Essential Oil Components Research Articles

Transcriptional regulation and functional validation analysis of the McbZIP1 in Mentha canadensis L.

Monoterpenoids are the main components of Mentha canadensis essential oil. Monoterpene biosynthetic pathways have been explored, but the regulatory mechanisms remain unclarified. We identified an abscisic acid (ABA)-inducible A-type basic leucine zipper (bZIP) transcription factor McbZIP1 that was localized in the nucleus and positively regulates monoterpene synthesis. McbZIP1 was expressed in most M. canadensis tissues and was induced under ABA, mannitol, and NaCl treatments. McbZIP1 had transcriptional activity in yeast and the N terminus (amino acids 75–117) was sufficient for transactivation. Yeast one-hybrid and Dual-Luciferase assays showed that McbZIP1 binds to ABA-responsive elements in the promoter region of limonene synthase gene. Yeast two-hybrid and biomolecular fluorescence complementation assays revealed that McbZIP1 interacts with McSnRK2.4. Overexpression of McbZIP1 in peppermint resulted in dramatically up-regulated monoterpene biosynthesis gene levels and increased menthol contents. The results support a transcriptional regulation mechanism in which McbZIP1 serves as a positive regulator of menthol biogenesis. These findings contribute to the molecular mechanism of monoterpenoid biogenesis, which may have uses in genetic engineering and menthol production.

Optimising essential oil yields and quality from Pimenta dioica (L.) merr. Leaf: impact of NaCl concentrations, pH media and sequential separation of essential oil components during hydrodistillation

The study examined the effects of herb drying, salt concentration, pH, and sampling approach on essential oil yield and composition in Pimenta dioica (L.) Merr. Fresh samples yielded higher essential oil (EO) (1.25%) than shade-dried ones. Increasing NaCl concentration correlated with higher EO yields, while a basic pH favoured superior yields. Gas Chromatography identified Eugenol and β-myrcene as primary constituents. Eugenol content peaked at 10% NaCl (56.429%) and was lowest at pH 4 (42.850%). β-myrcene content was highest at pH 4 (31.476%). Hydro distillation with systematic sampling evaluated the effects of 14 fractions in different time frames. Phenylpropanoids (mainly eugenol) and acyclic monoterpene (mainly β-myrcene) dominated all fractions, with cyclic monoterpene (mainly limonene) enriched in the first four fractions. Fractions 10 to 14 showed significant increases in eugenol compared to the control. These findings provide insights for meeting market demands, enhancing the commercial potential of P. dioica EO.

Chemical composition and antimycobacterial, anti-Malassezia furfur and cytotoxic activities of essential oils from Callistemon viminalis (Sol. ex Gaertn.) G. Don leaves and flowers

Callistemon viminalis has been widely known due to its therapeutic properties. Tuberculosis is a deadly infectious disease caused predominantly by Mycobacterium tuberculosis. Other respiratory diseases may also be caused by nontuberculous mycobacteria. Malassezia furfur causes dermal inflammation and tissue damage. This study aimed to evaluate in vitro inhibitory effects of essential oils (EOs) from C. viminalis leaves (EO-CL) and flowers (EO-CF) against M. tuberculosis, Mycobacterium kansasii, Mycobacterium avium and M. furfur strains. Their cytotoxic activity was evaluated by the brine shrimp assay. Resulting MIC values of all EOs under study were promising since they ranged from 50 to 100 µg/mL. Both EO-CL and EO-CF showed nontoxicity against Artemia salina by the brine shrimp assay (LC50 > 1000 µg/mL). GC-FID and GC-MS analyses showed that 1,8-cineole was the major component of both EOs. These results revealed the promising potential of EO-CL and EO-CF to develop new antibacterial and antifungal drugs.

Investigating the Endophyte Actinomycetota sp. JW0824 Strain as a Potential Bioinoculant to Enhance the Yield, Nutritive Value, and Chemical Composition of Different Cultivars of Anise (Pimpinella anisum L.) Seeds.

Anise (Pimpinella anisum L.) seeds have various nutritional and therapeutic benefits and are thus considered a valuable addition to animal and human health. Hence, in this study, we aimed to induce the nutritive and biological value of anise seeds. To this end, the potential biofortification effect of the endophytic Actinomycetota sp. JW0824 strain, isolated during the fall of 2023 from the medicinal plant Achyranthes aspera, exhibiting natural distribution in the Jazan region of Saudi Arabia, was investigated in four varieties of anise seeds from Egypt, Tunisia, Syria, and Morocco. Results revealed significant increments (p < 0.05) in the seed dry weight percentage (DW%) and oil yields. In line with increased biomass accumulation, the metabolism of the primary and secondary metabolites was increased. There were differential increases in proteins, sugars, flavonoids, alkaloids, phenols, vitamins (e.g., β-carotene, ascorbic acid), and essential oil components (e.g., phenylpropanoids and monoterpenes), along with their precursor phenylalanine. Consistently, the activity of L-phenylalanine aminolyase (PAL) was increased in the Egyptian and Tunisian varieties at 83.88% and 77.19%, respectively, while 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase (DAHPS) activity increased in all varieties, with a significant 179.31% rise in the Egyptian variety. These findings highlight the beneficial effects of Actinomycetota sp. JW0824 as a bioinoculant for anise seeds, suggesting its potential application in agricultural practices to improve seed yield and quality. Further field trials are recommended to assess the commercial viability of this endophyte for enhancing anise seed production and potentially benefiting other plant species.

Expression of the changes in essential oil components of Shirazi thyme (Zataria multiflora Boiss.) as affected by various drying methods

The purpose of this research was to investigate the impact of various drying techniques on the quality characteristics of Shirazi thyme (Zataria multiflora Boiss.) using a completely randomized design with three replications. The treatments included fresh samples, shade-drying (SHD), sun-drying (SD), oven and vacuum-drying (OD and VD) each at three different temperatures (45, 55, and 65 °C), and microwave-drying (MD) at three different power levels (200, 400, and 600 W). The results indicated that vacuum and oven-drying at 45 °C were effective in preserving valuable secondary metabolites compared to traditional drying methods. The essential oil (EO) content was lowest in the microwave-drying at 600 W (1.3 %), and highest in vacuum-drying at 45 °C (2.99 %). Vacuum-drying at 45 °C also produced the highest levels of carvacrol (72.5 %) and thymol (7.21 %) content, while the lowest levels were found in fresh samples. The main components in the EO were monoterpene hydrocarbons (11.47–27.33 %), oxygenated monoterpenes (74.81–86.9 %), and oxygenated sesquiterpenes (76.50–86.50 %). The results showed that the amount of sesquiterpene hydrocarbons and oxygenated monoterpenes were higher at low temperatures. Furthermore, the color parameters showed changes based on the drying methods, with vacuum-drying at 45 °C increasing the L* parameter (lightness), vacuum-drying at 65 °C increasing the a* parameter)brightness(, and oven-drying at 45 °C increasing the b* parameter)greenness). Understanding the different methods and operations of drying Shirazi thyme can provide valuable insight for its professional application and development in food and pharmaceutical industries.

Determination of in vitro synergy and antibiofilm activities of antimicrobials and essential oil components

Using existing adrentimicrobials with essential oil components to prevent antimicrobial resistance is an alternative strategy. This study aimed to evaluate the resistance status, synergistic combinations, and in vitro biofilm formation activities of clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA), Stenotrophomonas maltophilia and Candida albicans against antimicrobial agents and cinnamaldehyde, carvacrol, eugenol, limonene and eucalyptol. Antimicrobial activities were evaluated by microdilution, cytotoxicity by XTT, synergy by checkerboard and time-kill, and biofilm inhibition by microplate methods. Cinnamaldehyde and carvacrol showed strong antimicrobial activity. Synergistic effects were observed when using all essential oils with antimicrobials. Only two C. albicans isolates showed antagonism with cinnamaldehyde and fluconazole. The constituents showed cytotoxic effects in the L929 cell line (except limonene). A time-kill analysis revealed a bacteriostatic effect on S. maltophilia and MRSA isolates and a fungicidal effect on C. albicans isolates. These results are important for further research to improve antimicrobial efficacy or to develop new agents.

Inhibitory potential of natural antimicrobial compounds against histamine-forming lactic acid bacteria

This work evaluated the potential of natural antimicrobial compounds to prevent histamine formation by inhibiting the microbial growth of Lentilactobacillus parabuchneri and Limosilactobacillus reuteri, bacteria selected for their ability to produce histamine in cheese. Of the evaluated compounds, eugenol, carvacrol, thymol and cinnamaldehyde were the most effective in inhibiting histamine-forming lactic acid bacteria and, therefore, in reducing histamine generation, even at concentrations below the minimum bactericidal concentration (MBC). Carvacrol significantly impacted both microbial viability and the metabolism of bacteria with the inhibition of decarboxylase activity. In the case of L. parabuchneri, the use of 0.7 mg/mL carvacrol (MBC/2) resulted in an 88% reduction in histamine content, and for L. reuteri a 96% reduction was observed by using 0.65 mg/(MBC/2). Therefore, using essential oil components during food processing and preservation would be a good strategy to prevent histamine accumulating in cheese and to, consequently, mitigate its adverse effects.

A cleaner and eco-friendly approach to simultaneous extraction and characterization of essential oil and pectin from Assam lemon peel and its application for energy generation through TENG devices

Scientists have been working on developing a green bio-TENG for portable remote devices, including wearables in the biomedical sector. The process involves obtaining pectin, a green material with anti-microbial properties, as a Triboelectric material. This study focuses on the extraction of essential oil (EO) and pectin from Assam lemon peel simultaneously. A single-step strategy was optimized using a central composite design-based response surface approach. The extracted pectin yielded 4.19 ± 0.31 % and 11.53 ± 0.11 %, respectively. GC-MS analysis revealed 52 volatile components in the Assam lemon EOs, with limonin being 94.47 % and β-Bisabolene being 1.26 %. Only khusilal was found in the EOs, a rare discovery in the scientific domain. The extracted pectin showed good purity and antimicrobial properties. The in vitro activities of the citrus EO against microbial cultures revealed its activity in controlling and eradicating bacterial and fungal growth. Hydro distillation followed by enzyme treatment is a promising approach that combines two separate extraction procedures. The produced biopolymer showed the generation of electrical signals under minimal pressure and stretching and prevented microbial degeneration when applied to a nanogenerator.

Effects of linalool on respiratory neuron activity in the brainstem-spinal cord preparation from newborn rats.

Linalool and linalyl acetate are major components of lavender essential oil. These substances possess many biological activities, such as anti-inflammatory activity, analgesic and anxiolytic effects, and anticonvulsant properties, and they also induce modulation of neuronal activity in the autonomic nervous system. However, there are no reports of the direct effects of linalool on respiratory activity. In the present study, we analyzed the effects of linalool and linalyl acetate on central respiratory activity in the brainstem-spinal cord preparation isolated from newborn rats. Linalool dose-dependently decreased the rate of respiratory activity. This effect was reversed by bicuculline, suggesting that linalool enhanced inhibitory synaptic connections via GABAA receptors. In addition, linalool reduced the coefficient of variation of inspiratory burst intervals and thus could work to stabilize the respiratory rhythm. Linalyl acetate did not cause inhibitory effects as observed in linalool treatment. Linalool depressed burst activity of pre-inspiratory neurons in the medullary respiratory networks and increased the amplitude of inspiratory inhibitory postsynaptic potentials of pre-inspiratory neurons. We concluded that linalool caused inhibitory effects on respiratory rhythm generation mainly through activation of presynaptic GABAA receptors of pre-inspiratory neurons.

Evaluation of Different Drying Treatments with Respect to Essential Oil Components, Phenolic and Flavonoid Compounds, and Antioxidant Capacity of Ajowan (Trachyspermum ammi L.).

Ajowan (Trachyspermum ammi L.) is considered a valuable spice and medicinal herb. In this study, the essential oil content and composition of the aerial parts of ajowan were investigated under different drying treatments (sun, shade, oven at 45 °C, oven at 65 °C, microwave, and freeze drying). Moreover, the phenolic content, flavonoid content, and antioxidant capacity of samples were also assessed. Fresh samples produced the highest essential oil content (1.05%), followed by those treated under sun (0.7%) and shade drying (0.95%). Based on gas chromatography-mass spectrometry (GC-MS), thirty compounds were determined in which thymol (34.84-83.1%), carvacrol (0.15-32.36%), p-cymene (0.09-13.66%), and γ-terpinene (3.12-22.58%) were the most abundant. Among the drying methods, freeze drying revealed the highest thymol content, followed by drying in a 45 °C oven. The highest TPC (total phenolic content) and TFC (total flavonoid content) were obtained in the fresh sample (38.23 mg TAE g-1 dry weight (DW)) and in the sample oven-dried at 45 °C (7.3 mg QE g-1 DW), respectively. Based on the HPLC results, caffeic acid (18.04-21.32 mg/100 gDW) and ferulic acid (13.102-19.436 mg/100 g DW) were the most abundant phenolic acids, while among flavonoids, rutin constituted the highest amount (10.26-19.88 mg/100 gDW). Overall, freeze drying was the most promising method of drying for preserving the phenolic (TPC) and flavonoid (TFC) compounds and oil components.

Hydrazinated geraniol derivatives as potential broad-spectrum antiprotozoal agents.

Geraniol, a primary component of several essential oils, has been associated with broad-spectrum antiprotozoal activities, although moderate to weak. This study primarily concentrated on the synthesis of hydrazinated geraniol derivatives as potential antiprotozoal agents. The synthesised compounds were tested in vitro against different parasitic protozoans of clinical relevance, including Trypanosoma brucei brucei, Trypanosoma brucei rhodesiense, Trypanosoma cruzi and Leishmania infantum. Compounds 6, 8, 13, 14 and 15 demonstrated low micromolar activity against the different parasites. Compounds 8, 13, 14 and 15 had the highest efficacy against Trypanosoma brucei rhodesiense, as indicated by their respective IC50 values of 0.74, 0.56, 1.26 and 1.00 µM. Compounds 6, 14 and 15 displayed the best activity against Trypanosoma brucei brucei, with IC50 values of 1.49, 1.48 and 1.85 µM, respectively. The activity of compounds 6, 14 and 15 also extended to intracellular Trypanosoma cruzi, with IC50 values of 5.14, 6.30 and 4.90 µM, respectively. Compound 6, with an IC50 value of 11.73 µM, and compound 14, with an IC50 value of 8.14 µM, demonstrated some modest antileishmanial activity.

Identification of Transcription Factors of Santalene Synthase Gene Promoters and SaSSY Cis-Elements through Yeast One-Hybrid Screening in Santalum album L.

The main components of sandalwood heartwood essential oil are terpenoids, approximately 80% of which are α-santalol and β-santalol. In the synthesis of the main secondary metabolites of sandalwood heartwood, the key gene, santalene synthase (SaSSY), can produce α-santalene and β-santalene by catalyzed (E, E)-FPP. Furthermore, santalene is catalyzed by the cytochrome monooxygenase SaCYP736A167 to form sandalwood essential oil, which then produces a fragrance. However, the upstream regulatory mechanism of the key gene santalene synthase remains unclear. In this study, SaSSY (Sal3G10690) promoter transcription factors and SaSSY cis-elements were screened. The results showed that the titer of the sandalwood cDNA library was 1.75 × 107 CFU/mL, 80% of the inserted fragments identified by PCR were over 750 bp in length, and the positivity rate of the library was greater than 90%. The promoter region of the SaSSY gene was shown to have the structural basis for potential regulatory factor binding. After sequencing and bioinformatics analysis, we successfully obtained 51 positive clones and identified four potential SaSSY transcriptional regulators. Sal6G03620 was annotated as the transcription factor MYB36-like, and Sal8G07920 was annotated as the small heat shock protein HSP20 in sandalwood. Sal1G00910 was annotated as a hypothetical protein of sandalwood. Sal4G10880 was annotated as a homeobox-leucine zipper protein (ATHB-15) in sandalwood. In this study, a cDNA library of sandalwood was successfully constructed using a yeast one-hybrid technique, and the transcription factors that might interact with SaSSY gene promoters were screened. This study provides a foundation for exploring the molecular regulatory mechanism involved in the formation of sandalwood heartwood.

Insecticidal Activity of Some Major Essential Oil Components against Metopolophium dirhodum and Its Predators.

Essential oils (EOs) are plant metabolites with important insecticidal effects. Nevertheless, information on the efficacy of the major substances on aphids and their natural enemies is still missing. The objective of this paper is, therefore, to identify the efficacy of selected EO majority substances-β-citronellol, carvacrol, isoeugenol, and linalool, including their binary mixtures-on the mortality and fertility of the aphid Metopolophium dirhodum, an important cereal pest. The best efficacy was proven for the binary mixture of β-citronellol and linalool (1:1 ratio), for which the estimated LC50(90) is 0.56(1.58) mL L-1. This binary mixture applied in sublethal concentrations significantly reduced aphid fertility. It was found that the phenomenon can be attributed to β-citronellol, as the females treated with LC30 laid 45.9% fewer nymphs, on average, compared to the control. Although β-citronellol and linalool, including their 1:1 mixture, showed very good efficacy on aphid mortality, they were, on the other hand, very friendly to the larvae of Aphidoletes aphidimyza and Chrysoperla carnea, which are important aphid predators. Based on our results, the newly discovered synergically acting binary mixture β-citronellol/linalool can be recommended as an efficient substance suitable for the further development of botanical insecticides used against aphids.

Chitosan-Based Films with Essential Oil Components for Food Packaging

Chitosan-based films show great potential in terms of application in food preservation and are also promising carriers of biologically active ingredients. This paper presents the potential use of chitosan-based films with the addition of essential oil components, e.g., carvacrol, eugenol, and isoeugenol, intended for food packaging. The characteristics of the obtained films were determined, including antibacterial, mechanical, barrier, and structural parameters. In addition, the antibacterial and antioxidant effects of the essential oil components were assessed. Eugenol (44.41%) and isoeugenol (43.56%) showed high antiradical activities, similar to the activity of Trolox (44.33%), which is used as a standard antioxidant. In turn, carvacrol was characterized by the strongest effect against the examined strains of bacteria, both Gram-positive and Gram-negative. The chitosan film with carvacrol showed the most valuable antibacterial and mechanical properties (tensile strength and elongation at break). The antibacterial activities of the chitosan–carvacrol films were higher than that of the carvacrol solution. The inhibition zones of the chitosan–carvacrol films were in the range 29–41 mm (except for Enterococcus faecalis, with an inhibition zone of 15 mm) compared to the inhibition zones of the carvacrol solution (28 mm). The results showed that chitosan is an effective carrier of fragrance compounds, mainly carvacrol. However, all the tested chitosan-based films with the addition of fragrance compounds showed appropriate parameters (biological, mechanical, and barrier), which makes them an ecological alternative to plastics intended for food packaging.

Introduction to cultivation Angelica sylvestris var. sylvestris L.: Chemical composition of essential oil and antimicrobial activity

This pioneering study investigates the essential oil content, fruit yield, and antimicrobial activity of Angelica sylvestris. var. sylvestris, comparing specimens from wild populations and cultivated between 2017 and 2022. The research documented fruit yields, which were consistent across the years, ranging from 191.7 to 208.0 g/plant. Essential oils extracted from the fruits were analysed, revealing a content variation between 0.6% and 1.05%. The analysis identified 45 components, predominantly monoterpenes, including α-pinene, α-phellandrene, limonene, β-cymene, isopropyl hexanoate, and β-phellandrene. The chemical profiles of the essential oils from both naturally occurring and cultivated A. sylvestris var. sylvestris were largely similar. The antimicrobial activity of these essential oils was assessed against a range of pathogens, namely Salmonella typhimurium ATCC 14028, Methicillin-resistant Staphylococcus aureus ATCC 43300, Staphylococcus aureus ATCC 25923, Listeria monocytogenes ATCC 19115, and Escherichia coli ATCC 25922. The activity varied according to the harvest year and the type of microorganism. Cultivated A. sylvestris var. sylvestris not only yielded a rich variety of essential oil components but also exhibited enhanced antimicrobial activities compared to its wild counterparts. These findings suggest that cultivation can be a sustainable means of producing high-quality essential oils with potent antimicrobial properties.

Investigation of the Antitrichomonal Activity of Cinnamaldehyde, Carvacrol and Thymol and Synergy with Metronidazole.

Trichomonas vaginalis is a sexually transmitted protozoan parasite that usually causes infections in women. Metronidazole is used as the first choice in the treatment of this parasitic disease, but there is a need for new drugs since 1980's with increasing numbers of reported resistance. In this study, it was aimed to determine the antitrichomonal activity of the major components of Cinnamomum zeylanicum (cinnamon) and Thymus vulgaris (thyme) essential oils, cinnamaldehyde, carvacrol and thymol against metronidazole resistant and susceptible T. vaginalis strains, and to determine their interaction with metronidazole by checkerboard method. Cinnamaldehyde, carvacrol, thymol and metronidazole were obtained commercially. Two clinical isolates and one metronidazole resistant T. vaginalis reference strain were used in the study. MIC50 and MLC values of essential oil components and metronidazole were determined by broth microdilution method. The combinations of essential oil components with metronidazole were determined by the checkerboard method. According to in vitro activity tests, cinnamaldehyde was determined to be most effective essential oil component. Clinical isolates were susceptible to metronidazole. In combination study, metronidazole showed synergy with cinnamaldehyde and carvacrol, and partial synergy with thymol. It was determined that cinnamaldehyde, carvacrol and thymol, which are known to have high antimicrobial activity, also have strong activity against T. vaginalis isolates and show a synergistic interaction with metronidazole. The use of metronidazole at lower doses in the synergistic interaction may contribute to the literature in terms of reducing drug side effects, creating a versatile antimicrobial target, and reducing the rate of resistance development.

Essential oil components interacting with insect odorant-binding proteins: a molecular modelling approach

ABSTRACT Essential oils (EOs) are natural products currently used to control arthropods, and their interaction with insect odorant-binding proteins (OBPs) is fundamental for the discovery of new repellents. This in silico study aimed to predict the potential of EO components to interact with odorant proteins. A total of 684 EO components from PubChem were docked against 23 odorant binding proteins from Protein Data Bank using AutoDock Vina. The ligands and proteins were optimized using Gaussian 09 and Sybyl-X 2.0, respectively. The nature of the protein-ligand interactions was characterized using LigandScout 4.0, and visualization of the binding mode in selected complexes was carried out by Pymol. Additionally, complexes with the best binding energy in molecular docking were subjected to 500 ns molecular dynamics simulations using Gromacs. The best binding affinity values were obtained for the 1DQE-ferutidine (−11 kcal/mol) and 2WCH-kaurene (−11.2 kcal/mol) complexes. Both are natural ligands that dock onto those proteins at the same binding site as DEET, a well-known insect repellent. This study identifies kaurene and ferutidine as possible candidates for natural insect repellents, offering a potential alternative to synthetic chemicals like DEET.

Chemical composition, anticholinesterase activity, and molecular docking studies of Piper baccatum Blume (Piperaceae) essential oil

Piper baccatum is a woody climber and grows throughout the tropics mostly in Southeast Asia such as Thailand, Malaysia, Singapore, and Indonesia. The studies on essential oil composition and anticholinesterase activities were performed, along with molecular docking of all components. The essential oil was obtained by hydrodistillation and analyzed by GC-FID and GC-MS, while anticholinesterase activity was assessed using Ellman method. A total of 14 components were identified, representing 98.1% of the total composition of the essential oil. The major identified components were β-caryophyllene (30.7%), camphene (22.1%), eucalyptol (14.9%), γ-muurolene (6.9%), and α-pinene (5.3%). A moderate inhibitory effect was observed for acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) with IC50 values of 80.5 and 96.4 μg/mL, respectively. Molecular docking studies of P. baccatum components with AChE and BChE revealed binding energy ranges of -5.6 to -8.5 Kcal/mol and -5.2 to -7.8 Kcal/mol, respectively, predominantly involving hydrophobic interactions with active site residues. Notably, β-caryophyllene and γ-muurolene exhibited superior binding energy profiles with both AChE and BChE compared to other components. The docking results underscore the potential of P. baccatum essential oil components as cholinesterase inhibitors, with implications for applications in food, aromatherapy, and pharmaceutical industries. The identified components, particularly β-caryophyllene and γ-muurolene, showcase promising attributes for further exploration in developing therapeutic interventions targeting cholinesterase-related conditions. This essential oil in general could be potentially used as a cholinesterase inhibitor with possible applications in food, aromatherapy, and pharmaceutical industries.

Synergistic activity of clove essential oil and thyme essential oil and their interaction against Malassezia furfur, Escherichia coli, Staphylococcusaureus

Plant essential oils have excellent antioxidant and antibacterial properties, which can greatly reduce microbial resistance. However, the odor and cost issues caused by their high concentration use remain the main bottlenecks in their application as antibacterial agents. The present study was conducted to evaluate inhibitory activity of essential oils (EOs) against Escherichia coli and Staphylococcus aureus, and focus on synergistic activity of EOs against Malassezia furfur. The minimum inhibitory concentrations and the active components of various EOs and their combination were determined using the agar dilution method and gas chromatography–mass spectrometry, respectively. The synergistic effect of EO combination on Malassezia furfur was evaluated by analyzing its growth, morphology, and cell membrane fluidity using growth curve analyses, scanning electron microscopy, and N-phenyl-1-naphthylamine method, respectively. Additionally, the antioxidant activity of the EOs combination was evaluated using the free radical scavenging method. The mixture of EOs exerted a synergistic effect on M. furfur, causing logarithmic growth phase lag, cell damage, decreased membrane fluidity, and the mixture of EOs also had synergistic effect on DPPH free radical scavenging. Conclusively, the combination of EOs investigated in this study exhibited good antibacterial ability against M. furfur, may have potential applications in seborrheic dermatitis.

Chitosan and riboflavin treatments affect marjoram growth, yield, and chemical composition

Background Marjoram is primarily cultivated to produce dried leaves and essential oil. Its active components have a wide range of biological and pharmacological activities in modern medicine. There is an interest in increasing marjoram production for local production and export. Chitosan (CH) and riboflavin (R) are required to promote plant growth and active ingredients. Objective The purpose of this study was to investigate how marjoram performance was affected by foliar spraying of CH and R at different concentrations. Materials and methods This investigation was performed over two successive seasons at two cuts. The used concentrations of CH were 100, 150, and 200 ppm, while R concentrations were 50 and 100 ppm. They were applied four times as a foliar spray to the vegetative growth during the growth season. At each harvest, the following parameters were recorded: fresh and dry weight, oil yield, total carbohydrates %, protein %, macronutrient content, total phenolics content, flavonoids content, antioxidant activity, and essential oil constituents to study their response to different treatments. Results and conclusion All the treatments of CH and R enhanced the vegetative growth, essential oil percentage, yield, active constituents, and oil components compared with untreated plants. Foliar application of CH at 200 ppm and R at 100 ppm increased plant growth, yield of volatile oil as well as chemical constituents compared with other treatments; however, CH was more effective than R. The combined application between CH and R resulted in the greatest values especially when both were applied at high doses.