Melaleuca alternifolia (Tea Tree) oil: a review of antimicrobial and other medicinal properties

Effects of Melaleuca alternifolia Chell (Tea Tree) and Eucalyptus globulus Labill. Essential Oils on Antibiotic-Resistant Bacterial Biofilms

In the present investigation, the anti-biofilm potential of two essential oils (EOs), Melaleuca alternifolia Chell (Tea-Tree) (TTO) and Eucalyptus globulus Labill. (EEO) was characterized and tested "in vitro" against both mature biofilms and biofilms in the process of formation, produced by strains belonging to three main categories of antibiotic resistant bacteria (ARB): Vancomycin-resistant enterococci (VRE), methicillin-resistant Staphylococcus aureus (MRSA) and broad-spectrum β-lactamase-producing Escherichia coli (ESBL). The study was carried out in 96-well microtiter-plates using EOs alone, in association with each other and in combination with antibiotics against both single and multi-species biofilm. The study demonstrated the ability of TTO and EEO to counteract the ARB strains in sessile form, with promising results in particular against the biofilm in formation. Mature biofilm by ESBL E. coli was the most sensitive in the results from the quantification study of viable cells performed in multi-species biofilms. Lastly, in all tests, carried out using TTO/EEO associations and EOs/antibiotic combinations, the synergistic effect which emerged from the FIC-index has been confirmed, and both the reduction of biofilm in formation, and the removal of mature structure was obtained at very low concentrations, with values from 4 to >512-fold lower than the minimum inhibitory concentration (MIC) of the single compounds.

Antimicrobial Natural Hydrogels in Biomedicine: Properties, Applications, and Challenges-A Concise Review

Natural hydrogels are widely used as biomedical materials in many areas, including drug delivery, tissue scaffolds, and particularly wound dressings, where they can act as an antimicrobial factor lowering the risk of microbial infections, which are serious health problems, especially with respect to wound healing. In this review article, a number of promising strategies in the development of hydrogels with biocidal properties, particularly those originating from natural polymers, are briefly summarized and concisely discussed. Common strategies to design and fabricate hydrogels with intrinsic or stimuli-triggered antibacterial activity are exemplified, and the mechanisms lying behind these properties are also discussed. Finally, practical antibacterial applications are also considered while discussing the current challenges and perspectives.

The Role of Essential Oils in Homemade Cosmetics: A Study of 140 Recipes

Two recent trends that have developed simultaneously are a mistrust of health products by some of the population and the growing popularity of essential oils. The objective of this study was to analyze recipes with essential oils found on the internet and to assess their level of photoprotective efficacy. Therefore, we conducted a study of 140 recipes for personal care and hygiene products that incorporate one or more essential oils. This analysis revealed that numerous essential oils are called for in these recipes, derived from plants belonging to a wide diversity of botanical families. There was a significant difference (p=0.0026) in the number of essential oils listed in the recipes for facial care and body care recipes. There was also a statistically significant difference (p=2.54E-5) in the amount of essential oil to be added, expressed in drops, according to the type of product being made. A common characteristic of most of the recipes was the absence of any antimicrobial agents or antioxidants, which poses serious issues of preservation for the finished products. Recipes with essential oils pose many issues. The first issue lies in the quantities of the different raw materials to be incorporated; it influences the final essential oil concentration. The second issue concerns the adverse effects (photosensitization, for example) and contraindications (pregnant women, nursing women) of certain essential oils. Finally, it is not possible to carry out physicochemical testing raw materials and finish preparation.

Cosmetic Formulations with Melaleuca alternifolia Essential Oil for the Improvement of Photoaged Skin: A Double-Blind, Randomized, Placebo-Controlled Clinical Study

This aim of this study was to evaluate the penetration depth, antioxidant capacity and the clinical efficacy of Melaleuca alternifolia pure essential oil and in a nanoemulsion to prevent skin photoaging. For this, 2% of pure essential oil or 2% of this essential oil in a nanoemulsion were vehiculated in a formulation. The skin penetration was evaluated using confocal Raman microspectroscopy. The radical protection factor was evaluated using electron paramagnetic resonance spectroscopy. For a clinical study, 40 male participants, aged 18-28 years, were enrolled, being divided into three groups: vehicle formulation, M. alternifolia pure essential oil and M. alternifolia Nanoemulsion. All the participants also received a sunscreen SPF 50 to use during the day. Before and after 90 days of study, skin hydrolipidics and morphological characteristics were performed by skin imaging and biophysical techniques. The nanoemulsion presented a lower antioxidant capacity and a higher penetration through the stratum corneum, reaching the viable epidermis, improving the stratum granulosum morphology. The groups presented an increase in the papillary depth, improving in the dermis echogenicity and the collagen fibers. Melaleuca alternifolia essential provides the potential to improve photoaged skin, being the application of nanoemulsion able to reach deeper skin layers.

Complementary and alternative medicine for alopecia areata: A systematic review

BACKGROUND

Despite high use of complementary and alternative medicine (CAM) for alopecia areata (AA), efficacy and safety remain unclear.

OBJECTIVE

To identify all CAM therapies studied for treatment of AA. Outcomes of interest included disease course and psychologic well-being.

METHODS

PubMed and Embase were searched to identify English articles containing original data investigating CAM in individuals with AA from 1950-2018. Quality was assessed with Oxford Centre for Evidence Based Medicine criteria.

RESULTS

Of 1015 initial citations, 16 articles met inclusion criteria: 5 randomized controlled trials, 5 prospective controlled cohorts, 4 prospective noncontrolled cohorts, 1 retrospective cohort, and 1 case series. CAM therapies with best evidence and efficacy for hair growth in AA include essential oil aromatherapy, topical garlic, and oral glucosides of peony with compound glycyrrhizin. Hypnosis and mindfulness psychotherapy represent low-quality evidence for improvement of psychologic and quality of life outcomes. Adverse events were rare and mild for all therapies evaluated.

LIMITATIONS

Inconsistent or poorly reported study methodology and nonstandardized outcomes limit the conclusions that can be made from these studies.

CONCLUSIONS

This work serves to inform physician treatment of patients with AA seeking CAM while encouraging further investigation into these therapies to address some of the therapeutic challenges of AA.

Enhanced antimicrobial and antioxidant capacity of Thymus vulgaris, Lippia sidoides, and Cymbopogon citratus emulsions when combined with mannosylerythritol a lipid biosurfactant

Essential oils (EOs) are natural and effective agents for controlling microorganisms which cause biodeterioration and disease. However, their application is hampered/restricted due to hydrophobicity and rapid vaporization of these compounds. Encapsulation technology provides an effective approach to maintain EO stabilization and prevent the loss of volatile ingredients. Meanwhile, using a synthetic surfactant is seen as counter-productive; therefore, a natural biosurfactant is more reasonable and can potentially increase activity due to its other biological proprieties. This work aims to evaluate the mannosylerythritol lipid (MEL) biosurfactant combined with Thymus vulgaris, Lippia sidoides, and Cymbopogon citratus essential oil emulsions (O/W) and evaluate its antimicrobial and antioxidant capacity. The biosurfactant MEL demonstrated activity against Bacillus subtilis and Penicillium sp. After emulsification, the antimicrobial activity of Thymus vulgaris and Lippia sidoides was increased against Escherichia coli (500 µg/mL), Staphylococcus aureus (600 µg/mL), Bacillus subtilis (120 µg/mL), Pseudomonas aeruginosa (1500 µg/mL), Penicillium sp. (62.25 µg/mL), Aspergillus flavus (250 µg/mL), Fusarium oxysporum (100 and 250 µg/mL), and Candida albicans (125 and 250 µg/mL). We report that emulsions prepared with MEL have high inhibitory activity, maintain the active concentration, and increase antioxidant capacity by 7.33% (Thymus vulgaris), 13.71% (Lippia sidoides), and 3.15% (Cymbopogon citratus).

Pharmaceutical based cosmetic serums

The growth and demand for cosmeceuticals (cosmetic products that have medicinal or drug-like benefits) have been enhanced for the last few decades. Lately, the newly invented dosage form, i.e., the pharmaceutical-based cosmetic serum has been developed and widely employed in various non-invasive cosmetic procedures. Many pharmaceutical-based cosmetic serums contain natural active components that claim to have a medical or drug-like effect on the skin, hair, and nails, including anti-aging, anti-wrinkle, anti-acne, hydrating, moisturizing, repairing, brightening and lightening skin, anti-hair fall, anti-fungal, and nail growth effect, etc. In comparison with other pharmaceutical-related cosmetic products (creams, gels, foams, and lotions, etc.), pharmaceutical-based cosmetic serums produce more rapid and incredible effects on the skin. This chapter provides detailed knowledge about the different marketed pharmaceutical-based cosmetic serums and their several types such as facial serums, hair serums, nail serums, under the eye serum, lip serum, hand, and foot serum, respectively. Moreover, some valuable procedures have also been discussed which provide prolong effects with desired results in the minimum duration of time after the few sessions of the serum treatment.

Efficacy and safety of Melaleuca alternifolia (tea tree) oil for human health-A systematic review of randomized controlled trials

Introduction: Leaves of the Australian tea tree plant Melaleuca alternifolia were used traditionally by First Nations Australians for treating wounds, burns, and insect bites. Tea tree oil, the essential oil steam-distilled from M. alternifolia, is well-known for its medicinal properties, the evidence for most applications however is limited. This review aimed to critically appraise evidence from clinical trials examining the therapeutic efficacy and safety of tea tree oil on outcomes. Methods: Randomized controlled trials with participants of any age, gender, or health status, comparing tea tree oil to any control were included, without limit on publication date. Electronic databases were searched on 12 August 2022 with additional records sourced from article reference sections, reviews, and industry white papers. Risk of bias was assessed by two authors independently using the Cochrane risk-of-bias 1.0 tool. Results were summarized and synthesized thematically. Results: Forty-six articles were eligible from the following medical fields (Dentistry n = 18, Dermatology n = 9, Infectious disease n = 9, Ophthalmology n = 6, Podiatry n = 3; and Other n = 1). Results indicate that oral mouthwashes with 0.2%-0.5% tea tree oil may limit accumulation of dental plaque. Gels containing 5% tea tree oil applied directly to the periodontium may aid treatment of periodontitis as an adjunctive therapy to scaling and root planing. More evidence is needed to confirm the benefits of tea tree oil for reducing acne lesions and severity. Local anti-inflammatory effects on skin, if any, also require further elucidation. Topical tea tree oil regimens show similar efficacy to standard treatments for decolonizing the body from methicillin-resistant Staphylococcus aureus, although intra-nasal use of tea tree oil may cause irritation to mucous membranes. Tea tree oil with added iodine may provide an effective treatment for molluscum contagiosum lesions in young children. More evidence on efficacy of tea tree oil-based eyelid wipes for Demodex mite control are needed. Side effects were reported in 60% of included studies and were minor, except where tea tree oil was applied topically in concentrations ≥ 25%. Discussion: Overall, the quality of research was poor to modest and higher quality trials with larger samples and better reporting are required to substantiate potential therapeutic applications of tea tree oil. Systematic Review Registration: PROSPERO, identifier [CRD42021285168].

Essential Oils against Sarcoptes scabiei

Herbal remedia are widely employed in folk medicine, and have been more and more often studied and considered in the treatment of several infections. Sarcoptic mange (scabies, when referring to human patients) is a highly contagious skin disease caused by Sarcoptes scabiei (sarcoptiformes, Sarcoptinae), an astigmatid mite which burrows into the epidermis, actively penetrating the stratum corneum. This parasitosis negatively affects livestock productions and represents a constraint on animal and human health. The treatment relies on permethrine and ivermectine but, since these molecules do not have ovicidal action, more than a single dose should be administered. Toxicity, the possible onset of parasite resistance, the presence of residues in meat and other animal products and environmental contamination are the major constraints. These shortcomings could be reduced by the use of plant extracts that have been in vitro or in vivo checked against these mites, sometimes with promising results. The aim of the present study was to review the literature dealing with the treatment of both scabies and sarcoptic mange by plant-derived agents, notably essential oils.

Effects of EOs vs. Antibiotics on E. coli Strains Isolated from Drinking Waters of Grazing Animals in the Upper Molise Region, Italy

The health and safety of grazing animals was the subject of microbiological monitoring on natural source of drinking waters in the upper Molise region, Italy. Surface water samples, on spring-summer season, were collected and submitted to analyses using sterile membrane filtration, cultural medium, and incubation. The level of environmental microbial contamination (Total viable microbial count, yeasts and fungi) and faecal presence (Total and faecal coliforms, E. coli, and Salmonellae spp.) were carried out. By the selective microbiological screening, twenty-three E. coli strains from drinking waters were isolated and submitted to further studies to evaluate antibiotic resistance by antibiograms vs. three animal and two diffuse human antibiotics. Furthermore, after a fine chemical characterization by GC and GC-MS, three Essential Oils (EOs) of aromatic plants (Timus vulgaris, Melaleuca alternifolia, Cinnamomun verum) aromatograms were performed and results statistically compared. The effects of EOs vs. antibiotics on E. coli strains isolated from drinking waters showed a total absence of microbial resistance. In our experimental conditions, even if some suggestions will be further adopted for better managements of grazing animals, because the health and safety represent a guarantee for both animals and humans.

Safety assessment and adverse drug reaction reporting of tea tree oil ( Melaleuca aetheroleum )

Tea tree (Melaleuca alternifolia) essential oil is widely used as an antiseptic. It mainly consists of monoterpenes with terpinen-4-ol as the major constituent. The aim of this study was to review literature on safety data about tea tree oil and to assess its safety by investigating 159 cases of adverse reactions possibly caused by the oil, reported to the World Health Organization (WHO) from December 1987 until September 2021. To extract these data, VigiBase, the WHO global database of individual case safety reports maintained by the Uppsala Monitoring Centre (UMC), was used. All cases were categorized and analysed and 16 serious cases further assessed. It was concluded that tea tree oil should never be administered orally, as it can lead to central nervous system depression and pneumonitis. Applied topically, skin disorders may occur, especially when the oil had been exposed to light or air. This yields monoterpene oxidation products, being potent skin irritants. Tea tree oil stored under appropriate conditions and not exceeding the expiration date should be considered safe to use by non-vulnerable people for non-serious inflammatory skin conditions, although the occurrence of adverse reactions such as contact allergies is difficult to predict.

Biobased polymer resources and essential oils: a green combination for antibacterial applications

To fight nosocomial infections, the excessive use of antibiotics has led to the emergence of multidrug-resistant microorganisms, which are now considered a relevant public health threat by the World Health Organization. To date, most antibacterial systems are based on the use of petro-sourced polymers, but the global supplies of these resources are depleting. Besides, silver NPs are widely accepted as the most active biocide against a wide range of bacterial strains but their toxicity is an issue. The growing interest in natural products has gained increasing interest in the last decade. Therefore, the design of functional antibacterial materials derived from biomass remains a significant challenge for the scientific community. Consequently, attention has shifted to naturally occurring substances such as essential oils (EOs), which are classified as Generally Recognized as Safe (GRAS). EOs can offer an alternative to the common antimicrobial agents as an inner solution or biocide agent to inhibit the resistance mechanism. Herein, this review not only aims at providing developments in the antibacterial modes of action of EOs against various bacterial strains and the recent advances in genomic and proteomic techniques for the elucidation of these mechanisms but also presents examples of biobased polymer resource-based EO materials and their antibacterial activities. Especially, we describe the antibacterial properties of biobased polymers, e.g. cellulose, starch, chitosan, PLA PHAs and proteins, associated with EOs (cinnamon (CEO), clove (CLEO), bergamot (BEO), ginger (GEO), lemongrass (LEO), caraway (CAEO), rosemary (REO), Eucalyptus globulus (EGEO), tea tree (TTEO), orange peel (OPEO) and apricot (Prunus armeniaca) kernel (AKEO) essential oils). Finally, we discuss the influence of EOs on the mechanical strength of bio-based materials.

First Evidence of a Combination of Terpinen-4-ol and α-Terpineol as a Promising Tool against ESKAPE Pathogens

Antimicrobial resistance is a major public health issue raising growing concern in the face of dwindling response options. It is therefore urgent to find new anti-infective molecules enabling us to fight effectively against ever more numerous bacterial infections caused by ever more antibiotic-resistant bacteria. In this quest for new antibacterials, essential oils (or compounds extracted from essential oils) appear to be a promising therapeutic option. In the present work, we investigate the potential antibacterial synergy between a combination of terpinen-4-ol and α-terpineol (10:1) compared to standard tea tree oil. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) were determined. Then, time kill assays, in vitro cytotoxicity and bactericidal activity on latent bacteria (persisters) were investigated. Finally, an in silico study of the pharmacokinetic parameters of α-terpineol was also performed. Altogether, our data demonstrate that the combination of terpinen-4-ol and α-terpineol might be a precious weapon to address ESKAPE pathogens.

Surfaces with instant and persistent antimicrobial efficacy against bacteria and SARS-CoV-2

Surfaces contaminated with bacteria and viruses contribute to the transmission of infectious diseases and pose a significant threat to global public health. Modern day disinfection either relies on fast-acting (>3-log reduction within a few minutes), yet impermanent, liquid-, vapor-, or radiation-based disinfection techniques, or long-lasting, but slower-acting, passive antimicrobial surfaces based on heavy metal surfaces, or metallic nanoparticles. There is currently no surface that provides instant and persistent antimicrobial efficacy against a broad spectrum of bacteria and viruses. In this work, we describe a class of extremely durable antimicrobial surfaces incorporating different plant secondary metabolites that are capable of rapid disinfection (>4-log reduction) of current and emerging pathogens within minutes, while maintaining persistent efficacy over several months and under significant environmental duress. We also show that these surfaces can be readily applied onto a variety of desired substrates or devices via simple application techniques such as spray, flow, or brush coating.

Tea tree oil nanoliposomes: optimization, characterization, and antibacterial activity against Escherichia coli in vitro and in vivo

The purpose of this study was to formulate tee tree oil nanoliposomes (TTONL) and evaluate its characterization and antibacterial activity. TTONL was prepared by thin film hydration and sonication technique, and the preparation conditions were optimized by Box-behnken response surface method. The characterization (morphology, size, zeta potential, and stability) and antibacterial activity of TTONL against Escherichia coli (E. coli) in vitro and in vivo were evaluated. The optimal preparation conditions for TTONL: lecithin to cholesterol mass ratio of 3.7:1, TTO concentration of 0.5%, and pH of the hydration medium of 7.4, which resulted in a TTONL encapsulation rate of 80.31 ± 0.56%. TTONL was nearly spherical in shape and uniform in size, and the average particle size was 227.8 ± 25.3 nm with negative charge. The specific disappearance of the TTO peak in the infrared spectrum suggested the successful preparation of TTONL, which showed high stability at 4°C within 35 d. The result of MIC test found that the nanoliposomes improved antibacterial activity of TTO against various E. coli strains. TTONL exposure in vitro caused different degrees of structural damage to the E. coli. TTONL by oral administration alleviated the clinical symptoms and intestinal lesion of chickens induced with E. coli challenge. Furthermore, TTONL treatment remarkably lowered the mRNA expression of NLRP3 and NF-κB (p65) in the duodenum and cecum of E. coli-infected chickens. In conclusion, the prepared TTONL had good stability and slow-release property with dose-dependent inhibition and killing effects on different strains of E. coli, and exerted a preventive role against chicken colibacillosis through inhibition.

Optimization and characterization of a novel tea tree oil-integrated poly (ε-caprolactone)/soy protein isolate electrospun mat as a wound care system

A set of poly (ε-caprolactone)/soy protein isolate (PCL/SPI) mats with different ratios of PCL to SPI was fabricated using the electrospinning method. The mat with PCL to SPI ratio of 95:5 (PS 95:5) had the narrowest nanofibers, the highest percentage of porosity, the lowest swelling ratio, the least vapor transmission, and the slowest degradation rate among the prepared mats. The hemolysis assay indicated that all mats can be considered biocompatible biomaterials. In continue, three different weight ratios of tea tree oil (TTO) were loaded into the PS 95:5 mat. The release profiles illustrated that higher amounts of TTO could be released in an acidic environment. The antioxidant activity of the mats increased by the increase in their TTO content. The cell viability test, cell adhesion images, and live/dead assay of TTO-loaded mats affirmed that all fabricated mats were biocompatible. The scratch wound assay expressed that TTO accelerates the rate of wound closure. The TTO-loaded mats illustrated antibacterial activity against both Escherichia coli and Staphylococcus aureus bacteria. The obtained outcomes revealed that TTO-loaded PCL/SPI mats can be considered promising potential wound dressings.

Updated Perspectives on the Diagnosis and Management of Onychomycosis

Onychomycosis is the most common nail disease encountered in clinical practice and can cause pain, difficulty with ambulation, and psycho-social problems. A thorough history and physical examination, including dermoscopy, should be performed for each patient presenting with nail findings suggestive of onychomycosis. Several approaches are available for definitive diagnostic testing, including potassium hydroxide and microscopy, fungal culture, histopathology, polymerase chain reaction, or a combination of techniques. Confirmatory testing should be performed for each patient prior to initiating any antifungal therapies. There are several different therapeutic options available, including oral and topical medications as well as device-based treatments. Oral antifungals are generally recommended for moderate to severe onychomycosis and have higher cure rates, while topical antifungals are recommended for mild to moderate disease and have more favorable safety profiles. Oral terbinafine, itraconazole, and griseofulvin and topical ciclopirox 8% nail lacquer, efinaconazole 10% solution, and tavaborole 5% solution are approved by the Food and Drug Administration for treatment of onychomycosis in the United States and amorolfine 5% nail lacquer is approved in Europe. Laser treatment is approved in the United States for temporary increases in clear nail, but clinical results are suboptimal. Oral fluconazole is not approved in the United States for onychomycosis treatment, but is frequently used off-label with good efficacy. Several novel oral, topical, and over-the-counter therapies are currently under investigation. Physicians should consider the disease severity, infecting pathogen, medication safety, efficacy and cost, and patient age, comorbidities, medication history, and likelihood of compliance when determining management plans. Onychomycosis is a chronic disease with high recurrence rates and patients should be counseled on an appropriate plan to minimize recurrence risk following effective antifungal therapy.

Controlled Release of Tea Tree Oil from a Chitosan Matrix Containing Gold Nanoparticles

Chitosan is a biopolymer that, due to its versatile bioactive properties, has applications in several areas, including food, medicine and pharmaceuticals. In the field of tissue engineering, chitosan can be used, for example, as a dressing to treat wounds or dermal damage, such as burns or abrasions. This work deals with the controlled release of tea tree oil from chitosan-based polymeric films and droplets containing gold nanoparticles (AuNP). AuNPs were successfully incorporated into the chitosan matrix using two different approaches. Both solutions were loaded with tea tree oil, and from these solutions, it was possible to obtain drop-cast films and droplets. The controlled release of oil in water was performed both in the films and in the droplets. The addition of AuNP in the controlled release system of melaleuca oil favored a release time of around 25 h. A series of experiments was carried out to investigate the effects of different reaction temperatures and acetic acid concentrations on the formation of AuNPs in the presence of chitosan. For this purpose, images of the AuNP films and droplets were obtained using transmission electron microscopy. In addition, UV-vis spectra were recorded to investigate the release of tea tree oil from the different samples.

Polymer-Based Hydrogels Enriched with Essential Oils: A Promising Approach for the Treatment of Infected Wounds

Among the factors that delay the wound healing process in chronic wounds, bacterial infections are a common cause of acute wounds becoming chronic. Various therapeutic agents, such as antibiotics, metallic nanoparticles, and essential oils have been employed to treat infected wounds and also prevent the wounds from bacterial invasion. Essential oils are promising therapeutic agents with excellent wound healing, anti-inflammatory and antimicrobial activities, and good soothing effects. Some essential oils become chemically unstable when exposed to light, heat, oxygen, and moisture. The stability and biological activity of essential oil can be preserved via loading into hydrogels. The polymer-based hydrogels loaded with bioactive agents are regarded as ideal wound dressings with unique features, such as controlled and sustained drug release mechanisms, good antibacterial activity, non-toxicity, excellent cytocompatibility, good porosity, moderate water vapour transmission rate, etc. This review addresses the pre-clinical outcomes of hydrogels loaded with essential oils in the treatment of infected wounds.

Antibacterial interactions between two monofloral honeys and several topical antiseptics, including essential oils

Background

Honey has broad spectrum antibacterial activity against clinically important organisms and may be suitable for treating superficial bacterial infections. However, very little data are available describing potential interactions between honey and other topically applied agents such as antiseptics or essential oils.

Methods

Interactions between pairs of antibacterial agents were investigated by performing checkerboard assays and determining the fractional inhibitory concentration indices (FICIs). Interactions between the two monofloral honeys marri (from Corymbia calophylla) and manuka, and the antiseptic agents benzalkonium chloride, chlorhexidine digluconate, silver (I) nitrate, tea tree oil, and Eucalyptus polybractea oil were investigated against Staphylococcus aureus ATCC® 43300 and Pseudomonas aeruginosa ATCC® 27853.

Results

Additive or indifferent interactions (FICI 0.5—2) were observed for all combinations against both organisms tested, with the exception of chlorhexidine and honey. Chlorhexidine and marri honey showed an antagonistic relationship against S. aureus (median FICI 2.00, range 1.25—4.83). Similarly, chlorhexidine and manuka honey showed antagonism against S. aureus (median FICI 2.33, range 2.00—2.67).

Conclusions

With the exception of chlorhexidine, these data indicate that honey does not interfere with the antimicrobial activity of the tested agents, and that honey may be suitable for combination therapy with other topically applied antibacterial agents for treating superficial bacterial infections.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-022-03695-x.

Individual and Synergistic Effects of Tea Tree Oil and Neem Extract on Candida albicans Adhesion to Denture Soft Liner

Background

Inflammation is present in denture stomatitis. Denture stomatitis's etiology is complex, but there is evidence that it is brought on by Candida albicans growing in biofilms on its surface.

Objective

This study aimed to examine and assess the effectiveness of several herbal products, such as tea tree oil and neem extracts, on Candida albicans adhesion to denture soft liners.

Method

Each wall of the tissue culture plate was filled with 30 acrylic blocks lined with soft liners, followed by the addition of 0.1 ml of the standardized Candida albicans suspension, which was then left to incubate for 48 hours. Each specimen was placed in a disinfectant solution for 10 minutes. A colony was counted after 0.1ml of the solution was plated on a sabouraud dextrose agar (SDA) plate and cultured for 72 hours. Data were compared using a one-way analysis of variance (ANOVA) test.

Results

The mean colony forming units (CFU) per ml for combined tea tree oil and neem extract was least (0.40), followed by tea tree oil (2.30), followed by neem extract (30.33). The treated blocks were effective in reducing the growth of Candida albicans.

Conclusion

Combining tea tree oil and neem extract significantly reduced the growth of Candida albicans, suggesting a new form of intraoral effective antifungal treatment.

Antiparasitic Activity of Tea Tree Oil (TTO) and Its Components against Medically Important Ectoparasites: A Systematic Review

Ectoparasites are pathogens that can infect the skin and cause immense pain, discomfort, and disease. They are typically managed with insecticides. However, the fast-emerging antimicrobial resistance and the slow rate of development of new bio-actives combined with environmental and health concerns over the continued use of neurotoxic insecticides warrant newer and alternative methods of control. Tea tree oil (TTO), as an alternative agent, has shown remarkable promise against ectoparasites in recent studies. To our knowledge, this is the first systematic review to assess preclinical and clinical studies exploring the antiparasitic activity of TTO and its components against clinically significant ectoparasites, such as Demodex mites, scabies mites, house dust mites, lice, fleas, chiggers, and bed bugs. We systematically searched databases, including PubMed, MEDLINE (EBSCOhost), Embase (Scopus), CENTRAL, Cochrane Library, CINAHL, ScienceDirect, Web of Science, SciELO, and LILACS in any language from inception to 4 April 2022. Studies exploring the therapeutic activity of TTO and its components against the ectoparasites were eligible. We used the ToxRTool (Toxicological data reliability assessment) tool, the Joanna Briggs Institute (JBI) critical appraisal tools, and the Jadad scale to assess the methodological qualities of preclinical (in vitro and in vivo) studies, non-randomised controlled trials (including cohort, case series, and case studies), and randomised controlled trials, respectively. Of 497 identified records, 71 studies were included in this systematic review, and most (66%) had high methodological quality. The findings of this review revealed the promising efficacy of TTO and its components against ectoparasites of medical importance. Most importantly, the compelling in vitro activity of TTO against ectoparasites noted in this review seems to have translated well into the clinical environment. The promising outcomes observed in clinical studies provide enough evidence to justify the use of TTO in the pharmacotherapy of ectoparasitic infections.

The Biological Activity of Tea Tree Oil and Hemp Seed Oil

The interest in hemp seed oil (HSO) and tea tree oil (TTO) in the medical and food industries is increasing. The current study compares their bioactivity to other plant oils, mainly focusing on hemp seed oils (HSOs) with various cannabidiol (CBD) contents. A DPPH assay was employed to evaluate the antioxidant activity. The antimicrobial activity against Escherichia coli, Staphylococcus aureus, and Salmonella enteritidis was evaluated using time–kill, minimum inhibition concentration (MIC), and Kirby–Bauer disk diffusion methods. Tea tree oil showed significantly higher antimicrobial activity against S. enteritidis compared to E. coli and S. aureus (p < 0.05). The antioxitant activity range (lowest to highest) was sesame < vetiver < rosehip < tea tree < organic hemp < pure hemp < 5% CBD < vitamin C. Tea tree oil and 5% CBD showed antioxidant activity at IC50 of 64.45 μg/mL and 11.21 μg/mL, respectively. The opposing antimicrobial and antioxidant results for TTO and HSO indicate that these activities arise from different components within the oil compositions.

Essential Oils as a Good Weapon against Drug-Resistant Candida auris

Candida auris is a recently found Candida species, mainly associated with nosocomial outbreaks in intensive care hospital settings, and unlike other Candida species, it can be transmitted through person-to-person or by contact with surfaces. C. auris is described as resistant to first-line antifungals and, consequently, associated with high mortality. Nowadays, essential oils (EOs) are known to be effective against fungal and bacterial infections. This work aimed to evaluate the effect of four EOs (tea tree, niaouli, white thyme and cajeput) against C. auris. The EO’s effect on C. auris planktonic growth was evaluated by the minimum inhibitory concentration determination and by the agar disc diffusion method. Then, the same effect was evaluated on biofilm by colony-forming units’ enumeration. The results showed that EOs were able to inhibit the C. auris planktonic growth, with an MIC50 between 0.78 and 1.56% and halos of 20–21 mm for white thyme and tea tree and 13–14 mm for cajeput and niaouli. In addition, the EOs were also able to completely inhibit biofilm formation. Moreover, white thyme and cajeput completely eradicate pre-formed biofilms, while tea tree and niaouli significantly reduce it. Thus, this work demonstrates that EOs are a possible therapeutic alternative and a future perspective for the hard fight against C. auris.

Melaleuca armillaris essential oil as an odor reducer in intestinal ostomy bags: a semi-experimental study

OBJECTIVE

Evaluate the effect of essential oil in odor reduction for intestinal ostomy bags.

METHOD

Primary study, semi-experimental, prospective clinical trial with quantitative approach. A product prepared with Melaleuca armillaris leaves was tested in ostomy pouches, with and without effluents, for adhesion and odor control. Instrument: Labeled Magnitude Scale.

RESULTS

Colostomized participants, with a mean age of 73 ± 14.94, predominantly males; and informal caregivers, with a mean age of 44 ± 8.98, predominantly females. In the visual evaluation of the oil, 100% of the participants perceived its adherence. Regarding the evaluation of effluent odor by the colostomized, five reported "strong odor" before oil use and, six reported "weak" odor after use (p = 0.005). Five informal caregivers reported "very strong" effluent odor before oil use; and one reported "weak" and nine reported "moderate" after use (p = 0.0025).

CONCLUSION

There was a reduction in the odor of effluents in the ostomy pouches with the essential oil of Melaleuca armillaris at 10%. Application for patent registration in the Brazilian National Institute of Industrial Property (INPI) under no. BR 10 2020 026987 9.

Development of Biodegradable/Biocompatible Nanoliposome-Encapsulated Antimicrobial Essential Oils for Topical Creams and Gels

Nanoencapsulation with safe materials improves delivery, stability, and activity of bioactive components. We report a novel safe, and effective method for the development of encapsulated antimicrobial essential oils (EO) for topical creams and gels. The method developed features three aspects that, to our knowledge, had not been previously demonstrated: (1) use of novel liposomes (LPs) to encapsulate EOs, (2) use of the EOs to replace synthetic organic solvents that are potentially toxic and/or leave harmful residues, and (3) an encapsulation process at temperatures below the boiling point of water. The LPs were made from soy lecithin, phytosterol, and α-tocopherol (vitamin E) that were synthesized using the EOs as the solvent. The liposomes were converted to nanoliposomes (NLPs) through a series of sonication, homogenization, and extrusion steps. Transmission electron microscopy indicated that the NLPs alone and nanoliposome encapsulated EOs (NLP-EOs) were spherical in shape with sizes ranging between 50 and 115 nm diameter and with negative zeta potentials ranging from -34 to -43 mV. There was no significant heavy metal contamination [As, Pb, Cd, Hg] based on inductively coupled plasma (ICP) mass spectrometry MS analyses. Nearly complete EO encapsulation (95% encapsulation efficiency) was achieved and confirmed by GC/MS. Three of the NLP-EOs made of various essential oils were used to make topical formulations (cream and gel) which exhibited antimicrobial activities against Escherichia coli (Gram negative) and Bacillus subtilis (Gram positive) bacteria. The creams with NLP-EOs were as active against the two bacteria in the antimicrobial assays as the conventional antibiotic Kanamycin that was used as positive control.

Effectiveness of tea tree oil versus chlorhexidine in the treatment of periodontal diseases: a systematic review

Background Plaque biofilm that adheres to tooth surfaces and gingiva is the main aetiology of periodontitis. Chlorhexidine (CHX) is considered as a gold standard anti-plaque and anti-gingivitis agent but it has side effects such as permanent staining of teeth and dysgeusia. Tea tree oil (TTO) is an essential oil extracted from the leaves of Melaleuca alternifolia. Many studies have reported that TTO exerts strong antibacterial, antifungal, antiviral and anti-inflammatory activities.Primary study objective The review aims to answer the question of whether TTO (intervention) is a viable alternative to CHX (comparator) for the management of gingival and periodontal disease (outcomes) in adolescents and adults (population).Methods/design The following search terms were used in PubMed, Scopus, Proquest, Web of Science, EBSCO (dentistry and open access), Cochrane database, Clinical.gov.org and ctri.nic.in to search for relevant articles: patients with periodontal disease; OR periodontitis; OR gingivitis; OR gingival inflammation; AND essential oil; OR tea tree oil; OR Melaleuca alternifolia; AND chlorhexidine; AND reduction in gingival index; OR reduction in plaque index; OR reduction in bleeding from gums. The initial check for the title and abstract screening followed by removal of duplicates in Mendeley Reference Manager (version 1.19.4) based on the inclusion and exclusion criteria were performed.Primary outcome measures Parameters such as plaque index (PI), plaque surface score, gingival index (GI), bleeding index or bleeding as measured by % of sites with bleeding on probing (BOP) or bleeding scores, papillary bleeding index (PBI), were the primary outcomes considered.Results TTO is found to be superior to CHX in reducing signs of gingival inflammation; however, CHX is superior to TTO in inhibiting plaque formation, probably due to its increased substantivity.Conclusion TTO may be used as an alternative to CHX for reduction of gingival inflammation in conjunction with efficient plaque control measures.

Natural Compounds: A Hopeful Promise as an Antibiofilm Agent Against Candida Species

The biofilm communities of Candida are resistant to various antifungal treatments. The ability of Candida to form biofilms on abiotic and biotic surfaces is considered one of the most important virulence factors of these fungi. Extracellular DNA and exopolysaccharides can lower the antifungal penetration to the deeper layers of the biofilms, which is a serious concern supported by the emergence of azole-resistant isolates and Candida strains with decreased antifungal susceptibility. Since the biofilms’ resistance to common antifungal drugs has become more widespread in recent years, more investigations should be performed to develop novel, inexpensive, non-toxic, and effective treatment approaches for controlling biofilm-associated infections. Scientists have used various natural compounds for inhibiting and degrading Candida biofilms. Curcumin, cinnamaldehyde, eugenol, carvacrol, thymol, terpinen-4-ol, linalool, geraniol, cineole, saponin, camphor, borneol, camphene, carnosol, citronellol, coumarin, epigallocatechin gallate, eucalyptol, limonene, menthol, piperine, saponin, α-terpineol, β–pinene, and citral are the major natural compounds that have been used widely for the inhibition and destruction of Candida biofilms. These compounds suppress not only fungal adhesion and biofilm formation but also destroy mature biofilm communities of Candida. Additionally, these natural compounds interact with various cellular processes of Candida, such as ABC-transported mediated drug transport, cell cycle progression, mitochondrial activity, and ergosterol, chitin, and glucan biosynthesis. The use of various drug delivery platforms can enhance the antibiofilm efficacy of natural compounds. Therefore, these drug delivery platforms should be considered as potential candidates for coating catheters and other medical material surfaces. A future goal will be to develop natural compounds as antibiofilm agents that can be used to treat infections by multi-drug-resistant Candida biofilms. Since exact interactions of natural compounds and biofilm structures have not been elucidated, further in vitro toxicology and animal experiments are required. In this article, we have discussed various aspects of natural compound usage for inhibition and destruction of Candida biofilms, along with the methods and procedures that have been used for improving the efficacy of these compounds.

Tea Tree Oil Nanoemulsion-Based Hydrogel Vehicle for Enhancing Topical Delivery of Neomycin

The present investigation aims to improve the antimicrobial influence of certain antibacterial drugs, namely, neomycin (NEO), exploiting the benefits of natural oils such as tea tree oil (TTO). Therefore, a distinctive nanolipid formulation, namely, a nanoemulsion (NE), was developed using a Central Composite Factorial Design (CCD) approach depending on the amount of TTO and tween 80 as surfactant. The optimized NEO-NE formula exhibiting minimum globular size and maximum in vitro release was selected. For efficient topical delivery, NEO-NE was incorporated into a pre-formulated hydrogel. The developed NEO-NE-hydrogel was characterized by its physical characteristics such as pH, viscosity, and spreadability. Next, it was tested for stability under different conditions for 3 months. Ultimately, an irritation test was conducted followed by an antibacterial examination. The preparation demonstrated acceptable properties to be successfully applied topically. It showed non-significant changes in stability in both conditions up to 3 months storage when compared to a fresh preparation. It exhibited no irritation when applied on hairless animal skin. Finally, TTO revealed a good inhibition for the bacterial growth that could improve the influence of NEO antibacterial activity, indicating the efficiency of NE containing NEO prepared with TTO to be a promising antibacterial nanocarrier.

Novel Formula of Antiprotozoal Mixtures

Antimicrobial resistance (AMR) is becoming more common in both bacteria and pathogenic protozoa. Therefore, new solutions are being sought as alternatives to currently used agents. There are many new ideas and solutions, especially compounds of natural origin, including essential oils. In the present study, the antiprotozoal activity of a mixture of essential oils (eucalyptus, lavender, cedar and tea tree), organic acids (acetic acid, propionic acid and lactic acid) and metal ions (Cu, Zn, Mn) were tested. As a model, protozoans were selected: Euglena gracilis, Gregarina blattarum, Amoeba proteus, Paramecium caudatum, Pentatrichomonas hominis. The tested concentrations of mixtures were in the range of 0.001–1.5%. The analyses show unexpected, very strong protozoicidal activity of combinations, presenting the synergy of compounds via determination of LD50 and LD100 values. Obtained mixtures showed significantly higher activity against protozoans, compared to chloramphenicol and metronidazole. Most of the analyzed samples show high antiprotozoal activity at very low concentration, in the range of 0.001–0.009%. The most effective combinations for all analyzed protozoans were the cedar essential oil and tea tree essential oil with a mixture of acids and manganese or zinc ions. Innovative combinations of essential oils, organic acids and metal ions are characterized by very high antiprotozoal activity at low doses, which, after further investigation, can be applicable for control of protozoan pathogens.

The Role of Herbal Medicine in the Treatment of Acne Vulgaris: A Systematic Review of Clinical Trials

Over the past few decades, interest in medicinal plants and phytochemicals for the treatment of skin disorders, including acne vulgaris, has progressively increased. Acne vulgaris is a chronic inflammatory disease of the pilosebaceous unit, which mainly occurs in adolescents and young adults. The treatment focuses on the four main factors involved in its pathogenesis: increased sebum production, hyperkeratinization, overgrowth of Cutibacterium acnes, and inflammation. The treatment includes topical retinoids, benzoyl peroxide, antibiotics, and oral isotretinoin. In this regard, the use of herbal medicine as a complementary and alternative medicine is a promising strategy. The main objective of this study was to systematically evaluate the efficacy and safety of medicinal plants and phytochemicals in the treatment of acne vulgaris. Three scientific databases (PubMed, Web of Science, and Scopus) were searched from inception to January 2021. Clinical trials comparing herbal therapies with placebo or other medicines for the treatment of acne vulgaris were included and analyzed. Outcome measures of interest comprised acne lesions (inflammatory and noninflammatory), sebum production, acne severity, and quality of life. The risk of bias in the included randomized controlled trials (RCTs) was assessed using the Cochrane risk-of-bias tool. A total of 34 clinical trials involving 1753 participants met the inclusion criteria for this systematic review. Most trials showed that herbal medicine significantly reduces inflammatory and noninflammatory acne lesions and has a relevant effect on acne severity. Some medicinal plants revealed equal or higher efficacy to standard treatments. No significant difference between groups in sebum production and quality of life was observed and no severe adverse events were reported. This systematic review provides evidence that medicinal plants and phytochemicals are promising treatments for mild to moderate acne vulgaris. However, more quality of evidence and standardized methodologies are needed to support their effectiveness and safety claims.

Terpinen-4-ol, the Main Bioactive Component of Tea Tree Oil, as an Innovative Antimicrobial Agent against Legionella pneumophila

Legionella pneumophila (Lp), responsible for a severe pneumonia called Legionnaires’ disease, represents an important health burden in Europe. Prevention and control of Lp contamination in warm water systems is still a great challenge often due to the failure in disinfection procedures. The aim of this study was to evaluate the in vitro activity of Terpinen-4-ol (T-4-ol) as potential agent for Lp control, in comparison with the essential oil of Melaleuca alternifolia (tea tree) (TTO. Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) of T-4-ol were determined by broth micro-dilution and a micro-atmosphere diffusion method to investigate the anti-Lp effects of T-4-ol and TTO vapors. Scanning Electron Microscopy (SEM) was adopted to highlight the morphological changes and Lp damage following T-4-ol and TTO treatments. The greatest antimicrobial activity against Lp was shown by T-4-ol with a MIC range of 0.06–0.125% v/v and MBC range of 0.25–0.5% v/v. The TTO and T-4-ol MIC and MBC decreased with increasing temperature (36 °C to 45 ± 1 °C), and temperature also significantly influenced the efficacy of TTO and T-4-ol vapors. The time-killing assay showed an exponential trend of T-4-ol bactericidal activity at 0.5% v/v against Lp. SEM observations revealed a concentration- and temperature- dependent effect of T-4-ol and TTO on cell surface morphology with alterations. These findings suggest that T-4-ol is active against Lp and further studies may address the potential effectiveness of T-4-ol for control of water systems.

Potential Use of Tea Tree Oil as a Disinfectant Agent against Coronaviruses: A Combined Experimental and Simulation Study

The COVID-19 pandemic has highlighted the relevance of proper disinfection procedures and renewed interest in developing novel disinfectant materials as a preventive strategy to limit SARS-CoV-2 contamination. Given its widely known antibacterial, antifungal, and antiviral properties, Melaleuca alternifolia essential oil, also named Tea tree oil (TTO), is recognized as a potential effective and safe natural disinfectant agent. In particular, the proposed antiviral activity of TTO involves the inhibition of viral entry and fusion, interfering with the structural dynamics of the membrane and with the protein envelope components. In this study, for the first time, we demonstrated the virucidal effects of TTO against the feline coronavirus (FCoVII) and the human coronavirus OC43 (HCoV-OC43), both used as surrogate models for SARS-CoV-2. Then, to atomistically uncover the possible effects exerted by TTO compounds on the outer surface of the SARS-CoV-2 virion, we performed Gaussian accelerated Molecular Dynamics simulations of a SARS-CoV-2 envelope portion, including a complete model of the Spike glycoprotein in the absence or presence of the three main TTO compounds (terpinen-4-ol, γ-terpinene, and 1,8-cineole). The obtained results allowed us to hypothesize the mechanism of action of TTO and its possible use as an anti-coronavirus disinfectant agent.

Ultrastructural Damages to H1N1 Influenza Virus Caused by Vapor Essential Oils

Influenza viruses are transmitted from human to human via airborne droplets and can be transferred through contaminated environmental surfaces. Some works have demonstrated the efficacy of essential oils (EOs) as antimicrobial and antiviral agents, but most of them examined the liquid phases, which are generally toxic for oral applications. In our study, we describe the antiviral activity of Citrus bergamia, Melaleuca alternifolia, Illicium verum and Eucalyptus globulus vapor EOs against influenza virus type A. In the vapor phase, C. bergamia and M. alternifolia strongly reduced viral cytopathic effect without exerting any cytotoxicity. The E. globulus vapor EO reduced viral infection by 78% with no cytotoxicity, while I. verum was not effective. Furthermore, we characterized the EOs and their vapor phase by the head-space gas chromatography–mass spectrometry technique, observing that the major component found in each liquid EO is the same one of the corresponding vapor phases, with the exception of M. alternifolia. To deepen the mechanism of action, the morphological integrity of virus particles was checked by negative staining transmission electron microscopy, showing that they interfere with the lipid bilayer of the viral envelope, leading to the decomposition of membranes. We speculated that the most abundant components of the vapor EOs might directly interfere with influenza virus envelope structures or mask viral structures important for early steps of viral infection.

Prevalence of endocrine disorders among children exposed to Lavender Essential Oil and Tea Tree Essential Oils

Background

Lavender essential oil and tea tree essential oil have become popular ingredients in personal care and household products in recent decades. Questions regarding the safety of these oils in pediatric populations have been raised, proposing a link between these essential oils and endocrine disruption in children, specifically prepubertal gynecomastia. To date, no epidemiological studies have been conducted to evaluate this proposed link.

Methods

This is a cross sectional study conducted among parents of children in the United States to identify the prevalence of endocrine disruption in children aged 2-15 years old. This study also evaluates the potential for a relationship between the exposure of lavender essential oil and tea tree essential oil products and endocrine disrupting outcomes.

Results

In 556 children with a mean age of 6.33 (SD = 3.92), prevalence of endocrine disruption was .016 (SD = 0.13). No cases of prepubertal gynecomastia were identified in either group, and prevalence of precocious puberty, delayed puberty, growth hormone deficiency, and hypothyroidism were all consistent with population norms. Total risk of endocrine disorders among those exposed (0.0194) did not differ from the risk of those unexposed (0.0069). The risk ratio was 2.796 (95% CI: 0.352, 22.163, P = .458).

Conclusion

Children who were regularly exposed to lavender or tea tree essential oils experienced the same risk of endocrine disorders as those who were not exposed.

Exploring correlations between MS and NMR for compound identification using essential oils: A pilot study

INTRODUCTION

In this era of 'omics' technology in natural products studies, the complementary aspects of mass spectrometry (MS)- and nuclear magnetic resonance (NMR)-based techniques must be taken into consideration. The advantages of using both analytical platforms are reflected in a higher confidence of results especially when using replicated samples where correlation approaches can be used to statistically link results from MS to NMR.

OBJECTIVES

Demonstrate the use of Statistical Total Correlation (STOCSY) for linking results from MS and NMR data to reach higher confidence in compound identification.

METHODOLOGY

Essential oil samples of Melaleuca alternifolia and M. rhaphiophylla (Myrtaceae) were used as test objects. Aliquots of 10 samples were collected for GC-MS and NMR data acquisition [proton (¹ H)-NMR, and carbon-13 (¹³ C)-NMR as well as two-dimensional (2D) heteronuclear single quantum correlation (HSQC), heteronuclear multiple-bond correlation (HMBC), and HSQC-total correlated spectroscopy (TOCSY) NMR]. The processed data was imported to Matlab where STOCSY was applied.

RESULTS

STOCSY calculations led to the confirmation of the four main constituents of the sample-set. The identification of each was accomplished using; MS spectra, retention time comparison, ¹³ C-NMR data, and scalar correlations of the 2D NMR spectra.

CONCLUSION

This study provides a pipeline for high confidence in compound identification using a set of essential oils samples as test objects for demonstration.

Antibacterial and Antibiofilm Activities of Some Plant Essential Oils and Synergistic Effects of Cinnamon Essential Oil with Vancomycin against Clostridioides difficile: in vitro study

The detection of resistant strains of Clostridioides difficile against existing antibiotics and the side effects led to the investigation of alternative agents. Inhibition zones of various essential oils to four strains of C.difficile and other Clostridium species ranged from 8.32-44.18 mm. The highest zone was observed in cinnamon and tea tree essential oils. and The MIC values varied between 0.39-25 (%, v/v). The main components were cinnamaldehyde (85.64%) in cinnamon essential oil, 4-terpineol (83.6%) was determined in tea tree essential oil. Additive effects were found between cinnamon essential oil and vancomycin and between cinnamon and tea tree essential oils, and the FICI values were 0.512 and 0.517, respectively. Both cinnamon and tea tree essential oils showed antibiofilm activities against all tested C. difficile strains at all tested concentrations. Essential oils may be used as a supplement in addition to treatment in the control of C. difficile-related diseases.

Spreading Allergic Contact Dermatitis to Tea Tree Oil in an Over-the-Counter Product Applied on a Wart

Tea tree oil is an essential oil obtained by distillation from the leaves and terminal branchlets of Melaleuca alternifolia and is now present in numerous products for body care and self-medication. We report a case of allergic contact dermatitis to tea tree oil in a young man who was applying a lotion containing tea tree oil on a wart localized on the plantar aspect of the right big toe, which had previously been treated with cryotherapy. He developed a severe eczematous eruption on the right foot and the right leg, with subsequent id reactions affecting the right thigh, the contralateral lower limb, the trunk and the upper limbs. The lotion was discontinued, and the dermatitis resolved after topical corticosteroid therapy. Patch testing with the aforementioned lotion 10% pet. and oxidized tea tree oil 5% pet. identified tea tree oil as the culprit agent of the dermatitis. This case report confirms that products made of natural ingredients, often perceived to be harmless, can cause allergic reactions.

Meta-analysis of the antifungal activities of three essential oils as alternative therapies in dermatophytosis infections

Aims

This work examines the available scientific evidence about the efficiency of essential oils (EO) as an alternative therapy to traditional treatment of fungal infections, including onychomycosis, assessing the effect of the three EO most frequently studied for their antifungal activity (thyme, cinnamon and tea tree EO) against three causative agents of fungal diseases in humans: Trichophyton rubrum, Trichophyton mentagrophytes complex and Candida albicans.

Methods and Results

The PRISMA statement protocol was followed to conduct a bibliographical search and 54 articles that met all the inclusion criteria were retrieved. Differences were observed in the MIC and MFC values depending on the micro‐organism strain and the EO used. The lowest MIC were observed with Cinnamomum zeylanicum EO (0.013–1120 μl ml⁻¹) against the three micro‐organisms. For MFC, the lowest value was found for Thymus vulgaris EO (4.2 μl ml⁻¹) against Trichophyton rubrum.

Conclusions

The antifungal effects of EO could be a very promising solution to overcome the therapeutic shortcomings of antimycotic medication. More experiments are needed to examine the properties of these oils to devise effective and nonaggressive therapies for treatment of dermatophytosis.

Significance and Impact of Study

The results indicate that EO remain good candidates for future treatments and could provide a solution for failed medications and/or adverse reactions to current pharmacological treatments.

Examination of VOC Concentration of Aroma Essential Oils and Their Major VOCs Diffused in Room Air

This study analyzed temporal variation of the composition of volatile organic compounds (VOCs) at different diffusion time of gaseous phase of aroma compounds of four essential oils, lavender, tea tree, eucalyptus, and melissa. GC/MS methodology with the trace gas sampling by a thermal desorption tube is used to quantitatively determine the concentration of the corresponding 14 kinds of major and original VOCs in four essential oils. This study revealed for the first time that the concentration level of gaseous phase composition is varied, with a diffusion time from that of the liquid phase at equilibrium with it and the VOCs in the essential oils are classified into two groups, depending on whether their concentration with the time. It is verified that the total concentration of VOCs of these essential oils in the room air diffused by the ultrasonic diffuser is as low as 0.6 ppb and decreased soon below 0.1 ppb.

Chemical and Biological Characterization of Melaleuca alternifolia Essential Oil

The essential oil of Melaleuca alternifolia, commonly known as tea tree oil, has many beneficial properties due to its bioactive compounds. The aim of this research was to characterize the tea tree essential oil (TTEO) from Slovakia and its biological properties, which are specific to the chemical composition of essential oil. Gas chromatography/mass spectroscopy revealed that terpinen-4-ol was dominant with a content of 40.3%. γ-Terpinene, 1,8-cineole, and p-cymene were identified in contents of 11.7%, 7.0%, and 6.2%, respectively. Antioxidant activity was determined at 41.6% radical inhibition, which was equivalent to 447 μg Trolox to 1 mL sample. Antimicrobial activity was observed by the disk diffusion method against Gram-positive (G⁺), Gram-negative (G^-) bacteria and against yeasts, where the best antimicrobial activity was against Enterococcus faecalis and Candida albicans with an inhibition zone of 10.67 mm. The minimum inhibitory concentration showed better susceptibility by G⁺ and G^- planktonic cells, while yeast species and biofilm-forming bacteria strains were more resistant. Antibiofilm activity was observed against Pseudomonas fluorescens and Salmonella enterica by MALDI-TOF, where degradation of the protein spectra after the addition of essential oil was obtained. Good biological properties of tea tree essential oil allow its use in the food industry or in medicine as an antioxidant and antimicrobial agent.

Airborne pathogenic microorganisms and air cleaning technology development: A review

Transmission of pathogens through air is a critical pathway for the spread of airborne diseases, as airborne pathogenic microorganisms cause several harmful infections. This review summarizes the occurrence, transmission, and adverse impacts of airborne pathogenic microorganisms that spread over large distances via bioaerosols. Air cleaning technologies have demonstrated great potential to prevent and reduce the spread of airborne diseases. The recent advances in air cleaning technologies are summarized on the basis of their advantages, disadvantages, and adverse health effects with regard to the inactivation mechanisms. The application scope and energy consumption of different technologies are compared, and the characteristics of air cleaners in the market are discussed. The development of high-efficiency, low-cost, dynamic air cleaning technology is identified as the leading research direction of air cleaning. Furthermore, future research perspectives are discussed and further development of current air cleaning technologies is proposed.

Isolation and Identification of Acylphloroglucinols in the Medicinal Plant, Melaleuca alternifolia (Australian Tea Tree)

Melaleuca alternifolia (tea tree), family Myrtaceae, is endemic to the northern rivers of NSW, Australia. Since 1925, the volatile components of the hydro- and steam-distilled oils of the leaves have been studied in detail. However, the less-volatile compounds have not been investigated. Using an ethanolic extract of the seedling leaves, the non-volatile components were studied using gas chromatography-mass spectrometry (GC/MS) and liquid chromatography- mass spectrometry (LC/MS). Four of these less-volatile components were isolated by preparative-HPLC from young seedling leaves and identified as the acylphloroglucinols 1-(2,6-dihydroxy-4-methoxy-3-methylphenyl)-2-methylpropan-1-one, callisalignone A, 1-(2,6-dihydroxy-4-methoxyphenyl)-3-methylbutan-1-one and pulverulentone B described here for the first time from M. alternifolia. These compounds change in concentration in the leaf sets as later seedling leaves mature on the seedling.

Chemical Composition and Synergistic Potential of Mentha pulegium L. and Artemisia herba alba Asso. Essential Oils and Antibiotic against Multi-Drug Resistant Bacteria

The essential oils were obtained by hydrodistillation from aerial parts of Mentha pulegium L. (M. pulegium L.) and Artemisia herba alba (A. herba alba) Asso. and analyzed by gas chromatography-flame ionization detector chromatograpy (GC-FID) and gaz chromatography-mass spectrometry (GC-MS). The antibacterial activities of the oils were determined by the disk diffusion method and a microdilution broth assay against six bacteria stains. The combinations of these essential oils with antibiotics were evaluated against two multi-drug-resistant bacteria strains: imipenem-resistant Acinetobacter baumannii (IRAB S3310) and methicillin-resistant Staphylococcus aureus (MRSA S19). The chemical analysis of M. pulegium essential oil revealed the presence of pulegone (74.8%) and neoisomenthol (10.0%). A. herba alba essential oil was characterized by camphor (32.0%), α-thujone (13.7%), 1,8-cineole (9.8%), β-thujone (5.0%), bornéol (3.8%), camphene (3.6%), and p-cymene (2.1%). All strains tested except Pseudomonas aeruginosa were susceptible to these oils. The combinations of essential oils with antibiotics exerted synergism, antagonism, or indifferent effects. The best effect was observed with A. herba alba essential oil in association with cefoxitin (CX) against MRSA S19. However, for IRAB S3310, the strongest synergistic effect was observed with M. pulegium in association with amikacin (AK). This study demonstrated that M. pulegium and A. herba alba essential oils have antibacterial activities which could be potentiated by antibiotics especially in the case of IRAB S3310.

Review of air disinfection approaches and proposal for thermal inactivation of airborne viruses as a life-style and an instrument to fight pandemics

COVID-19 (Coronavirus Disease 2019) pandemic highlighted the importance of air biosecurity because SARS-CoV-2 is mainly transmitted from person to person via airborne droplets. Preventing infectious droplets from entering the body is one of the best ways to protect against infection. This paper reviews the transmission patterns of airborne pathogens and air disinfection methods. A particular emphasis is put on studies devoted to the thermal inactivation of viruses. These reviews reveal that air heat treatment has not been seriously considered as a possible air disinfection approach. Simple calculations show that the energy input required for thermal disinfection of human's air daily consumption is almost the same as for daily water consumption (by heat treatment from room temperature to 100 °C). Moreover, it is possible to organize a continuous heat recovery from the air already heated during disinfection to the inlet air, thus significantly increasing the energy efficiency. Therefore, I propose a solution for the thermal inactivation of airborne pathogens based on air heating and its subsequent cooling in a heat exchanger with heat recovery. Such a solution could be used to create mobile personal and stationary indoor air disinfectors, as well as heating, ventilation, and air conditioning systems. Thermal disinfection of air to breathe might one day be part of people's daily life like thermal disinfection of drinking water. Aside from limiting infectious disease transmission, thermal inactivation might be the basis for developing inhaled vaccines using thermally inactivated whole pathogens.

Tea Tree Oil Terpinen-4-ol Protects Gut Barrier Integrity by Upregulation of Tight Junction Proteins via the ERK1/2-Signaling Pathway

Tea tree oil (TTO) exhibits a potent antioxidant, antibacterial, and anti-inflammatory activity and is commonly used in skincare products. However, it is not clear whether TTO can protect gut barrier damage in inflammatory bowel disease (IBD) patients. Herein, we report the impact of terpinen-4-ol (TER, the primary constituent of TTO), on lipopolysaccharide (LPS)-induced intestinal epithelial cell barrier function impairment in intestinal porcine epithelial cell lines (IPEC-J2) and dextran sulfate sodium (DSS)-induced IBD in mice. TER protected against LPS-induced damage in IPEC-J2 cells in vitro and attenuated DSS-induced colitis in vivo. Added TER promoted the tight junction (TJ) proteins expressing in vitro and in vivo and attenuated the LPS-induced upregulation of ERK phosphorylation in IPEC-J2 cells. However, when an inhibitor of ERK phosphorylation was added, TER did not promote the expression of TJ protein, denoting that the ERK signaling pathway mediates the upregulation of TJ proteins. Our data may propose the potential application of TER in treating IBD.