Carvacrol Chemotype Research Articles

Thymus algeriensis essential oil: Phytochemical investigation, bactericidal activity, synergistic effect with colistin, molecular docking, and dynamics analysis against Gram-negative bacteria resistant to colistin

Due to the increasing resistance prevalence to the last line of antibiotics, such as colistin, and the rising threat of multi-drug resistant bacteria, it is crucial to find alternative therapeutic options. The current study focuses on evaluating antibacterial activities alone and in combination with colistin of Thymus algeriensis essential oil (TA-EO) against colistin-resistant Klebsiella pneumoniae, Pseudomonas aeruginosa, and Escherichia coli co-harboring mcr-1 gene. GC/MS was used to determine the chemical composition of TA-EO. Disc diffusion and microdilution techniques were used to evaluate the antimicrobial activities of TA-EO. Synergism between colistin and TA-EO was evaluated by checkerboard assay. The major compounds of TA-EO were docked with known enzymes involved in resistance to colistin, as well as the biosynthesis of peptidoglycan and amino acids. GC/MS revealed that TA-EO was of carvacrol chemotype (67.94 %). The TA-EO showed remarkable antibacterial activities against all Gram-negative bacterial strains, with the diameter of inhibition zones varied between 30 and 50 mm and a ratio MBC/MIC equal to 1 for the vast majority of bacterial isolates. Interestingly, the checkerboard showed synergism between TA-EO and colistin against colistin-resistant Escherichia coli co-harboring mcr-1 gene (FICI˂1) and reduced the MIC of colistin by 16- to 512-fold and those of TA-EO by 4- to 16-fold. The docking study demonstrated that carvacrol had high binding free energies against MCR-1, a phosphoethanolamine transferase extracellular domain, and its catalytic domain implicated in resistance to colistin, and undecaprenyl pyrophosphate synthase in complex with magnesium which is involved in bacterial peptidoglycan biosynthesis. The molecular dynamics study for 100-ns also revealed the stability of the MCR-1/carvacrol complex with a constant surface area over the simulation. These results support using carvacrol or TA-EO as a bactericidal agent, either alone or in combination with colistin, to treat infections caused by colistin-resistant Gram-negative bacteria.

GC-MS evaluation of the essential oils from the newly developed cultivars of Satureja montana grown in southern Ukraine

Satureja montana L. is widely used in traditional medicine and culinary. New varieties of this species are created and grown with different purposes. The essential oil (EsO) samples were obtained from the fresh flowering shoots of four new Ukrainian cultivars of S. montana: 'Krymski smaragd', 'Lunata', '697-1', and 'N3-18'. The EsO of cultivars ''Lunata' and 'Krymski smaragd' were studied in two following harvest years (2019 and 2020). The EsO samples were analyzed using gas chromatography-mass spectrometry (GC-MS). More than 60 components were identified in the studied EsO. Carvacrol was the principal component of all the samples (58.3-87.0% (as GC-MS relative abundances). p-Cymene was the second predominant component (5.0–8.8%) in the EsO of all the cultivars collected in the 2020 year, while cultivars ''Lunata' and 'Krymski smaragd' gathered in 2019 contained it in much fewer amounts (1.7% and 0.5%, respectively). γ-Terpinene was the third main component of EsO of the most studied varieties (0.9% to 6.6%). Only cultivar 'N697-1' contained carvacrol methyl ether at a significant level (11.7%). All the tested samples met the requirements of International Standard Organization (ISO) 79284:1991(E), supposing that the qualitative composition of the S. montana EsO should comprise the following main constituents: γ-terpinene, p-cymene, linalool, terpinen-4-ol, and carvacrol. It can be concluded that we dealt with the carvacrol chemotypes of S. montana. It was also revealed that growth year influenced the EsO composition of 'Krymski smaragd' and 'Lunata' cultivars. Our results afforded to compare the EsO of the S. montana new cultivars

Microbiological Studies on the Influence of Essential Oils from Several Origanum Species on Respiratory Pathogens.

Essential oils (EOs) with established and well-known activities against human pathogens might become new therapeutics in multidrug-resistant bacterial infections, including respiratory tract infections. The aim of this study was to evaluate the antimicrobial activity of EOs obtained from several samples of Origanum vulgare, O. syriacum, and O. majorana cultivated in Poland. EOs were analyzed by GC-MS and tested against four bacterial strains: Staphylococcus aureus (MRSA), Haemophilus influenzae, Haemophilus parainfluenzae, and Pseudomonas aeruginosa. Chemical analyses showed that the Eos were characterized by a high diversity in composition. Based on the chemical data, four chemotypes of Origanum EOs were confirmed. These were carvacrol, terpineol/sabinene hydrate, caryophyllene oxide, and thymol chemotypes. Thin-layer chromatography-bioautography confirmed the presence of biologically active antibacterial components in all tested EOs. The highest number of active spots were found among EOs with cis-sabinene hydrate as the major compound. On the other hand, the largest spots of inhibition were characteristic to EOs of the carvacrol chemotype. Minimal inhibitory concentrations (MICs) were evaluated for the most active EOs: O. vulgare 'Hirtum', O. vulgare 'Margarita', O. vulgare 'Hot & Spicy', O. majorana, and O. syriacum (I) and (II); it was shown that both Haemophilus strains were the most sensitive with an MIC value of 0.15 mg/mL for all EOs. O. majorana EO was also the most active in the MIC assay and had the highest inhibitory rate in the anti-biofilm assay against all strains. The most characteristic components present in this EO were the trans-sabinene hydrate and terpinen-4-ol. The strain with the least sensitivity was the MRSA with an MIC of 0.6 mg/mL for all EOs except for O. majorana, where the MIC value reached 0.3 mg/mL. Scanning electron microscopy performed on the Haemophilus influenzae and Haemophilus parainfluenzae biofilms showed a visible decrease in the appearance of bacterial clusters under the influence of O. majorana EO.

Origanum heracleoticum Essential Oils: Chemical Composition, Phytotoxic and Alpha-Amylase Inhibitory Activities

Many studies have demonstrated the herbicidal effects of several essential oils and their possible use as substitutes for chemical herbicides. Several enzymes play a very significant role in seed germination: among these, α-amylase could be involved in essential oil phytotoxic processes. The aims of this study were to compare the chemical composition of the essential oils of two ecotypes of O. heracleoticum growing in Cilento (Southern Italy) and to study their possible use as natural herbicide using Raphanus sativus, Sinapis arvensis and Lolium multiflorum seeds. Moreover, a possible inhibitory activity on the α-amylase enzyme extracted from germinating seeds was evaluated as a possible mechanism of action. Both oils, characterized by GC-MS, belonged to a carvacrol chemotype. The alpha-amylase activity was determined using DNSA (dinitrosalicylic acid) assay quantifying the reducing sugar produced. Furthermore, the essential oils demonstrated phytotoxicity at the highest dose tested, and an inhibitory effect on α-amylase, probably correlated with the phytotoxic effects, was registered. The oils showed interesting phytotoxic and alpha-amylase inhibitory activities, which deserve to be further investigated.

Exploring the nexus between the composition of essential oil and the bacterial phytobiome associated with different compartments of the medicinal plants Origanum vulgare ssp. vulgare, O. vulgare ssp. hirtum, and O. heracleoticum

The emergence of new multidrug-resistant (MDR) pathogens brought attention to the need for new antimicrobial compounds. One of the advances in addressing the global issue of antibiotic resistance is the discovery that microorganisms residing inside medicinal plants (i.e., the endophytes) may contribute to the production of metabolites of pharmaceutical interest. In this work, the composition of the essential oil (EO) and the cultivable bacterial communities isolated from three different species belonging to the genus Origanum , i.e., O. vulgare ssp . vulgare, O. vulgare ssp . hirtum and O. heracleoticum were analyzed, to check the possible nexus existing between them. The three species exhibited different EO aroma profiles, revealing two trans -sabinene hydrate chemotypes and a carvacrol chemotype. The composition of the bacterial endophytic cultivable microbiome isolated from flowers, leaves, and stems and the bacterial communities isolated from bulk soil were characterized at the genus, species, and/or strain level. The analyses revealed a high degree of biodiversity and a low number of strains shared between the three plant species and compartments of the same plant, suggesting the existence of one or more forces responsible for the distribution of the endophytes in the different microenvironments of the plant. Data obtained also suggested that the composition of the EO might be involved in the structuring of the microbial community and that bacteria might be able to colonize the plant since they are resistant to the antimicrobial activity exhibited by the EO itself and/or able to utilize some compounds as a carbon and energy source. Lastly, the composition of microbial communities might enhance or influence the EO composition. Schematic representation of the experimental strategy used in the present work . • Three Origanum plants exhibited different essential oil aroma profiles. • Cultivable bacterial endophytes were isolated and molecularly characterized. • A very low number of bacterial strains was shared between plants. • Different plant compartments were inhabited by different endophytic communities. • Essential oil composition might be involved in the structuring of the microbiome.

Variation in essential oil composition within and among Tunisian Thymus algeriensis Boiss et Reut. (Lamiaceae) populations: Effect of ecological factors and incidence on antiacetylcholinesterase and antioxidant activities

The variation of the essential oil composition of fourteen Tunisian Thymus algeriensis populations and their antioxidant and antiacetylcholinesterase activities were assessed. At the species level, α-pinene, 1,8-cineole, camphor, caryophyllene oxide and carvacrol were the main compounds. Significant variation in the essential oil composition was observed between populations according to ecological factors. Six chemotypes were revealed (1,8-cineole-β-panasinsene/1,8-cineole/caryophyllene oxide/1,8-cineole-camphor-caryophyllene oxide/1,8-cineole-camphor-caryophyllene oxide-terpenyl acetate/carvacrol) with the distinction of upper arid populations (Ta 13 and Ta 14) with the dominance of carvacrol chemotype. The occurrence of the carvacrol was positively correlated to the evapotranspiration, summer drought stress and the temperature of the warmest months of the year.High chemical intrapopulation variability was also observed, revealing the presence of seven chemotypes (carvacrol/terpenyl acetate/caryophyllene oxide/linalool-linalyl acetate/1,8-cineole-β-panasinsene/1,8-cineole/1,8-cineole-camphor). The level of antioxidant and anti-acetylcholinesterase activity was linked to their chemical composition difference. The best activities were revealed for populations Ta 13 and Ta 14 from the most arid zones, characterized by their carvacrol richness.

Impact of Edaphic and Climatic Factors on Thymus pulegioides Essential Oil Composition and Potential Prevalence of Chemotypes.

Intraspecific chemical polymorphism is characteristic of essential oil bearing Thymus pulegioides (Lamiaceae). Soil chemical composition and climatic conditions can influence not only quantitative and qualitative composition of essential oils, but also on prevalence of different chemotypes in space. The purpose of study was to determine the impact of edaphic and climatic factors on T. pulegioides essential oil composition and potential chemotypes prevalence. It were investigated 131 habitats of T. pulegioides in all ten climatic sub-districts of Lithuania. Essential oils were isolated by hydrodistillation and analysed by GC-FID and GC-MS. The content of humus was estimated by oxidation method, the content of mobile potassium (K2O) and mobile phosphorus (P2O5)—flame photometry using 0.2 M HCl solution, the soil pH—electrometrically and 15 elements of soil—by energy-dispersive X-ray fluorescence. The meteorological data (temperature, rainfall, photosynthetically active solar radiation and sunshine duration) were obtained from the meteorological bulletins. Results showed that humus in soil positively, manganese and cobalt—negatively influenced on the essential oil accumulation in T. pulegioides. Carvacrol was the most common compound in the essential oil of T. pulegioides; higher amounts of sulphur and mobile phosphorus, lower amounts of sodium in soil, higher rainfall in blooming period are favourable for this compound and for potential prevalence of carvacrol chemotype. Geraniol was frequent in the eastern and the central part of Lithuania, where the temperature in vegetation season is higher, and in soils characterised by higher and lower amounts of sodium and chlorine, respectively. Thymol, linalool and α-terpinyl acetate were rare. Edaphic and climatic conditions can differently influence on essential oil yield and chemical composition of species as well as on potential prevalence of different chemotypes of same species in space.

The chemical biogeography of a widespread aromatic plant species shows both spatial and temporal variation.

Plants produce a wide variety of secondary metabolites, but intraspecific variation in space and time can alter the ecological interactions these compounds mediate. The aim of this work was to document the spatial and temporal chemical biogeography of Monarda fistulosa. I collected leaves from 1587 M. fistulosa individuals from 86 populations from Colorado to Manitoba, extracted and analyzed their terpenes with gas chromatography, mapped monoterpene chemotypes, and analyzed chemical variation with principal component analysis. I also measured the amounts of terpenes in different plant tissues to examine intraplant variation and monitored leaf terpene chemistry over a single growing season to examine temporal patterns. Finally, I extracted terpenes from herbarium samples up to 125 years old and compared the chemotypes with recent samples from the same sites. M. fistulosa populations consisted mostly of thymol (T) and carvacrol (C) chemotypes, but geraniol (G) and (R)‐(−)‐linalool (L), a chemotype new to this species, were also present. A principal component analysis showed that most of the chemical variation across populations was due to the amounts of the dominant terpene in plants. Intraplant tissue chemistry revealed that leaves mostly had the greatest amounts of terpenes, followed by floral structures, stems, and roots. Short‐term temporal variation in leaf chemistry of T and C plants over a growing season showed that plants produced the highest levels of biosynthetic precursors early in the season and their dominant monoterpenes peaked in mid‐summer. Plant chemotype was discernable in the oldest herbarium samples, and 15 of 18 historic samples matched the majority chemotype currently at the site, indicating that population chemotype ratios may remain stable over longer time scales. Overall, the results show that plant species' secondary chemistry can vary both spatially and temporally, which may alter the biological interactions that these compounds mediate over space and time.

Geraniol and Carvacrol in Essential Oil Bearing Thymus pulegioides: Distribution in Natural Habitats and Phytotoxic Effect.

Phenolic and non-phenolic chemotypes of Thymus pulegioides L. are common in Europe. Essential oils of these chemotypes, as various compositions of allelochemicals, can have different phytotoxic effects on neighboring plants in natural habitats. The aim of this study was to establish the distribution of carvacrol and geraniol in T. pulegioides, growing wild in Lithuania, and compare phytotoxity of essential oils of carvacrol and geraniol chemotypes on selected plant species. In investigating 131 T. pulegioides habitats, essential oils were isolated by hydrodistillation and analyzed by GC-FID and GC-MS. Phytotoxity of essential oils extracted from carvacrol and geraniol chemotypes transmitted through water and air to selected plants was determined under laboratory conditions. Pharmacologically valuable Hypericum perforatum L. and the important forage grass Phleum pratense L. were respectively selected for experimentation from among 35 medicinal plants and 10 feed Poaceae species, growing in T. pulegioides habitats. Field results showed that carvacrol is common throughout Lithuania’s territory, whereas the geraniol is predominantly located under the continental climatic conditions of the eastern region of the country. In the laboratory experiment, it was established that there was stronger inhibition of P. pratense seed germination by the essential oil of the geraniol chemotype than the carvacrol chemotype. None of the H. perforatum seeds germinated after exposure to the essential oil of the geraniol chemotype. In general, this study builds on previous studies by providing further evidence that different T. pulegioides chemotypes have contrasting phytotoxic effects on neighboring plants within their natural habitats.

Antioxidant and Antimicrobial Activities of Thymus vulgaris L. Essential Oil Growing Wild in Tunisia

The aim of this work is to investigate the chemical composition, antioxidant, and antimicrobial activities of Tunisian Thymus vulgaris essential oil (TVEO). DPPH, superoxide anion, reducing power, chelating effect on ferrous ions and β-Carotene assays have been employed to determine the antioxidant potential of TVEO. In contrast, 24 reference bacterial strains and 16 fungal strains have been used for the assessment of the antimicrobial activity. Results revealed that TVEO has as carvacrol (67.33%) chemotype, it was equipped with an important antioxidant capacity that is better (P<0.05) than synthetic antioxidants (BHT, BHA, Vitamin C and EDTA) except for superoxide anion test. A higher antimicrobial activity was also observed with IZ, MIC and MBC values of bacterial strains were ranged from 10.33±0.57 to 37.33±0.57mm; 0.019 to 0.078 mg/mL and 0.039 to 0.31 mg/mL respectively. But those of fungal strains were varied between 24.66±1-47.33±1.53 mm; 0.004-0.078 mg/mL and 0.019-0.15 mg/mL respectively. In summary, the obtained data makes TVEO as a good and suitable candidate for its use in food and pharmaceutical purposes.

Terpene synthase gene expression evaluation through RT-qPCR in Thymus caespititius

Thymus caespititius Brot. is an interesting aromatic plant due to the valuable monoterpenes it produces considering their properties and biological activities. Several chemotypes have been identified in this species, however, essential oil composition can vary throughout the year in the terpenes’ relative percentage. The first objective was to evaluate chemical stability, based on a 20-month survey in essential oil (EO) composition through GC and GC-MS, in two accessions belonging to the carvacrol chemotype, Tc2 and Tc4. Together with this evaluation, a quantitative study of gene expression was performed through reverse transcription quantitative PCR (RT-qPCR), for the most important genes involved in the biosynthesis of γ-terpinene (precursor of thymol and carvacrol), TcTPS2 and TcTPS4, and α-terpineol, TcTPS5. This second objective addressed the correlation between seasonal EO variation and terpene synthase gene expression patterns and compared the trends of seasonal variation between both plant accessions. The results show 22, 48 and 90-fold variation in gene expression for TcTPS2, TcTPS4 and TcTPS5, respectively. Expression of TcTPS5 was much more variable than those coding for γ-terpinene synthase. The two accessions evaluated showed Tc2 had a more stable gene expression compared to Tc4. Although gene expression and terpene accumulation were in accordance for most timepoints, no significant overall correlation could be found. Our results suggest a transcriptional regulation for TcTPS2 and TcTPS4. For TcTPS5 regulation at post transcriptional level must be present, accounting for differences in the α-terpineol relative amount and adding new layers of complexity in specialized metabolism. Further studies should be pursued to identify all the players involved in controlling the final bouquet of essential oil composition.

Antifungal activity of Zataria multiflora Boiss. essential oils and changes in volatile compound composition under abiotic stress conditions

There is an increasing need for natural compounds for pest control and food preservation in agriculture, food and dairy industries. To satisfy this need, essential oils (EOs) from aromatic plants can serve as flavors, food preservatives and ecofriendly pesticides. This study investigated the potential of different EOs from field-collected leaves of fourteen Zataria multiflora Boiss. populations representing three different chemotypes (carvacrol, thymol and linalool) to inhibit a broad spectrum of fungal pathogens important in food industry and agriculture and the relationship between total leaf elements concentration and EOs compounds. Furthermore, a greenhouse experiment was performed to elucidate the effects of heat stress (33 °C vs. 20 °C), drought stress (50 % reduced irrigation), and ultraviolet light intensity (3, 6 and 9 W m−2 UV-A radiation) on the relative content of specific volatile compounds. The results indicated that low concentrations of carvacrol and thymol, but not of linalool chemotype EOs inhibit significantly the growth of pre- and postharvest pathogens Colletotrichum lindemuthianum, Fusarium sambucinum, Fusarium culmorum, Alternaria dauci and Botrytis cinerea (thymol/carvacrol EOs: 0.8−1 μL, linalool EOs: 4 μL). The analyses revealed further significant correlations between the concentrations of mineral elements in Z. multiflora leaves and relative amounts of EO compounds and antifungal activity. Abiotic stresses, particularly heat and the interaction of drought and heat, induced changes in plants of the linalool chemotype resulting in higher relative amounts of carvacrol (22.7 % and 32.9 % vs. 1.5 %), while drought stress alone did not influence the relative amount of the main volatile compounds of Z. multiflora (carvacrol 1.7 %). Furthermore, the relative amount of linalool was slightly reduced in the linalool chemotype, when plants were subjected to high intensities of UV-A radiation (33.9 % vs. 44.6 %), whilst the relative amount of carvacrol was slightly increased (20.1 % vs. 9%). Moreover, the main volatile compounds of plants from the carvacrol chemotype did not change in response to abiotic stresses. Understanding the effect of environmental conditions on aromatic plant populations and chemotype development helps agriculture and food industry fully exploiting the potential of aromatic plants as a source of natural sustainable fungicides or insecticides.

Genetic and Flower Volatile Diversity in Natural Populations of Origanum vulgare subsp. hirtum (Link) Ietsw. in Bulgaria: Toward the Development of a Core Collection.

We studied the genetic and flower volatile diversity in natural populations of Origanum vulgare subsp. hirtum (Link) Ietsw. in Bulgaria using simple sequence repeat (SSR) and sequence-related amplified polymorphism (SRAP) markers and gas chromatography/mass spectrometry (GC/MS) analysis of flower volatiles from individual plants. Two regions, including the Kresna Gorge and Eastern Rhodopes, typical for the species comprising eight populations and 239 individual plants were included in this study. An analysis with 11 SSR markers and eight SRAP primer combinations showed that SRAP markers were substantially more informative than the SSR markers and were further used for genetic diversity analysis. The results showed low-range to mid-range genetic differentiation between the populations with pairwise fixation index (Fst) values ranging between 0.0047 and 0.11. A total of 10 genetic clusters were identified. An analysis of the flower volatile diversity identified a total of 63 compounds with the vast majority of plants belonging to the carvacrol chemotype and just a single plant to the thymol chemotype. Large deviations were observed for individual compounds within each region as well as within the populations. Hierarchical clustering showed a clear sample grouping based on the two different regions. In addition, an in-depth analysis identified six major and 23 minor metabolite clusters. The overall data set and cluster analysis were further used for the development and testing of a simple and straightforward strategy for the selection of individual plants for the development of a core collection representing the sampled natural populations for this species in Bulgaria. The proposed strategy involves precise genetic clustering of the tested plants followed by the selection of a minimal set from each genetic cluster representing the different metabolite clusters. The selected core set was further compared with a core set extracted by the PowerCore software. A comparison of the genetic and metabolic affiliation of the members of both sets showed that the reported approach selected representatives from each genetic cluster and minor metabolic cluster, whereas some metabolic clusters were unrepresented in the PowerCore set. The feasibility and efficiency of applying the pointed strategy for the development of a core collection representing both the genetic and metabolite diversity of natural populations in aromatic and medicinal plants toward subsequent steps of selection and breeding are discussed.

Biofilm inhibition by biocompatible poly(ε-caprolactone) nanocapsules loaded with essential oils and their cyto/genotoxicity to human keratinocyte cell line

Essential oils (EOs) of Thymus capitatus (Th) carvacrol chemotype and Origanum vulgare (Or) thymol and carvacrol chemotype were encapsulated in biocompatible poly(ε-caprolactone) nanocapsules (NCs). These nanosystems exhibited antibacterial, antifungal, and antibiofilm activities against Staphylococcus aureus, Escherichia coli, and Candida albicans. Th-NCs and Or-NCs were more effective against all tested strains than pure EOs and at the same time were not cytotoxic on HaCaT (T0020001) human keratinocyte cell line. The genotoxic effects of EO-NCs and EOs on HaCaT were evaluated using an alkaline comet assay for the first time, revealing that Th-NCs and Or-NCs did not induce DNA damage compared with untreated control HaCaT cells in vitro after 24 h. The cells morphological changes were assessed by label-free live cell Raman imaging. This study demonstrate the ability of poly(ε-caprolactone) nanocapsules loaded with thyme and oregano EOs to reduce microbial and biofilm growth and could be an ecological alternative in the development of new antimicrobial strategies.

Antioxidant Capacity of Origanum heracleoticum L. Flower and Leaf Extracts and Their Essential Oil Profiles of Plants from Micropropagation and Collection from Natural Habitats

The composition of the essential oils and the antioxidant properties of Origanum heracleoticum L. leaves and flowers collected from four different natural populations in Bulgaria (two locations in Kresna Gorge and two locations in Rhodopes Mountain) were studied and compared with those of micropropagated and field-adapted plants. Explants for micropropagation from wild-growing plants from Gorna Breznitsa (Kresna Gorge) were used. The enzyme antioxidant potential characterised by the activity of superoxide dismutase, catalase, guaiacol peroxidase, ascorbate peroxidase as well as the non-enzyme antioxidant potential characterized by the content of phenols, flavonoids, water- and lipid-soluble antioxidant metabolites, were affected by environmental conditions and type of propagation (wild or micro). The highest enzyme antioxidant potential was observed in the flowers and leaves of the micropropagated plants, followed by the plants collected from Gorna Breznitsa. The variation in the content of metabolites with antioxidant potential in the Greek oregano collected from the two locations from each two areas of Bulgaria was detected. The higher content of phenols and flavonoids was detected in micropropagated plants as well as in wild-plants collected from two localities from Kresna Gorge, when compared with the wild-plants collected from Eastern Rhodopes. Forty-five compounds in the O. heracleoticum essential oil collected from the native populations were identified. Based on the essential oil composition, and especially on the carvacrol and thymol contents, the O. heracleoticum plants from all investigated natural populations in Bulgaria belonged to the carvacrol chemotype. Besides environmental conditions, another factor that affected the composition of O. heracleoticum essential oil was the existence of chemotypes.

Variation in Phytochemical, Morphological, and Ploidy Levels of Iranian Thymus Species.

Thymus is one of the most important genera of the Lamiaceae family. This work was performed to assess inter and intra species variation, which is an indispensable prerequisite for the selection and the exploitation of the germplasm, using yield, secondary metabolites, and ploidy level criteria. Nineteen Iranian populations belonging to 11 Thymus species which includes T. vulgaris were used in this study. The results of cytological observations on the 19 populations revealed the three root-tip chromosome numbers of 2n=2x=30, 2n=4x=56 or 60 (diploid and tetraploid). This study also presents the results of a two-year field experiment that evaluates the agronomic and morphology of the 19 populations of Thymus spp. Cluster analysis grouped the populations into six groups and explained the relationships among ploidy levels, morphological traits, and essential oils (EOs). In general, diploid species belonged to the thymol chemotype, whilst carvacrol chemotype consistently dependent on the gene-dosage effect. Thymus migricus, T. daenensis-2, T. serpyllum, and T. trautvetteri populations with diverse thymol background were the best selection as the parents to improve thymol in a breeding program. Moreover, dry and fresh weight criteria can be used to improve EO content in thyme. Achieving this goal would be expected by crossing T. migricus and T. daenensis-2. Finally, providing relevant information on the ploidy level of Thymus species, with emphasis on morphology and EO components variations, may be recommended for the selection of populations or species to improve bioactive components as well as morphological traits in future breeding programs.

Bioactivity of Different Chemotypes of Oregano Essential Oil against the Blowfly Calliphora vomitoria Vector of Foodborne Pathogens.

Simple SummaryCalliphora vomitoria L. is a very common synanthropic blowfly. Since it is attracted by human food, it plays a main role in the transmission of foodborne diseases. Among aromatic plant essential oils (EOs), those of spices are the most suitable to protect food from insect pests. In the present work, we determined the bioactivity of three oregano EOs against C. vomitoria. The chemical analyses showed that the EOs belonged to three chemotypes, one with a prevalence of carvacrol and two with a prevalence of thymol. The bioassays showed that the bioactivity of the EOs significantly varies among chemotypes, with the thymol chemotype showing an overall higher efficacy compared to the carvacrol one.Blowflies play a substantial role as vectors of microorganisms, including human pathogens. The control of these insect pests is an important aspect of the prevention of foodborne diseases, which represent a significant public health threat worldwide. Among aromatic plants, spices essential oils (EOs) are the most suitable to protect food from insect pests. In this study, we determined the chemical composition of three oregano EOs and assessed their toxicity and deterrence to oviposition against the blowfly Calliphora vomitoria L. The chemical analyses showed that the EOs belonged to three chemotypes: one with a prevalence of carvacrol, the carvacrol chemotype (CC; carvacrol, 81.5%), and two with a prevalence of thymol, the thymol/p-cymene and thymol/γ-terpinene chemotypes (TCC and TTC; thymol, 43.8, and 36.7%, respectively). The bioassays showed that although all the three EOs chemotypes are able to exert a toxic activity against C. vomitoria adults (LD50 from 0.14 to 0.31 μL insect−1) and eggs (LC50 from 0.008 to 0.038 μL cm−2) as well as deter the oviposition (Oviposition Activity Index, OAI, from 0.40 ± 0.04 to 0.87 ± 0.02), the bioactivity of oregano EOs significantly varies among the chemotypes, with the thymol-rich EOs (TCC and TTC) overall demonstrating more effectiveness than the carvacrol-rich (CC) EO.

Antimicrobial and Antibiofilm Activities of Essential Oils against Escherichia coli O157:H7 and Methicillin-Resistant Staphylococcus aureus (MRSA).

The emergence of multidrug resistant microorganisms represents a global challenge due to the lack of new effective antimicrobial agents. In this sense, essential oils (EOs) are an alternative to be considered because of their anti-inflammatory, antiviral, antibacterial, and antibiofilm biological activities. Therefore, multiple efforts have been made to consider the potential use of EOs in the treatment of infections which are caused by resistant microorganisms. In this study, 15 EOs of both Colombian and introduced aromatic plants were evaluated against pathogenic strains of E. coli O157:H7 and methicillin resistant Staphylococcus aureus (MRSA) in planktonic and sessile states in order to identify relevant and promising alternatives for the treatment of microbial infections. Forty different compounds were identified in the 15 EO with nine of them constituted mainly by oxygenated monoterpenes (OM). EOs from Lippia origanoides, chemotypes thymol, and carvacrol, displayed the highest antibacterial activity against E. coli O157:H7 (MIC50 = 0.9 and 0.3 mg/mL, respectively) and MRSA (MIC50 = 1.2 and 0.6 mg/mL, respectively). These compounds from EOs had also the highest antibiofilm activity (inhibition percentage > 70.3%). Using scanning electron microscopy (SEM), changes in the size and morphology of both bacteria were observed when they were exposed to sub-inhibitory concentrations of L. origanoides EO carvacrol chemotype. EOs from L. origanoides, thymol, and carvacrol chemotypes represented a viable alternative for the treatment of microbial infections; however, the Selectivity Index (SI ≤ 3) indicated that it was necessary to study alternatives to reduce its in vitro cytotoxicity.

Chemical diversity in leaf and stem essential oils of Origanum vulgare L. and their effects on microbicidal activities

Essential oils (EOs) from the stems and leaves of Origanum vulgare L. grown in Saudi Arabia and Jordan were analyzed by gas chromatography–mass spectrometry (GC–MS) and GC–flame ionization detector (FID) techniques on two different columns (polar and nonpolar). A detailed phytochemical analysis led to the identification of 153 constituents of these essential oils. Both Saudi and Jordanian plants are classified by chemotypes rich in cymyl-compounds. However, the Saudi Origanum contains carvacrol as the major component and is, thus, characterized as a carvacrol chemotype, while the Jordanian Origanum contains thymol as the major component, and, thus, it is classified as a thymol chemotype. In addition, the antimicrobial activities of the studied EOs and their major components, including carvacrol and thymol, were evaluated against various Gram-positive and Gram-negative microorganisms. All the tested compounds exhibited significant antimicrobial activity against all the tested bacteria. Among them, thymol demonstrated superior activity against all the tested organisms, followed by carvacrol. Moreover, results on oil composition and oil yield of O. vulgare L. from different parts of the world is compared in detail with the present outcomes.

Morphological, Biochemical, and Molecular Analysis of Origanum vulgare L.

Background: The variation on morphological, biochemical, and genetic characters is very important in germplasm management and conservation strategies. Objective: To determine the diversity of 23 accessions from Origanum vulgare L. and a commercial cultivar on the basis of agronomical, biochemical and genetic features. Methods: Different characters related to vegetative growth and essential oil production were studied while the genetic relationships between the individuals were evaluated with the use of Amplified Fragment Length Polymorphism. Results: Despite the accessions exhibited cymyl- and acyclic-compounds, all the essential oil chemotypes according to the prevalence of essential oil fractions were phenotypically varied. A considerable amount of biomass with maximum values in plant height was achieved by thymol/γ-terpinene chemotype and carvacrol chemotype making them of particular interest for the production of high-quality plant material and further for the mechanical harvest. The AFLP analysis, performed using 10 primer combinations, to obtain a dendrogram of genetic similarity, revealed a genetic variability that could be useful for the selection of the proper genetic groups in future breeding programs. Conclusion: We identified two chemotypes thymol/γ-terpinene and carvacrol with their suitability for the production of biomass and essential oil and for the mechanical harvest. The results of the molecular characterization of the species may support and contribute to breeding programmes for agronomic and biochemical traits.