Individual Essential Oils Research Articles

Optimization, characterization and biosafety of oregano, rosemary and mint oil mixture against Penicillium digitatum in citrus using L-optimal mixture design

The increasing demand for natural alternatives to synthetic fungicides has prompted research into natural products like essential oils for postharvest disease management. This study investigated the antifungal, antioxidant, cytotoxic, and genotoxic potential of essential oil mixtures derived from oregano, rosemary, and mint against Penicillium digitatum, the predominant fungal pathogen causing green mold in orange fruits. P. digitatum NPAGRASU 2024 was isolated and identified as the most abundant species (60.2%) from infected oranges. It was deposited in GenBank with gene accession number PP930644 and deposited in MIRCEN culture collection as EMCC 358874. The antimicrobial activity of individual essential oils was evaluated, with oregano exhibiting the highest antifungal activity (inhibition zone diameter of 4.2 cm) against P. digitatum. L-optimal mixture design of response surface methodology (RSM) optimization revealed a highly effective mixture (Run 8) comprising 46.26% oregano and 53.74% rosemary, with a 99.65% actual growth reduction. The oregano oil demonstrated potent antioxidant activity, reaching approximately 75% DPPH radical scavenging at 3.125 mg/mL. Cytotoxicity assessment using the MTT assay showed morphological changes and reduced cell viability in liver cells treated with the PEOs mixture at 300 µg/mL. However, the optimized mixture did not induce significant chromosomal aberrations compared to the control, suggesting minimal genotoxic effects. In vivo, evaluation on oranges revealed 60% inhibition of green mold by the 1% (v/v) optimized mixture for 7 days. Histological analysis indicated low toxicity to the liver at the highest tested concentration (1% mixture). GC-MS analysis identified major compounds like cavarcol, caryophyllene, eucalyptol, phenols and levomenthol in oregano oil, contributing to its bioactivities. This study demonstrates the potential of optimized essential oil mixtures as effective and eco-friendly alternatives for postharvest disease control.

A cinnamon and clove essential oil mix microencapsulated with hydroxypropyl-β-cyclodextrin: Study on physicochemical, antibacterial, and low salt pickles preservation properties.

In order to overcome the technical challenges of poor stability and weak antibacterial effects of individual essential oil in food preservation applications, the present study aimed to encapsulate cinnamon and clove essential oil compound by using spray-drying technique. The combination of cinnamon and clove essential oils was determined to have good synergistic bacteriostatic effects by the checkerboard dilution method, and the best bacteriostatic effect could be obtained when the volume ratio was 7:3 for compounding. Microcapsules were prepared using hydroxypropyl-β-cyclodextrin (HPCD) as wall material and compound essential oil as core material, the optimal conditions for the microcapsule preparation process through a one-way test were: homogenizing speed of 8000r/min, wall material addition of 2%, HPCD to EO ratio of 1:3, EO to T-80 ratio of 1.5:1, and homogenizing time of 8min. The physicochemical properties of the prepared compound essential oil microcapsules (EOM) were characterized, and the results showed that the EOM was successfully encapsulated in HPCD with good physicochemical properties, and the encapsulation rate of the prepared microcapsules was measured to be 65.82±4.00%. The thermal stability of the encapsulated EOM was improved, and volatilization of the essential oils was effectively inhibited. In addition, the EOM showed antibacterial activity against the five types of bacteria tested, and the number of surviving bacteria decreased by about 17-18% after 72h. The preservation experiment of low salt pickles showed that the EOM was more effective in maintaining the quality and prolonging the shelf life of the pickles compared with commercial sodium benzoate, which also demonstrated the potential application of EOM in preserving low-salt pickles. This study provides a feasible and new technical strategy for more effective application of plant essential oils in food preservation.

Evaluation of the insecticidal activity of Acorus calamus rhizome and Chrysopogon zizanioides roots essential oils against mealybug, Phenacoccus solenopsis

The mealybug, Phenacoccus solenopsis, a polyphagous insect pest, is considered a destructive pathogen and has invaded almost all parts of the world. The main aim of the study is to extract essential oil from Acorus calamus rhizome and Chrysopogon zizanioides roots against P. solenopsis. The essential oils were subjected to an in vitro toxicity analysis on the second and third instar stages of papaya mealybugs. At 10 μL/mL, A. calamus showed 33 ± 1.2% mortality after 24 h, and it was high (61 ± 1.7% mortality) at 50 μL/mL essential oil (p < 0.01). The combination of A. calamus and C. zizanioides essential oils exhibited a lower LC50 value than individual essential oils and revealed a synergistic effect. The essential oils inhibited the expression of acetylcholinesterase and glutathione-S-transferase in mealybugs and were dose-dependent (p < 0.05). The mealybugs were exposed to different concentrations of A. calamus rhizome, roots of C. zizanioides, a mixture of these two essential oils, imidacloprid (the positive control), and water (the negative control). The amount of total protein content was 0.47 ± 0.01 µg/g in the control animals, and it was reduced in the essential oil (A. calamus)-treated mealybug (p < 0.01). Similarly, the essential oil of C. zizanioides treated mealybugs showed reduced carbohydrate (p < 0.01) and lipid content (p < 0.05). The 2nd and 3rd instar stages of mealybugs were used to inoculate papaya trees. The spray treatment was used to analyze the effect of essential oils on the mealybug population. After 24 h treatment, 1.25% A. calamus induced 47 ± 1.2 mortality and was increased to 49.5 ± 0.4% after 72 h. The mortality increased with an increasing concentration of essential oil spray than treatment time (p < 0.01). The combination of these two essential oils improved mortality more than individual essential oils revealed synergy (p < 0.01). The present finding provides for the use of essential oils to control mealybugs in papaya plantations, and the application of eco-friendly pesticides could reduce the usage of synthetic pesticides.

Strategic addition of rosemary essential oil in natural rubber-toughened poly(lactic acid)/cinnamon oil blends for antimicrobial packaging

Bacterial spoilage in fruits and vegetables has emphasised the importance of extending the shelf life of food and ensuring a secure and dependable food supply that requires suitable packaging. This study presents an innovative biodegradable film for active food packaging, incorporating poly(lactic acid) (PLA) and natural rubber (NR) with cinnamon essential oil (CEO) and rosemary essential oil (REO). Although past research has examined individual essential oils in packaging, the combined effects of CEO and REO in a PLA/NR matrix remain unexplored. The influence of different CEO-to-REO ratios on the properties of PLA/NR/CEO blends was comprehensively investigated. Tensile tests showed that incorporating REO substantially improved the mechanical properties, with PLA/NR/1CEO:4REO and PLA/NR/1CEO:1REO exhibiting the highest tensile strength and elongation at break, respectively. Notably, REO incorporation effectively reduced essential oil release in aqueous environments, enabling controlled hydrolytic degradation of the PLA/NR/CEO blend. Thermal analysis showed that higher REO content increased both the thermal stability and crystallinity of the PLA/NR/CEO blends, addressing a common limitation in biodegradable packaging materials. All active films showed good antimicrobial properties against Escherichia coli and Bacillus cereus. Overall, the addition of REO to the PLA/NR/CEO blend synergistically improves the mechanical and thermal properties of the active films.

Enhancing Antibacterial Efficacy: Synergistic Effects of Citrus aurantium Essential Oil Mixtures against Escherichia coli for Food Preservation

Essential oils (EOs) from various medicinal and aromatic plants are known for their diverse biological activities, including their antimicrobial effects. Citrus aurantium EO is traditionally used for therapeutic benefits due to its high content of bioactive compounds. Therefore, this study focuses on its potential use as a food preservative by investigating the combined antibacterial properties of EOs from leaves (EO1), flowers (EO2), and small branches (EO3) of Citrus aurantium against six bacterial strains by the agar disk diffusion, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) methods. The chemical compositions of the EOs were analysed by gas chromatography–mass spectrometry (GC-MS) and revealed the presence of numerous compounds responsible for their antimicrobial properties. The MIC values for the EOs were 3.12 mg/mL, 4.23 mg/mL, and 1.89 mg/mL, for EO1, EO2 and EO3, respectively, while the MBC values were 12.5 mg/mL, 6.25 mg/mL, and 6.25 mg/mL, respectively. A simplex centroid design was created to analyse the effect of the individual and combined EOs against E. coli. The combined EOs showed enhanced antibacterial activity compared to the individual oils, suggesting a synergistic effect (e.g., trial 9 with an MIC of 0.21 mg/mL), allowing the use of lower EO concentrations and reducing potential negative effects on food flavour and aroma. Additionally, the practical application of investigated EOs (at concentrations twice the MIC) was investigated in raw chicken meat stored at 4 °C for 21 days. The EOs, individually and in combination, effectively extended the shelf life of the meat by inhibiting bacterial growth (total bacterial count of less than 1 × 104 CFU/g in the treated samples compared to 7 × 107 CFU/g in the control on day 21 of storage). The study underlines the potential of C. aurantium EOs as natural preservatives that represent a sustainable and effective alternative to synthetic chemicals in food preservation.

Synergistic effect of essential oils and chlorhexidine against planktonic and biofilm-forming cells of Malassezia pachydermatis

Malassezia (M.) pachydermatis, is often associated with secondary infection of the skin and external auditory canal in dogs and cats. The treatment of Malassezia infections is based on the local application of antifungals often combined with antiseptics. Due to increased resistance of yeast to commonly used antimycotics, especially in biofilm-forming cells, the use of natural substances, e.g. plant essential oils, appears as a new promised option. In this study, the efficacy of selected plant essential oils (EO) – oregano, rosemary, bergamot, clove, cinnamon, and thyme – in combination with chlorhexidine on both planktonic and biofilm-forming cells of M. pachydermatis, was investigated. The checkerboard test was used to determine the effect of chlorhexidine combined with individual EOs. According to the FICI (fractional inhibitory concentration index) in planktonic cells, most combinations showed additive effect, except for thyme and rosemary EO, where a synergistic effect was found (33.3 % and 16.7 % respectively). In the biofilm-forming cells, a synergistic effect was noted in chlorhexidine combined with bergamot EO, recorded in 6 isolates (33.3 %), and with thyme and oregano EO, detected in 3 isolates (16.7 %). A significant decrease (p ˂ 0.05) was found in FIC (fractional inhibitory concentration) compared to MIC (minimum inhibitory concentration), for both planktonic and biofilm-forming cells. Based on the obtained results, we can conclude that the combination of chlorhexidine with EOs achieved better efficiency than when using each agent alone and made it possible to reduce the concentration of both, and a sufficient antifungal and antibiofilm effect was achieved in M. pachydermatis strains.

Essential oils work synergistically to mitigate pathogenic impact of Meloidogyne incognita, Rhizoctonia solani and Sclerotinia rolfsii

The phytochemical analysis and potential synergistic interactions between the essential oils (EOs) of Vitex negundo L. Piper longum L. and Vitex agnus-castus L. and their pesticidal efficacy were the main focus of this study. To examine their synergistic interactions with pesticidal activities, the recovered EOs were mixed in binary and ternary combinations at similar ratios and the nematicidal activity of individual EOs and their mixtures was evaluated. Using the disc-diffusion method, antifungal activity was evaluated. For comparison means of biological activities, a two-way ANOVA was carried out, at a significance level of 5% (p < 0.05). The main EO compounds were subjected to a molecular docking investigation to look into how they interacted with target proteins in comparison with standard inhibitors physostigmine (AChE), ethacrynic acid (GST-1), and hexaconazole (CYP51). The chemical compounds of EOs were identified via GC-MS analysis. Based on GC-MS analysis β-pinene, cis-nerolidol, 2-heptyl acetate, and α-pinene were the major compounds identified in PLAO; while in VACAO viridiflorol, β-caryophyllene, and 5-(1-isopropenyl-4,5-dimethyl bicyclo [4.3.0]nonan-5-yl)-3-methyl-2-pentenol acetate were detected as main components. Similarly, 1,8-cineole, (E)-β-ocimene, α-terpinyl acetate, and (Z)-β-ocimene were identified as major compounds in VACAO. When three EOs of P. longum, V. negundo, and V. agnus-castus were mixed, pesticidal activity results revealed a high synergy. These results validate synergistic interactions amongst the studied essential oils, which may support sustainable agriculture when applied as natural products against pathogens. The molecular docking results showed good binding affinities and attributed the strongest inhibitory activity to 5-(1-isopropenyl-4,5-dimethyl bicyclo [4.3.0]nonan-5-yl)-3-methyl-2-pentenol acetate for all the target proteins.

Micromeria fruticosa and Foeniculum vulgare essential oils inhibit melanoma cell growth and migration by targeting MMP9 and NFkB signaling

BackgroundFennel (Fe), also known scientifically as Foeniculum vulgare, and Micromeria fruticose are herbaceous plants endemic to the Mediterranean Region. The use of their essential oils for their health-promoting effects has been seen in Middle-Eastern societies, where they have been used as a type of traditional medicine. These oils have been used to treat a variety of diseases, including headaches, abdominal pains, skin and eye infections, colds, and wounds. This study looks at the chemical makeup of essential oils extracted from Palestine-grown fennel seeds and Micromeria fruticose leaves. The anticancer properties of each essential oil, as well as the combined mixture of both oils, were evaluated against the melanoma cell line.ResultsGC–MS was used to study the essential oils (EOs) from Micromeria fruticose leaves and fennel seeds that were extracted by hydrodistillation. Analysis of M. fruticose EO allowed the identification of 20 compounds, accounting for 97.73% of the EO's overall composition, with pulegone (81.77%), β-caryophyllene (2.95%), isomenthone (2.17%), piperitenone oxide (1.78%), and p-mentha-3-en-8-ol (1.38%) being the primary components. 24 phytochemicals were identified in the essential oil of fennel seeds, accounting for 100% of its composition, of which trans-anethole (93.69%), fenchone (3.93%), and sylvestrene (0.83%) were the major constituents. Although the EOs derived from M. fruticosa leaves and fennel seeds have shown potential for inhibiting the growth of several types of cancer, their impact on the proliferation and migration of melanoma cells has not been investigated. The results of our study demonstrate that the application of both oils, either separately or in combination (referred to as Mix-EO therapy), effectively suppressed the growth of melanoma cells in a manner that was dependent on the dosage. Furthermore, both treatments resulted in the upregulation of pro-apoptotic Bax and the downregulation of apoptosis-inhibiting Bcl2 expression in an in vitro setting. The anti-proliferative effects were confirmed using a murine melanoma model in vivo. Furthermore, both the individual EOs that were assessed and their combination (Mix-EO) exhibited inhibitory properties against the migration of melanoma cells. Both EOs and Mix-EO were found to decrease the intracellular levels of the transcription factor nuclear factor kappa B (NFkB) and one of its downstream targets, matrix metalloproteinase9 (MMP9), in melanoma and tumor-associated mesenchymal stem cells. Finally, we demonstrate for the first time that EOs from M. fruticose leaves, fennel seeds, and their combination exert anti-cancer characteristics by inhibiting NFkB and MMP9 in melanoma (autocrine) and tumor-associated mesenchymal stem (paracrine) cells, thereby inducing melanoma cell apoptosis and preventing cell migration.ConclusionsThe findings of our investigation indicate that the EOs derived from the fennel seeds and the M. fruticose leaves encompass a diverse array of biologically active chemicals, which have robust anticancer effects. The results of this study hold promise for application in the advancement of innovative natural medications. Additional investigation is required to delve into the medicinal capacity of these essential oils in biological entities.Graphical

A systematically evolved method for the effective use of essential oil blends for the structural maintenance of palm leaf manuscripts

Palm leaf manuscripts (PLMs) are traditional carriers that contain a wealth of knowledge from different disciplines written by ancient scholars. However, PLMs are susceptible to deterioration due to moisture, light, fungi and bacteria. An existing method of applying essential oils (EOs) to preserve PLMs does not currently appear successful, hence the study presented here which aimed to maximise the preservation characteristics of six different EO blends, prepared and applied to palm leaves, which were then tested for stiffness, brightness and weight gain. The interpretation of the efficiency of EO blends in the preservation of PLMs is attributed to the compatibility between the oils due to the various constituents present in the individual EOs. FTIR spectroscopy was used to understand the compatibility of the oils in a blend and any EO blend rendering a higher stiffness and brightness was identified as having a high preservation performance. Based on the investigation, good compatibility is observed between the FTIR spectrum of Blend-E with its contributing EOs of citronella, neem and mustard. On the other hand, Blend-B exhibits poor preservation characteristics and incompatibility. The study concludes with the recommendation that Blend-E is suitable for the treatment and regular maintenance of PLMs as it can help reduce physical and chemical damage.

The Formulation and Evaluation of Melaleuca alternifolia Cheel and Cymbopogon flexuosus Linn Essential Oils Emulgel for the Treatment of Vulvovaginal Candidiasis.

The global concern regarding the occurrence of antifungal resistance to synthetic conventional azoles used for treating vulvovaginal candidiasis, along with the associated side effects, is significant. Consequently, the pursuit for substitutes such as natural therapies has ensued. Essential oils, derived from plants, have been extensively researched and found to possess antibacterial and antifungal properties. This study aimed to assess the antifungal efficacy of two essential oils, both alone and in combination, against Candida albicans. Essential oils were formulated into an emulgel separately and as combinations. The essential oils of Melaleuca alternifolia and Cymbopogon flexuosus were used in this study. The resulting emulgel formulations were characterized for their antifungal activity against Candida albicans. Physiochemical properties such as pH, viscosity, and appearance were also determined. The prepared emulgels were thereafter observed for stability over a period of 1 month. The MIC of Melaleuca alternifolia was seen to be 50 µL/mL while Cymbopogon flexuous was seen to be more potent at 25 µL/mL against C. albicans exhibiting strong synergistic effect at 0.4. The emulgel formed was white in color, smooth on skin, and had the odor of the essential oils, which is sweet to the nose. The pH of the formulations with the essential oils were acidic in the range of 3.70-3.83, making them suitable for vagina application. The emulgels had viscosities ranging from 4417.6 to 8968.7 mPas, owing to the thickness of the essential oils contained. The emulgel formulation with the combination of essential oils was more potent that the two with individual essential oils; furthermore, the one with Cymbopogon flexuous was more potent than the one with Melaleuca alternifolia. Based on the properties of the formulated emulgels and their activity against the test organism, the preparations have significant potential in the management of vulvovaginal candidiasis.

Systematic analysis of antimicrobial activity, phytochemistry, and in silico molecular interaction of selected essential oils and their formulations from different Indian spices against foodborne bacteria

Essential oils (EOs) from Indian spices like Elettaria cardamomum (L.) Maton (small green cardamom), Syzygium aromaticum (L.) Merr. & L.M. Perry (clove), Cinnamomum zeylanicum Blume (cinnamon quills), and Cinnamomum tamala (Buch.-Ham.) T. Nees & C. H. Eberm (Indian bay leaves) exhibit a broad spectrum range of biological activity including antibacterial and antifungal activity. Yet, there is a lack of data regarding the antimicrobial activity of their formulations. Also, the link between the antimicrobial effect of individual EO with their chemical composition and molecular interaction with bacterial pathogens has not been systematically explored. Therefore, the objectives of the current study were to evaluate the antimicrobial activity and phytochemical characterization of EOs and to bridge the gap between them through in-silico molecular interactions. The antibacterial activity of EOs of four different spices and their formulations against foodborne pathogens such as Bacillus subtilis, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa was evaluated using the disc volatilization method. The chemical profile of the individual EO was determined through GC-MS analysis and molecular interactions of identified major components with bacterial proteins were carried out through molecular docking studies. All EOs and their formulations exhibited antibacterial activity ranging from 5.92 to 24.55 mm and 11–23.52 mm, respectively. Among all EOs, cinnamon and formulation C (cardamom: cinnamon- 2:1) exhibited the highest antibacterial activity. The composition of the EOs included sesquiterpenes, monoterpenoids, monoterpenes, and, phenylpropanoids such as (E)-cinnamaldehyde, δ-cadinene, α-copaene, eugenol, caryophyllene, eugenol acetate, methyl eugenol, menthadiene, eucalyptol, α-terpinyl acetate, and sabinene. Furthermore, docking study revealed that the abundant compounds from cinnamon EO mainly α-copaene and δ-cadinene had a high binding affinity towards the bacterial essential proteins which increases the bacterial susceptibility towards cinnamon EO. The selected EOs and their formulations were systematically analysed and they were effective against foodborne pathogens. The current findings suggest the application of these EOs against food pathogens with further research.

Foliar application of either melatonin or sodium nitpoprusside regulates the antioxidant status, and the morpho-physiological attributes and essential oil production in sage (Salvia officinalis L.) under salinity stress

Soil salinity is one of the most severe abiotic stress factors affecting crop growth and yield. Among the molecules used to mitigate the adverse effects of salt, melatonin (MT) and the nitric oxide donor sodium nitroprusside (SNP) played a crucial role in mediating plant responses to salt stress. However, the molecules are worthy of further consideration and investigation with regard to the secondary metabolism of plants suffering from salt stress. Herein, the potential role of MT and SNP in alleviating/buffering the negative effects of salt stress on sage (Salvia officinalis L.) seedlings was investigated. In this context, MT (0, 50 µM, and 100 µM) and SNP (0, 50 µM, and 100 µM) were applied individually. The interactive effects of each molecule with salt stress (50 and 100 mM NaCl) were assessed using a range of morpho-physiological, biochemical and analytical parameters of sage. The results of the study showed that high salinity (100 mM NaCl) critically reduced growth and photosynthetic traits and increased oxidative stress damage parameters. On the other hand, high concentrations (100 µM) of MT or SNP treatments significantly improved growth, enhanced photosynthetic traits and mitigated oxidative stress damage parameters. For instance, individual treatments of both MT and SNP enhanced tolerance of sage against salinity stress by increasing relative water content, proline, total carbohydrates, total phenolics and flavonoid content, and the antioxidant enzymes and DPPH scavenging activities. Essential oil yield and individual essential oil compounds were also increased by MT and SNP. Overall, these molecules can be considered as potential protective agents against salinity stress in sage seedlings.

Salvia officinalis L. and Salvia sclarea Essential Oils: Chemical Composition, Biological Activities and Preservative Effects against Listeria monocytogenes Inoculated into Minced Beef Meat.

In this study, Salvia officinalis L. and Salvia sclarea essential oils (EOs) were investigated using gas chromatography-mass spectrometry (GC-MS) to describe their chemical composition. The obtained results show, for both EOs, a profile rich in terpene metabolites, with monoterpenes predominating sesquiterpenes but with significant qualitative and quantitative differences. The main compound found in the Salvia officinalis EO (SOEO) was camphor (19.0%), while in Salvia sclarea EO (SCEO), it was linalyl acetate (59.3%). Subsequently, the in vitro antimicrobial activity of the EOs against eight pathogenic strains was evaluated. The disc diffusion method showed a significant lysis zone against Gram-positive bacteria. The minimum inhibitory concentrations (MICs) ranged from 3.7 mg/mL to 11.2 mg/mL, indicating that each EO has specific antimicrobial activity. Both EOs also showed significant antiradical activity against DPPH radicals and total antioxidant activity. In addition, the preservative effect of SOEO (9.2%) and SCEO (9.2%), alone or in combination, was tested in ground beef, and the inhibitory effect against Listeria monocytogenes inoculated into the raw ground beef during cold storage was evaluated. Although the effect of each individual EO improved the biochemical, microbiological, and sensory parameters of the samples, their combination was more effective and showed complete inhibition of L. monocytogenes after 7 days of storage at 4 °C. The results show that both EOs could be used as safe and natural preservatives in various food and/or pharmaceutical products.

Emulsions containing composite (clove, oregano, and cinnamon) essential oils: Phase inversion preparation, physicochemical properties and antibacterial mechanism.

Natural essential oils (EOs), especially those combining different individual EOs (also termed composite EOs) with enhanced performance, are becoming healthy, market-sought food preservatives/additives. This study aims to provide insights into the challenge regarding EOs processing due to their low solubility and the elusive mechanism under the enhanced bio-reactivity of composite EOs. A unique oil/water interacting network was created by phase-inversion processing, which enhances EO solubilization and emulsification to form composite EO formulations (EOFs) containing ordinary cinnamon, oregano and clove EOs. These EOFs mainly contained cinnamaldehyde, carvacrol and eugenol and exhibited excellent post-storage stability. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging ability of EOFs (at 15.880μL/mL) was>88%, and the Ferric reducing antioxidant power (FRAP) was 1.8mM FeSO4·7H2O. The minimum inhibitory concentration (MIC) of EOFs against E. coli and S. aureus was ∼7.940μL/mL. The EOFs could cause quick deterioration of bacterial structures, demonstrating high efficacy in bacteria-killing and anti-biofilm formation.

Microcapsules of a cinnamon, peppermint, and lemon essential oil mix by spray drying: Preparation, characterization and antibacterial functions

Plant essential oils (EO) are increasingly used as food preservatives due to their antibacterial and antioxidant activities. For such applications, EO are commonly microencapsulated to overcome their poor stability, low solubility and dominant aromas. But, typically, individual EO act against only a narrow range of bacterial species. Therefore, in this study, we aimed to develop a microencapsulated preservative using a combination of three EO and to determine its anti-bacterial action against three common food contaminants, viz. Escherichia coli, Salmonella and Staphylococcus aureus, and one, usually, beneficial species, viz. Lactoplantibacillus plantarum. The EO of cinnamon (Cinnamomum cassia), peppermint (Mentha haplocalyx) and lemon (Citrus limon) were combined in the proportions, 1.0 : 1.8: 2.4, respectively and were encapsulated in gelatin-chitosan by spray drying. The particle size, zeta potential, moisture content, and encapsulation rate of the essential oil microcapsules (EOM) were measured. With increasing EOM exposure time, the concentrations of E. coli, Salmonella, S. aureus and L. plantarum decreased by 3, 3, 4, and 5 orders of magnitude, respectively. Cell apoptosis accompanied loss of membrane integrity and permeability, inhibition of lactate dehydrogenase activity and disruption of organic acid metabolism. Gram-positive bacteria (S. aureus and L. plantarum) were more susceptible to those effects of EOM than Gram-negative bacteria (E. coli and Salmonella). It also demonstrates that in applications as preservatives for probiotic foods requiring live L. plantarum, EOM comprising cinnamon, peppermint or lemon EO should be avoided.

Toxic and synergetic effect of plant essential oils along with nano-emulsion for control of three mosquito species

Nano-emulsion containing Eucalyptus grandis (W. Hill ex Maiden) and Corymbia citrodora (Hook.) K.D.Hill & L.A.S.Johnson (common synonym Eucalyptus citriodora Hook.) leaf essential oils individual, combination was evaluated its larvicidal activity against Anopheles stephensi, Aedesaegypti and Culex quinquefasciatus mosquito larvae at 24 h post treatment. Nano-emulsion had low polydispersivity index and mean droplet size was below 66 nm. After 24 h E. grandis essential oil exhibited significant larvicidal activity with LC50 and LC90 values in A. aegypti (23.667; 438.797 ppm in A. aegypti A. stephensi (10.984; 277.535 ppm) and C. quinquefasciatus (4.676; 106.415 ppm). Similarly in C. citrodora showed low LC50 and LC90 values in A. aegypti (18.430; 1048.599 ppm), A. stephensi (6.573; 176.737 ppm) and C. quinquefasciatus (7.917; 287.720 ppm) respectively. The combination of E. grandis and C. citrodora essential oils showed higher mortality rates than individual essential oils, with low LC50 and LC90 values in A. aegypti (3.625; 58.962 ppm), A. stephensi (3.245; 34.473 ppm) and C. quinquefasciatus (3.002; 30.153 ppm). Nano-emulsion exhibited toxic effects similar to combination group with LC50 and LC90 values in A. aegypti (5.344; 113.362 ppm), A. stephensi (3.183; 83.112 ppm) and C. quinquefasciatus (2.832; 166.665 ppm). Chemical constituents of both essential oil were analyzed using GC-MS and FT-IR, result showed E. grandis contain different compounds namely; alpha-pinene, (31.74%); o-cymene, (17.84%); Eucalyptol (16.24%); Bicyclo[2.2.1]heptane (3.2%) and C. citrodora showed Citronellol (49.31%); dl-Isopulegol (25.39%) as a major compound while their synergistic action may be due to type’s composition of EOs might produce the synergist effect along with nanoemulsions. Our findings suggest that combination of essential oil E. grandis and C. citrodora can be used for mosquito control as green approach.

Volatile metabolites from new cultivars of catnip and oregano as potential antibacterial and insect repellent agents.

Plant based natural products have been widely used as antibacterial and insect repellent agents globally. Because of growing resistance in bacterial plant pathogens and urban pests to current methods of control, combined with the long- and short-term negative impact of certain chemical controls in humans, non-target organisms, and the environment, finding alternative methods is necessary to prevent and/or mitigate losses caused by these pathogens and pests. The antibacterial and insect repellent activities of essential oils of novel cultivars of catnip (Nepeta cataria L. cv. CR9) and oregano (Origanum vulgare L. cv. Pierre) rich in the terpenes nepetalactone and carvacrol, respectively, were evaluated using the agar well diffusion assay and petri dish repellency assay. The essential oils exhibit moderate to high antibacterial activity against three plant pathogens, Pseudomonas cichorii, Pseudomonas syringae and Xanthomonas perforans of economic interest and the individual essential oils, their mixtures and carvacrol possess strong insect repellent activity against the common bed bug (Cimex lectularius L.), an urban pest of major significance to public health. In this study, the essential oils of catnip and oregano were determined to be promising candidates for further evaluation and development as antibacterial agents and plant-based insect repellents with applications in agriculture and urban pest management.

Screening of Antifungal Activity of Essential Oils in Controlling Biocontamination of Historical Papers in Archives.

The main challenge in controlling the microbiological contamination of historical paper is finding an adequate method that includes the use of cost-effective, harmless, and non-toxic biocides whose effectiveness is maintained over time and without adverse effects on cultural heritage and human health. Therefore, this study demonstrated the possibility of using a non-invasive method of historical paper conservation based on plant essential oils (EOs) application. Evaluation of antimicrobial effects of different EOs (lemongrass, oregano, rosemary, peppermint, and eucalyptus) was conducted against Cladosporium cladosporoides, Aspergillus fumigatus, and Penicillium chrysogenum, which are commonly found on archive papers. Using a mixture of oregano, lemongrass and peppermint in ratio 1:1:1, the lower minimal inhibition concentration (0.78%) and better efficiency during a vapour test at the highest tested distance (5.5 cm) compared with individual EOs was proven. At the final step, this EOs mixture was used in the in situ conservation of historical paper samples obtained from the Archives of Vojvodina. According to the SEM imaging, the applied EOs mixture demonstrates complete efficiency in the inhibition of fungi colonization of archive papers, since fungal growth was not observed on samples, unlike the control samples.

Optimization of antibacterial activity of essential oil mixture obtained from three medicinal plants: Evaluation of synergism with conventional antibiotics and nanoemulsion effectiveness

• Mixture design of L. maroccana, T. vulgaris and A. leucotricus were established. • Synergistic interactions were recorded and optimized EO mixture was defined. • Optimal mixture decreased the antibiotics MICs by 2- to 64-fold. • Optimized EO mixture showed high antibacterial effect in nanoemulsion. The present study aimed to optimize the antibacterial activity of essential oil (EO) mixture obtained from Ammodaucus leucotrichus Cosson, Thymus vulgaris L. and Lavandula maroccana (Murb.) against three multi-drug resistant bacteria, using augmented simplex-centroid design. GC–MS analysis showed that A. leucotrichus EO was characterized by the abundance of l -perillaldehyde (50.39%), d -limonene (21.61%) and bornyl angelate (7.09%). T. vulgaris EO was dominated by thymol (42.34%), p -cymene (19.71%) and γ-terpinene (11.50%), while carvacrol (71.62%) represents the main component of L. maroccana EO. Regarding antibacterial assays, individual EOs displayed moderate activity with MIC and MBC values ranging from 0.06% to 5.00%, while the coefficient terms of the different tested combinations revealed synergistic interactions. The results of predicted optimization showed that the optimal EOs mixture composed by 55% of T. vulgaris, 41% of L. maroccana and 4% of A. leucotrichus, significantly decreased the MICs against Staphylococcus aureus (0.0225%), Escherichia coli (0.05%) and Pseudomonas aeruginosa (0.688%). The optimal mixture exhibited a significant decrease in the MICs of gentamicin (4-fold) and amoxicillin (2- to 64-fold), and achieve the highest antibacterial effect in nanoemulsion formulation. The optimized EO mixture based on the studied plants should be considered as a potential alternative to control foodborne, and resistant bacteria.

Molecular docking, dynamics simulation and pharmacokinetic studies of Cyperus articulatus essential oil metabolites as inhibitors of Staphylococcus aureus

Cyperus articulatus has been extensively studied for its essential oil (EO), active components and antibacterial activities against a wide range of bacteria such as Bacillus megaterium, Streptococcus pyogenes, Staphylococcus epidermidis, Escherichia coli and Staphylococcus aureus. However, knowledge of the biomolecular interaction of the individual EO metabolites responsible for its inhibition activities is lacking. The multi-drug-resistant bacteria S. aureus, which is of prime concern, has been reported to be inhibited by Cyperus articulatus rhizome EO. The present work analyzed the molecular interactions of the major Cyperus articulatus rhizome EO metabolites with the target enzyme TyrRS of S. aureus and studied the conformational dynamics and stability of the protein-ligand complexes. Molecular docking studies of selected EO metabolites such as mustakone, longifolenaldehyde, cyperotundone, α-copaene, β-calacorene, α-calacorene and khusinol were conducted along with standard drug chloramphenicol for comparative analysis of their binding affinity with S. aureus TyrRS. The metabolites khusinol, mustakone, β-calacorene and α-calacorene generated comparable docking scores (−6.4, −6.2, −6.1 and −6.2 kcal/mol, respectively) with that of the drug chloramphenicol (−6.3 kcal/mol). Most EO metabolites did not exhibit H-bonding with the S. aureus TyrRS residues and were stabilized through pi-interactions. The MD simulation study illustrated that compounds like mustakone could effectively bind to the receptors of S. aureus TyrRS with high stability and integrity. Pharmacokinetic, drug-like properties and toxicity analysis of the EO metabolites supported the candidature of mustakone and khusinol as pharmacologically important antibacterial drug ingredients. The study envisaged the structural framework of the EO metabolites for antibacterial drug design. Communicated by Ramaswamy H. Sarma