In vitro evaluation of the antimicrobial properties of terpinen-4-ol on apical periodontitis-associated bacteria.

Manuka oil and tea tree oil are essential oils with known antibacterial properties that are believed to be caused by one main component: terpinen-4-ol. Terpinen-4-ol has potent antibacterial activity against caries-related microorganisms. However, few studies have investigated the antimicrobial effects of terpinen-4-ol on bacteria in apical periodontitis. Thus, the objective of the present study was to evaluate the antibacterial and antibiofilm potential of terpinen-4-ol against Enterococcus faecalis, Porphyromonas gingivalis, Prevotella intermedia, and Fusobacterium nucleatum, which have all been detected in apical periodontitis. The minimum inhibitory and minimum bactericidal concentrations of terpinen-4-ol were determined to assess its activity against biofilms. The minimum inhibitory concentration of terpinen-4-ol was 0.25% against E. faecalis and F. nucleatum, 0.05% against P. gingivalis, and 0.1% against P. intermedia. The minimum bactericidal concentration of terpinen-4-ol was 1.0% against E. faecalis, 0.2% against P. gingivalis and P. intermedia, and 0.5% against F. nucleatum. In the biofilm evaluations, all terpinen-4-ol-treated bacteria had significant reductions in biofilm viability compared with controls in experiments assessing attachment inhibitory activity. Furthermore, structural alterations and decreased bacterial cell clumping were observed under scanning electron microscopy, and significantly decreased cell survival was noted using fluorescence microscopy. Together, these results suggest that terpinen-4-ol is a potential antibacterial agent with bactericidal properties, and can also act on established biofilms.

Lavender Essential Oil Modulates Hepatic Cholesterol Metabolism in HepG2 Cells.

Cholesterol is an essential lipid that guarantees several biological processes in eukaryotic cells. Its metabolism is regulated by a complex protein network that could be significantly influenced by numerous exogenous sources, such as essential oils (EOs). For instance, it has been speculated that monoterpenoid and sesquiterpenoid compounds contained in lavender essential oil (LEO) may exert important hypocholesterolemic activities. However, the molecular mechanisms by which LEO influences cholesterol homeostasis are not characterized. In this work, we evaluated the ability of LEO to regulate the protein network that controls cholesterol metabolism in the HepG2 cell line. The main findings indicate that LEO administration increases intracellular cholesterol content. Concurrently, LEO affects the expression of proteins involved in cholesterol uptake, biosynthesis, and trafficking. These effects are partially mediated by terpinene-4-ol, one of the most abundant compounds in LEO. These results demonstrate that LEO modulates cholesterol metabolism in hepatic cells.

Cytochrome P450 gene CYP6BQ8 mediates terpinen-4-ol susceptibility in the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae).

Cytochrome P450 proteins (CYPs) in insects can encode various detoxification enzymes and catabolize heterologous substances, conferring tolerance to insecticides. This study describes the identification of a P450 gene (CYP6BQ8) from Tribolium castaneum (Herbst) and investigation of its spatiotemporal expression profile and potential role in the detoxification of terpinen-4-ol, a component of plant essential oils. The developmental expression profile showed that TcCYP6BQ8 expression was relatively higher in early- and late-larval stages of T. castaneum compared with other developmental stages. Tissue expression profiles showed that TcCYP6BQ8 was mainly expressed in the head and integument of both larvae and adults. The expression profiling of TcCYP6BQ8 in developmental stages and tissues is closely related to the detoxification of heterologous substances. TcCYP6BQ8 expression was significantly induced after exposure to terpinen-4-ol, and RNA interference against TcCYP6BQ8 increased terpinen-4-ol-induced larval mortality from 47.78 to 66.67%. This indicates that TcCYP6BQ8 may be involved in T. castaneum's metabolism of terpinen-4-ol. Correlation investigation between the CYP6BQ8 gene and terpinen-4-ol resistance in T. castaneum revealed that the TcCYP6BQ8 gene was one of the factors behind T. castaneum's resistance to terpinen-4-ol. This discovery may provide a new theoretical foundation for future regulation of T. castaneum.

Terpinen-4-ol Induces Ferroptosis of Glioma Cells via Downregulating JUN Proto-Oncogene.

According to previous research, turmeric seeds exhibit anti-inflammatory, anti-malignancy, and anti-aging properties due to an abundance of terpinen-4-ol (T4O). Although it is still unclear how T4O works on glioma cells, limited data exist regarding its specific effects. In order to determine whether or not glioma cell lines U251, U87, and LN229 are viable, CCK8 was used as an assay and a colony formation assay was performed using different concentrations of T4O (0, 1, 2, and 4 µM). The effect of T4O on the proliferation of glioma cell line U251 was detected through the subcutaneous implantation of the tumor model. Through high-throughput sequencing, a bioinformatic analysis, and real-time quantitative polymerase chain reactions, we identified the key signaling pathways and targets of T4O. Finally, for the measurement of the cellular ferroptosis levels, we examined the relationship between T4O, ferroptosis, and JUN and the malignant biological properties of glioma cells. T4O significantly inhibited glioma cell growth and colony formation and induced ferroptosis in the glioma cells. T4O inhibited the subcutaneous tumor proliferation of the glioma cells in vivo. T4O suppressed JUN transcription and significantly reduced its expression in the glioma cells. The T4O treatment inhibited GPX4 transcription through JUN. The overexpression of JUN suppressed ferroptosis in the cells rescued through T4O treatment. Taken together, our data suggest that the natural product T4O exerts its anti-cancer effects by inducing JUN/GPX4-dependent ferroptosis and inhibiting cell proliferation, and T4O will hope-fully serve as a prospective compound for glioma treatment.

[Terpinen-4-ol inhibits proliferation of VSMCs exposed to high glucose via regulating KLF4/NF-κB signaling pathway].

This study aimed to observe the effect of terpinen-4-ol(T4O) on the proliferation of vascular smooth muscle cells(VSMCs) exposed to high glucose(HG) and reveal the mechanism via the Krüppel-like factor 4(KLF4)/nuclear factor kappaB(NF-κB) signaling pathway. The VSMCs were first incubated with T4O for 2 h and then cultured with HG for 48 h to establish the model of inflammatory injury. The proliferation, cell cycle, and migration rate of VSMCs were examined by MTT method, flow cytometry, and wound healing assay, respectively. The content of inflammatory cytokines including interleukin(IL)-6 and tumor necrosis factor-alpha(TNF-α) in the supernatant of VSMCs was measured by enzyme-linked immunosorbent assay(ELISA). Western blot was employed to determine the protein levels of proliferating cell nuclear antigen(PCNA), Cyclin D1, KLF4, NF-κB p-p65/NF-κB p65, IL-1ß, and IL-18. The KLF4 expression in VSMCs was silenced by the siRNA technology, and then the effects of T4O on the cell cycle and protein expression of the HG-induced VSMCs were observed. The results showed that different doses of T4O inhibited the HG-induced proliferation and migration of VSMCs, increased the percentage of cells in G_1 phase, and decreased the percentage of cells in S phase, and down-regulated the protein levels of PCNA and Cyclin D1. In addition, T4O reduced the HG-induced secretion and release of the inflammatory cytokines IL-6 and TNF-α and down-regulated the expression of KLF4, NF-κB p-p65/NF-κB p65, IL-1ß, and IL-18. Compared with si-NC+HG, siKLF4+HG increased the percentage of cells in G_1 phase, decreased the percentage of cells in S phase, down-regulated the expression of PCNA, Cyclin D1, and KLF4, and inhibited the activation of NF-κB signaling pathway. Notably, the combination of silencing KLF4 with T4O treatment further promoted the changes in the above indicators. The results indicate that T4O may inhibit the HG-induced proliferation and migration of VSMCs by down-regulating the level of KLF4 and inhibiting the activation of NF-κB signaling pathway.

Functional analysis of a cytochrome P450 gene CYP9Z6 responding to terpinen-4-ol in the red flour beetle, Tribolium castaneum.

Tribolium castaneum is an agricultural and stored pest found throughout the world. The cytochrome P450 genes of T. castaneum can encode various detoxification enzymes and catabolize heterologous substances, conferring tolerance to insecticides. Herein, we describe the identification of a P450 gene (CYP9Z6) from T. castaneum and investigated its expression profile and potential role in the detoxification of terpinen-4-ol. TcCYP9Z6 expression was significantly induced after exposure to terpinen-4-ol, and RNA-mediated silencing of TcCYP9Z6 increased terpinen-4-ol-induced larval mortality from 47.75% to 63.92%, showing that TcCYP9Z6 is closely related to the detoxification of terpinen-4-ol. The developmental expression profile revealed that TcCYP9Z6 was mainly expressed in late adults and late larvae. Tissue expression profiling revealed that the highest TcCYP9Z6 expression occurred in the head, in both the adult and the larval tissues, followed by the gut in larvae and the antennae in adults. These developmental stages and tissues with high TcCYP9Z6 expression are closely related to the detoxification of heterologous substances. These results indicated that TcCYP9Z6 may play a pivotal role in the detoxification of terpinen-4-ol, which provides support for using TcCYP9Z6 a potential gene for the RNAi-mediated prevention and control of T. castaneum.

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.

Integration of metabolomics and transcriptomics indicates changes in MRSA exposed to terpinen-4-ol.

BACKGROUND: This study investigated the effects of terpinen-4-ol on methicillin-resistant Staphylococcus aureus (MRSA) and its biofilm, and the possible mechanisms governing this effect. RESULTS: We observed that terpinen-4-ol has good antibacterial activity and inhibits the formation of MRSA biofilm. The MIC and MBC values for terpinen-4-ol against S. aureus were 0.08% ~ 0.32%. And terpinen-4-ol at 0.32% could kill all bacteria and clear all biofilms. Untargeted metabolomic and transcriptomic analyses showed that terpinen-4-ol strongly inhibited DNA and RNA biosynthesis in MRSA at 2 h after treatment by affecting genes and metabolites related to purine and pyrimidine metabolic pathways. Some differential genes which play important roles in DNA synthesis and the production of eDNA from biofilm exposed to terpinen-4-ol was also significantly decreased compared with that of the control. CONCLUSIONS: Terpinen-4-ol has good antibacterial activity and significantly inhibits the formation of MRSA biofilm by inhibiting purine and pyrimidine metabolism.

The ameliorative effect of terpinen-4-ol on ER stress-induced vascular calcification depends on SIRT1-mediated regulation of PERK acetylation.

Endoplasmic reticulum (ER) stress-mediated phenotypic switching of vascular smooth muscle cells (VSMCs) is key to vascular calcification (VC) in patients with chronic kidney disease (CKD). Studies have shown that activation/upregulation of SIRT1 has a protective effect on CKD-VC. Meanwhile, although terpinen-4-ol has been shown to exert a protective effect against cardiovascular disease, its role and underlying mechanism in VC remain unclear. Herein, we explored whether terpinen-4-ol alleviates ER stress-mediated VC through sirtuin 1 (SIRT1) and elucidated its mechanism to provide evidence for its application in the clinical prevention and treatment of VC. To this end, a CKD-related VC animal model and ß-glycerophosphate (ß-GP)-induced VSMC calcification model were established to investigate the role of terpinen-4-ol in ER stress-induced VC, in vitro and in vivo. Additionally, to evaluate the involvement of SIRT1, mouse and VSMC Sirt1-knockdown models were established. Results show that terpinen-4-ol inhibits calcium deposition, phenotypic switching, and ER stress in VSMCs in vitro and in vivo. Furthermore, pre-incubation of VSMCs with terpinen-4-ol or a SIRT1 agonist, decreased ß-GP-induced calcium salt deposition, increased SIRT1 protein level, and inhibited PERK-eIF2α-ATF4 pathway activation, thus, alleviating VC. Similar results were observed in VSMCs induced to overexpress SIRT1 via lentivirus transcription. Meanwhile, the opposite results were obtained in SIRT1-knockdown models. Further, results suggest that SIRT1 physically interacts with, and deacetylates PERK. Specifically, mass spectrometry analysis identified lysine K889 as the acetylation site of SIRT1, which regulates PERK. Finally, inhibition of SIRT1 reduced the effect of terpinen-4-ol on the deacetylation of PERK in vitro and in vivo and weakened the inhibitory effect of terpinen-4-ol against ER stress-mediated VC. Cumulatively, terpinen-4-ol was found to inhibit post-translational modification of PERK at the K889 acetylation site by upregulating SIRT1 expression, thereby ameliorating VC by regulating ER stress. This study provides insights into the underlying molecular mechanism of terpinen-4-ol, supporting its development as a promising therapeutic agent for CKD-VC.

Essential Oil Composition and Bioactivity of Two Juniper Species from Bulgaria and Slovakia.

Juniperus excelsa M. Bieb and J. sabina L. contain essential oil (EO), while J. sabina also contains podophyllotoxin, which is used as a precursor for anti-cancer drugs. Two studies were conducted. The first assessed the variability in the EO profile and podophyllotoxin concentration of the two junipers, depending on the location and tree gender. The main EO constituents of J. excelsa were α-cedrol, α-limonene and α-pinene, while the constituents in J. sabina were sabinene, terpinen-4-ol, myrtenyl acetate and α-cadinol. The podophyllotoxin yield of 18 J. sabina accessions was 0.07-0.32% (w/w), but this was not found in any of the J. excelsa accessions. The second study assessed the effect of hydrodistillation (Clevenger apparatus) and steam distillation (in a semi-commercial apparatus) on the EO profile and bioactivity. The extraction type did not significantly alter the EO composition. The EO profiles of the two junipers and their accessions were different and may be of interest to the industry utilizing juniper leaf EO. Breeding and selection programs could be developed with the two junipers (protected species) in order to identify chemotypes with (1) a high EO content and desirable composition, and (2) a high concentration of podophyllotoxin in J. sabina. Such chemotypes could be established as agricultural crops for the commercial production of podophyllotoxin and EO.

Comparison of the efficacy of tea tree (Melaleuca alternifolia) oil with other current pharmacological management in human demodicosis: A Systematic Review.

Various treatments are found to be moderately effective in managing Demodex-related diseases except tea tree oil (TTO) and terpinen-4-ol (T4O), which showed superior miticidal and anti-inflammatory effects in numerous clinical studies. Their possible effects include lowering mite counts, relieving Demodex-related symptoms, and modulating the immune system. This review summarizes the current clinical topical and oral treatments in human demodicosis, their possible mechanisms of action, side-effects and resistance in treating this condition. TTO (especially T4O) is found to be the most effective followed by metronidazole, ivermectin and permethrin in managing the disease. This is because TTO has anti-parasitic, anti-bacterial, anti-fungal, anti-inflammatory and wound-healing effects. Furthermore, nanoTTO can even release its contents into fungus and Pseudomonas biofilms. Combinations of different treatments are occasionally needed for refractory cases, especially for individuals with underlying genetic predisposal or are immuno-compromised. Although the current treatments show efficacy in controlling the Demodex mite population and the related symptoms, further research needs to be focused on the efficacy and drug delivery technology in order to develop alternative treatments with better side-effects profiles, less toxicity, lower risk of resistance and are more cost-effective.

Effects of terpinen-4-ol fumigation on protein levels of detoxification enzymes in Tribolium confusum.

Terpinen-4-ol has high fumigating activity to stored-grain pests including Tribolium confusum. To understand the detoxification of terpinen-4-ol in insects, proteomic analysis was performed to identify related proteins and pathways in response to terpinen-4-ol fumigation in T. confusum. By using isobaric tags for relative and absolute quantitation (iTRAQ)-based strategy, 4,618 proteins were obtained from T. confusum adults in the present study. Comparative proteomic analysis showed that 148 proteins were upregulated and 137 proteins were downregulated in beetles under the LC50 of terpinen-4-ol treatment for 24 hr. According to functional classifications, differentially expressed proteins (DEPs) were enriched in xenobiotic metabolism pathways. In the detoxification pathway, the levels of 25 cytochrome P450s, 5 glutathione S-transferases, and 2 uridine diphosphate (UDP)-glucuronosyltransferases were changed, most of which were upregulated in T. confusum exposed to terpinen-4-ol. The results indicated that terpinen-4-ol was potentially metabolized and detoxified by enzymes like P450s in T. confusum.

Transcriptome analysis of Botrytis cinerea in response to tea tree oil and its two characteristic components.

Tea tree oil (TTO) and its two characteristic components (terpinen-4-ol and 1,8-cineole) have been shown to inhibit Botrytis cinerea growth. In this study, we conducted a transcriptome analysis to determine the effects of TTO and its characteristic components, alone and in combination, against B. cinerea. Most differentially expressed genes (DEGs) from B. cinerea cells treated with terpinen-4-ol participated in the biosynthesis of secondary metabolites, and the metabolism of amino acids, carbohydrates, and lipids. All treatments containing terpinen-4-ol potentially induced mitochondrial dysfunction and oxidative stress. These were further confirmed by the decreased activities of several enzymes (e.g., succinate dehydrogenase (SDH), malate dehydrogenase (MDH), α-ketoglutarate dehydrogenase (α-KGDH), isocitrate dehydrogenase (ICDH)), the increased activities of certain enzymes (e.g., catalase (CAT), peroxidase (POD), superoxide dismutase (SOD)), and increased content of hydrogen peroxide (H2O2). 1,8-Cineole mainly affected DEGs involved in genetic information processing, resulting in cell death. This study provides insight into the molecular mechanism of B. cinerea inhibition by TTO, and explains the synergistic effect of terpinen-4-ol and 1,8-cineole on B. cinerea.

Knockdown of NADPH-cytochrome P450 reductase and CYP6MS1 increases the susceptibility of Sitophilus zeamais to terpinen-4-ol.

Terpinen-4-ol showed highly insecticidal activity to stored-grain pest Sitophilus zeamais, and cytochrome P450s were strongly induced in response to terpinen-4-ol fumigation. Understanding of the function of P450 enzyme system in the susceptibility to terpinen-4-ol in S. zeamais will benefit the potential application of terpinen-4-ol in controlling stored-grain pests. In the present study, the synergist piperonyl butoxide increased the toxicity of terpinen-4-ol to S. zeamais, with a synergism ratio of 3.5-fold. Two isoforms of NADPH-cytochrome P450 reductase (SzCPR) were identified, with the difference at the N-terminal. SzCPR contained an N-terminal membrane anchor, FMN, FAD, and NADP binding domains. Expression levels of SzCPR were upregulated by tea tree oil (TTO) and its main constituent terpinen-4-ol under different concentrations and time periods. RNAi was generated for S. zeamais by feeding adults dsRNA and the knockdown of SzCPR increased the susceptibility of S. zeamais to terpinen-4-ol, with higher mortality of adults than control under terpinen-4-ol fumigation. Further RNAi analysis showed that P450 gene CYP6MS1 mediated the susceptibility of S. zeamais to terpinen-4-ol. These results revealed that cytochrome P450 enzyme system, especially CYP6MS1 participated in the susceptibility of S. zeamais to terpinen-4-ol. The findings provided a foundation to clarify the metabolic mechanisms of terpinen-4-ol in stored-grain pests.

Terpinen-4-ol as an Antibacterial and Antibiofilm Agent against Staphylococcus aureus.

Staphylococcus aureus is able to rapidly develop mechanisms of resistance to various drugs and to form strong biofilms, which makes it necessary to develop new antibacterial drugs. The essential oil of Melaleuca alternifolia is used as an antibacterial, a property believed to be mainly due to the presence of terpinen-4-ol. Based on this, the objective of this study was to evaluate the antibacterial and antibiofilm potential of terpinen-4-ol against S. aureus. The Minimal Inhibitory and Minimal Bactericidal Concentrations (MIC and MBC) of terpinen-4-ol were determined, and the effect of its combination with antibacterial drugs as well as its activity against S. aureus biofilms were evaluated. In addition, an in silico analysis of its pharmacokinetic parameters and a molecular docking analysis were performed. Terpinen-4-ol presented a MIC of 0.25% (v/v) and an MBC of 0.5% (v/v) (bactericidal action); its association with antibacterials was also effective. Terpinen-4-ol has good antibiofilm activity, and the in silico results indicated adequate absorption and distribution of the molecule in vivo. Molecular docking indicated that penicillin-binding protein 2a is a possible target of terpinen-4-ol in S. aureus. This work highlights the good potential of terpinen-4-ol as an antibacterial product and provides support for future pharmacological studies of this molecule, aiming at its therapeutic application.

Identification and Field Assay of Two Aggregation Pheromone Components Emitted by Males of the Bark Beetle Polygraphus punctifrons (Coleoptera: Curculionidae).

The bark beetle Polygraphus punctifrons (Coleoptera: Curculionidae) is a species that feeds on Norway spruce (Picea abies) and is found in the Northern parts of Europe and Russia. The release of volatile organic compounds (VOCs) produced by males and females of P. punctifrons when the beetles bore into spruce stem sections in a laboratory environment was studied using solid phase microextraction (SPME). The sampled VOCs emitted by boring beetles were analysed by gas chromatography and mass spectrometry (GCMS). (+)-2-[(1R,2S)-1-Methyl-2-(prop-1-en-2-yl)cyclobutyl]ethanol [(+)-(1R,2S)-grandisol] and (-)-(R)-1-isopropyl-4-methyl-3-cyclohexen-1-ol [(-)-(R)-terpinen-4-ol] were identified to be male specific volatiles. The identity of the compounds was confirmed by comparison with synthetic samples. Field trials with synthetic compounds in Sweden showed that racemic grandisol per se was strongly attractive for both males and females, while (-)-(R)-terpinen-4-ol was not. Further, when adding (-)-(R)-terpinen-4-ol to rac-grandisol, a synergistic effect was observed as the trap catch of P. punctifrons was fourfold. (-)-(R)-Terpinen-4-ol by its own did not attract P. punctifrons but Polygraphus poligraphus, and the latter was also attracted to traps baited with a 10:90 mixture of the two compounds. Thus, we have identified (+)-(1R,2S)-grandisol as a main component and (-)-(R)-terpinen-4-ol as a minor component of the aggregation pheromone of P. punctifrons. This opens future possibilities to monitor and, if necessary, manage populations of P. punctifrons.

Terpinen-4-ol and carvacrol affect multi-species biofilm composition.

The aim of this study was to investigate the cytotoxic activity and inhibitory effect of terpinen-4-ol (T4ol) and carvacrol against single- and multi-species biofilms. The toxicity of each compound was tested on oral keratinocytes and evaluated by XTT assay. Inhibition and eradication of single-species biofilms were analyzed by crystal violet assay and the effect on multi-species biofilm composition was evaluated by qPCR. T4ol and carvacrol did not affect the epithelial cell viability, in contrast to chlorhexidine, which showed a high cytotoxic effect. Inhibition and eradication of single-species biofilms treated with T4ol and carvacrol were observed. The same inhibitory effect was observed for multi-species biofilms, especially on periodontal pathogens. In conclusion, specific concentrations of T4ol and carvacrol without toxicity towards the epithelial cells reduced the numbers of periodontal pathogens in single- and multi-species biofilms.

Antifungal activity and Shore A hardness of a tissue conditioner incorporated with terpinen-4-ol and cinnamaldehyde.

PURPOSE: This study investigated the anti-Candida activity and the Shore A hardness of a tissue conditioner (Softone™) modified by incorporation of terpinen-4-ol and cinnamaldehyde. MATERIAL AND METHODS: Agar diffusion, microdilution, and mechanism of action methods were performed to determine to evaluate the antifungal activity of phytoconstituents. Then, phytoconstituents in varying concentrations were incorporated into the tissue conditioner. The anti-Candida effect of the modified conditioner was evaluated through agar punch well and biofilm formation methods. Shore A hardness of the experimental liners was evaluated after baseline, 24 h, 48 h, 4 days, and 7 days immersion on artificial saliva. RESULTS: The phytoconstituents incorporated into Softone showed completely inhibited fungal growth in concentrations of 20-40% and did not present significant antifungal activity until their concentrations where higher than 5%. There were differences between non-modified Softone and M5, M10, C10, and T10% (p < 0.05). The groups containing 10-40% of cinnamaldehyde incorporated into Softone were able to completely inhibit the biofilm. Concentrations below 40% of terpinen-4-ol showed unsatisfactory biofilm inhibition. The T40% and C40% groups presented the lowest Shore A hardness values. Hardness values from groups T40% at 7 days (p = 0.476); C40% at 4 days (p = 0.058); and T20% (p = 0.058), C20% (p = 0.205), T30% (p = 0.154), and C30% (p = 0.874) after 48 h did not differ from the control group. CONCLUSIONS: Cinnamaldehyde incorporated into Softone inhibited Candida biofilm formation at concentrations of 10-40%, being more effective than terpinen-4-ol modification despite of halo inhibition observed by both products. CLINICAL RELEVANCE: All modifications showed a very similar pattern of hardness being useful for clinical practice.

In Vitro Effects of Tea Tree Oil (Melaleuca Alternifolia Essential Oil) and its Principal Component Terpinen-4-ol on Swine Spermatozoa.

The growing interest towards essential oils stems from their biological capabilities that include antibacterial and antioxidant effects. Such properties may be extremely useful in the reproductive field; nonetheless essential oils show toxic effects that can lead to cell disruption. The present study aimed to evaluate and compare the effects of tea tree oil (TTO) and its principal component terpinen-4-ol (TER) on the morpho-functional parameters of swine spermatozoa. Experimental samples were prepared by suspending 15 × 107 spermatozoa in 5 mL of medium with different concentrations of the above-mentioned compounds: from 0.2 to 2 mg/mL at an interval of 0.2 for TTO, while TER concentrations were adjusted according to its presence in TTO (41.5%). After 3 h incubation at 16 °C, samples were analyzed for pH, viability, acrosome status, and objective motility. The results highlighted a concentration-dependent effect of TTO with total motility as the most sensitive parameter. TER was better tolerated, and the most sensitive parameters were related to membrane integrity, suggesting a different pattern of interaction. The study confirms the importance of evaluating the effects of natural compounds on spermatozoa before exploiting their beneficial effects. Spermatozoa seem to be good candidates for preliminary toxicological screenings in the light of their peculiar properties.

Can the tea tree oil (Australian native plant: Melaleuca alternifolia Cheel) be an alternative treatment for human demodicosis on skin?

Australian tea tree oil (TTO) and its extract terpinen-4-ol (T4O) are found to be effective in moderating demodex-related diseases. Their possible effects are lowering the mite counts, relieving the demodex-related symptoms and modulating the immune system especially the inflammatory response. This review summarizes the topical treatments of TTO and T4O in human demodicosis, their possible mechanism of actions, side-effects and potential resistance in treating this condition. Although current treatments other than TTO and T4O are relatively effective in controlling the demodex mite population and the related symptoms, more research on the efficacy and drug delivery technology is needed in order to assess its potential as an alternative treatment with minimal side-effect profile, low toxicity and low risk of demodex resistance.