Natural Monoterpenoid Research Articles

Thymol as adjuvant in oncology: molecular mechanisms, therapeutic potentials, and prospects for integration in cancer management.

Cancer remains a global health challenge, prompting a search for effective treatments with fewer side effects. Thymol, a natural monoterpenoid phenol derived primarily from thyme (Thymus vulgaris) and other plants in the Lamiaceae family, is known for its diverse biological activities. It emerges as a promising candidate in cancer prevention and therapy. This study aims to consolidate current research on thymol's anticancer effects, elucidating its mechanisms and potential to enhance standard chemotherapy, and to identify gaps for future research. A comprehensive review was conducted using databases like PubMed/MedLine, Google Scholar, and ScienceDirect, focusing on studies from the last 6years. All cancer types were included, assessing thymol's impact in both cell-based (in vitro) and animal (in vivo) studies. Thymol has been shown to induce programmed cell death (apoptosis), halt the cell division cycle (cell cycle arrest), and inhibit cancer spread (metastasis) through modulation of critical signaling pathways, including phosphoinositide 3-kinase (PI3K), protein kinase B (AKT), extracellular signal-regulated kinase (ERK), mechanistic target of rapamycin (mTOR), and Wnt/β-catenin. It also enhances the efficacy of 5-fluorouracil (5-FU) in colorectal cancer treatments. Thymol's broad-spectrum anticancer activities and non-toxic profile to normal cells underscore its potential as an adjunct in cancer therapy. Further clinical trials are essential to fully understand its therapeutic benefits and integration into existing treatment protocols.

Synthesis and antibacterial potential of novel thymol derivatives against methicillin-resistant Staphylococcus aureus and P. aeruginosa pathogenic bacteria.

The increasing threat of antibiotic resistance has created an urgent need for new antibacterial agents, particularly plant-based natural compounds and their derivatives. Thymol, a natural monoterpenoid phenolic compound derived from Monarda citriodora, is known for its aromatic and therapeutic properties, including antibacterial activity. This study focuses on synthesizing dihydropyrimidinone and dihydropyridine derivatives of thymol and exploring their antibacterial properties. The synthesized compounds were tested for their in vitro antibacterial potential against pathogenic microorganisms, specifically Pseudomonas aeruginosa (Gram-negative) and methicillin-resistant Staphylococcus aureus (MRSA) (Gram-positive). Among the synthesized derivatives, compound 3i (ethyl 4-(4-hydroxy-5-isopropyl-2-methylphenyl)-2-imino-6-methyl-1,2,3,4-tetrahydropyrimidine-5-carboxylate) exhibited the most promising antibacterial activity, with minimum inhibitory concentration (MIC) values of 12.5µM against P. aeruginosa and 50.0µM against MRSA. Additionally, compound 3i demonstrated a synergistic effect when combined with vancomycin, enhancing its antibacterial efficacy. The optimum fractional inhibitory concentration index (FICI) observed was 0.10 and 0.5 for MRSA and P. aeruginosa, respectively, in combination with vancomycin. In silico analysis of the physiochemical properties of 3i indicated compliance with all drug-likeness rules. Furthermore, molecular docking studies revealed that compound 3i has a stronger binding affinity to the target protein than thymol, providing valuable insights into its potential mechanism of action.

In silico study of therapeutic deep eutectic solvent for tetracaine liquid delivery

The development of a drug delivery liquid formulation of ester – based tetracaine local anaesthetic is synthesised in silico via the formation of a therapeutic deep eutectic solvent in combination with citral, a natural monoterpenoid. The properties of the obtained liquid system, studied at the nanoscopic level, are derived from a combination of quantum chemistry and classical molecular dynamics simulations. The intermolecular forces (hydrogen bonding) were analysed and their relationship with liquid phase properties were established. Water effect on the liquid phase properties were also considered in terms of competing for hydrogen bonding sites in the components of the developed fluid. The systems proposed in this work were studied using CIT (HBA) 1:1 TET (HBD) molar ratio at temperatures ranging from 288 K to 318 K and 1 bar. The hydrogen bond network developed between the oxygen atom in citral molecules and the –NH group in tetracaine molecules under those conditions, confirmed via minimal cluster analysis, is maintained during the addition of water up to 1.3 wt% as the water molecules do not disrupt the intermolecular hydrogen bond but develop new interactions (hydrogen bonds) with citral and tetracaine monomers presented in the fluid. The reported results probed the suitability of the considered system as an alternative drug delivery method as well as the possibility of developing deep eutectic-based formulation of anaesthetics using natural compounds due to the formation of effective and strong intermolecular hydrogen bonds.

Geraniol attenuates oxygen-glucose deprivation/reoxygenation-induced ROS-dependent apoptosis and permeability of human brain microvascular endothelial cells by activating the Nrf-2/HO-1 pathway.

Blood-brain barrier breakdown and ROS overproduction are important events during the progression of ischemic stroke aggravating brain damage. Geraniol, a natural monoterpenoid, possesses anti-apoptotic, cytoprotective, anti-oxidant, and anti-inflammatory activities. Our study aimed to investigate the effect and underlying mechanisms of geraniol in oxygen-glucose deprivation/reoxygenation (OGD/R)-induced human brain microvascular endothelial cells (HBMECs). Apoptosis, caspase-3 activity, and cytotoxicity of HBMECs were evaluated using TUNEL, caspase-3 activity, and CCK-8 assays, respectively. The permeability of HBMECs was examined using FITC-dextran assay. Reactive oxygen species (ROS) production was measured using the fluorescent probe DCFH-DA. The protein levels of zonula occludens-1 (ZO-1), occludin, claudin-5, β-catenin, nuclear factor erythroid 2-related factor 2 (Nrf2), and heme oxygenase-1 (HO-1) were determined by western blotting. Geraniol showed no cytotoxicity in HBMECs. Geraniol and ROS scavenger N-acetylcysteine (NAC) both attenuated OGD/R-induced apoptosis and increase of caspase-3 activity and the permeability to FITC-dextran in HBMECs. Geraniol relieved OGD/R-induced ROS accumulation and decrease of expression of ZO-1, occludin, claudin-5, and β-catenin in HBMECs. Furthermore, we found that geraniol activated Nrf2/HO-1 pathway to inhibit ROS in HBMECs. In conclusion, geraniol attenuated OGD/R-induced ROS-dependent apoptosis and permeability in HBMECs through activating the Nrf2/HO-1 pathway.

Mechanistic insight into the membrane disrupting properties of thymol in Candida species

Candida infection is a major problem in immunocompromised patients and has become a significant public health concern in recent years due to high toxicity, multidrug resistance and unfavourable side effects of conventional antifungal drugs. This study aims to investigate the antifungal efficacy of thymol, a natural monoterpenoid, on the membrane integrity of Candida albicans, Candida glabrata and Candida tropicalis. Minimum inhibitory concentrations (MICs) of thymol were 32 µg/ml, 63 µg/ml, and 125 µg/ml for C. albicans, C. tropicalis and C. glabrata, respectively. The minimum fungicidal concentrations (MFC) were 64 µg/ml, 110 µg/ml and 240 µg/ml, respectively. At MIC, thymol treated cells showed complete suppression of cell growth (growth kinetics, disc diffusion), altered morphology (scanning electron microscopy), leakage of intracellular macromolecules (absorption at 260 nm), significant reduction in ergosterol levels and inhibition of plasma membrane H+-ATPase (Pma1) activity. The disruption of the fungal membranes by thymol was further confirmed by propidium iodide uptake using flow cytometry and confocal microscopy. In silico studies with membrane-bound proteins (lanosterol 14-α demethylase (LDM) and Pma1), showed good binding affinity of −6.3 kcal/mol and −6.7 kcal/mol, respectively, and formed hydrogen bonds with crucial amino acid residues at the active site of target proteins. With low MIC values, negligible host toxicity, desirable ADME properties, thymol has immense potential as a potent antifungal drug that can be used for developing mechanism-based drugs as it has specific binding affinity for specific target proteins. Studies using animal models are required for further validation.

Anti-Cancer Study of Carvacrol in Hypoxic-Induced Colorectal Cancer Cell

Introduction: Colorectal cancer presents a complex global health challenge, characterized by complications arising from metastasis development due to rapid proliferation, adaptation to hypoxia, and angiogenesis. Carvacrol, a natural monoterpenoid phenol derived from various plants, has interest for its diverse pharmacological properties, particularly its antitumor effects. Methods: We aimed to assess the inhibitory effect of carvacrol on cell migration and proliferation in the hypoxic colorectal cancer cell line (SW480). Chemical induction of hypoxia using cobalt chloride and serially diluted concentrations of carvacrol (400, 200, 100, 50, 25, and 12.5 µg/ml) were employed to evaluate the cytotoxic effect via the MTT assay. Smaller concentrations (low IC50) were used to examine the impact of carvacrol on SW480 cell migration through a cell migration assay (50, 25, 12.5, and 6.25 µg/ml). Results: The results demonstrated a significant, dose-dependent reduction in both cell proliferation and migration with carvacrol doses. Conclusion: The findings suggest that carvacrol could be useful as an adjuvant therapy and a promising addition for patients with highly metastatic colorectal cancer.

A molecular informatics and in-vitro approach to evaluate the HMG-CoA reductase inhibitory efficacy of monoterpenes, carvacrol and geraniol

Currently, statins, the β-hydroxy-β-methyl-glutaryl-CoA reductase (HMG-R) inhibitors, are widely used to lower cholesterol, nevertheless, they have several side effects. Consequently, the present study is designed to unravel the cardioprotective role of selected natural monoterpenoids (carvacrol and geraniol) via in-vitro targeting and molecular informatics study of HMG-R. Computational molecular informatics study revealed that carvacrol and geraniol efficiently occupies the catalytic site of HMG-R with the binding affinity (ΔG) of −4.60, and −1.99 Kcal/mol, respectively, and molecular mechanical-generalized Born surface area (MM-GBSA) free binding energy was depicted as −17.05 and −29.48 Kcal/mol, respectively. Further, molecular dynamics simulation was carried out for 100 ns. Carvacrol and geraniol potentially and competitively inhibit the in-vitro HMG-R activity with an IC50 value of 78.23 ± 2.21 µM, and 72.91 ± 2.92 µM, respectively. Thus, both carvacrol and geraniol exhibited significant anti-hypercholesterolemic activity while the molecular simulation studies depicted that the GR complex showed better stability than the carvacrol complex.

Natural Compounds with Antifungal Properties against Candida albicans and Identification of Hinokitiol as a Promising Antifungal Drug.

Candida albicans is an opportunistic yeast that causes most fungal infections. C. albicans has become increasingly resistant to antifungal drugs over the past decade. Our study focused on the identification of pure natural compounds for the development of antifungal medicines. A total of 15 natural compounds from different chemical families (cinnamic derivatives, aromatic phenols, mono- and sesquiterpenols, and unclassified compounds) were screened in this study. Among these groups, hinokitiol (Hi), a natural monoterpenoid extracted from the wood of the cypress family, showed excellent anti-C. albicans activity, with a MIC value of 8.21 µg/mL. Hi was selected from this panel for further investigation to assess its antifungal and anti-inflammatory properties. Hi exhibited significant antifungal activity against clinically isolated fluconazole- or caspofungin-resistant C. albicans strains. It also reduced biofilm formation and hyphal growth. Treatment with Hi protected Caenorhabditis elegans against infection with C. albicans and enhanced the expression of antimicrobial genes in worms infected with C. albicans. Aside from its antifungal activities against C. albicans, Hi challenge attenuated the LPS-induced expression of pro-inflammatory cytokines (IL-6, IL-1β, and CCL-2) in macrophages. Overall, Hi is a natural compound with antifungal and anti-inflammatory properties, making Hi a promising platform with which to fight against fungal infections.

Phytochemical and GC-MS analysis of Acrostichum aureum Linn.

Acrostichum aureum Linn. is a mangrove fern belonging to Division Pterophyta. Rhizome and leaves of the plant have been reported to possess several medicinal properties. But no reports on phytochemical analysis of hexane extract of leaves of this plant is available as on date. Hence an attempt has been made to analyze the phytochemicals present in hexane extract of leaves of Acrostichum aureum Linn. From the analysis it was found that the hexane extract of Acrostichum aureum Linn. contains phytochemicals like alkaloids, glycosides, flavonoids, tannins, phenols, saponins, proteins and carbohydrates. From the GC-MS analysis it was found that Eucalyptol, a monoterpenoid was the major compound followed by alpha.-Terpinyl acetate, a natural monoterpenoid. It was concluded that the hexane extract of Acrostichum aureum contains multitude of phytochemicals which accounts for its medicinal properties.

Structure Confirmation of Dechlorotrichotoxin A through Stereoselective Total Synthesis.

The stereoselective total synthesis of dechlorotrichotoxin A, alongside the synthesis of a 1:1 10E/Z mixture of trichotoxin A, was successfully achieved, commencing from the natural monoterpenoid (-)-citronellal. Key steps in the synthesis involved introducing three alkenes and establishing a stereogenic secondary alcohol center. These transformations were accomplished through olefin cross-metathesis, Tebbe olefination, and enantioselective allylation using a chiral phosphoric acid. A comparison of the spectroscopic data between the synthetic dechlorotrichotoxin A and the reported spectra confirmed that the polyketide isolated from a Smenospongia species corresponds to trichotoxin A rather than dechlorotrichotoxin A.

Hinokitiol for hypertensive emergencies: effects on peripheral resistance, cardiac load, baroreflex sensitivity, and electrolytes balance

Hinokitiol, a natural monoterpenoid, has been shown previously to possess a potent vasodilating activity in vitro in both control and hypertensive aortae. Here, the antihypertensive and cardioprotective effects of an intravenous hinokitiol injection were fully investigated in angiotensin II-induced hypertensive emergency in rats. Hinokitiol intravenous injection was prepared in the form of self-nanoemulsifying drug delivery system. Rat’s arterial and ventricular hemodynamics were measured in real-time recordings in addition to surface electrocardiogram while slow injection of cumulative doses of hinokitiol or vehicle as well as time control. Hinokitiol at dose 10 mg/kg showed a considerable reduction in the raised systolic blood pressure (30 mmHg) within only 30 min. The decrease in blood pressure seems to be mediated through a reduction in peripheral resistance, as appears from the decreases in diastolic pressure, dicrotic notch pressure, and pulse pressure. In addition, hinokitiol injection reduced heart load due to the decrease in heart rate, increases in cycle duration (particularly the non-ejection duration) and diastolic duration, and decreases in end-diastolic pressure. An effect most likely mediated via prolongation of ventricular repolarization as appears from the increases in PR, QTc, and JT intervals. However, acute intravenous injection of hinokitiol neither affected the baroreflex sensitivity nor sodium/potassium balance. In conclusion, acute hinokitiol intravenous injection markedly reduced severe hypertension in rats. This effect seems to be mediated through decreasing peripheral resistance and decreasing cardiac load, suggesting that it is an effective treatment in hypertensive emergencies after clinical evaluation.

Antimicrobial and Antivirulence Activities of Carvacrol against Pathogenic Aeromonas hydrophila.

Aeromonas hydrophila is a ubiquitous Gram-negative opportunistic pathogen in the freshwater environment and the most common cause of bacterial septicemia in aquaculture. In this study, we investigated the impact of carvacrol, a natural monoterpenoid found in herbs, on the virulence of A. hydrophila in vitro and the antibacterial effect in combination with antibiotics. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of carvacrol against A. hydrophila NJ-35 were 125 µg/mL and 250 µg/mL, respectively. Carvacrol could inhibit the virulence factors (biofilm, protease, exopolysaccharide, and hemolysin) of A. hydrophila, and the antibiofilm potential of carvacrol was further verified by microscopic detection. Transcriptional analyses showed that the gene expression of flaB, ompA, aha, ahp, ela, act, aerA, AhyR, and hly were marked as downregulated. The checkerboard assay results showed that carvacrol did not have an antagonistic effect in combination with antibiotics (florfenicol, enrofloxacin, thiamphenicol, or doxycycline hydrochloride) commonly used in aquaculture but possessed an additive-synergistic effect with neomycin sulfate. In vivo studies demonstrated that carvacrol protected grass carp (Ctenopharyngodon idella) from A. hydrophila infection. Our results indicated that carvacrol possessed significant anti-bacterial and anti-virulence effects on A. hydrophila.

Carvacrol Derivatives as Antifungal Agents: Synthesis, Antimicrobial Activity and in Silico Studies on Carvacryl Esters.

Chemical modifications of natural monoterpenoids to various derivatives have been reported to result in enhancement of biological activities when compared to parent compounds. In this context a well-known biocide and food additive, carvacrol, served as a basic scaffold onto which a phenolic functionality transformation by introducing acyl groups was performed. By using this simple methodology, we obtained a small series of 25 esters. For each of the obtained compounds we have performed structural characterization, in vitro antimicrobial testing and in silico calculation of physico-chemical, pharmacokinetic and toxicological properties. Despite numerous data on the synthesis and bioactivity of carvacryl ester lower homologues, there are scarce data on esters with acid components higher than C9, so that among 25 compounds, 10 were reported for the first time (spectral characterization for 12 are herein the first reported). Our research is also the first comprehensive study of carvacryl esters antifungal and of medium/long chain fatty acid esters antibacterial activities. Interesting result is that all the synthesized esters, regardless the nature of the R residue, have shown activity on fungal strain Aspergilus niger and on yeast Candida albicans comparable to carvacrol. Besides presented experimental data, implementation of in silico calculation of physico-chemical, pharmacokinetic and toxicological properties on the prepared compounds, may be valuable information in further research.

Vortex-assisted dispersive liquid–liquid microextraction using thymol based natural deep eutectic solvent for trace analysis of sulfonamides in water samples: Assessment of the greenness profile using AGREE metric, GAPI and analytical eco-scale

Applying the concepts of green analytical chemistry (GAC) across the whole method development is gaining more interest with the aim of using eco-friendly solvents and minimizing waste generation. Therefore, replacing the conventional methods with benign alternatives has been the aim of many researchers and practitioners worldwide. Natural deep eutectic solvents (NDESs) can be considered as a green alternative to the toxic organic solvents. In this work, a thymol based NDES was utilized for the first time in the extraction and trace analysis of four different sulfonamides (Sulfapyridine, sulfamethazine, sulfamethoxazole and Sulfaphenazole) in different water samples using dispersive liquid–liquid microextraction (DLLME). Two different groups of hydrophobic NDESs were prepared and tested as microextraction solvents, using the natural monoterpenoids (menthol and thymol) in combination with different acids and an alcohol. The results revealed that thymol/acetic acid DES had the best extraction recovery. Dispersion of the extracting solvents was achieved via vortex mixing. All DLLME parameters were optimized. The optimized method showed low detection limits (0.78 – 3.42 ng mL−1). A good linearity (5–5000 ng mL−1) with excellent determination coefficients (r2 ≥ 0.9991) was obtained. Accuracy and precision showed good results with % recovery in the range of 81.3–105.2 % and %RSD ranging from 1.3 to 7.9. The proposed method was successfully applied for the trace analysis of the target analytes in different water samples. Finally, the greenness profile was assessed by Analytical Eco-scale, Green Analytical Procedure Index (GAPI) and AGREE metric and comparison showed the superiority of the proposed method over other published methods. In conclusion, the reported method can be considered as a valid eco-friendly alternative for the classical and conventional hydrophobic DES-based DLLME methods for the routine analysis of sulfonamides in different water samples.

Competitive interaction of thymol with cviR inhibits quorum sensing and associated biofilm formation in Chromobacterium violaceum.

Biofilm formation associated with quorum sensing (QS) is a community behaviour displayed by many gram-negative pathogenic bacteria that provide survival advantages in hostile conditions. The inhibitors of QS interrupt bacterial communication and coordinated cell signalling for community aggregation in the biofilm. Thymol, a natural monoterpenoid, was tested against QS in Chromobacterium violaceum. As the first step, the interaction of thymol with cviR protein was investigated using in silico approach followed by validation using detailed in vitro experiments. The QS and biofilm studies were performed using the wild type of strain C. violaceum ATCC 12,472 and a mini-Tn5 mutant CV026. The MIC of thymol was established by the broth micro-dilution method, and IC50 value for violacein inhibition was quantified spectrophotometrically by extracting the violacein from the treated cells. Inhibitory effect of thymol on the biofilm was quantified by the crystal violet staining method, and scanning electron microscopy (SEM) was employed for biofilm visualization. The expression of biofilm associated genes (hmsH, hmsR, pilB, and pilT) was evaluated by qRT-PCR analysis. The in silico molecular interactions of thymol with cviR exhibited a G-score of - 5.847kcal/mol, binding with TYR-80 and SER-155 by Pi-Pi stacking and H-bond, respectively. The MIC of thymol was 160µg/mL, and the IC50 for violacein inhibition was estimated to be 28µg/mL. The thymol treatment significantly reduced the biofilm viability and biomass by > 80% along with disruption of the well-organized biofilm architecture. QS inhibitory activity of thymol resulted in the reduction of exopolysaccharide production, swarming motility, and downregulation of biofilm-associated hmsH, hmsR, pilB, and pilT genes. This data establishes the QS inhibitory role of thymol in the biofilm formation in C. violaceum.

Citronellol exerts lung protective and anti‐inflammatory effects through hampering NF‐κB in lipopolysaccharide‐induced acute lung injury in mice

BackgroundAcute lung injury (ALI) is one of the most serious conditions characterized by an exacerbation of inflammatory response in the lungs that can result from lung infection. Citronellol, a natural monoterpenoid found in citronella oil and other natural sources. In this study, the lung protective and anti‐inflammatory effects of citronellol were investigated in ALI induced by Lipopolysaccharide (LPS) in mice.Methodadult mice were allocated into groups, control mice received normal saline. Mice in the induction group received LPS 10mg/kg/day intraperitoneally and euthanized 2 hours later. Mice in the treatment groups received either 50mg or 100mg/kg/day of oral citronellol for 5 consecutive days prior to LPS injection.ResultsPretreatment with citronellol (50mg/kg/day) attenuated lung inflammatory events as observed from the significant reduction of TNF‐α (6.02±1.039 vs 29.20±4.77) and COX2 (4.12±0.23 vs 10.58±0.77) mRNA expressions in lung tissue compared to non‐treated mice. Interestingly, increasing the dose of citronellol to 100mg/kg/day also resulted in a significant reduction in both TNF‐α (3.30±0.745 vs 29.20±4.77) and COX2 (4.62±0.58 vs 10.58±0.77) mRNA expression compared to non‐treated mice.Looking for the upstream events revealed that NF‐κB gene expression was significantly hampered by citronellol 50mg/kg/day (5.11 ± 1.096 vs 11.88±1.57) and 100mg/kg/day (3.22± 0.253 vs 11.88±1.57) compared to non‐treated mice. Analysis of the data revealed that the effect of citronellol were dose dependent in terms of TNF‐α and NF‐κB gene expression.ConclusionThis study clearly revealed that citronellol exerted anti‐inflammatory and lung‐protective effects in LPS‐induced acute lung injury. The observed effects were dose‐independent and resulted through hampering of NF‐κB pathway.

Vapour–liquid coexistence of natural phenolic monoterpenoid, thymol: comparison with structural isomer, carvacrol

Thymol, a naturally occurring structural isomer of carvacrol, is known to exhibit medicinal properties. Since vapour–liquid equilibria data are critical for the design of efficient separation processes, theoretical methods and molecular simulations in conjunction with a simple united atom force field are employed to predict the coexistence properties; also at high temperatures where experimental data are scarce. Process design simulators used to model separation processes employ the equation of state approach which requires as input the critical state properties and acentric factor. Here, these inputs are computed using structure–property relations for use with the theoretical approach and are also determined from the more fundamental molecular simulations to be Tc = 70216 K, Pc = 336 bar, Vc = 48637 cc/mol and ω = 0.459. The structure of the coexisting liquid phase has been investigated using the radial distribution functions and number integrals to determine the extent of association present. The simple united atom force field captures the differences in the phase behaviour of thymol with that of carvacrol that arise due to steric effects of the relative placement of the hydroxyl group with respect to the methyl and isopropyl groups on the aromatic ring.

Molecular determinants for the chemical activation of the warmth-sensitive TRPV3 channel by the natural monoterpenoid carvacrol

Transient receptor potential vanilloid 3 (TRPV3), robustly expressed in the skin, is a nonselective calcium-permeable cation channel activated by warm temperature, voltage, and certain chemicals. Natural monoterpenoid carvacrol from plant oregano is a known skin sensitizer or allergen that specifically activates TRPV3 channel. However, how carvacrol activates TRPV3 mechanistically remains to be understood. Here, we describe the molecular determinants for chemical activation of TRPV3 by the agonist carvacrol. Patch clamp recordings reveal that carvacrol activates TRPV3 in a concentration-dependent manner, with an EC50 of 0.2 mM, by increasing the probability of single-channel open conformation. Molecular docking of carvacrol into cryo-EM structure of TRPV3 combined with site-directed mutagenesis further identified a unique binding pocket formed by the channel S2-S3 linker important for mediating this interaction. Within the binding pocket consisting of four residues (Ile505, Leu508, Arg509, and Asp512), we report that Leu508 is the most critical residue for the activation of TRPV3 by carvacrol, but not 2-APB, a widely used nonspecific agonist and TRP channel modulator. Our findings demonstrate a direct binding of carvacrol to TRPV3 by targeting the channel S2-S3 linker that serves as a critical domain for chemical-mediated activation of TRPV3. We also propose that carvacrol can function as a molecular tool in the design of novel specific TRPV3 modulators for the further understanding of TRPV3 channel pharmacology.

Therapeutic Potential of Perillaldehyde in Ameliorating Vulvovaginal Candidiasis by Reducing Vaginal Oxidative Stress and Apoptosis.

Vulvovaginal candidiasis (VVC) is one of the most frequent diseases induced by Candida albicans (C. albicans) during pregnancy, which results in enormous pain to women and their partners in daily life. Perillaldehyde (PAE), a natural monoterpenoid, has significant anti-microbial, anti-inflammatory and anti-oxidation effects. Reactive oxygen species (ROS) are key factors for the host to resist the invasion of fungi. However, excess ROS can cause additional damage independent of the pathogen itself, and the mechanism of ROS in VVC has not been investigated. In this murine study, we revealed that C. albicans infection increased the expression of NADPH oxidase 2 (NOX2) and the content of malonaldehyde (MDA). C. albicans inhibited the activity of antioxidant enzymes in the vagina, including superoxide dismutase (SOD), Catalase (CAT), glutathione peroxidase (GSH-PX) and heme oxygenase (HO-1), which were returned to normal levels after treatment with PAE. Furthermore, PAE inhibited the activities of Keap1 and promoted Nrf2 transfer from cytoplasm to nucleus, which were mediated by excessive accumulation of ROS in the VVC mice. In this study, we also indicated that PAE inhibited the apoptosis of vagina cells via Caspase 9- Caspase 7-PARP pathway and prevented the release of IL-1ꞵ in VVC mice. In summary, this study revealed that the treatment of VVC in mice with PAE might be mediated by inhibition of ROS, and established the therapeutic potential of PAE as an antifungal agent for the treatment of VVC.

Growth-phase specific regulation of cviI/R based quorum sensing associated virulence factors in Chromobacterium violaceum by linalool, a monoterpenoid.

Quorum sensing (QS)-dependent gene regulation in bacteria performs a vital role in synchronization of cell-density-dependent functions. In Chromobacterium violaceum QS-dependent cviI/R regulatory genes are activated during the mid- or late-exponential phase of growth. However, sufficient evidence is lacking on the role of QS inhibitors on gene regulation at different phases of growth. Hence, we report the role of linalool, a natural monoterpenoid on QS mediated gene regulation at different stages of growth in C. violaceum by performing biosensor, growth kinetic and gene expression studies. In vitro and in vivo studies were performed for establishing role of linalool in reducing the virulence and infection by using HEK-293T cell lines and Caenorhabditis elegans models respectively. C. violaceum CV026 with C6-HSL was used as control. The results showed linalool to be a QS inhibitor with an estimated IC50 of 63µg/mL for violacein inhibition. At this concentration the cell density difference (delta OD600) of 0.14 from the compound was observed indicating the quorum concentration. The expression of cviI/R was initiated at mid-log phase (~ 18h) and reached the maximum at 36h in control whereas in treatment it remained significantly downregulated at all time points. The expression of violacein biosynthetic genes vioA, vioC, vioD and vioE was also downregulated by linalool. Infection studies with linalool showed higher survival rates in HEK-293T cell lines and C. elegans compared to the infection control. Taken together, this study proves linalool to be a QS inhibitor capable of attenuation of QS by controlling the cell density through cviI/R downregulation at the early phase of growth and hence offering scope for its application for controlling infections.