Use of Pinus sylvestris L. (Pinaceae), Origanum vulgare L. (Lamiaceae), and Thymus vulgaris L. (Lamiaceae) essential oils and their main components to enhance itraconazole activity against azole susceptible/not-susceptible Cryptococcus neoformans strains

Clinical Evidence on Expansion of Essential Oil-Based Formulation's Pharmacological Activity in Bovine Mastitis Treatment: Antifungal Potential as Added Value

Bovine mastitis, as a significant and prevalent health problem in dairy herds, is primarily attributed to bacterial infections. Yeasts, although considered relatively rare causative agents, have also been associated with mastitis in dairy cattle. Current mastitis treatment predominantly relies on antibiotics, with limited emphasis on antifungal treatment. However, mycotic mastitis is challenging to treat, since these fungi are often resistant to antibiotics and may even utilize them for energy. In the current research, the in vivo antimicrobial activity of the essential oil-based formulation (Phyto-Bomat), as a possible alternative mastitis treatment associated with yeasts, was studied. This study involved a total of 68 animals from two dairy farms with diagnosed mastitis, and three treatment groups were established: conventional antibiotic treatment, Phyto-Bomat treatment, and the combination of both. The findings suggest significant variations in the presence of Candida samples based on the treatment administered, and the most significant difference was noted in cows treated with the combination (Phyto-Bomat and antibiotics). Yet, it is important to note that the results reveal that, regardless of the treatment type, there are statistically significant differences in the presence of Candida samples across the examined time points. These results aim to provide valuable insights into the potential of EOs as an alternative therapy in bovine mastitis, specifically targeting yeasts. Such findings could offer new strategies in the mycotic mastitis control and reducing the occurrence of secondary infections following antibiotic treatment.

In Vitro Antifungal Activity of Selected Essential Oils against Drug-Resistant Clinical Aspergillus spp. Strains

BACKGROUND

Treatment options for aspergillosis include amphotericin B (AMB) and azole compounds, such as itraconazole (ITZ). However, serious side effects related to these antifungal agents are increasingly evident, and resistance continues to increase. Currently, a new trend in drug discovery to overcome this problem is represented by natural products from plants, or their extracts. Particularly, there is a great interest in essential oils (EOs) recognized for their antimicrobial role towards bacteria, fungi and viruses.

METHODS

In this study, we evaluated the antifungal activity of eleven commercial EOs-clove, eucalyptus, geranium, hybrid lavender, lavender, lemon, lemongrass, neroli, oregano, tea tree and red red thyme-in comparison with AMB and ITZ against Aspergillus flavus, A. fumigatus and A. niger clinical isolates. Antifungal activity was determined by broth microdilution method, agar diffusion technique, fungistatic and fungicidal activities and vapor contact assay.

RESULTS

Gas chromatography-mass spectrometry analysis displayed two groups of distinct biosynthetical origin: monoterpenes dominated the chemical composition of the most oils. Only two aromatic compounds (eugenol 78.91% and eugenyl acetate 11.64%) have been identified as major components in clove EO. Lemongrass EO exhibits the strongest antimicrobial activity with a minimum inhibitory concentration of 0.56 mg/mL and a minimum fungicidal concentration of 2.25-4.5 mg/mL against Aspergillus spp. strains. Clove and geranium EOs were fairly effective in inhibiting Aspergillus spp. growth.

CONCLUSIONS

These results demonstrate the antimicrobial potential of some EOs and support the research of new alternatives or complementary therapies based on EOs.

CRYPTOCOCCOSIS: A bibliographic narrative review on antifungal resistance

Cryptococcosis is an infectious fungal disease widely studied for its epidemiological importance in the context of public health, given the high morbidity and mortality associated with this invasive fungal infection. Many cases of the disease present clinical resistance and progress to death, even in the presence of antifungal therapy. The prolonged use of triazole drugs to maintain the treatment of cryptococcosis in AIDS patients, can lead to selective pressure from mutant strains, among other resistance mechanisms, justifying the poor clinical evolution of some cases. In this study, a narrative review of the literature on the occurrence of antifungal resistance in cryptococcosis agents was performed. Publications from 2010 to 2022 that address this topic were selected using Google Scholars and Scopus website. Data from the studies were analyzed for the values of minimum inhibitory concentration (MIC) of drugs used in the management of cryptococcosis. The review showed that the highest MIC values occurred for voriconazole, especially against C. neoformans. It is concluded that there is a lack of studies with statistical analysis of the data obtained, in order to provide a better dimensioning of the resistance rates of cryptococcosis agents to different antifungal agents, both in geographical and temporal context.

Immune Defences: A View from the Side of the Essential Oils

The use of essential oils is increasingly being investigated among new therapeutic approaches based on medicinal plants and their extracts. With the wide use of synthetic and semi-synthetic antimicrobial drugs, the spread of drug-resistant clinical isolates has increased, and research is directed towards natural products, such as essential oils, as useful antimicrobial resources. In the context of a prospective infection, we compared the impact of essential oils and common antimicrobial agents on the microbicidal activity of human phagocytes. Here, we present the results of our decades-long investigation into the effectiveness of thyme red oil (26.52% thymol chemotype), tea tree oil (TTO), and Mentha of Pancalieri [(Mentha x piperita (Huds) var. officinalis (Sole), form rubescens (Camus) (Lamiaceae)] essential oils on human polymorphonuclear leukocytes (PMNs) capacity to kill clinical strains of Candida albicans and C. krusei when compared to three antifungal drugs used to treat candidiasis (fluconazole, anidulafungin, and caspofungin) These essential oils demonstrate antifungal drug-like and/or superior efficacy in enhancing intracellular killing by PMNs, even at subinhibitory concentrations. Our results are compared with data in the literature on essential oils and immune system interactions. This comparison would aid in identifying therapeutic solutions to the increasingly prevalent antibiotic resistance as well as filling in any remaining knowledge gaps on the bioactivity of essential oils.

Review on Plant-Based Management in Combating Antimicrobial Resistance - Mechanistic Perspective

Antimicrobial resistance (AMR) occurs when microbes no longer respond to any pharmacological agents, rendering the conventional antimicrobial agents ineffective. AMR has been classified as one of the top 10 life-threatening global health problems needed multilevel attention and global cooperation to attain the Sustainable Development Goals (SDGs) according to the World Health Organization (WHO), making the discovery of a new and effective antimicrobial agent a priority. The recommended treatments for drug-resistant microbes are available but limited. Furthermore, the transformation of microbes over time increases the risk of developing drug resistance. Hence, plant metabolites such as terpenes, phenolic compounds and alkaloids are widely studied due to their antibacterial, antiviral, antifungal and antiparasitic effects. Plant-derived antimicrobials are preferred due to their desirable efficacy and safety profile. Plant metabolites work by targeting microbial cell membranes, interfering with the synthesis of microbial DNA/RNA/enzymes and disrupting quorum sensing and efflux pump expression. They also work synergistically with conventional antibiotics to enhance antimicrobial effects. Accordingly, this review aims to identify currently available pharmacological therapies against microbes and AMR, as well as to discuss the importance of plant and secondary metabolites as a possible solution for AMR together with their mechanisms of action. All the information was obtained from government databases, WHO websites, PubMed, Springer, Google Scholar and Science Direct. Based on the information obtained, AMR is regarded as a significant warning to global healthcare. Plant derivatives such as secondary metabolites may be considered as potential therapeutic targets to mitigate the non-ending AMR.

Vapor-Phase of Essential Oils as a Promising Solution to Prevent Candida Vaginal Biofilms Caused by Antifungal Resistant Strains

Background: Vulvovaginal candidiasis (VVC) is a disease with high incidence, a huge impact on the quality of life and health of women, and which represents a great challenge to treat. The growing need to apply antifungal intensive therapies have contributed to an emergence of drug-resistant Candida strains. Thus, effective therapeutic options, to meet the antifungal-resistance challenge and to control high resilient biofilms, are urgently needed. This study aimed to investigate the antifungal activity of essentials oils (EOs) on drug-resistant Candida vaginal isolates. Method: Therefore, the antimicrobial effect of tea tree, niaouli, white thyme, and cajeput EOs on the planktonic growth of Candida isolates was initially evaluated by an agar disc diffusion method. Then, the vapor-phase effect of tea tree EO (VP-TTEO) on biofilm formation and on pre-formed biofilms was evaluated by crystal violet staining, XTT reduction assay, colony forming units’ enumeration, and scanning electron microscopy. Results: The results revealed high antifungal activity of EOs against drug-resistant Candida isolates. Additionally, the VP-TTEO showed a significant inhibitory effect on the biofilm formation of all tested isolates and was able to provoke an expressive reduction in mature Candida albicans biofilms. Conclusions: Overall, this study suggests that the VP-EO may be a promising solution that is able to prevent biofilm-related VVC caused by antifungal-resistant strains.

Essential Oils in Respiratory Mycosis: A Review

Respiratory mycosis is a major health concern, due to the expanding population of immunosuppressed and immunocompromised patients and the increasing resistance to conventional antifungals and their undesired side-effects, thus justifying the development of new therapeutic strategies. Plant metabolites, namely essential oils, represent promising preventive/therapeutic strategies due to their widely reported antifungal potential. However, regarding fungal infections of the respiratory tract, information is disperse and no updated compilation on current knowledge is available. Therefore, the present review aims to gather and systematize relevant information on the antifungal effects of several essential oils and volatile compounds against the main type of respiratory mycosis that impact health care systems. Particular attention is paid to Aspergillus fumigatus, the main pathogen involved in aspergillosis, Candida auris, currently emerging as a major pathogen in certain parts of the world, and Cryptococcus neoformans, one of the main pathogens involved in pulmonary cryptococcosis. Furthermore, the main mechanisms of action underlying essential oils’ antifungal effects and current limitations in clinical translation are presented. Overall, essential oils rich in phenolic compounds seem to be very effective but clinical translation requires more comprehensive in vivo studies and human trials to assess the efficacy and tolerability of these compounds in respiratory mycosis.

A Focused Insight into Thyme: Biological, Chemical, and Therapeutic Properties of an Indigenous Mediterranean Herb

A perennial wild shrub from the Lamiaceae family and native to the Mediterranean region, thyme is considered an important wild edible plant studied for centuries for its unique importance in the food, pharmaceutical, and cosmetic industry. Thyme is loaded with phytonutrients, minerals and vitamins. It is pungent in taste, yet rich in moisture, proteins, crude fiber, minerals and vitamins. Its chemical composition may vary with geographical location but is mainly composed of flavonoids and antioxidants. Previous studies have illustrated the therapeutic effects of thyme and its essential oils, especially thymol and carvacrol, against various diseases. This is attributed to its multi-pharmacological properties that include, but are not limited to, antioxidant, anti-inflammatory, and antineoplastic actions. Moreover, thyme has long been known for its antiviral, antibacterial, antifungal, and antiseptic activities, in addition to remarkable disruption of microbial biofilms. In the COVID-19 era, some thyme constituents were investigated for their potential in viral binding. As such, thyme presents a wide range of functional possibilities in food, drugs, and other fields and prominent interest as a nutraceutical. The aims of the current review are to present botanical and nutritive values of this herb, elaborate its major constituents, and review available literature on its dietetic and biological activities.

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.

Dealkenylation of neoandrographolide, a phytochemical from Andrographis paniculata stimulates FXR (Farnesoid X Receptor) and enhances gallstone dissolution

FXR (Farnesoid X Receptor) is one of the nuclear receptors expressed in the liver performing a significant role in the maintenance of bile acid concentration. An imbalance of cholesterol and bile acid ratio due to any undefined reason could cause gallstone formation. Hence, this paper aims to screen phytochemicals that could maintain a requisite balance of cholesterol and bile acid by targeting FXR and thereby contributing to the dissolution of gallstone. Nineteen phytochemicals were selected and queried for Pa and Pi in the way2drug online server for hepatoprotective property, cholesterol synthesis and absorption inhibition property, and β-glucuronidase inhibiting activity. Cianidanol, neoandrographolide, cynarine, saponins, and tanins with satisfying stated properties were docked with the screened FXR (PDB ID- 1OSH) using HADDOCK server, followed by pharmacokinetics study utilizing SwissADME tool. Neoandrographolide fits best among the other selected literature-based phytochemicals with minor violation of 'Brenk's rule'. The violation was corrected with the removal of an alkene group in the provided ChemDraw space of SwissADME. This Dealkenylated compound was further docked with FXR. The promising response under the static condition of the Dealkenylated compound was analyzed for molecular dynamic simulation at physiological conditions for 100 ns. Dealkenylated Neoandrographolide (DN) exhibited hepatoprotective, cholesterol synthesis and absorption inhibition property, and β-glucuronidase inhibition activity with a superior binding score of -42.6+/-1.5 with FXR. The interaction of the FXR receptor and the DN showed exceptional stability at physiological conditions during MD simulation and fit for the ADME properties, therefore it could be a potent candidate to dissolve gallstones.Communicated by Ramaswamy H. Sarma.

The Inhibition of Non-albicans Candida Species and Uncommon Yeast Pathogens by Selected Essential Oils and Their Major Compounds

The epidemiology of yeast infections and resistance to available antifungal drugs are rapidly increasing, and non-albicans Candida species and rare yeast species are increasingly emerging as major opportunistic pathogens. In order to identify new strategies to counter the threat of antimicrobial resistant microorganisms, essential oils (EOs) have become an important potential in the treatment of fungal infections. EOs and their bioactive pure compounds have been found to exhibit a wide range of remarkable biological activities. We investigated the in vitro antifungal activity of nine commercial EOs such as Thymus vulgaris (thyme red), Origanum vulgare (oregano), Lavandula vera (lavender), Pinus sylvestris (pine), Foeniculum vulgare (fennel), Melissa officinalis (lemon balm), Salvia officinalis (sage), Eugenia caryophyllata (clove) and Pelargonium asperum (geranium), and some of their main components (α-pinene, carvacrol, citronellal, eugenol, γ-terpinene, linalool, linalylacetate, terpinen-4-ol, thymol) against non-albicans Candida strains and uncommon yeasts. The EOs were analyzed by GC-MS, and their antifungal properties were evaluated by minimum inhibitory concentration and minimum fungicidal concentration parameters, in accordance with CLSI guidelines, with some modifications for EOs. Pine exhibited strong antifungal activity against the selected non-albicans Candida isolates and uncommon yeasts. In addition, lemon balm EOs and α-pinene exhibited strong antifungal activity against the selected non-albicans Candida yeasts. Thymol inhibited the growth of all uncommon yeasts. These data showed a promising potential application of EOs as natural adjuvant for management of infections by emerging non-albicans Candida species and uncommon pathogenic yeasts.

Carvacrol as a Potential Neuroprotective Agent for Neurological Diseases: A Systematic Review Article

BACKGROUND & OBJECTIVE

Neurological diseases are becoming a significant problem worldwide, with the elderly at a higher risk of being affected. Several researchers have investigated the neuroprotective effects of Carvacrol (CAR) (5-isopropyl-2-methyl phenol). This review systematically surveys the existing literature on the impact of CAR when used as a neuroprotective agent in neurological diseases.

METHOD

The systematic review involved English articles published in the last ten years obtained from PubMed, Google Scholar, and Scopus databases. The following descriptors were used to search the literature: "Carvacrol" [Title] AND "neuroprotective (neuroprotection)" [Title] OR "stroke, traumatic brain injury, Alzheimer's disease, Parkinson's disease, seizure, epilepsy [Title].

RESULTS

A total of 208 articles were retrieved during the search process, but only 20 studies met the eligibility criteria and were included for review. A total of 20 articles were identified, in which the efficacy of CAR was described in experimental models of stroke, traumatic brain injury, Parkinson's disease, Alzheimer's disease, , epilepsy, and seizure, through motor deficits improvements in neurochemical activity, especially antioxidant systems, reducing inflammation, oxidative stress and apoptosis as well as inhibition of TRPC1 and TRPM7.

CONCLUSION

The data presented in this study support the beneficial impact of CAR on behavioural and neurochemical deficits. CAR benefits accrue because of its anti-apoptotic, antioxidant, and anti-inflammatory properties. Therefore, CAR has emerged as an alternative treatment for neurological disorders based on its properties.

A systematic review on ethnopharmacology, phytochemistry and pharmacological aspects of Thymus vulgaris Linn

Thymus vulgaris Linn. is a medicinal and culinary herb from the Southern European region known for its anti-infective, cardioprotective, gastroprotective, anti-inflammatory, and immunomodulatory activities since the Egyptian era. The reported pharmacological activities of T. vulgaris L. include antibacterial, antioxidant, anti-inflammatory, antiviral, and anti-cancerous activities. In this review, a comprehensive approach is put forth to scrutinize and report the available data on phytochemistry, ethnopharmacology, pharmacology, and toxicology of the plant. The different extracts and essential oil obtained from the plant have been assessed and reported to treat ailments like microbial infections, inflammation, non-communicable diseases like cancer, and sexually transmitted diseases like HIV-1 and Herpes. The literature review has also indicated the use of volatile oils, phenolic acids, terpenoids, flavonoids, saponins, steroids, tannins, alkaloids, and polysaccharides in pharmacotherapy. Applications of these compounds including antidiabetic, anti-Alzheimer's, cardio, neuro and hepatoprotective, anti-osteoporosis, sedative, immunomodulatory, antioxidant, anti-tyrosinase, antispasmodic, antinociceptive, gastroprotective, anticonvulsant, antihypertensive, antidepressant, anti-amnesia, and anti-helminthic activities have been mentioned. Further, based on research gaps, recommendations have been provided to evaluate T. vulgaris L. systematically to develop plant-based drugs, nutraceuticals, and to evaluate their clinical efficiency and safety.

Antifungal Properties of Essential Oils and Their Compounds for Application in Skin Fungal Infections: Conventional and Nonconventional Approaches

Essential oils (EOs) are known to have varying degrees of antimicrobial properties that are mainly due to the presence of bioactive compounds. These include antiviral, nematicidal, antifungal, insecticidal and antioxidant properties. This review highlights the potential of EOs and their compounds for application as antifungal agents for the treatment of skin diseases via conventional and nonconventional approaches. A search was conducted using three databases (Scopus, Web of Science, Google Scholar), and all relevant articles from the period of 2010-2020 that are freely available in English were extracted. In our findings, EOs with a high percentage of monoterpenes showed strong ability as potential antifungal agents. Lavandula sp., Salvia sp., Thymus sp., Citrus sp., and Cymbopogon sp. were among the various species found to show excellent antifungal properties against various skin diseases. Some researchers developed advanced formulations such as gel, semi-solid, and ointment bases to further evaluate the effectiveness of EOs as antifungal agents. To date, most studies on the application of EOs as antifungal agents were performed using in vitro techniques, and only a limited number pursued in vivo and intervention-based research.

Validation of Qualitative Broth Volatilization Checkerboard Method for Testing of Essential Oils: Dual-Column GC–FID/MS Analysis and In Vitro Combinatory Antimicrobial Effect of Origanum vulgare and Thymus vulgaris against Staphylococcus aureus in Liquid and Vapor Phases

Combinatory action of antimicrobial agents such as essential oils (EOs) show to be an effective strategy to overcome the problem with increasing antibiotic resistance of microorganisms, including Staphylococcus aureus. The objective of this study was to evaluate in vitro antimicrobial interactions between Origanum vulgare and Thymus vulgaris EOs against various S.aureus strains in both liquid and vapor phases using the broth volatilization checkerboard method. Fractional inhibitory concentrations (FICs) were determined for both liquid and vapor phases, and the composition of EOs was analyzed by gas chromatography-mass spectrometry using dual-column/dual-detector gas chromatograph. Results of oregano and thyme EOs combination showed additive effects against all S. aureus strains in both phases. In several cases, sums of FICs were lower than 0.6, which can be considered a strong additive interaction. The lowest FICs obtained were 0.53 in the liquid phase and 0.59 in the gaseous phase. Chemical analysis showed that both EOs were composed of many compounds, including carvacrol, thymol, γ-terpinene, and p-cymene. This is the first report on oregano and thyme EOs interactions against S. aureus in the vapor phase. It also confirms the accuracy of the broth volatilization checkerboard method for the evaluation of combinatory antimicrobial effects of EOs in the vapor phase.

Synergistic antifungal evaluation of over-the-counter antifungal creams with turmeric essential oil or Aloe vera gel against pathogenic fungi

BACKGROUND

The frequent incidence of fungal infection and widespread of antibiotic resistance are emergent concerns in public health. Hence, there is a need to harness the potential of natural bioactive compounds from plant towards treatment of fungal infection. Combination effect of antibiotic creams with natural products from plants is prospective strategy to produce new antifungal agent. This study therefore, revealed antifungal effect of combined Antifungal Creams (AFCs) with Turmeric Essential Oil (TEO) or Aloe vera Gel (AVG).

METHODS

Phytochemicals and bioactive compounds in TEO and AVG were revealed using GC-MS. Bioactive compounds in plant extracts were compared to known compounds in database library of National Institute of Standards and Technology (U.S.). Antifungal activity and synergistic effect of AFCs with TEO or AVG were carried out using agar well diffusion method.

RESULTS

Phenol, flavonoids, saponins, alkaloids, steroids, terpenoids and cardiac glycosides were present in TEO and AVG. GCMS revealed thirty-six (36) and eighteen (18) bioactive compounds in TEO and AVG, respectively. AFCs displayed zones of inhibition with values ranged from 5.0 to 14.3 mm, TEO was 5.0 to 11.0 mm and AVG was 8.0 to 11.7 mm against tested fungi. Minimum Inhibitory Concentration (MIC) by AFCs, TEO and AVG ranged from 1.25 to 10.0 mg/ml. Combinatory effects of AFCs with TEO or AVG revealed synergistic and indifferent properties.

CONCLUSION

Development of novel products using bioactive ingredients from plants with commercially available AFCs will serve as potential alternative therapy to cure dermatological infections with no side effects.

An Overview of the Potential Therapeutic Applications of Essential Oils

The emergence of antimicrobial resistance (AMR) has urged researchers to explore therapeutic alternatives, one of which includes the use of natural plant products such as essential oils (EO). In fact, EO obtained from clove, oregano, thymus, cinnamon bark, rosemary, eucalyptus, and lavender have been shown to present significant inhibitory effects on bacteria, fungi, and viruses; many studies have been done to measure EO efficacy against microorganisms. The strategy of combinatory effects via conventional and non-conventional methods revealed that the combined effects of EO-EO or EO-antibiotic exhibit enhanced efficacy. This paper aims to review the antimicrobial effects of EO, modes of EO action (membrane disruption, efflux inhibition, increase membrane permeability, and decrease in intracellular ATP), and their compounds' potential as effective agents against bacteria, fungi, and viruses. It is hoped that the integration of EO applications in this work can be used to consider EO for future clinical applications.

Antifungal Activity of Melaleuca alternifolia Essential Oil (TTO) and Its Synergy with Itraconazole or Ketoconazole against Trichophyton rubrum

Over the past 20–30 years, Trichophyton rubrum represented the most widespread dermatophyte with a prevalence accounting for 70% of dermatophytosis. The treatment for cutaneous infections caused by Trichophyton spp. are imidazoles (ketoconazole (KTZ)) and triazoles (itraconazole (ITZ)). T. rubrum can develop resistance to azoles after prolonged exposure to subinhibitory concentrations resulting in therapeutic failures and chronic infections. These problems have stimulated the search for therapeutic alternatives, including essential oils, and their potential use in combination with conventional antifungals. The purpose of this study was to evaluate the antifungal activity of tea tree oil (TTO) (Melaleuca alternifolia essential oil) and the main components against T. rubrum and to assess whether TTO in association with KTZ/ITZ as reference drugs improves the antifungal activity of these drugs. We used a terpinen-4-ol chemotype (35.88%) TTO, and its antifungal properties were evaluated by minimum inhibitory and minimum fungicidal concentrations in accordance with the CLSI guidelines. The interaction between TTO and azoles was evaluated through the checkerboard and isobologram methods. The results demonstrated both the fungicide activity of TTO on T. rubrum and the synergism when it was used in combination with azoles. Therefore, this mixture may reduce the minimum effective dose of azole required and minimize the side effects of the therapy. Synergy activity offered a promise for combination topical treatment for superficial mycoses.

A Human IRE1 Inhibitor Blocks the Unfolded Protein Response in the Pathogenic Fungus Aspergillus fumigatus and Suggests Noncanonical Functions within the Pathway

The unfolded protein response (UPR) is a signaling pathway that maintains endoplasmic reticulum (ER) homeostasis, with functions that overlap virulence mechanisms in the human-pathogenic mold Aspergillus fumigatus. The canonical pathway centers on HacA, its master transcriptional regulator. Translation of this protein requires the removal of an unconventional intron from the cytoplasmic mRNA of the hacA gene, which is achieved by an RNase domain located in the ER-transmembrane stress sensor IreA. Here, we show that targeting this RNase activity with a small-molecule inhibitor effectively blocked UPR activation, resulting in effects that mirror the consequences of genetic deletion of the RNase domain. However, these phenotypes were surprisingly narrow in scope relative to those associated with a complete deletion of the hacA gene. These findings expand the understanding of UPR signaling in this species by supporting the existence of noncanonical functions for the unspliced hacA mRNA in ER stress response.

The unfolded protein response (UPR) is a signaling network that maintains homeostasis of the endoplasmic reticulum (ER). In the human-pathogenic fungus Aspergillus fumigatus, the UPR is initiated by activation of an endoribonuclease (RNase) domain in the ER transmembrane stress sensor IreA, which splices the downstream mRNA hacA^u into its active form, hacAⁱ, encoding the master transcriptional regulator of the pathway. Small-molecule inhibitors against IRE1, the human ortholog of IreA, have been developed for anticancer therapy, but their effects on the fungal UPR are unexplored. Here, we demonstrate that the IRE1 RNase inhibitor 4μ8C prevented A. fumigatus from increasing the levels of hacAⁱ mRNA, thereby blocking induction of downstream UPR target gene expression. Treatment with 4μ8C had minimal effects on growth in minimal medium but severely impaired growth on a collagen substrate that requires high levels of hydrolytic enzyme secretion, mirroring the phenotype of other fungal UPR mutants. 4μ8C also increased sensitivity to carvacrol, a natural compound that disrupts ER integrity in fungi, and hygromycin B, which correlated with reduced expression of glycosylation-related genes. Interestingly, treatment with 4μ8C was unable to induce all of the phenotypes attributed to the loss of the canonical UPR in a ΔhacA mutant but showed remarkable similarity to the phenotype of an RNase-deficient IreA mutant that is also unable to generate the hacAⁱ mRNA. These results establish proof of principle that pharmacological inhibition of the canonical UPR pathway is feasible in A. fumigatus and support a noncanonical role for the hacA^u mRNA in ER stress response.

IMPORTANCE The unfolded protein response (UPR) is a signaling pathway that maintains endoplasmic reticulum (ER) homeostasis, with functions that overlap virulence mechanisms in the human-pathogenic mold Aspergillus fumigatus. The canonical pathway centers on HacA, its master transcriptional regulator. Translation of this protein requires the removal of an unconventional intron from the cytoplasmic mRNA of the hacA gene, which is achieved by an RNase domain located in the ER-transmembrane stress sensor IreA. Here, we show that targeting this RNase activity with a small-molecule inhibitor effectively blocked UPR activation, resulting in effects that mirror the consequences of genetic deletion of the RNase domain. However, these phenotypes were surprisingly narrow in scope relative to those associated with a complete deletion of the hacA gene. These findings expand the understanding of UPR signaling in this species by supporting the existence of noncanonical functions for the unspliced hacA mRNA in ER stress response.

Multidrug and Pan-Antibiotic Resistance—The Role of Antimicrobial and Synergistic Essential Oils: A Review

Bacterial resistance to antibiotics continues to be a grave threat to human health. Because antibiotics are no longer a lucrative market for pharmaceutical companies, the development of new antibiotics has slowed to a crawl. The World Health Organization reported that the 8 new bacterial agents approved since July 2017 had limited clinical benefits. While a cohort of biopharmaceutical companies recently announced plans to develop 2-4 new antibiotics by 2030, we needn’t wait a decade to find innovative antibiotic candidates. Essential oils (EOs) have long been known as antibacterial agents with wide-ranging arsenals. Many are able to penetrate the bacterial membrane and may also be effective against bacterial defenses such as biofilms, efflux pumps, and quorum sensing. EOs have been documented to fight drug-resistant bacteria alone and/or combined with antibiotics. This review will summarize research showing the significant role of EOs as nonconventional regimens against the worldwide spread of antibiotic-resistant pathogens. The authors conducted a 4-year search of the US National Library of Medicine (PubMed) for relevant EO studies against methicillin-resistant Staphylococcus aureus, multidrug-resistant (MDR) Escherichia coli, EO combinations/synergy with antibiotics, against MDR fungal infections, showing the ability to permeate bacterial membranes, and against the bacterial defenses listed above. EOs are readily available and are a needed addition to the arsenal against resistant pathogens.

Effects of Origanum vulgare essential oil and its two main components, carvacrol and thymol, on the plant pathogen Botrytis cinerea

Background

Botrytis cinerea causes serious gray mold disease in many plants. This pathogen has developed resistance to many fungicides. Thus, it has become necessary to look for new safe yet effective compounds against B. cinerea.

Methods

Essential oils (EOs) from 17 plant species were assayed against B. cinerea, of which Origanum vulgare essential oil (OVEO) showed strong antifungal activity, and accordingly its main components were detected by GC/MS. Further study was conducted on the effects of OVEO, carvacrol and thymol in vitro on mycelium growth and spore germination, mycelium morphology, leakages of cytoplasmic contents, mitochondrial injury and accumulation of reactive oxygen species (ROS) of B. cinerea. The control efficacies of OVEO, carvacrol and thymol on tomato gray mold were evaluated in vivo.

Results

Of all the 17 plant EOs tested, Cinnamomum cassia, Litsea cubeba var. formosana and O. vulgare EOs had the best inhibitory effect on B. cinerea, with 0.5 mg/mL completely inhibiting the mycelium growth of B. cinerea. Twenty-one different compounds of OVEO were identified by gas chromatography–mass spectrometry, and the main chemical components were carvacrol (89.98%), β-caryophyllene (3.34%), thymol (2.39%), α-humulene (1.38%) and 1-methyl-2-propan-2-ylbenzene isopropyl benzene (1.36%). In vitro experiment showed EC₅₀ values of OVEO, carvacrol and thymol were 140.04, 9.09 and 21.32 μg/mL, respectively. Carvacrol and thymol completely inhibited the spore germination of B. cinerea at the concentration of 300 μg/mL while the inhibition rate of OVEO was 80.03%. EC₅₀ of carvacrol and thymol have significantly (P < 0.05) reduced the fresh and dry weight of mycelia. The collapse and damage on B. cinerea mycelia treated with 40 μg/mL of carvacrol and thymol was examined by scanning electron microscope (SEM). Through extracellular conductivity test and fluorescence microscope observation, it was found that carvacrol and thymol led to increase the permeability of target cells, the destruction of mitochondrial membrane and ROS accumulation. In vivo conditions, 1000 μg/mL carvacrol had the best protective and therapeutic effects on tomato gray mold (77.98% and 28.04%, respectively), and the protective effect was significantly higher than that of 400 μg/mL pyrimethanil (43.15%). While the therapeutic and protective effects of 1,000 μg/mL OVEO and thymol were comparable to chemical control.

Conclusions

OVEO showed moderate antifungal activity, whereas its main components carvacrol and thymol have great application potential as natural fungicides or lead compounds for commercial fungicides in preventing and controlling plant diseases caused by B. cinerea.

Essential Oils: An Impending Substitute of Synthetic Antimicrobial Agents to Overcome Antimicrobial Resistance

Antimicrobial resistance (AMR) is an emerging problem in the world that has a significant impact on our society. AMR made conventional drugs futile against microorganisms and diseases untreatable. Plant-derived medicines are considered to be safe alternatives as compared to synthetic drugs. Active ingredients and the mixtures of these natural medicines have been used for centuries, due to their easy availability, low cost, and negligible side effects. Essential oils (EOs) are the secondary metabolites that are produced by aromatic plants to protect them from microorganisms. However, these EOs and their constituents have shown good fighting potential against drug-resistant pathogens. These oils have been proved extremely effective antimicrobial agents in comparison to antibiotics. Also, the combination of synthetic drugs with EOs or their components improve their efficacy. So, EOs can be established as an alternative to synthetic antimicrobial agents to eradicate tough form of infectious microorganisms. EO's can interact with multiple target sites, like the destruction of cytoplasm membrane or inhibition of protein synthesis and efflux pump, etc. The purpose of this review is to provide information about the antimicrobial activity of EOs attained from different plants, their combination with synthetic antimicrobials. In addition, mechanism of antimicrobial activity of several EOs and their constituents was reported.

Antifungal activity of selected volatile essential oils against Penicillium sp

Phytopathogenic fungi have been responsible for considerable economic losses in vineyards, and therefore, more attention should be paid to the development and implementation of preventative treatment that is environmentally friendly. The aim of this study was to evaluate the antifungal activity of ten essential oils (EOs) (viz. Lavandula angustifolia Mill., Carum carvi L., Pinus mugo var. pumilio, Mentha piperita L., Foeniculum vulgare L., Pinus sylvestris L., Satureja hortensis L., Origanum vulgare L., Pimpinella anisum L. and Rosmarinus officinalis L.). For the antifungal activity evaluation against Penicillium brevicompactum, P. citrinum, P. crustosum, P. expansum, P. funiculosum, P. glabrum, P. chrysogenum, P. oxalicum, P. polonicum and Talaromyces purpurogenus a disc diffusion method was used. The ten EOs exhibited different antifungal properties. Three tested EOs (Carum carvi L., Satureja hortensis L. and Pimpinella anisum L.) at concentrations of 0.75, 0.50, 0.25 and 0.125 µL/mL showed antifungal activity, inhibiting the mycelial growth. The Origanum vulgare L. EOs exhibited a lower level of inhibition. Overall, Lavandula angustifolia Mill., Pinus mugo var. pumilio, Mentha piperita L., Foeniculum vulgare L., Pinus sylvestris L., Satureja hortensis L., Pimpinella anisum L. and Rosmarinus officinalis L. were effective as fungicidal agents but their efficiency varied between the strains of fungi. Carum carvi L. showed strong antifungal activity against all tested strains at both full strength and reduced concentrations. These EOs could be considered as potential sources of antifungal compounds for treating plant fungal diseases.

Evaluation of antimicrobial activity of the hydrolate of Coridothymus capitatus (L.) Reichenb. fil. (Lamiaceae) alone and in combination with antimicrobial agents

Background

Hydrolates, complex mixtures containing traces of essential oils (EOs), are inexpensive, easy to make and less toxic than their corresponding EOs. The antibacterial and antifungal activity of the hydrolate of Coridothymus capitatus (L.) Reichenb. fil. (Lamiaceae) alone and in combination with antimicrobial drugs, such as tetracycline and itraconazole, were evaluated.

Methods

The chemical composition was analysed by gas-chromatography-mass spectrometry (GC-MS). Standard methods were performed to evaluate the susceptibility of some Gram-positive and Gram-negative bacteria, and Candida spp. to the hydrolate, in comparison with its EO. The hydrolate mechanism of action was assayed by propidium iodide and MitoTracker staining. Checkerboard tests were carried out for combinations studies.

Results

GC-MS identified 0.14% (v/v) of total EO content into hydrolate and carvacrol as a dominant component. The hydrolate showed a good antimicrobial activity against bacteria and yeasts. It exhibited a synergistic effect with itraconazole against Candida krusei, and an additive effect with tetracycline against methicillin-resistant Staphylococcus aureus strains. Hydrolate changed the membranes permeability of bacteria and yeasts and altered mitochondrial function of yeasts.

Conclusions

Our study extends the knowledge by exploiting non-conventional antimicrobial agents to fight the emergence of antibiotic resistance.

New Tricks for Old Guys: Recent Developments in the Chemistry, Biochemistry, Applications and Exploitation of Selected Species from the Lamiaceae Family

Lamiaceae is one of the largest families of flowering plants comprising about 250 genera and over 7,000 species. Most of the plants of this family are aromatic and therefore important source of essential oils. Lamiaceae are widely used as culinary herbs and reported as medicinal plants in several folk traditions. In the Mediterranean area oregano, sage, rosemary, thyme and lavender stand out for geographical diffusion and variety of uses. The aim of this review is to provide recent data dealing with the phytochemical and pharmacological studies, and the more recent applications of the essential oils and the non-volatile phytocomplexes. This literature survey suggests how the deeper understanding of biomolecular processes in the health and food sectors as per as pest control bioremediation of cultural heritage, or interaction with human microbiome, fields, leads to the rediscovery and new potential applications of well-known plants.

Effect of monoterpenes on ex vivo transungual delivery of itraconazole for the management of onychomycosis

BACKGROUND

Onychomycosis, a fungal nail infection, is an important problem as it may cause local pain, paresthesia, difficulties in performing activities of daily life, and impair social interactions. Systemic treatment of onychomycosis presents safety issues due to possible drug-drug interactions and severe side effects. Although topical therapy of onychomycosis is advantageous due to its localized effect, the efficacy of such therapy depends on achieving effective concentrations of antifungal agents at the infection site. An approach to reach to this end would be driving benefit from synergic activity of antifungal agents for example itraconazole and monoterpenes. However, because of low transungual penetration of itraconazole, a molecule with high molecular weight and very low water-solubility, the effect of the latter compounds on itraconazole nail delivery should be investigated, which was the aim of this study.

METHODS

Ex vivo permeation experiments were carried out through soaking the nail clippings of ten healthy volunteers in control and working solutions containing itraconazole (1 mg mL^-1 ) and itraconazole (1 mg mL^-1 ) plus 6% of each monoterpene including camphor, eucalyptol, menthol, and thymol, respectively, for 36 hours. The amount of itraconazole in nail clippings was quantified hereafter using a validated HPLC method.

RESULTS

Statistical analysis showed that itraconazole transungual permeation was not influenced by the studied monoterpenes (P value > .05).

CONCLUSION

These results provided a new perspective for designing topical dosage forms for the treatment of onychomycosis.

Enhanced Killing of Candida krusei by Polymorphonuclear Leucocytes in the Presence of Subinhibitory Concentrations of Melaleuca alternifolia and "Mentha of Pancalieri" Essential Oils

The aim of this study was to evaluate the influence of tea tree oil (TTO) and "Mentha of Pancalieri" essential oil (MPP) on intracellular killing of Candida krusei, often resistant to conventional drugs, by polymorphonuclear leucocytes (PMNs). Intracellular killing was investigated by incubating yeasts and PMNs with essential oils (EOs) at 1/4 and 1/8 × MIC (Minimal Inhibitory Concentration), in comparison with anidulafungin, used as a reference drug. Killing values were expressed as Survival Index (SI) values. The cytotoxicity of EOs was evaluated by 3-[4,-5-dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay. Both EOs were more efficaceous at 1/8 × MIC than 1/4 × MIC, with killing values higher than observed in EO-free systems and in presence of anidulafungin, indicating that the decreasing concentrations did not cause lower candidacidal activity. This better activity at 1/8 × MIC is probably due to the EOs' toxicity at 1/4 × MIC, suggesting that at higher concentrations EOs might interfere with PMNs functionality. TTO and MPP at 1/8 × MIC significantly increased intracellular killing by PMNs through their direct action on the yeasts (both EOs) or on phagocytic cells (MPP), suggesting a positive interaction between EOs and PMNs to eradicate intracellular C. krusei. These data showed a promising potential application of TTO and "Mentha of Pancalieri" EO as natural adjuvants in C. krusei infection management.

Essential Oils and Their Natural Active Compounds Presenting Antifungal Properties

The current rise in invasive fungal infections due to the increase in immunosuppressive therapies is a real concern. Moreover, the emergence of resistant strains induces therapeutic failures. In light of these issues, new classes of antifungals are anticipated. Therefore, the plant kingdom represents an immense potential of natural resources to exploit for these purposes. The aim of this review is to provide information about the antifungal effect of some important essential oils, and to describe the advances made in determining the mechanism of action more precisely. Finally, the issues of toxicity and resistance of fungi to essential oils will be discussed.

Chemical Composition and Antimicrobial Activity of Essential Oils from the Aerial Parts of Pinus eldarica Grown in Northwestern Iran

Pinus eldarica (Pinaceae), an evergreen plant, is distributed across the warm and dry climates of western Asia, including Asia Minor, the Middle East, and land surrounding the Caspian Sea. Essential oils (EOs) from different aerial parts of this tree have been used in traditional medicine. We aimed to investigate the chemical profile and antimicrobial activity of the EO from P. eldarica grown in northwestern Iran. EO from the needles, bark, and pollen were extracted with boiling water using a Clevenger apparatus at yield of 0.7–1.2 cm³/100 g of dry plant material. The main chemical components of the EO from the needles were D-germacrene (18.17%), caryophyllene (15.42%), γ-terpinene (12.96%), and β-pinene (10.62%); those from the bark were limonene (16.99%), caryophyllene oxide (13.22%), and drimenol (13.2%); and those from the pollen were α-pinene (25.64%) and limonene (19.94%). In total, 83 constituents were characterized in the EOs, using gas chromatography mass spectrometry analysis; mainly, sesquiterpene hydrocarbons in needle EO and monoterpene hydrocarbons in pollen and bark EOs. β-Pinene, β-myrcene, limonene, and caryophyllene were identified in the EOs from all three plant parts. The antibacterial and antifungal properties of the EOs were examined: pollen EO exhibited antibacterial activity against Escherichia coli; bark EO inhibited the growth of Candida albicans and Staphylococcus aureus; and the needle EO inhibited the growth of S. aureus. Thus, the EOs from aerial parts of P. eldarica can benefit the EO industry and antibiotic development.

Evaluation of the Antifungal Activity of Mentha x piperita (Lamiaceae) of Pancalieri (Turin, Italy) Essential Oil and Its Synergistic Interaction with Azoles

The promising antimicrobial activity of essential oils (EOs) has led researchers to use them in combination with antimicrobial drugs in order to reduce drug toxicity, side effects, and resistance to single agents. Mentha x piperita, known worldwide as “Mentha of Pancalieri”, is produced locally at Pancalieri (Turin, Italy). The EO from this Mentha species is considered as one of the best mint EOs in the world. In our research, we assessed the antifungal activity of “Mentha of Pancalieri” EO, either alone or in combination with azole drugs (fluconazole, itraconazole, ketoconazole) against a wide panel of yeast and dermatophyte clinical isolates. The EO was analyzed by GC-MS, and its antifungal properties were evaluated by minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) parameters, in accordance with the CLSI guidelines, with some modifications. The interaction of EO with azoles was evaluated through the chequerboard and isobologram methods. The results suggest that this EO exerts a fungicidal activity against yeasts and a fungistatic activity against dermatophytes. Interaction studies with azoles indicated mainly synergistic profiles between itraconazole and EO vs. Candida spp., Cryptococcus neoformans, and Trichophyton mentagrophytes. Thus, the “Mentha of Pancalieri” EO may act as a potential antifungal agent and could serve as a natural adjuvant for fungal infection treatment.