial activity of reconstituted emulsions relative to neomycin ranked in the order: E coli < Klebsiella sp < S aureus < P mirabilis.

Antimicrobial LDPE/EVOH Layered Films Containing Carvacrol Fabricated by Multiplication Extrusion.

This work describes the fabrication of antimicrobial multilayered polymeric films containing carvacrol (used as a model essential oil) by co-extrusion and multiplication technique. The microlayering process was utilized to produce films, with up to 65 alternating layers, of carvacrol-containing low-density polyethylene (LDPE) and ethylene vinyl alcohol copolymer (EVOH). Carvacrol was melt compounded with LDPE or loaded into halloysite nanotubes (HNTs) in a pre-compounding step prior film production. The detailed nanostructure and composition (in terms of carvacrol content) of the films were characterized and correlated to their barrier properties, carvacrol release rate, and antibacterial and antifungal activity. The resulting films exhibit high carvacrol content despite the harsh processing conditions (temperature of 200 °C and long processing time), regardless of the number of layers or the presence of HNTs. The multilayered films exhibit superior oxygen transmission rates and carvacrol diffusivity values that are more than two orders of magnitude lower in comparison to single-layered carvacrol-containing films (i.e., LDPE/carvacrol and LDPE/(HNTs/carvacrol)) produced by conventional cast extrusion. The (LDPE/carvacrol)/EVOH and (LDPE/[HNTs/carvacrol])/EVOH films demonstrated excellent antimicrobial efficacy against E. coli and Alternaria alternata in in vitro micro-atmosphere assays and against A. alternata and Rhizopus in cherry tomatoes, used as the food model. The results presented here suggest that sensitive essential oils, such as carvacrol, can be incorporated into plastic polymers constructed of tailored multiple layers, without losing their antimicrobial efficacy.

A kinetic study of essential oil components distillation for the recovery of carvacrol rich fractions

The distillation kinetics of the different essential oil components from four Lamiaceae herbs was investigated. Origanum vulgare L. ssp. hirtum, Origanum onites L., Origanum dictamnus L., and Satureja thymbra L. (harvests of 2013–2015), that present similar composition of essential oil were distilled in a laboratory-scale steam distiller. The recovery of the essential oil (EO) and its components was adequately described by non-steady state diffusion kinetics. The results clearly evidenced that the components present different distillation rates, thus resulting in variation of the EO composition during the process. The distillation rate constants decreased with the increase of the individual components boiling points, therefore, the heavy volatiles, such as carvacrol, could be recovered separately after the distillation of the most volatile compounds. This hypothesis was experimentally confirmed for O. vulgare and S. thymbra; the separate fractions were obtained from 40 and 50 min respectively up to the end of distillations. GC–MS analyses of the fractions revealed very high carvacrol content that amounted up to 92.5% for O. vulgare. The procedure could be applicable in industrial practice in order to recover fractions with pre-designed quality characteristics.

Nema

The evaluation of the inhibition effect achieved by essential oils of dill ( Anethum graveolens L . ), oregano ( Origanum vulgare L.), juniper (Juniperus communis L.), sage ( Salvia officinalis L.) and winter savory ( Satureja montana L.) on seed germination and shoot growth of Johnson grass ( Sorghum halepense L.) was tested in laboratory. The chemical composition of essential oils was analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). The major constituents were carvon (40.5%) and limonene (32.2%) for A. graveolens essential oil, carvacrol (73.7%) for O. vulgare essential oil, α-pinene (43.5%) for J. communis essential oil, b-thujone (32.7%) and camphor (17.2%) for S. officinalis essential oil, thymol (44.6%) and p- cimene (13.4%) for S. montana essential oil. The in vitro study on herbicidal activity was carried out on seed germination and shoots length of S. halepense ; A. graveolens , O. vulgare , S. montana essential oils significantly inhibited the germination and shoot length and their herbicidal activity could be attributed mainly to their high content of carvone, carvacrol and thymol. A. graveolens , O. vulgare and S. montana essential oils reduced seed germination by 61.5%, 52.7% and 47.3%, respectively, while J. communis and S. officinalis essential oils stimulated germination (7.7% and 2.2%, respectively). The shoot growth reduction for almost all essential oils, except J. communis essential oil , was more than 30%. The solution of A. graveolens , O. vulgare and S. montana essential oils exhibited more powerful bio-herbicidal effect compared to J. communis and S. officinalis essential oils on the germination and shoot growth of S. halepense .

Spectroscopic examination and release of microencapsulated oregano essential oil

Oregano essential oil (EO) of Greek origin with high carvacrol content (86.84 %) was encapsulated by spray drying using Arabic gum, modified starch and maltodextrin (75:12.5:12.5) as wall materials. The spray-dried product (EOSD) consisted of roundish particles with narrow size distribution. FT-IR and Raman spectroscopy identified the EO in EOSD, with Raman spectra showing more distinct peaks and a small shift of the peak at 1260 cm-1 (assigned to the stretching vibration of the bond of C-O of the phenol), implying only minor chemical interaction with the wall materials. Release of the EO from EOSD was described by the Hixson-Crowell equation (R2=0.986) with apparent diffusion coefficient 8.3x10-10 m2/s. These findings indicate that microencapsulation by spray drying did not affect the quality of the oregano EO and provided relatively fast and complete release.