Bioactivity Of Essential Oil Research Articles

A Machine Learning Approach to Evaluating the Impact of Natural Oils on Alzheimer’s Disease Progression

Alzheimer’s Disease is among the major chronic neurodegenerative diseases that affects more than 50 million people worldwide. This disease irreversibly destroys memory, cognition, and the overall daily activities which occur mainly among the elderly. Few drugs are approved for Alzheimer’s Disease management despite its high prevalence. To date, the available drugs in the market cannot reverse the damage of neurons caused by the disease leading to the exacerbation of symptoms and possibly death. Medicinal plants are considered a rich source of chemical constituents and have been contributing to modern drug discovery in many therapeutic areas including cancer, infectious, cardiovascular, neurodegenerative and Central Nervous System (CNS) diseases. Moreover, essential oils that are extracted from plant organs have been reported for a wide array of biological activities, and their roles as antioxidants, antiaging, cytotoxic, anti-inflammatory, antimicrobial, and enzyme inhibitory activities. This article highlights the promising potential of plants’ essential oils in the discovery of novel therapeutic options for Alzheimer’s Disease and halting its progression. In this article, 428 compounds were reported from the essential oils isolated from 21 plants. A comparative study is carried out by employing a variety of machine learning techniques, validation, and evaluation metrics, to predict essential oils’ efficacy against Alzheimer’s Disease progression. Extensive experiments on essential oil data suggest that a prediction accuracy of up to 82% can be achieved given the proper data preprocessing, feature selection, and model configuration steps. This study underscores the potential of integrating machine learning with natural product research to prioritize and expedite the identification of bioactive essential oils that could lead to effective therapeutic interventions for Alzheimer’s Disease. Further exploration and optimization of machine learning techniques could provide a robust platform for drug discovery and development, facilitating faster and more efficient screening of potential treatments.

Bioactive components and bioactivity of essential oils, hydrosol and water steam distillation solvents of lemongrass leaves (Cymbopogon citratus)

Abstract Hydrosol is a by-product of the distillation process which contains water-soluble compounds. Hydrosols are becoming increasingly popular in the cosmetic, pharmaceutical, and food industries. Lemongrass (Cymbopogon citratus) is an herbal plant widely used as a flavoring agent in herbal teas, frozen desserts, and meat products. The water extract of lemongrass leaves contains alkaloids, phenolics, tannins, and flavonoids, which have antioxidant and antibacterial properties. This research aims to identify the bioactive components and bioactivity of essential oils, hydrosols, and solvents used in the distillation of lemongrass leaves (Cymbopogon citratus). Fresh lemongrass leaves were water steam distilled for three hours. The antioxidant activity of lemongrass leaf essential oil, hydrosols, and solvents was determined using the DPPH assay. The chemical composition of lemongrass leaf essential oil, hydrosol, and solvent was analyzed using GCMS. The GCMS test results showed that the essential oil, hydrosol, and solvent of lemongrass leaves had different chemical components. There are 17 compounds found in the lemongrass leaf essential oil, with 5 major compounds namely E-citral (44.22%), Z-citral (32.78%), β-myrcene (15.66%), trans-4,5-epoxi-carane (3.51%) and geranyl acetate (0.82%). In the hydrosol, 3 compounds were identified, namely isolongifolene (18.81%), epiglobulol (64.09%), and 4,7-Epoxy-1H-isoindole-1,3(2H)-dione (17.10%). One compound, (Z,Z)-3,9-cis-6,7-epoxy-nonadecadiene, has been identified in the solvent. The antioxidant activity of hydrosols and solvents is the same as the lemongrass leaf essential oil. The findings of this study suggest that distillation waste in the form of hydrosols and distillation solvents for lemongrass leaves has the potential to be functional ingredients that may have applications in both the food and non-food sectors.

Lactobacillus-isolated exopolysaccharide as emulsifier ensure extended stability of eugenol encapsulation, potent anti-microbial activity, and application on fresh produce

In this study, we employed a novel encapsulation approach to develop a stable eugenol oil-in-water (O/W) emulsion by using Lactobacillus plantarum ATCC 8014 isolated exopolysaccharide (EPS) as a natural emulsifier. The emulsion was optimized and analyzed for physical stability, microstructure, rheology, and chemical behavior using fourier-transform infrared analysis (FTIR). The eugenol emulsion consisting of a 40:60 O/W ratio with 3 % w/v EPS exhibited a desired droplet size of 192 ± 1.89 nm with multimodal size distribution, polydispersity index of 0.362 ± 0.01 and zeta-potential of −32 ± 1.90 mV. Scanning electron microscopy (SEM) revealed porous and granulated structures with profound consistency. EPS maintained its emulsifying activity across processing conditions (−20 to 70 °C, pH 3–9, salinity 1 %–30 %), with stability over 90 days. Both EPS and eugenol synergistically enhanced the antimicrobial activity of emulsion against Listeria monocytogenes B600 and Salmonella Poona 36. The practical application of optimized emulsion was assessed by demonstrating a reduction in microbial load on the lettuce surface. Microbial load was determined by immersion and sprayed treatment methods which resulted in more than 3.0 log reduction. This potential application of lactobacillus–derived EPS as a natural emulsifier for encapsulating bioactive essential oils will enable its future applications for food safety.

Bio-active essential oils derived from medicinal plants and their insecticidal potential on houseflies and cockroaches

The plant essential oils are intricate blends of semi-volatile and volatile substances. They primarily consist of monoterpenes and sesquiterpenes; however, very trace amounts of diterpenes, triterpenes, and tetraterpenes are also present. In view of environmental concerns, highly aromatic essential oils, exhibit a variety of bioactivities against the targeted species as a novel pest control alternative to synthetic insecticides. As a result, the study aims to evaluate the impact of essential oils (EO) extracted from various plant species: Azadirachta indica, Citrus limon, Eucalyptus globulus, Laurus nobilis, Mentha piperita, and Ocimum tenuiflorum. Gas chromatography and Mass spectrometry (GC–MS) were used to determine the chemical components of these essential oils. Furthermore, the extracted oils were subjected to individual and combination formulations of bio-insecticides, which were assessed on houseflies and cockroaches in comparison to a blank control and the positive control dichlorvos (dimethyl 2, 2-dichlorovinyl phosphate). The findings showed that the maximum essential oil yields from the leaves of A. indica, E. globulus, and O. tenuiflorum were 11.38, 9.64 and 10.41 %, respectively. Compared to DDVP, which killed all insects within the 12-hour period, the combined form of leaf essential oils at 100 % concentration proved to be more effective in controlling insect mortality. It accounted for 98 % of the deaths in houseflies and 76.4 % of the deaths in cockroaches, according to the contact toxicity evaluation. The active insecticidal components in the formulation include eucalyptol, undecane, tetradecane, estragole, pentadecane, and caryophyllene.

Comparative assessment of encapsulated essential oils through the innovative electrohydrodynamic processing and the conventional spray drying, and freeze-drying techniques

This study evaluates the encapsulation of an essential oils blend (EOB) using electrohydrodynamic processing (EHDP), spray drying, and freeze-drying techniques. EOB, comprising oregano, rosemary, hypericum, and chamomile oils, was encapsulated in a whey protein isolate-pullulan (WPI-PL) matrix. Spray drying achieved the highest encapsulation efficiency (EE > 90%) and optimal release profiles, while electrospun structures showed gradual release and better preservation. Freeze-drying exhibited the highest encapsulation yield (EY = 83.16%) but lower efficiency (∼66%). The electrospun nanostructures (EHDP) had a diameter of 543.00 ± 15.86 nm, whereas spray-dried microparticles measured 4.91 ± 3.356 μm. All encapsulated structures followed a Fickian diffusion mechanism (n ≤ 0.45). This research highlights the potential of natural bioactive compounds in food applications, contributing to sustainable, synthetic-free nutrition by enhancing stability and bioactivity of essential oils through encapsulation, reducing reliance on synthetic additives, and promoting a more natural approach to modern nutrition.

In silico Exploration of Essential Oil Constituents in Combating Multidrug-Resistant Staphylococcus aureus Infected Wounds

This research explores the multifaceted pharmacological actions of essential oils and its constituents, derived as secondary metabolites from aromatic plants, with a particular focus on their potent wound healing and antibacterial activities, elucidating their significance in therapeutic approach towards infected wounds. An in silico screening was carried out to identify the interaction between the bioactive essential oil contituents (EOC) such as cinnamaldehyde, citral, geraniol, linalool, and p-cymene, docked against various target proteins associated with antibiotic resistance and wound healing, including mec A (PDB ID- 4DK1), nor A (PDB ID- 7LO8), TGF- β1 (PDB ID- 1PY5), TGF- β2 (PDB ID- 1M9Z), VEGF (PDB ID-3QTK), GSK-3β (PDB ID-1Q5K) and MMP-9 (PDB ID-5UE4). The docking was done with AutoDock V 4.0 using five EOCs against seven receptors and the binding energy was gaged. The binding energy of EOCs were observed to be ranging from -5.3 kcal/mol to -2.55 kcal/mol. Notably, all the screened EOCs exhibited favourable binding affinity with GSK-3β, indicating their potential role in the inflammatory phase of wound healing. Additionally, towards antibiotic resistance, all EOC displayed adequate binding affinity with norA, suggesting their potential in modulating multidrug resistant efflux pumps. Compliance with Lipinski's rule, positions these EOC as promising candidates for drug development, particularly in the context of wound healing and antibiotic resistance. This study holds the promise of contributing novel insights to the field of wound care and combating antibiotic resistance, paving the way for innovative approaches in addressing the challenges posed by multi-drug resistant Staphylococcus aureus (MDRSA) infected wounds.

Sequential Extraction and Characterization of Essential Oil, Flavonoids, and Pectin from Industrial Orange Waste.

Orange is one of the primary fruits processed into juice and other products worldwide, leading to a vast amount of waste accumulation. Such waste has been considered as an attractive candidate for upcycling to obtain bioactive components remaining. The present study investigated the extraction of essential oil (EO), flavonoids, and pectin from industrial orange waste with a holistic approach. To maximize EO yield and d-limonene concentration, hydrodistillation (HD) conditions were selected to be 5.5 mL water/g solid for 180 min. Remaining solids were further used for flavonoid extraction where conventional solvent, sequential ultrasound + solvent, and ultrasound-assisted extraction (UE) were applied. UE applied for 50 min with 120 mL solvent/g solid yielded the highest total phenolic (TPCs) and total flavonoid contents (TFCs), antioxidant capacity, and hesperidin and neohesperidin concentrations. In terms of TPC, TFC, antioxidant capacity, and antibacterial activity, both EO and flavonoid fractions demonstrated moderate to high bioactivity. At the final step, ethanol precipitation was applied to obtain the pectin that was solubilized in hot water during HD and it was characterized by Fourier transform infrared, degree of esterification, and galacturonic acid content. Practical application: to ensure utilization in the food, pharmaceutical, and cosmetic industries, this study presents a combined method to obtain several value-added compounds from industrial orange waste. Bioactive EO and flavonoids obtained could have applications in functional food, supplements, or cosmetic formulations, whereas extracted pectin can be used in many formulated foods and drugs.

Exploring the Efficacy of Four Apiaceae Essential Oils against Nine Stored-Product Pests in Wheat Protection.

The Apiaceae family, known for aromatic plants producing bioactive essential oils (EOs), holds significance across sectors, including agrochemicals. This study evaluated the insecticidal potential of four Apiaceae EOs from Crithmum maritimum L., Trachyspermum ammi (L.) Sprague ex Turrill, Smyrnium olusatrum L., and Elwendia persica (Boiss.) Pimenov and Kljuykov against various significant storage pests (Sitophilus oryzae (L.), Trogoderma granarium Everts, Rhyzopertha dominica (F.), Tribolium castaneum (Herbst), T. confusum Jacquelin du Val, Oryzaephilus surinamensis (L.), Alphitobius diaperinus (Panzer), Acarus siro L., and Tenebrio molitor L.) on wheat. Insect mortality rates were monitored at intervals of 1, 2, 3, 4, 5, 6, and 7 days. Smyrnium olusatrum EO exhibited the highest efficacy, followed by T. ammi, C. maritimum, and E. persica EOs, although efficacy varied by species, developmental stage, and concentration. Notably, complete mortality occurred for several pests at 1000 ppm of S. olusatrum and T. ammi EOs. Gas chromatography-mass spectrometry (GC-MS) analysis revealed key compounds in these EOs, including myrcene, germacrone, and curzerene in S. olusatrum EO, and thymol, γ-terpinene, and p-cymene in T. ammi EO. These findings emphasize their potential as botanical insecticides. Smyrnium olusatrum and T. ammi EOs emerge as promising eco-friendly pest management options due to their efficacy, highlighted compound composition, and availability of biomass from both wild and cultivated sources.

Gallic acid as a phytostimulant enhancing yield and quality of Mentha spicata L. under deficit- and well-watered conditions

Here, we propose gallic acid (GA) as a phytostimulant for Mentha spicata subsp. spicata L. (spearmint), an aromatic herb of great global economic importance. Our evidence would suggest the potential of GA in promoting the acclimation of spearmint to drought stress (DS), also improving yield and quality of its essential oil (EO). We observed that GA and DS did not induce significant morphometric (e.g., stem length) and physiological (e.g., redox state, water content) modifications, indicating an innate tolerance of M. spicata to both these factors. However, spectrophotometric, HPLC-DAD and GC-MS analyses revealed that GA tended to induce the accumulation of some phytochemicals (e.g., terpenoids), mainly responsible for fragrance, quality and bioactivity of EO. Additionally, plants exposed to GA increased the number of peltate glandular trichomes and their content in mono- and sesqui-terpenes. Finally, we demonstrated that DS determined a reduction of spearmint EO yield, while GA significantly favoured it, especially at low doses, both in deficit- and well-watered conditions. Since an increase of GA concentration in roots and/or leaves of the treated plants was not observed, we hypothesised that the proposed phytostimulant exerted its activity indirectly, that is by modulating rhizobiota and/or soil structure and features or triggering signalling transduction pathways starting from the rhizodermis.

Chemical composition and bioactivity of essential oils against Ephestia kuehniella and their impact on beneficial parasitoid Bracon hebetor

Chemical composition and bioactivity of essential oils against Ephestia kuehniella and their impact on beneficial parasitoid Bracon hebetor

Zebrafish models for the evaluation of essential oils (EOs): A comprehensive review

Essential oils (EOs) derived from crops, especially aromatic plants, have been well-acknowledged to provide several health benefits for humans. Zebrafish as an unprecedented tool has been widely used as an excellent vertebrate model in labs owing to its many useful characteristics. Its applications for rapidly and economically screening and identifying toxicity, safety, and bioactivity of EOs may serve to meet the rising demand for nutraceuticals, food supplements, and natural cosmetics. In this study, we summarized the research progress of zebrafish models in evaluating EOs. In addition, toxicity, safety, and various bioactivities of EOs were summarized using a wide variety of readily applicable zebrafish models covering antioxidant, anti-inflammatory, angiogenesis inhibition, neuromodulation, anesthesia, anti-melanogenesis, analgesic activities, etc. In conclusion, zebrafish is a valuable animal model for evaluating the bioactivity and safety of EOs, and using such a model may contribute to speeding up the identification of novel EOs with potential health functions and quality assessment, which in turn boosts the recognition of aromatic plants as important industrial crops and encourages a healthier way of life.

Bioactivity of essential oils in nanoemulsions formulation against Varroa Mite and their selectivity for Apis mellifera under laboratory and colony conditions

Bioactivity of essential oils in nanoemulsions formulation against Varroa Mite and their selectivity for Apis mellifera under laboratory and colony conditions

Cellulose Nanocrystal-Based Emulsion of Thyme Essential Oil: Preparation and Characterisation as Sustainable Crop Protection Tool

Essential oil-based pesticides, which contain antimicrobial and antioxidant molecules, have potential for use in sustainable agriculture. However, these compounds have limitations such as volatility, poor water solubility, and phytotoxicity. Nanoencapsulation, through processes like micro- and nanoemulsions, can enhance the stability and bioactivity of essential oils. In this study, thyme essential oil from supercritical carbon dioxide extraction was selected as a sustainable antimicrobial tool and nanoencapsulated in an oil-in-water emulsion system. The investigated protocol provided high-speed homogenisation in the presence of cellulose nanocrystals as stabilisers and calcium chloride as an ionic crosslinking agent. Thyme essential oil was characterised via GC-MS and UV-vis analysis, indicating rich content in phenols. The cellulose nanocrystal/essential oil ratio and calcium chloride concentration were varied to tune the nanoemulsions’ physical–chemical stability, which was investigated via UV-vis, direct observation, dynamic light scattering, and Turbiscan analysis. Transmission electron microscopy confirmed the nanosized droplet formation. The nanoemulsion resulting from the addition of crosslinked nanocrystals was very stable over time at room temperature. It was evaluated for the first time on Pseudomonas savastanoi pv. savastanoi, the causal agent of olive knot disease. In vitro tests showed a synergistic effect of the formulation components, and in vivo tests on olive seedlings demonstrated reduced bacterial colonies without any phytotoxic effect. These findings suggest that crosslinked cellulose nanocrystal emulsions can enhance the stability and bioactivity of thyme essential oil, providing a new tool for crop protection.

Anticancer, antidiabetic, and antioxidant activities of endemic Stachys buttleri Mill. and Stachys pinardii Boiss. essential oils

There are numerous species in genus Stachys which are known for valuable and bioactive essential oils. For this study, essential oils of Stachys buttleri (SBE) and S. pinardii (SPE) were obtained by hydrodistillation method and the chemical composition of essential oils were determined by GC-MS analysis. Anticancer, antidiabetic, and antioxidant activities of essential oils were tested by MTT assay, α-glucosidase inhibitory, and ABTS radical scavenging methods, respectively. Forty-one compounds were determined in SBE (83.5%) which kolavelool (34.9%) was the main compound and diterpenoids (61.2%) were the dominant group of SBE. Thirty-three constituents were identified in SPE (90.6%) and trans-nerolidol (35.7%) and geranyl-α-terpinene (17.2%) were the most abundant compounds. SPE was characterized by its high proportion of oxygenated sesquiterpenes (39.1%), diterpenoids (21.4%), aromatics (14.8%), and sesquiterpenes (10.8%). Both essential oils showed strong anticancer activity against A549, U87MG, Ishikawa, and MCF-7 cell lines. These results indicated that SBE and SPE had potent anticancer activity. The IC50 values of essential oils were between 21.33-98.3 μg/mL. Both essential oils showed moderate antioxidant and antidiabetic activities. This study is the first report on the chemical composition and biological activities of the essential oils of S. buttleri and S. pinardii.

Chemical composition and bioactivity of essential oils from Piper nigrum L. and Piper retrofractum Vahl. against Callosobruchus maculatus (F.)

Plants containing substances with insecticidal properties can be used for pest control. Essential oils of Piper nigrum L. and Piper retrofractum Vah. from dried seeds and fresh leaves extracted by hydrodistillation was determined using Gas Chromatography-Mass Spectrometry (GC-MS). The fumigation toxicity and bioactivity bioassay were investigated using vapor-phase test. Experiment was performed under completely randomized design (CRD) with 4 replications. Adult mortality, number of eggs and adult emergence of F1 progeny of C. maculatus were recorded. Chemical compounds of essential oils from dried seeds and fresh leaves of P. nigrum and P. retrofractum were determined at 22-27 components (90.34-93.27%). Major compounds in dried seeds and fresh leaves of P. nigrum and P. retrofractum were alpha-bergamotene, caryophyllene, beta-selinene, germacrene D, naphthalene, undecane, 5-octadecene, cyclohexene, limonene and 2-beta-pinene. Both essential oils contained limonene, linalool, caryophyllene and naphthalene in seeds and leaves. These four components showed insecticidal properties. Essential oils at concentrations of 5 µL/L air P. nigrum and 10 µL/L air P. retrofractum extracted from dried seeds were more effective in oviposition inhibition and adult emergence of C. maculatus than essential oils extracted from fresh leaves. P. nigrum essential oil from dried seeds at a concentration of 5 µL/L air was the highest efficiency of oviposition inhibition with 55.17% and adult emergence inhibition of 71.09% of C. maculatus. This suggested that P. nigrum essential oil extracted from dried seeds could be used for protection on C. maculatus in stored grain.

Extraction and chemical characterisation of agro-waste from turmeric leaves as a source of bioactive essential oils with insecticidal and antioxidant activities

Turmeric (Curcuma longa L.) is a significant crop that has historically been used worldwide as a medicinal plant, spice, food colouring agent, and a significant ingredient in cosmetic industries. After harvesting rhizomes, leaves are considered waste material. This research study aims to extract and chemically characterise the essential oil from the leaves waste of turmeric with an evaluation of different insecticidal, antioxidant, and phytotoxic activities. Subsequently, the contact toxicity, fumigant toxicity, and repellent activity were evaluated against two key stored grain insect species. The gas chromatography-mass spectrometry (GC–MS) characterisation revealed that α-phellandrene (28.95%), 2-carene (16.51%), eucalyptol (10.54%) and terpinolene (10.24%) were the major chemical constituents. The study's findings on the insecticidal effects of essential oils extracted from turmeric leaves revealed noteworthy repellent, contact (at 24 h, LC50 = 6.51 mg/cm2 for Tribolium castaneum and LC50 = 4.74 mg/cm2 for Rhyzopertha dominica) and fumigant toxicities (at 24 h, LC50 = 2.57 mg/L air for T. castaneum and LC50 = 2.83 mg/L air for R. dominica), against two key stored grain insects. In addition, turmeric leaf essential oil showed notable antioxidant activity (IC50 = 10.04 ± 0.03 µg/mL for DPPH assay; IC50 = 14.12 ± 0.21 µg/mL for ABTS assay. Furthermore, a phytotoxicity study was carried out on stored paddy seeds and no toxic effects were found on germination rate and seedling growth. So, it might be expected that the essential oils extracted from the turmeric leaf waste could be valorised and demonstrate their potential as safe botanical insecticides against stored-product insects, with noble antioxidant properties.

Yield, Chemical Composition and Bioactivity of Essential Oils from Common Juniper (Juniperus communis L.) from Different Spanish Origins.

Essential oils (EOs) obtained from Juniperus communis L. are frequently used in the production of bioproducts. However, there are no studies regarding industrial crops' production, allowing for better control of the quality and production of juniper EOs. To select the plant material for developing future crops of this species in northern Spain, four locations where this shrub species grows in the wild were selected and samples of both genera were collected. The EOs were obtained by steam distillation, and their chemical composition and bioactivity were evaluated. The results showed that the yield of EOs from male and female samples were within the usual reported ranges, varying between 0.24 and 0.58% (dry basis, d.b.). However, limonene content in three locations varied between 15 and 25%, which is between 100% and 200% higher than the values usually reported for other European countries. The antibacterial activity was determined by broth microdilution and showed that gram-positive bacteria were more susceptible to the tested EOs since, in general, lower MIC values were obtained compared to gram-negatives. The EOs from location 1 (L1F) and 2 (L2M) inhibited the growth of six out of the eight clinical strains tested. Samples from location 1 were particularly effective, exhibiting MBC against two gram-negative (E. coli and P. mirabilis) and one gram-positive bacteria (E. faecalis). Moreover, the majority of the EOs tested showed anti-inflammatory activity. Cytotoxic effect has been demonstrated in tumor cell lines, with the best results observed against gastric carcinoma (AGS) cells (GI50 between 7 to 77 µg/mL). Although generally presenting higher GI50, most samples also inhibited the growth of non-tumoral cells, particularly hepatocytes (PLP2 cells). Therefore, its use for their anti-proliferative activity should consider specific conditions to avoid damaging normal cells. Finally, the results and conclusions obtained led to the selection of the female shrubs from location 1 (L1F) as the plant material to be propagated in order to produce plants for a future juniper crop.

Antibacterial, bacteriolytic, and antibiofilm activities of the essential oil of temu giring (Curcuma heyneana Val.) against foodborne pathogens.

Foodborne pathogens may cause foodborne illness, which is among the major health problems worldwide. Since the therapeutic options for the treatment of the disease are becoming limited as a result of antibacterial resistance, there is an increasing interest to search for new alternatives of antibacterial. Bioactive essential oils from Curcuma sp become potential sources of novel antibacterial substances. The antibacterial activity of Curcuma heyneana essential oil (CHEO) was evaluated against Escherichia coli, Salmonella typhi, Shigella sonnei, and Bacillus cereus. The principal constituents of CHEO are ar-turmerone, β-turmerone, α-zingiberene, α-terpinolene, 1,8-cineole, and camphor. CHEO exhibited the strongest antibacterial activity against E. coli with a MIC of 3.9 µg/mL, which is comparable to that of tetracycline. The combination of CHEO (0.97 µg/mL) and tetracycline (0.48 µg/mL) produced a synergistic effect with a FICI of 0.37. Time-kill assay confirmed that CHEO enhanced the activity of tetracycline. The mixture disrupted membrane permeability of E. coli and induced cell death. CHEO at MIC of 3.9 and 6.8 µg/mL significantly reduced the formation of biofilm in E. coli. The findings suggest that CHEO has the potential to be an alternative source of antibacterial agents against foodborne pathogens, particularly E. coli.

Metabolomic Analysis of the Effect of Lippia origanoides Essential Oil on the Inhibition of Quorum Sensing in Chromobacterium violaceum.

Bacteria can communicate through quorum sensing, allowing them to develop different survival or virulence traits that lead to increased bacterial resistance against conventional antibiotic therapy. Here, fifteen essential oils (EOs) were investigated for their antimicrobial and anti-quorum-sensing activities using Chromobacterium violaceum CV026 as a model. All EOs were isolated from plant material via hydrodistillation and analyzed using GC/MS. In vitro antimicrobial activity was determined using the microdilution technique. Subinhibitory concentrations were used to determine anti-quorum-sensing activity by inhibition of violacein production. Finally, a possible mechanism of action for most bioactive EOs was determined using a metabolomic approach. Among the EOs evaluated, the EO from Lippia origanoides exhibited antimicrobial and anti-quorum activities at 0.37 and 0.15 mg/mL, respectively. Based on the experimental results, the antibiofilm activity of EO can be attributed to the blockage of tryptophan metabolism in the metabolic pathway of violacein synthesis. The metabolomic analyses made it possible to see effects mainly at the levels of tryptophan metabolism, nucleotide biosynthesis, arginine metabolism and vitamin biosynthesis. This allows us to highlight the EO of L. origanoides as a promising candidate for further studies in the design of antimicrobial compounds against bacterial resistance.

Bioactivity of Essential Oil from Citrus aurantium Peel against the Pulse Beetle Callosbruchus maculatus F. on Chickpea

Plant essential oils (EOs) and their active compounds are recognized as sustainable tools for the management of arthropod pests. The bitter orange, Citrus aurantium L. (Rutaceae), is a widespread tree in the Mediterranean region that is used especially as a rootstock for other Citrus. Although most of this plant’s parts are accredited with medicinal properties, its fruits are not consumable and generally considered as non-valued waste. The aim of this work was to assess the potential use of the EO extracted by hydrodistillation from C. aurantium peel in the fumigation of chickpea seeds against Calloosbruchus maculatus. Analysis of EO of the bitter orange peel by gas chromatography coupled with a mass spectrometer (GC-MS) identified twenty-two compounds with limonene as the major component (86%). EOs of C. aurantium peel exerted toxic effects, in a concentration-dependent manner, on eggs (LC50 = 62.7 µL/L air), larval stages inside the seed (LC50 = 62.8 µL/L air), and adults (females: LC50 = 148 μL/L air and males: LC50 = 109 µL/L air). The C. aurantium EO also negatively affected the biological and demographic performances of the weevil compared to the untreated control. Fecundity and the number of emerged adults were reduced by more than 57 and 71, respectively, while the net reproduction rate and the intrinsic rate of increase were respectively decreased by over 71% and 37%, resulting in the total extinction of the pest at a concentration equal to 100 µL/L air. Our findings suggest the possible valorization of bitter orange peel by using them as a source of bioinsecticide to be integrated within sustainable programs for the management of stored product pests. Further studies are needed to verify similar uses of essential oils extracted from solid wastes from citrus-processing industries.