Search Results (252)

The global rise in antimicrobial resistance has spurred increased interest in alternative antimicrobial agents, particularly essential oils (EOs). These oils are complex mixtures of volatile compounds that exhibit documented biological activity. This study evaluated antimicrobial and antibiofilm effects of selected EOs against clinically relevant bacterial and fungal pathogens. Antimicrobial activity against planktonic cells was assessed using disc diffusion assays with DMSO-diluted EO solutions against Escherichia coli (E.coli), Staphylococcus aureus (S.aureus), Pseudomonas aeruginosa, Klebsiella pneumoniae, and Candida albicans. Antibiofilm activity of E. coli and S. aureus was examined using ethanol-based EO formulations, with biofilm viability quantified by colony forming unit (CFU) enumeration. Cinnamon (Cinnamomum verum) oil showed the strongest and most consistent activity, inhibiting planktonic and biofilm models. Tea tree (Melaleuca alternifolia), lemongrass (Cymbopogon citratus), rosemary (Rosmarinus officinalis), rose (Rosa damascena), and jasmine (Jasminum officinale) oils showed significant planktonic antimicrobial effects, while jasmine oil (Jasminum officinale) demonstrated pronounced antibiofilm activity against S. aureus, including strong biofilm eradication in several replicates. In contrast, chamomile (Matricaria chamomilla) and sandalwood (Santalum austocaledonicum) oils showed limited or no activity. These findings highlight differences between planktonic and biofilm responses, emphasizing the importance of incorporating biofilm models into antimicrobial evaluation. Overall, Cinnamomum verum and Jasminum officinale oils may serve as complementary antimicrobial agents, warranting further investigation. Full article

This study developed an active packaging material by incorporating tea tree oil (TTO)-loaded lotus stalk biochar (BC@TTO) into a chitosan (CS) matrix. Biochar was prepared from lotus stalks via pyrolysis at 600 °C and characterized, revealing a mesoporous structure with a specific surface area of 35.9 m²/g. Adsorption studies demonstrated that BC exhibited high affinity for TTO, following pseudo-first-order kinetics and the Langmuir isotherm model, with a maximum adsorption capacity of 295.6 mg/g. Chitosan-based composite membranes with varying BC@TTO contents (1–7 wt%) were fabricated by solution casting. The incorporation of BC@TTO significantly enhanced the tensile strength, elongation at break, barrier properties (water vapor and oxygen), and antioxidant/antibacterial activities of the membranes, with optimal performance observed at 3 wt% loading. However, higher loadings led to filler aggregation, reduced transparency, and compromised mechanical properties. In vitro release studies indicated that TTO release followed the Avrami model, suggesting a diffusion-controlled mechanism. Preservation tests on blueberries showed that the CS-3BC@TTO membrane effectively reduced weight loss and maintained fruit quality during storage. This work presents a promising strategy for designing bioactive packaging materials with sustained release functionality for food preservation applications. Full article

The Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Liviidae) is the vector of the devastating citrus disease Huanglongbing, posing a significant threat to the global citrus industry and necessitating environmentally sound management strategies. This study aimed to evaluate Australian tea tree oil (TTO) and its primary constituents as potential botanical insecticides. Gas chromatography-mass spectrometry (GC-MS) was performed to analyze the chemical profile of commercial TTO, and behavioral effects on D. citri adults were assessed using a Y-tube olfactometer. Direct spray bioassays were conducted to determine contact toxicity. A total of 12 compounds were identified, with TTO being a Terpinen-4-ol chemotype, dominated by Terpinen-4-ol (40.62%), γ-Terpinene (21.46%), and α-Terpinene (10.45%). TTO demonstrated potent, concentration-dependent repellency, achieving 100% repellency at 10 g/L. In contrast, Terpinen-4-ol alone was attractive to psyllids at low concentrations, suggesting synergistic or masking effects within the complex oil blend. TTO and its major constituents also exhibited significant dose- and time-dependent contact toxicity. Although the 72 h LC₅₀ of TTO (19.18 g/L) indicates lower potency compared to conventional insecticides (0.59–1.23 g/L), its combined repellent and toxic properties make it a promising candidate for integrated pest management (IPM) programs aimed at controlling D. citri and mitigating insecticide resistance. Full article

This study evaluated the effect of applying tea tree essential oil (TTEO) on the sensory, microbiological, and antioxidant quality of grated anco squash (Cucurbita moschata). To this end, different application methodologies and concentrations of TTEO were applied to the product, and their effect on sensory characteristics, microbiological quality and bioactive compounds was evaluated. The anco squash was washed, disinfected, cut, peeled, grated, and then treated with TTEO at concentrations of 4 and 8 μL/mL using different application methods: spraying (TS), immersion (TI), and absorbent strips impregnated with EO attached to the trays to generate vapors (TV). In addition, an immersion treatment with NaClO (100 ppm, 3 min) (TH) and a water-immersion control (TC) were included. All samples were packaged in PVC trays, sealed with 35 µm polypropylene bags, and stored at 5 °C for 8 days. According to sensory evaluation, TTEO spray treatments (TS) maintained the highest scores until day 4, and were therefore identified as the most effective strategy for application. Antioxidant capacity initially increased for all TTEO treatments compared to the control, while phenolic compound levels remained stable and carotenoid content decreased progressively during storage. Overall, TTEO treatments maintained the quality of grated anco squash for up to 4 days at 5 °C, highlighting their potential to improve nutraceutical properties and extend shelf life when integrated with complementary preservation technologies. Full article

Developing potential skincare formulations capable of simultaneously managing infection and promoting tissue repair remains a critical challenge in dermatological care. This study engineered bioactive oleogels using sunflower wax (SFW), rice bran wax (RBW), and 12-hydroxystearic acid (HSA) to deliver a synergistic essential oil blend (ginger, cinnamon, tea tree, geranium). A D-optimal mixture design optimized formulations to match the textural profile of a commercial benchmark. Crucially, the fatty acid architecture of the carrier oil emerged as a primary determinant of network integrity; the high oleic acid content in camellia oil facilitated robust RBW crystallization by minimizing steric hindrance, whereas the polyunsaturated, kinked structure of linoleic acid in almond oil disrupted SFW networks, resulting in lower stiffness. Thermal characterization (DSC) established a distinct stability hierarchy with RBW exhibiting the highest melting point (Tp = 60.1 °C) and enthalpy (ΔHm = 7.79 ± 0.74 J/g). Thermogravimetric analysis (TGA) confirmed high thermal resistance for wax-based systems (Tdeg ≈ 357 °C), whereas HSA displayed a biphasic degradation starting at ~206 °C. FTIR spectroscopy verified the stable physical entrapment of bioactives, with the lipid vehicle dominating the spectral fingerprint. Rheological profiling revealed that RBW oleogels, structured in high-oleic camellia oil, formed rigid networks (G′ ≈ 5.7 × 104 Pa) with high yield stress (20.91 Pa), offering superior retention. In contrast, HSA oleogels displayed “smart” thixotropic recovery with lower stiffness (G′ ≈ 2.1 × 104 Pa) and a distinct melting peak at 22.5 °C, compared to 60.1 °C for RBW. All formulations achieved a >2 Log₁₀ reduction (99%) in Staphylococcus aureus and Pseudomonas aeruginosa viability after 12 h. Furthermore, in vitro keratinocyte assays identified a hormetic therapeutic window at 1–5 μg/mL (essential oil blend equivalent); specifically, SFW oleogels at 5 μg/mL stimulated proliferation to 158.07% relative to controls. These findings confirm that optimizing the lipid vehicle–bioactive interface creates dual-action scaffolds capable of simultaneously managing infection and stimulating in vitro keratinocyte proliferation. Full article

Growing interest in natural therapies has increased the demand for essential oils; however, the complex interactions within their mixtures that dictate their final efficacy remain poorly understood. This study aimed to optimize a blend of ginger, cinnamon, tea tree, and geranium essential oils to develop an active ingredient, with synergistic multifunctional bioactivities, that was relevant to cutaneous healing. Initially, the composition and cytotoxicity for individual oils were determined; subsequently, a D-optimal mixture design was employed to evaluate three biological responses related to skin recovery: ultraviolet B radiation absorption, red blood cell lysis inhibition, and catalase enzyme activity. GC-FID analysis revealed the following major components (% w/w): cinnamon (cinnamaldehyde, 77.56%), ginger (α-zingiberene, 33.77%), geranium (citronellol, 33.6%), and tea tree (terpinen-4-ol, 38.38%). Dose–response data from essential oils tested against Detroit ATCC 551 skin fibroblasts revealed a clear cytotoxic hierarchy (IC₅₀ µg/mL): cinnamon (21.03) > ginger (25.3) > tea tree (41.67) > geranium (92.51). Cinnamaldehyde content was the primary contributor to photoprotective capacity, with a maximum sun protection factor (SPF) of 4.5. Inhibition against erythrocyte membrane lysis was not attributable to a single component; maximum protection (98.4%) was achieved through synergy between oxygenated monoterpenoids (geranium and tea tree), sesquiterpenes (ginger), and aromatic aldehydes (cinnamon). Highest catalase activity (160.86 kU/g Hb) was reached in mixtures with high cinnamaldehyde and eugenol contents, whereas an antagonistic effect was observed between tea tree and geranium oils. Finally, an optimal formulation (desirability = 0.927) was identified (% w/w): 31.7% ginger, 39.1% cinnamon, 14.5% tea tree, and 14.7% geranium. Experimental validation confirmed no significant difference compared with developed predictive models. This optimized mixture constitutes a bioactive natural component with potential for use in products aimed at promoting skin health, warranting further investigation into direct models of skin healing. Full article

(1) Background: The oral cavity is a complex ecological environment that integrates elements of both the digestive and respiratory systems, contributing to its extensive microbial diversity. Despite its effectiveness, chlorhexidine is associated with undesirable effects, such as mucosal irritation and tooth staining, which have prompted research into natural alternatives. This study aimed to compare the antimicrobial activity of mouthwashes containing tea tree oil (TTO) alone and in combination with cannabidiol (CBD) and spilanthol with that of a chlorhexidine digluconate-based mouthwash (CHX) against selected oral bacterial and fungal strains. (2) Methods: To assess the antimicrobial effects of the tested mouthwashes on reference microbial strains, the agar diffusion method was applied in accordance with the guidelines of the European Committee on Antimicrobial Susceptibility Testing (EUCAST). In addition, the microdilution method using 96-well microtiter plates was employed to determine the minimum inhibitory concentration (MIC) of the tested substances. Microbial viability was further evaluated using the WST-based colorimetric Microbial Viability Assay Kit, in which the intensity of the produced WST-formazan dye is directly proportional to the number of viable cells. (3) Results: In the disc diffusion assay, inhibition zones measured after 24 h varied among the tested microorganisms, with the largest zones observed for CHX against Candida parapsilosis (19.63 mm) and Streptococcus pyogenes (16.7 mm). In the microdilution assay against Candida albicans, the MIC₅₀ was achieved for preparations A and B at the highest tested concentrations (column 1), whereas for chlorhexidine (CHX), it was reached at lower concentrations (column 9). (4) Conclusions: ① All tested mouthwashes containing tea tree oil (TTO), either as a single active ingredient or in combination with cannabidiol (CBD) and spilanthol, demonstrated limited bacteriostatic and antifungal activity under the experimental conditions of this study. ② The chlorhexidine digluconate-based mouthwash exhibited significantly higher antibacterial and antifungal activity against all tested microbial strains compared to both the TTO-only mouthwashes and the formulation containing TTO combined with CBD and spilanthol. Full article

The work provides novel insight into the development of advanced antibacterial surfaces using the combination of essential oils, cinnamon oil, thyme oil, and tea tree oil, as well as their active compounds, including cinnamaldehyde, thymol, and terpinene-4-ol, embedded in the chitosan and sodium alginate matrix. All coatings obtained in a two-stage electrophoretic deposition process on stainless steel and titanium substrates were characterized by high adhesion strength. The microstructural differences between the coatings were mainly related to the size and location of the additives. Structural investigation showed the impact of individual oil components on intermolecular bonds between polysaccharide chains and the formation of molecular interactions in a specific spatial conformation. The surface of all coatings was minimally rough and had a hydrophilic character. A clear matrix-dependent trade-off between antibacterial efficacy and cytocompatibility was observed: alginate-based coatings achieved strong anti-Staphylococcus aureus activity (2.81 log CFU/mL) at the expense of increased cytotoxicity, while chitosan-based systems provided a more favorable cytocompatibility profile, maintaining cell viability above 70% for selected formulations. This work provides insight into the development of natural antibacterial surfaces by the combination of active compounds and shows the distinctions on many levels between the coatings with various polysaccharide matrices. Full article

Campylobacter jejuni is an important foodborne pathogen. To prevent human infections, special attention should be paid to prevention. Recently, methods involving essential oils have been considered as a means of reducing the number of contaminants in and on foods. This review summarizes the results of studies in which essential oils (EOs) with anti-campylobacter effects were tested. The most widely studied EOs were clove (28%), oregano (24%), thyme (22%), rosemary (8%), lavender (7%), sage (7%), and tea tree (4%), with other EOs studied to a lesser extent. The anti-Campylobacter efficacies of these EOs were demonstrated in vitro using a broad repertoire of methods, such as minimal inhibitory and bactericidal concentrations, agar diffusion, time-kill assays, adhesion and biofilm inhibitory assays, two-dimensional polyacrylamide gel electrophoresis, quantitative reverse-transcription PCR, and liquid chromatography–mass spectrometry. Recent studies have also focused on the practical application of such EOs, with experiments performed on different food matrices, typically chicken, duck, and beef. The most frequent treatment methods were mixing, dipping, and short-time freezing, either in packed or unpacked forms, and storage at different temperatures (typically 4 °C), although experiments were also performed at 25 °C, 32 °C, and 42 °C using different EO concentrations. In summary, these experiments revealed the anti-Campylobacter effects of thyme, cinnamon, coriander, lime, oregano, chrysanthemum, and basil. Full article

The threat of antimicrobial resistance (AMR) and the need for sustainable disinfectants have spurred interest in natural antimicrobials such as essential oils (EOs). However, their application is limited by volatility, poor water solubility, and cytotoxicity. Herein, we present the development of bio-based core–shell sub-micro-/nanocapsules (NCs) with encapsulated oregano (OO), thyme (TO), eucalyptus (EuO), and tea tree (TTO) oils to enhance antimicrobial (AM) performance and reduce cytotoxicity. NCs were synthesized via a nanoencapsulation method using chemically modified zein or poly(methyl vinyl ether-co-maleic anhydride) (GZA) as shell polymers, with selected EOs encapsulated in their core (encapsulation efficacy > 98%). Chemical modification of zein with vanillin (VA) and GZA with either dodecyl amine (DDA) or 3-(glycidyloxypropyl)trimethoxysilane (EPTMS) resulted in improvement in particle size distributions, polydispersity indices (PDIs) of synthesized NCs, and in the stability of the NC-dispersions in water. Antibacterial testing against Staphylococcus aureus and cytotoxicity assays showed that encapsulation significantly reduced toxicity while preserving their antibacterial activity. Among the formulations, GZA-based NCs modified with EPTMS provided the best balance between safety and efficacy. Despite this, life cycle assessment revealed that zein-based NCs were more environmentally sustainable due to lower energy use and material impact. Overall, the approach offers a promising strategy for developing sustainable, effective, and safe EO-based antibacterial agents for AM applications. Full article

Extensive growth promoter use in livestock production has raised concerns about their role in selective pressure on resistant microorganisms, driving interest in natural alternatives such as essential oils (EOs). This study aimed to evaluate the effects of tea tree, holy wood, and citronella EOs on in vitro ruminal fermentation. The study follows a completely randomized design with the following five treatments: control, monensin (5 μM), tea tree EO (50 mg/L), holy wood EO (50 mg/L), and citronella EO (50 mg/L), each conducted in triplicate. Incubations were performed at 39 °C for 48 h in the rumen fluid collected from fistulated cattle fed a 20:80 forage-to-concentrate diet. Notably, EOs exhibited no significant effects on pH, microbial protein production, total volatile fatty acids, or in vitro dry matter digestibility (p > 0.05). Tea tree and holy wood EOs enhanced deamination activity, and all treatments increased ammonia concentration compared with that in the control. Monensin treatment increased acetate concentration and reduced in vitro neutral detergent fiber digestibility; holy wood EO exhibited a similar trend. Altogether, the findings of this study suggest that EOs can selectively modulate the ruminal microbiota, influencing nitrogen metabolism and fermentation patterns without impairing rumen stability. Full article

Background/Objectives: As antimicrobial dental treatments, based on chemical products, long tested for their efficacy, have been lately associated with developing antimicrobial resistance, there is a growing interest to identify and develop efficient alternatives. The aim of this paper is to assess the antimicrobial potential of eight selected essential oils (EOs): Cinnamon (Cinnamomum verum), Tea tree (Melaleuca alternifolia), Spearmint (Mentha spicata), Rosemary (Rosmarinus officinalis), Clove (Eugenia caryophyllata), Eucalyptus (Eucalyptus radiata), Cedarwood (Juniperus virginiana), and Lemongrass (Cymbopogon flexuosus), more or less recognized and investigated for this particular therapeutic effect, on Streptococcus mutans (S. mutans), a key pathogen involved in oral pathology. Materials and methods: The chemical constituents of the EOs were identified and quantified by Gas Chromatography-Mass Spectrometry (CG-MS) method. Saliva samples, collected from nine patients with active dental caries, were tested in vitro. To assess the bacterial susceptibility of the selected EOs against S. mutans, the inhibition zones (IZ), minimum inhibitory concentrations (MIC), and minimum bactericidal concentrations (MBC) were determined. Results: All EOs tested showed antimicrobial activity against S. mutans, with IZs over 20 mm. The highest antimicrobial efficacy was observed for spearmint, followed by Eucalyptus, Tea tree, and Lemongrass. The next in descending order were Cinnamon Bark, Clove, Rosemary, and Cedarwood. Considering the mean MIC and MBC values, the spearmint EO proved to be the most effective in inhibiting the growth of S. mutans, as well as in annihilating it, followed by the Eucalyptus EO, Tea tree EO and Lemongrass EO. The less effective were determined to be Cinnamon, Clove, Rosemary and Cedarwood EOs. Conclusions: The eight selected EOs demonstrated antimicrobial activity against S. mutans, with Spearmint and Eucalyptus showing the most significant effects, advocating for their potential in dental caries prevention and treatment, and their potential role in oral hygiene applications. Full article

The rise in antimicrobial resistance and tolerance over time represents a significant threat to human and animal health. This has led to a notable increase in interest within the scientific community in the development of herbal-based therapeutic alternatives to antibiotics. The present study aimed at evaluating the in vitro antimicrobial activity of 18 essential oils (EOs) against a total of 17 strains belonging to both Gram-positive and Gram-negative bacteria, by employing the spot-on-agar method using two different culture media, Brain Heart Infusion (BHI) and Mueller–Hinton (MH). The antimicrobial properties of these essential oils were investigated, as well as their antimicrobial stability over a period of seven days. The overall efficacy of the EOs remained consistent over seven days, regardless of the solid medium used. However, the antimicrobial effects of the EOs were more pronounced in BHI than in MH for Gram-positive bacteria. While variations in antimicrobial activity were recorded among different species and strains, oregano EO proved to be the most effective against both Gram-positive and Gram-negative bacteria, followed by thyme and tea tree. The findings of this study support the notion that EOs could be employed as a promising therapeutic strategy to combat antibiotic-resistant bacteria, thereby enhancing the efforts aimed at addressing antibiotic resistance. Furthermore, the divergent antimicrobial effects exhibited by the two growth media employed here may facilitate the establishment of standardised protocols for the testing of EOs against bacteria. Full article

Malassezia pachydermatis, an important opportunistic secondary pathogen, is often associated with atopic dermatitis or otitis externa in dogs. Recent studies indicate an increase in resistance of this yeast to commonly used antifungal agents. Therefore, the search for new antifungal agents is a challenge. In the present study, the susceptibility of M. pachydermatis strains to 10 plant essential oils—EOs (bergamot, grapefruit, coriander, hyssop, lavender, tea tree, nutmeg, oregano, rosemary, and Spanish sage) was determined using the broth microdilution method. All 15 clinical strains tested were susceptible to coriander (100%). A good antifungal activity was shown for EO from nutmeg (93.33%), bergamot (86.66), Spanish sage and hyssop (73.33%) and rosemary (66.67%). Lower antifungal efficacy was identified in EOs from grapefruit, lavender, tea tree and oregano (53.33%). The obtained results indicate promising prospects for the clinical use of essential oils in the treatment of M. pachydermatis infections. Full article

Essential oils (EOs) have gained recognition as promising alternatives to antibiotics due to their positive effects on bird growth performance, enhanced meat quality, and improved overall health, without producing the negative consequences associated with antibiotics. This study evaluated the effects of dietary supplementation of tea tree (TTEO) and thyme (TEO) EOs, individually or in combination with the probiotic BioPlus 2b (Bacillus subtilis and Bacillus licheniformis), on poultry broiler performance, including the meat quality. A total of 240 ROSS 308 broilers were assigned to eight dietary treatments over a 35-day trial. Parameters such as body weight (BW), feed conversion ratio (FCR), carcass portion, drip loss, and meat pH were evaluated. TTEO had a significant (p ≤ 0.05) impact on final carcass and breast portion, while in combination with probiotics, specifically TTEO with BioPlus significantly (p ≤ 0.05) reduced meat drip loss. GC-MS analysis identified terpinen-4-ol and γ-terpinene as the major constituents of TTEO, and thymol and carvacrol as the major constituents of TEO. In conclusion, combinations of TTEO, TEO, and probiotics can have beneficial effects on chicken raw meat quality, providing a complementary benefit to the industry and representing a viable alternative to conventional agents. Full article