Effects of monoterpenes on ion channels of excitable cells

Utilization of experimental design in the formulation and optimization of hyaluronic acid-based nanoemulgel loaded with a turmeric-curry leaf oil nanoemulsion for gingivitis

Numerous problems affect oral health, and intensive research is focused on essential oil-based nanoemulsions that might treat prevent or these problems. Nanoemulsions are delivery systems that enhance the distribution and solubility of lipid medications to targeted locations. Turmeric (Tur)- and curry leaf oil (CrO)-based nanoemulsions (CrO-Tur-self-nanoemulsifying drug delivery systems [SNEDDS]) were developed with the goal of improving oral health and preventing or treating gingivitis. They could be valuable because of their antibacterial and anti-inflammatory capabilities. CrO-Tur-SNEDDS formulations were produced using the response surface Box-Behnken design with different concentrations of CrO (120, 180, and 250 mg), Tur (20, 35, and 50 mg), and Smix 2:1 (400, 500, and 600 mg). The optimized formulation had a bacterial growth inhibition zone of up to 20 mm, droplet size of less than 140 nm, drug-loading efficiency of 93%, and IL-6 serum levels of between 950 ± 10 and 3000 ± 25 U/ml. The optimal formulation, which contained 240 mg of CrO, 42.5 mg of Tur, and 600 mg of Smix 2:1, was created using the acceptable design. Additionally, the best CrO-Tur-SNEDDS formulation was incorporated into a hyaluronic acid gel, and thereafter it had improved ex-vivo transbuccal permeability, sustained in-vitro release of Tur, and large bacterial growth suppression zones. The optimal formulation loaded into an emulgel had lower levels of IL-6 in the serum than the other formulations evaluated in rats. Therefore, this investigation showed that a CrO-Tur-SNEDDS could provide strong protection against gingivitis caused by microbial infections.

Antimicrobial peptides in combination with citronellal efficiently kills multidrug resistance bacteria

BACKGROUND

Antimicrobial peptides (AMPs) are considered as the most potential alternatives to antibiotics, but they have several drawbacks, including high cost, medium antimicrobial efficacy, poor cell selectivity, which limit clinical application. To overcome the above problems, combination therapy of AMPs with adjuvants might maximize the effectiveness of AMPs. We found that citronellal can substantially potentiate the ZY4R peptide efficacy against Escherichia coli ATCC25922. However, it is unclear whether ZY4R/citronellal combination poses synergistic antimicrobial effects against most bacteria, and their synergy mechanism has not been elucidated.

PURPOSE

To investigate synergistic antimicrobial efficacies, biosafety, and synergy mechanism of ZY4R/citronellal combination.

METHOD

Checkerboard, time-kill curves, cytotoxicity assays, and in vivo animal models were conducted to assess synergistic antimicrobial effects and biosafety of the ZY4R/citronellal combination. To evaluate their synergy mechanism, a series of cell-based assays and transcriptome analysis were performed.

RESULTS

ZY4R/citronellal combination exhibited synergistic antimicrobial effects against 20 clinically significant pathogens, with the fractional inhibitory concentration index (FICI) ranging from 0.313 to 0.047. Meanwhile, ZY4R/citronellal combination enhanced antimicrobial efficacies without compromising cell selectivity, contributing to decreasing drug dosage and improving biosafety. Compared with ZY4R (4 mg/kg) and citronellal (25 mg/kg) alone, ZY4R (4 mg/kg)/citronellal (25 mg/kg) combination significantly decreased the bacterial load in peritoneal fluid, liver, and kidney (P < 0.05) and alleviated pathological damage of the organs of mice. Mechanistic studies showed that ZY4R allowed citronellal to pass through the outer membrane rapidly and acted on the inner membrane together with citronellal, causing more potent membrane damage. The membrane damage prompted the continuous accumulation of citronellal in cells, and citronellal further induced energy breakdown and inhibited exopolysaccharide (EPS) production, which aggravated ZY4R-induced outer membrane damage, thereby resulting in bacterial death.

CONCLUSIONS

ZY4R/citronellal combination exhibited broad-spectrum synergy with a low resistance development and high biosafety. Their synergy mechanism acted on two important cellular targets (energy metabolism and membrane integrity). Combination therapy of ZY4R with citronellal may be a promising mixture to combat bacterial infections facing an antibiotic-resistance crisis.

Treating Epilepsy with Natural Products: Nonsense or Possibility?

Epilepsy is a neurological disease characterized by recurrent seizures that can lead to uncontrollable muscle twitching, changes in sensitivity to sensory perceptions, and disorders of consciousness. Although modern medicine has effective antiepileptic drugs, the need for accessible and cost-effective medication is urgent, and products derived from plants could offer a solution. For this review, we have focused on natural compounds that have shown anticonvulsant activity in in vivo models of epilepsy at relevant doses. In some cases, the effects have been confirmed by clinical data. The results of our search are summarized in tables according to their molecular targets. We have critically evaluated the data we present, identified the most promising therapeutic candidates, and discussed these in the text. Their perspectives are supported by both pharmacokinetic properties and potential interactions. This review is intended to serve as a basis for future research into epilepsy and related disorders.

Inhibitory effects of linalool, an essential oil component of lavender, on nociceptive TRPA1 and voltage-gated Ca2+ channels in mouse sensory neurons

Linalool, an essential oil component of lavender is commonly used in fragrances. It is known that linalool has anxiolytic, sedative, and analgesic actions. However, the mechanism of its analgesic action has not yet been fully clarified. Pain signals elicited by the activation of nociceptors on peripheral neurons are transmitted to the central nervous system. In the present study, we investigated the effects of linalool on transient receptor potential (TRP) channels and voltage-gated channels, both of which are important for pain signaling via nociceptors in somatosensory neurons. For detection of channel activity, the intracellular Ca²⁺ concentration ([Ca²⁺]_i) was measured using a Ca²⁺-imaging system, and membrane currents were recorded using the whole-cell patch-clamp technique. Analgesic actions were also examined in vivo. In mouse sensory neurons linalool at concentrations that did not induce [Ca²⁺]_i increases did not affect [Ca²⁺]_i responses to capsaicin and acids, TRPV1 agonists, but suppressed those induced by allyl isothiocyanate (AITC) and carvacrol, TRPA1 agonists. Similar inhibitory effects of linalool were observed in cells that heterologously expressed TRPA1. Linalool attenuated the [Ca²⁺]_i increases induced by KCl and voltage-gated Ca²⁺ currents but only slightly suppressed voltage-gated Na^＋currents in mouse sensory neurons. Linalool diminished TRPA1-mediated nociceptive behaviors. The present data suggest that linalool exerts an analgesic action via the suppression of nociceptive TRPA1 and voltage-gated Ca²⁺ channels.

Evaluation of the antinociceptive effect generated by citronellal monoterpene isomers

Due to the complex nature of pain and the participation of physical, cognitive, psychological and behavioral aspects, pain management has several approaches. The use of medicinal plants in developing countries is quite expressive. Seeking new options for the treatment of emerging or debilitating diseases. Therefore, the present study seeks to elucidate the effects of the monoterpene, citronellal, differentiating its activity by isomers (R)-(+) and (S)-(-) citronellal. The study used several methods to evaluate the effects of citronellal isomers on motor coordination, nociceptive response, and the involvement of opioid, glutamatergic, and transient receptor pathways. The methods included rota-rod, hot-plate, and formalin tests, as well as the use of specific inhibitors and agonists. Data were analyzed using inferential statistics with a 95% confidence level. Both isomers did not significantly affect the motor coordination of the studied animals. The isomer (S)-(-) citronellal showed better results in relation to its structural counterpart, managing to have an antinociceptive effect in the formalin and hot plate tests with a lower concentration (100 mg/kg) and presenting fewer side effects, however, the this study was not able to elucidate the mechanism of action of this isomer despite having activity in studies with substances that act on specific targets such as glutamate and capsaicin, its activity was not reversed with the use of antagonists for pathways related to nociception. While the (R)-(+) citronellal isomer, despite showing total activity only at a concentration of 150 mg/kg, was able to determine its mechanism of action related to the opioid pathway by reversing its activity by the antagonist naloxone, being this is a pathway already correlated with nociception control treatments, however, it is also related to some unwanted side effects. In this way, new studies are sought to elucidate the mechanism related to the isomer (S)-(-) citronellal and a possibility of use in other areas related to the treatment of pain or inflammation.

Transient receptor potential vanilloid 1 (TRPV1)-independent actions of capsaicin on cellular excitability and ion transport

Capsaicin is a naturally occurring alkaloid derived from chili pepper that is responsible for its hot pungent taste. Capsaicin is known to exert multiple pharmacological actions, including analgesia, anticancer, anti-inflammatory, antiobesity, and antioxidant effects. The transient receptor potential vanilloid subfamily member 1 (TRPV1) is the main receptor mediating the majority of the capsaicin effects. However, numerous studies suggest that the TRPV1 receptor is not the only target for capsaicin. An increasing number of studies indicates that capsaicin, at low to mid µM ranges, not only indirectly through TRPV1-mediated Ca²⁺ increases, but also directly modulates the functions of voltage-gated Na⁺ , K⁺ , and Ca²⁺ channels, as well as ligand-gated ion channels and other ion transporters and enzymes involved in cellular excitability. These TRPV1-independent effects are mediated by alterations of the biophysical properties of the lipid membrane and subsequent modulation of the functional properties of ion channels and by direct binding of capsaicin to the channels. The present study, for the first time, systematically categorizes this diverse range of non-TRPV1 targets and discusses cellular and molecular mechanisms mediating TRPV1-independent effects of capsaicin in excitable, as well as nonexcitable cells.

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.

Identification of D-Limonene Metabolites by LC-HRMS: An Exploratory Metabolic Switching Approach in a Mouse Model of Diet-Induced Obesity

Metabolic switching has been raised as an important phenomenon to be studied in relation to xenobiotic metabolites, since the dose of the exposure determines the formation of metabolites and their bioactivity. Limonene is a monoterpene mostly found in citrus fruits with health activity, and its phase II metabolites and activity are still not clear. The aim of this work was to evaluate the effects of D-limonene in the development of diet-induced obesity in mice and to investigate metabolites that could be generated in a study assessing different doses of supplementation. Animals were induced to obesity and supplemented with 0.1% or 0.8% D-limonene added to the feed. Limonene phase I and II metabolites were identified in liver and urine by LC-ESI-qToF-MS/MS. To the best of our knowledge, in this study three new phase I metabolites and ten different phase II metabolites were first attributed to D-limonene. Supplementation with 0.1% D-limonene was associated with lower weight gain and a trend to lower accumulation of adipose tissue deposits. The metabolites limonene-8,9-diol, perillic acid and perillic acid-8,9-diol should be explored in future research as anti-obesogenic agents as they were the metabolites most abundant in the urine of mice that received 0.1% D-limonene in their feed.

Mechanisms of Actions Involved in The Antinociceptive Effect of Estragole and its β-Cyclodextrin Inclusion Complex in Animal Models

(1) Background: estragole is a monoterpene found in the essential oils of several aromatic plants, which can be used for several pharmacological activities. The aim of this study was to evaluate the antinociceptive effect of estragole (Es) and its β-cyclodextrins inclusion complex (Es/β-CD). (2) Methods: the effects of Es and Es/β-CD on the central nervous system (CNS) were evaluated through open field and rota-rod assays, and the antinociceptive effect in formalin models, abdominal writhing induced by acetic acid, hot plate, tail flick test and plantar mechanical hyperalgesia. (3) Results: Es and Es/β-CD showed no alterations on the CNS evaluated parameters and the results suggested there was an antinociceptive action in the formalin, abdominal writhing, hot plate, tail flick tests and plantar mechanical hyperalgesia, proposing the involvement of the nitric oxide, glutamatergic signaling pathways, cyclic guanosine monophosphate and vanilloid pathways. (4) Conclusion: the results suggest that Es and Es/β-CD have a promising antinociceptive potential as a possible alternative for the pharmacological treatment of pain, also showing that the encapsulation of Es in β-cyclodextrins probably improves its pharmacological properties, since the complexation process involves much lower amounts of the compound, contributing to better bioavailability and a lower probability of adverse effect development.

Effects of cannabinoids on ligand-gated ion channels

Phytocannabinoids such as Δ⁹-tetrahydrocannabinol and cannabidiol, endocannabinoids such as N-arachidonoylethanolamine (anandamide) and 2-arachidonoylglycerol, and synthetic cannabinoids such as CP47,497 and JWH-018 constitute major groups of structurally diverse cannabinoids. Along with these cannabinoids, CB1 and CB2 cannabinoid receptors and enzymes involved in synthesis and degradation of endocannabinoids comprise the major components of the cannabinoid system. Although, cannabinoid receptors are known to be involved in anti-convulsant, anti-nociceptive, anti-psychotic, anti-emetic, and anti-oxidant effects of cannabinoids, in recent years, an increasing number of studies suggest that, at pharmacologically relevant concentrations, these compounds interact with several molecular targets including G-protein coupled receptors, ion channels, and enzymes in a cannabinoid-receptor independent manner. In this report, the direct actions of endo-, phyto-, and synthetic cannabinoids on the functional properties of ligand-gated ion channels and the plausible mechanisms mediating these effects were reviewed and discussed.

GC-MS Profiling of Naturally Extracted Essential Oils: Antimicrobial and Beverage Preservative Actions

The purpose of this study was to demonstrate the antimicrobial effects of natural essential oils (EO) and determine their preservative action. Eight natural essential oils were tested against Staphylococcus aureus, Escherichia coli, and Candida albicans representing gram positive, gram negative, and fungi, respectively. The plant materials were used in this study viz. Thymus vulgaris—thyme (TV), Mentha virdis (MV), Mentha longifolia (ML), Rosmarinus officinalis—rosemary (RO), Lavandula dentata—lavender (LD), Origanum majorana—oregano (OM), which belong to the Lamiaceae family. The other two plants were Cymbopogon citratus—lemon grass (family Poaceae) (CC), and Eucalyptus globulus (family Myrtaceae) (EG). Employing the disc diffusion susceptibility test, minimum inhibitory and minimum bactericidal concentrations were estimated for each oil, followed by the addition of oils to pasteurized apple juice after microbial induction. The results revealed that thyme oil showed the maximum zone of inhibition against all tested microbes enriched with monoterpenes class viz. eucalyptol (24.3%), thymol (17.4%), and γ-terpinene (15.2%). All other tested oils exhibited a concentration-dependent inhibition of growth and their MIC ranged from 0.1 to 100 µL/mL. The recorded minimum bactericidal concentration values were apparently double the minimum inhibitory concentration. The EO of Mentha virdis followed by Mentha longifolia showed maximum antimicrobial activity against the tested organisms in pasteurized apple juice. A gas chromatography–mass spectroscopy (GC–MS) analysis of lemon grass, thyme, and Mentha virdis essential oils showed their enrichment with monoterpenes class recording 97.10, 97.04, and 97.61%, respectively.

TRPA1-mediated repellency behavior in the red flour beetle Tribolium castaneum

The sensory perception of irritant chemicals results in escape and repellency behavioral patterns in insects. Transient receptor potential channels are cation channels that function as sensor proteins for several types of signals, such as light, sound, temperature, taste, as well as chemical and physical stimuli; among these, the TRPA channel is widely conserved and activated by irritant chemicals. Certain plant-derived essential oils (EOs), produced by secondary metabolism, are mixtures of volatile compounds, which are used as repellents because they contain environmentally sustainable ingredients. Citronellal, which is present in citronella EO from Cymbopogon species, is a potentially viable insect repellent; however, the repellency capability against coleopteran beetles remains limited. We investigated the citronellal-derived repellency behavior for the red flour beetle Tribolium castaneum, in which TcTRPA1 and odorant receptor co-receptor (Orco) expressions were mediated by RNA interference. Area-preference tests showed dose-dependent repellency behavior for citronellal; additionally, both TcTRPA1 and TcOrco double-strand RNA (dsRNA) micro-injection showed clear TcTRPA1 and TcOrco transcript reductions, and only TcTRPA1 dsRNA treatment significantly impaired repellency behavior. The relative expression level of the TcTRPA1 transcripts, evaluated by quantitative reverse-transcription PCR (qRT-PCR), revealed dominant expression in the antennae, indicating the antennae-expressed TcTRPA1-mediated repellency behavior.

γ-Terpinene complexed with β-cyclodextrin attenuates spinal neuroactivity in animals with cancer pain by Ca2+ channel block

OBJECTIVES

Considering that γ-terpinene (γ-TPN) is a monoterpene found in Cannabis oil, with high lipophilicity and limited pharmacokinetics, our objective was to evaluate whether its complexation in β-cyclodextrin (γ-TPN/β-CD) could improve its physicochemical properties and action on cancer pain, as well as verify the mechanisms of action involved.

METHODS

The γ-TPN/β-CD was prepared and submitted to physicochemical characterization. Animals with sarcoma 180 were treated (vehicle, γ-TPN 50 mg/kg, γ-TPN/β-CD 5 mg/kg or morphine) and assessed for hyperalgesia, TNF-α and IL-1β levels, iNOS and c-Fos activity. The effects of γ-TPN on calcium channels were studied by patch-clamp and molecular docking.

RESULTS

β-CD improved the physicochemical properties and prolonged the anti-hyperalgesic effect of γ-TPN. This compound also reduced the levels of IL-1β, TNF-α and iNOS in the tumour, and c-Fos protein in the spinal cord. In addition, it reduced Ca2+ current, presenting favourable chemical interactions with different voltage-dependent calcium channels.

CONCLUSION

These results indicate that the complexation of γ-TPN into β-CD increases its stability and time effect, reducing spinal neuroactivity and inflammation by blocking calcium channels.

Phytochemicals Profiling, Antimicrobial Activity and Mechanism of Action of Essential Oil Extracted from Ginger (Zingiber officinale Roscoe cv. Bentong) against Burkholderia glumae Causative Agent of Bacterial Panicle Blight Disease of Rice

Essential oils protect plants, and due to their natural origin, there is much interest in using them as antimicrobial agents. The purpose of this study was to determine the phytochemical constituents of ginger essential oil (GEO), antimicrobial activity, and mode of action against Burkholderia glumae (Bg). In addition, the volatile active compounds (AIs) were studied using GC-MS, FTIR, and Raman spectroscopy. A total of 45 phytochemical components were detected and the most prevalent bioactive compounds were Geranial, 1,8-Cineole, Neral, Camphene, α-Zingiberene, and α-Farnesene. Furthermore, it was found that the most dominant terpenes in GEO were monoterpenes. The diameter zone of inhibition values varied from 7.1 to 15 mm depending on the concentration tested. In addition, the MIC and MBC values were 112.5 µL/mL. Faster killing time and lower membrane potential were observed in 1xMIC treatment compared to 0.5xMIC treatment, whereas the control had the maximum values. From observations of various images, it was concluded that the mode of action of GEO affected the cytoplasmic membrane, causing it to lose its integrity and increase its permeability. Therefore, the antibacterial study and mechanism of action revealed that GEO is very effective in suppressing the growth of B. glumae.

Terpinolene as an enhancer for ultrasonic disinfection of multi-drug-resistant bacteria in hospital wastewater

The present study reports for the first time, a novel disinfection method that combines ultrasonication with a natural biocide terpinolene to inhibit tough and opportunistic antimicrobial-resistant (AMR) microorganisms isolated from hospital wastewater treatment plant (HWWTP). The enhancement of the disinfection process was evaluated for the effect of ultrasonication power, operating temperature, and inoculum size. A hybrid methodology combining terpinolene with traditional physico-chemical method of acoustic cavitation delivered efficient disinfection of the secondary effluent of field scale HWWTP, amended with a higher inoculum size of multi-drug-resistant coliform bacteria Enterobactor sp., Citrobacter freundii, and Klebsiella pneumonia. A bacterial load of 6.4 log CFU/mL was completely eliminated in 25 min. The present study also reports that due to the hybrid process, a very small concentration of 0.312 mM (0.25 × Minimum Inhibitory Concentration or MBC) of terpinolene was enough to completely disinfect the multi-drug-resistant coliforms. The leakage of intracellular nucleic acids during the disinfection process suggested disruption of cell membrane as the primary mechanism of disinfection followed by disruption of cellular metabolic function measured by respiratory chain dehydrogenase activity. Moreover, this study is the first to prove that terpinolene remained stable even after the cavitation process, thus revealing possibilities of recycling of the natural compound for wastewater disinfection. The results of the present research suggest that using terpinolene as a bio-additive can efficiently eliminate hazardous multi-drug-resistant bacteria and drastically reduce operational time and cost thus rendering it suitable to replace conventional wastewater disinfection.

Carvone and its pharmacological activities: A systematic review

Natural products from plants have gained prominence in the search for therapeutic alternatives. Monoterpenes, such as carvone, are suggested as candidates for the treatment of several diseases. Therefore, the objective of this study is to review the pharmacological activities of carvone in experimental models in vitro and in vivo. For this, the searches were carried out in May 2020 (upgraded in July 2021) in the databases of PubMed, Web of Science and Scopus and gathered studies on the pharmacological activities of carvone. Two independent reviewers performed the selection of articles using the Rayyan application, extracted the relevant data and assessed the methodological quality of the selected studies using Syrcle's risk of bias tool. Ninety-one articles were selected that described 10 pharmacological activities of carvone, such as antimicrobial, antispasmodic, anti-inflammatory, antioxidant, antinociceptive, anticonvulsant, among others. The evaluation of the methodological quality presented an uncertain risk of bias for most studies. In light of that, carvone stands out as a viable and promising alternative in the treatment of several pathological conditions. However, carrying out studies to evaluate possible mechanisms of action and the safety of this monoterpene is recommended.

Proteomic analysis suggests that monoterpenes in lemongrass disrupt Ca2+ homeostasis in Haemaphysalis longicornis leading to mitochondrial depolarization and cytotoxicity

Complex mixtures of bioactive ingredients in plant essential oils present complex chemistries which involve different modes of action. An increasing body of scientific reports has recently focused on the acaricidal activities of plant essential oils attributed to their monoterpene components, but information about their underlying molecular mechanism of action is scarce. Here, after the chemical analysis of lemongrass oil, a proteomic analysis of the ovary, salivary gland, and midgut of Haemaphysalis longicornis exposed to Cymbopogon citratus (lemongrass) essential oil was performed via data-independent acquisition mass spectrometry (DIA-MS) technology to further elucidate the molecular mechanisms involved. Pathway analysis reveals the activation of metabolic pathways mediated by oxidoreductases and transferases. Furthermore, the upregulation of various calcium-associated proteins and the upregulation of cytochrome c1, cytochrome c oxidase polypeptide IV, and programmed cell death protein 6-like isoform X1 suggest a cytotoxic mode of action via the formation of reactive oxygen species (ROS), mitochondrial Ca²⁺ overload, mitochondrial uncoupling, and depolarization, and ATP depletion leading to either apoptotic or necrotic death. Morphological alterations observed after the RNAi of a major detoxification enzyme (glutathione S-transferase) merit further investigation. Hence, the cytotoxic mode of action exhibited by C. citratus oil could be vital for the development of eco-friendly acaricide.

Transcriptome profile of Haemaphysalis longicornis (Acari: Ixodidae) exposed to Cymbopogon citratus essential oil and citronellal suggest a cytotoxic mode of action involving mitochondrial Ca2+ overload and depolarization

Haemaphysalis longicornis is an ixodid tick species of medical and veterinary importance. Investigation into the acaricidal activities of botanicals have increased recently but information about their molecular mechanism of action is scarce. Here, RNA-seq analysis of the ticks exposed to Cymbopogon citratus essential oil and citronellal was performed and the responsive genes were identified. More than 6.39 G clean reads with Q₂₀ ≥ 94.88% were obtained for each H. longicornis sample, with an average GC content of 50.94%. Using the Trinity method, 166,710 unigenes with a mean length of 869 bp and a maximum contig length of 29,156 bp were obtained. The upregulation of genes was concentration-dependent in most of the treated groups. Many genes responsive to C. citratus oil and citronellal were stress-related and they include genes associated with adrenergic signaling/calcium channels, cGMP-PKG signaling, apoptosis, focal adhesion, ECM-receptor interaction, ubiquitin-mediated proteolysis, mTOR signaling pathway, and longevity regulating pathway. The upregulation of genes (CACNAID, ADCY9, TPM1, and MYH6) associated with calcium channels suggests a neurotoxic mode of action, whereas, the upregulation of apoptosis-associated genes (CYC, DRONC, CASP7, CASP9, BCL2L1, bcl-xL, etc.) suggests a cytotoxic mode of action. The metabolism of C. citratus essential oil generates oxidative stress which increases the intra-mitochondrial free Ca²⁺ and triggers the formation of reactive oxygen species (ROS) that culminates to mitochondrial depolarization, ATP depletion, and either necrotic or apoptotic death. The neurotoxic and cytotoxic effects exhibited by the monoterpenes in H. longicornis is vital and could be exploited for the advancement of acaricide development and eco-friendly tick control.

Monoterpenes: current knowledge on food source, metabolism, and health effects

Monoterpenes, volatile metabolites produced by plants, are involved in the taste and aroma perception of fruits and vegetables and have been used for centuries in gastronomy, as food preservatives and for therapeutic purposes. Biological activities such as antimicrobial, analgesic and anti-inflammatory are well-established for some of these molecules. More recently, the ability of monoterpenes to regulate energy metabolism, and exert antidiabetic, anti-obesity and gut microbiota modulation activities have been described. Despite their promising health effects, the lack of reliable quantification of monoterpenes in food, hindered the investigation of their role as dietary bioactive compounds in epidemiological studies. Moreover, only few studies have documented the biotransformation of these compounds and identified the monoterpene metabolites with biological activity. This review presents up-to-date knowledge about the occurrence of monoterpenes in food, their bioavailability and potential role in the modulation of intermediate metabolism and inflammation, focusing on novel findings of molecular mechanisms, underlining research gaps and new avenues to be explored.

Phenol group of terpenoids is crucial for antibacterial activity upon ion leakage

Plant tissues are natural sources of bioactive molecules to control pathogens that cause infections in plants and humans, as they contain secondary metabolites with antibacterial activities. Especially, terpenoids are responsible for the protection of various plants against herbivores and pathogens. In this study, we studied the antibacterial activity of 12 different terpenoid or related structures in a comparative way and revealed that the phenolic terpenoids are superior to other substituted derivatives against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria. We also aimed to analyse effect of these compounds on the bacteria cell wall structure and maintenance of homeostasis. We observed an immediate loss of cell membrane integrity and ion leakage upon treatment of both Gram-negative and Gram-positive cells with phenolic terpenoids carvacrol and thymol. After prolonged treatment, leakage of genetic material and increase of membrane permeability for molecules were also observed. Hydroxyl group of the phenol moiety was essential for this effect, since neither the O-methyl derivatives nor the benzylic partners were as effective. We thus propose that perturbation of ion homeostasis upon increase in cell wall permeability is key for the action of terpenoids against bacteria cells.

Apigenin and Structurally Related Flavonoids Allosterically Potentiate the Function of Human α7-Nicotinic Acetylcholine Receptors Expressed in SH-EP1 Cells

Phytochemicals, such as monoterpenes, polyphenols, curcuminoids, and flavonoids, are known to have anti-inflammatory, antioxidant, neuroprotective, and procognitive effects. In this study, the effects of several polyhydroxy flavonoids, as derivatives of differently substituted 5,7-dihydroxy-4H-chromen-4-one including apigenin, genistein, luteolin, kaempferol, quercetin, gossypetin, and phloretin with different lipophilicities (cLogP), as well as topological polar surface area (TPSA), were tested for induction of Ca²⁺ transients by α7 human nicotinic acetylcholine (α7 nACh) receptors expressed in SH-EP1 cells. Apigenin (10 μM) caused a significant potentiation of ACh (30 μM)-induced Ca²⁺ transients, but did not affect Ca²⁺ transients induced by high K⁺ (60 mM) containing solutions. Co-application of apigenin with ACh was equally effective as apigenin preincubation. However, the effect of apigenin significantly diminished by increasing ACh concentrations. The flavonoids tested also potentiated α₇ nACh mediated Ca²⁺ transients with descending potency (highest to lowest) by genistein, gossypetin, kaempferol, luteolin, phloretin, quercetin, and apigenin. The specific binding of α7 nACh receptor antagonist [¹²⁵I]-bungarotoxin remained unchanged in the presence of any of the tested polyhydroxy flavonoids, suggesting that these compounds act as positive allosteric modulators of the α7-nACh receptor in SH-EP1 cells. These findings suggest a clinical potential for these phytochemicals in the treatment of various human diseases from pain to inflammation and neural disease.

α-Phellandrene exhibits antinociceptive and tumor-reducing effects in a mouse model of oncologic pain

Medical reports indicate a prevalence of pain in 50% of patients with cancer. In this context, this article investigated the antinociceptive activity of α-PHE using in vivo Sarcoma-180-induced hypernociception in mice to detail its mechanism(s) of antinociception under different conditions of treatment and tumor progression. Firsty, in vitro cytotoxic action was assessed using melanoma B-16/F-10 and S-180 murine cells and colorimetric MTT assays. For in vivo studies, acute treatment with α-PHE (6.25, 12.5, 25 and 50 mg/kg orally by gavage) was performed on the 1st day after S-180 inoculation. Subacute treatments were performed for 8 days starting on the next day (early protocol) or on day 8 after S-180 inoculation (late protocol). For all procedures, mechanical nociceptive evaluations were carried out by von Frey's technique in the subaxillary region peritumoral tissue (direct nociception) and in right legs of S-180-bearing mice (indirect nociception). α-PHE showed in vitro cytotoxic action on B-16/F-10 and S-180 (CI₅₀ values of 436.0 and 217.9 μg/mL), inhibition of in vivo tumor growth (ranging from 47.3 to 82.7%) and decreased direct (peritumoral tissue in subaxillary region) and indirect (right leg) mechanical nociception in Sarcoma 180-bearing mice with early and advanced tumors under acute or subacute conditions of treatment especially at doses of 25 and 50 mg/kg. It improved serum levels of GSH as well as diminished systemic lipid peroxidation, blood cytokines (interleukin-1β, -4, -6, and tumor necrosis factor-α). Such outcomes highlight α-PHE as a promising lead compound that combines antinociceptive and antineoplasic properties. Its structural simplicity make it a cost-effective alternative, justifying further mechanistic investigations and the development of pharmaceutical formulations. Moreover, the protocols developed and standardized here make it possible to use Sarcoma-180 hypernociception model to evaluate the capacity of new antinociceptive molecules under conditions of cancer-related allodynia.

Medicine in motion: Opportunities, challenges and data analytics-based solutions for traditional medicine integration into western medical practice

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional pharmacopeias have been developed by multiple cultures and evaluated for efficacy and safety through both historical/empirical iteration and more recently through controlled studies using Western scientific paradigms and an increasing emphasis on data science methodologies for network pharmacology. Traditional medicines represent likely sources of relatively inexpensive drugs for symptomatic management as well as potential libraries of new therapeutic approaches. Leveraging this potential requires hard evidence for efficacy that separates science from pseudoscience.

MATERIALS AND METHODS

We performed a review of non-Western medical systems and developed case studies that illustrate the epistemological and practical translative barriers that hamper their transition to integration with Western approaches. We developed a new data analytics approach, in silico convergence analysis, to deconvolve modes of action, and potentially predict desirable components of TM-derived formulations based on computational consensus analysis across cultures and medical systems.

RESULTS

Abstraction, simplification and altered dose and delivery modalities were identified as factors that influence actual and perceived efficacy once a medicine is moved from a non-Western to Western setting. Case studies on these factors highlighted issues with translation between non-Western and Western epistemologies, including those where epistemological and medicinal systems drive markets that can be epicenters for zoonoses such as the novel Coronavirus. The proposed novel data science approach demonstrated the ability to identify and predict desirable medicinal components for a test indication, pain.

CONCLUSIONS

Relegation of traditional therapies to the relatively unregulated nutraceutical industry may lead healthcare providers and patients to underestimate the therapeutic potential of these medicines. We suggest three areas of emphasis for this field: First, vertical integration and embedding of traditional medicines into healthcare systems would subject them to appropriate regulation and evidence-based practice, as viable integrative implementation mode. Second, we offer a new Bradford-Hill-like framework for setting research priorities and evaluating efficacy, with the goal of rescuing potentially valuable therapies from the nutraceutical market and discrediting those that are pseudoscience. Third, data analytics pipelines offer new capacity to generate new types of TMS-inspired medicines that are rationally-designed based on integrated knowledge across cultures, and also provide an evaluative framework against which to test claims of fidelity and efficacy to TMS made for nutraceuticals.

Herbal Medicine in the Treatment of Epilepsy

Epilepsy is one of the most common disorders of the central nervous system. Although epilepsy is common worldwide, approximately 80% of epileptic patients live in the developing countries or those with low-middle income. Up until the second decade of the 20th century, epilepsy was treated mostly by traditional remedies. Today, antiepileptic drugs are used as a general treatment instead to prevent and control epileptic seizures. However, patient access to these drugs is hindered due to the healthcare systems of their countries and a number of other reasons, such as cultural, socio-demographic, and financial poverty. In addition, approximately 30-40%of epileptic patients suffer from refractory epilepsy, additionally, AEDs have adverse side-effects that can lead to treatment failure or reduce the patient's quality of life. Despite recent advances in the treatment of epilepsy, there is still a need for improving medical treatment with a particular focus on efficacy, safety, and accessibility. Since herbal medicines have been used for many centuries around the world for treating epilepsy, it is, therefore, plausible that a rigorous study on herbal medicine and phytochemical components within plants of various species and origin may lead to the discovery of novel AEDs. Nowadays, many medicinal plants used in different cultures and regions of the world have been identified. Most phytochemical components of these plants have been identified and, in some cases, their targets located. Therefore, it is possible that new, effective, and accessible anticonvulsants drugs can be obtained from a medicinal plant.

Potential modulating effect of the Ascaris suum nicotinic acetylcholine receptor (nAChR) by compounds GSK575594A, diazepam and flumazenil discovered by structure-based virtual screening approach

Parasitic infections are a widespread health problem and research of novel anthelmintic compounds is of the utmost importance. In this study we performed a virtual screening campaign by coupling ligand-based pharmacophore, homology modeling and molecular docking. The virtual screening campaign was conducted using a joined pool of the Drugbank database and a library of purchasable compounds in order to identify drug like compounds with similar pharmacological activity. Our aim was to identify compounds with a potential antihelmintic modulatory effect on nicotinic acetylcholine receptors (nAChR). We derived a 3D pharmacophore model based on the chemical features of known Ascaris suum nAChR modulators. To evaluate the in silico predictions, we tested selected hit compounds in contraction assays using somatic muscle flaps of the Ascaris suum neuromuscular tissue. We tested the modulatory effects of GSK575594A, diazepam and flumazenil hit compounds on nematode contractions induced by acetyl choline (ACh). The compound GSK575594A (3 μM) increased the E_max by 21 % with the EC₅₀ dose ratio of 0.96. Diazepam (100 μM) decreased the E_max by 15 % (1.11 g to 0.95 g) with the EC₅₀ ratio of 1.42 (shifted to the left from 11.25 to 7.93). Flumazenil decreased the EC₅₀ value (from 11.22 μM to 4.88 μM) value showing dose ratio of 2.30, and increased the E_max by 4 % (from 1.54 g to 1.59 g). The observed biological activity was rationalized by molecular docking calculations. Docking scores were calculated against several binding sites within the Ascaris suum homology model. We constructed the homology model using the ACR-16 subunit sequence. The compound GSK575594A showed strong affinity for the intersubunit allosteric binding site within the nAChR transmembrane domain. The binding modes of diazepam and flumazenil suggest that these compounds have a comparable affinity for orthosteric and allosteric nAChR binding sites. The selected hit compounds displayed potential for further optimization as lead compounds. Therefore, such compounds may be useful in neutralizing the growing resistance of parasites to drugs, either alone or in combination with existing conventional anthelmintics.

Capsaicin Is a Negative Allosteric Modulator of the 5-HT3 Receptor

In this study, effects of capsaicin, an active ingredient of the capsicum plant, were investigated on human 5-hydroxytryptamine type 3 (5-HT₃) receptors. Capsaicin reversibly inhibited serotonin (5-HT)-induced currents recorded by two-electrode voltage clamp method in Xenopus oocytes. The inhibition was time- and concentration-dependent with an IC₅₀ = 62 μM. The effect of capsaicin was not altered in the presence of capsazepine, and by intracellular BAPTA injections or trans-membrane potential changes. In radio-ligand binding studies, capsaicin did not change the specific binding of the 5-HT₃ antagonist [³H]GR65630, indicating that it is a noncompetitive inhibitor of 5-HT₃ receptor. In HEK-293 cells, capsaicin inhibited 5-HT₃ receptor induced aequorin luminescence with an IC₅₀ of 54 µM and inhibition was not reversed by increasing concentrations of 5-HT. In conclusion, the results indicate that capsaicin acts as a negative allosteric modulator of human 5-HT₃ receptors.

Monoterpenes Differently Regulate Acid-Sensitive and Mechano-Gated K2P Channels

Potassium K_2P (“leak”) channels conduct current across the entire physiological voltage range and carry leak or “background” currents that are, in part, time- and voltage-independent. The activity of K_2P channels affects numerous physiological processes, such as cardiac function, pain perception, depression, neuroprotection, and cancer development. We have recently established that, when expressed in Xenopus laevis oocytes, K_2P2.1 (TREK-1) channels are activated by several monoterpenes (MTs). Here, we show that, within a few minutes of exposure, other mechano-gated K_2P channels, K_2P4.1 (TRAAK) and K_2P10.1 (TREK-2), are opened by monoterpenes as well (up to an eightfold increase in current). Furthermor\e, carvacrol and cinnamaldehyde robustly enhance currents of the alkaline-sensitive K_2P5.1 (up to a 17-fold increase in current). Other members of the K_2P potassium channels, K_2P17.1, K_2P18.1, but not K_2P16.1, were also activated by various MTs. Conversely, the activity of members of the acid-sensitive (TASK) K_2P channels (K_2P3.1 and K_2P9.1) was rapidly decreased by monoterpenes. We found that MT selectively decreased the voltage-dependent portion of the current and that current inhibition was reduced with the elevation of external K⁺ concentration. These findings suggest that penetration of MTs into the outer leaflet of the membrane results in immediate changes at the selectivity filter of members of the TASK channel family. Thus, we suggest MTs as promising new tools for the study of K_2P channels’ activity in vitro as well as in vivo.

A regulatory domain in the K2P2.1 (TREK-1) carboxyl-terminal allows for channel activation by monoterpenes

Potassium K_2P ('leak') channels conduct current across the entire physiological voltage range and carry leak or 'background' currents that are, in part, time- and voltage-independent. K_2P2.1 channels (i.e., TREK-1, KCNK2) are highly expressed in excitable tissues, where they play a key role in the cellular mechanisms of neuroprotection, anesthesia, pain perception, and depression. Here, we report for the first time that human K_2P2.1 channel activity is regulated by monoterpenes (MTs). We found that cyclic, aromatic monoterpenes containing a phenol moiety, such as carvacrol, thymol and 4-IPP had the most profound effect on current flowing through the channel (up to a 6-fold increase). By performing sequential truncation of the carboxyl-terminal domain of the channel and testing the activity of several channel regulators, we identified two distinct regulatory domains within this portion of the protein. One domain, as previously reported, was needed for regulation by arachidonic acid, anionic phospholipids, and temperature changes. Within a second domain, a triple arginine residue motif (R344-346), an apparent PIP₂-binding site, was found to be essential for regulation by holding potential changes and important for regulation by monoterpenes.

Plant-Climate Interaction Effects: Changes in the Relative Distribution and Concentration of the Volatile Tea Leaf Metabolome in 2014-2016

Climatic conditions affect the chemical composition of edible crops, which can impact flavor, nutrition and overall consumer preferences. To understand these effects, we sampled tea (Camellia sinensis (L.) Kuntze) grown in different environmental conditions. Using a target/nontarget data analysis approach, we detected 564 metabolites from tea grown at two elevations in spring and summer over 3 years in two major tea-producing areas of China. Principal component analysis and partial least squares-discriminant analysis show seasonal, elevational, and yearly differences in tea from Yunnan and Fujian provinces. Independent of location, higher concentrations of compounds with aromas characteristic of farmers' perceptions of high-quality tea were found in spring and high elevation teas. Yunnan teas were distinct from Fujian teas, but the effects of elevation and season were different for the two locations. Elevation was the largest source of metabolite variation in Yunnan yet had no effect in Fujian. In contrast seasonal differences were strong in both locations. Importantly, the year-to-year variation in chemistry at both locations emphasizes the importance of doing multi-year studies, and further highlights the challenge farmers face when trying to produce teas with specific flavor/health (metabolite) profiles.

Geraniol targets KV1.3 ion channel and exhibits anti-inflammatory activity in vitro and in vivo

Naturally occurring monoterpenes are known for their various pharmacological activities including anti-inflammation. K_V1.3 ion channel is a voltage-gated potassium channel and has been validated as a drug target for autoimmune and chronic inflammatory diseases like psoriasis. Here we experimentally test the direct interaction between monoterpenes and K_V1.3 ion channel. Our electrophysiological analysis determined that monoterpenes (geraniol, nerol, β-citronellol, citral and linalool) have inhibitory effects on K_V1.3 ion channel. Representatively, geraniol reversibly blocked K_V1.3 currents in a voltage-dependent manner with an IC₅₀ of 490.50 ± 1.04 μM at +40 mV in HEK293T cells. At the effective concentrations, geraniol also inhibited cytokine secretion of activated human T cells, including IL-2, TNF-α and IFN-γ. In an imiquimod-induced psoriasis-like animal model, geraniol administration significantly reduced psoriasis area and severity index scores, ameliorated the deteriorating histopathology and decreased the degree of splenomegaly. Together, our findings not only suggest that monoterpenes may serve as lead molecules for the development of K_V1.3 inhibitors, but also indicate that geraniol could be considered as a promising therapeutic candidate to treat autoimmune diseases.

Antibacterial Activity of Terpenes and Terpenoids Present in Essential Oils

Background: The antimicrobial activity of essential oils has been reported in hundreds of studies, however, the great majority of these studies attribute the activity to the most prevalent compounds without analyzing them independently. Therefore, the aim was to investigate the antibacterial activity of 33 free terpenes commonly found in essential oils and evaluate the cellular ultrastructure to verify possible damage to the cellular membrane. Methods: Screening was performed to select substances with possible antimicrobial activity, then the minimal inhibitory concentrations, bactericidal activity and 24-h time-kill curve studies were evaluated by standard protocols. In addition, the ultrastructure of control and death bacteria were evaluated by scanning electron microscopy. Results: Only 16 of the 33 compounds had antimicrobial activity at the initial screening. Eugenol exhibited rapid bactericidal action against Salmonella enterica serovar Typhimurium (2 h). Terpineol showed excellent bactericidal activity against S. aureus strains. Carveol, citronellol and geraniol presented a rapid bactericidal effect against E. coli. Conclusions: The higher antimicrobial activity was related to the presence of hydroxyl groups (phenolic and alcohol compounds), whereas hydrocarbons resulted in less activity. The first group, such as carvacrol, l-carveol, eugenol, trans-geraniol, and thymol, showed higher activity when compared to sulfanilamide. Images obtained by scanning electron microscopy indicate that the mechanism causing the cell death of the evaluated bacteria is based on the loss of cellular membrane integrity of function. The present study brings detailed knowledge about the antimicrobial activity of the individual compounds present in essential oils, that can provide a greater understanding for the future researches.

Capsaicin inhibits the function of α7-nicotinic acetylcholine receptors expressed in Xenopus oocytes and rat hippocampal neurons

Capsaicin is a naturally occurring alkaloid derived from Chili peppers fruits. Using the two-electrode voltage-clamp technique in Xenopus oocyte expression system, actions of capsaicin on the functional properties of α₇ subunit of the human nicotinic acetylcholine (α₇ nACh) receptor were investigated. Ion currents activated by ACh (100 μM) were reversibly inhibited with an IC₅₀ value of 8.6 μM. Inhibitory actions of capsaicin was independent of membrane potential. Furthermore, Ca²⁺-dependent Cl^- channels expressed endogenously in oocytes were not involved in inhibitory actions of capsaicin. In addition, increasing the ACh concentrations could not reverse the inhibitory effects of capsaicin. Importantly, specific binding of [¹²⁵I] α-bungarotoxin remained unaltered by capsaicin suggesting that its effect is noncompetitive. Whole cell patch-clamp technique was performed in CA1 stratum radiatum interneurons of rat hippocampal slices. Ion currents induced by choline, a selective-agonist of α₇-receptor, were reversibly inhibited by 10 min bath application of capsaicin (10 μM). Collectively, results of our investigation indicate that the function of the α7-nACh receptor expressed in Xenopus oocytes and in hippocampal interneurons are inhibited by capsaicin.

Oral administration of carvacrol/β-cyclodextrin complex protects against 6-hydroxydopamine-induced dopaminergic denervation

Carvacrol (CARV) presents valuable biological properties such as anti-inflammatory and antioxidant activities. However, pharmacological uses of CARV are largely limited due to disadvantages related to solubility, bioavailability, preparation and storage processes. The complexation of monoterpenes with β-cyclodextrin (β-CD) increases their stability, solubility and oral bioavailability. Here, the protective effect of oral treatment with CARV/β-CD complex (25 μg/kg/day) against dopaminergic (DA) denervation induced by unilateral intranigral injection of 6-hydroxydopamine (6-OHDA - 10 μg per rat) was analyzed, in order to evaluate a putative application in the development of neuroprotective therapies for Parkinson's disease (PD). Pretreatment with CARV/β-CD for 15 days prevented the loss of DA neurons induced by 6-OHDA in adult Wistar rats. This effect may occur through CARV anti-inflammatory and antioxidant properties, as the pretreatment with CARV/β-CD inhibited the release of IL-1β and TNF-α; besides, CARV prevented the increase of mitochondrial superoxide production induced by 6-OHDA in cultured SH-SY5Y cells. Importantly, hepatotoxicity or alterations in blood cell profile were not observed with oral administration of CARV/β-CD. Therefore, this study showed a potential pharmacological application of CARV/β-CD in PD using a non-invasive route of drug delivery, i.e., oral administration.

Camphor white oil induces tumor regression through cytotoxic T cell-dependent mechanisms

Bioactive derivatives from the camphor laurel tree, Cinnamomum camphora, are posited to exhibit chemopreventive properties but the efficacy and mechanism of these natural products are not fully understood. We tested an essential-oil derivative, camphor white oil (CWO), for anti-tumor activity in a mouse model of keratinocyte-derived skin cancer. Daily topical treatment with CWO induced dramatic regression of pre-malignant skin tumors and a two-fold reduction in cutaneous squamous cell carcinomas. We next investigated underlying cellular and molecular mechanisms. In cultured keratinocytes, CWO stimulated calcium signaling, resulting in calcineurin-dependent activation of nuclear factor of activated T cells (NFAT). In vivo, CWO induced transcriptional changes in immune-related genes identified by RNA-sequencing, resulting in cytotoxic T cell-dependent tumor regression. Finally, we identified chemical constituents of CWO that recapitulated effects of the admixture. Together, these studies identify T cell-mediated tumor regression as a mechanism through which a plant-derived essential oil diminishes established tumor burden.

Natural Negative Allosteric Modulators of 5-HT₃ Receptors

Chemotherapy-induced nausea and vomiting (CINV) remain the most common and devastating side-effects associated with cancer chemotherapy. In recent decades, several lines of research emphasize the importance of 5-hydroxytryptamine3 (5-HT3; serotonin) receptors in the pathogenesis and treatment of CINV. 5-HT₃ receptors are members of ligand-gated ion channels that mediate the rapid and transient membrane-depolarizing effect of 5-HT in the central and peripheral nervous system. These receptors play important roles in nausea and vomiting, as well as regulation of peristalsis and pain transmission. The development of antagonists for 5-HT₃ receptor dramatically improved the treatment of CINV in cancer patients. In fact, the most common use of 5-HT₃ receptor antagonists to date is the treatment of nausea and vomiting. In recent years, there has been an increasing tendency to use natural plant products as important therapeutic entities in the treatment of various diseases. In this article, we examined the results of earlier studies on the actions of natural compounds on the functional properties of 5-HT₃ receptors. It is likely that these natural modulators of 5-HT₃ receptors can be employed as lead structures for the synthesis of therapeutic agents for treating CINV in future clinical studies.

The essential oil of Lippia alba and its components affect Drosophila behavior and synaptic physiology

Lippia alba is a flowering shrub in the verbena family and its essential oil (EO) is known for its sedative, antidepressant and analgesic properties. In the Amazon region of Brazil, it is used in aquaculture to anesthetize fish during transport. Many of the specialized metabolites found in EOs presumably evolved to protect plants from herbivores, especially insects. We used Drosophila to test the behavioral and physiological actions of this EO and its components. We found that a 150 min exposure to the EO vapors resulted in immobilization of adult flies. Gas chromatography-mass spectrometry identified the major components of the EO as the monoterpenes citral (59%), carvone (7%) and limonene (7%). Fly immobilization by the EO was due to citral and carvone, with citral producing more rapid effects than carvone. We tested whether the EO affected synaptic physiology by applying it to the larval neuromuscular junction. The EO delivered at 0.012% (v/v) produced over a 50% reduction in excitatory postsynaptic potential (EPSP) amplitude within 3-4 min. When the EO components were applied at 0.4 mmol l^-1, citral and carvone produced a significant reduction in EPSP amplitude, with citral producing the largest effect. Measurement of miniature EPSP amplitudes demonstrated that citral produced over a 50% reduction in transmitter release. Calcium imaging experiments showed that citral produced about 30% reduction in presynaptic Ca²⁺ influx, which likely resulted in the decrease in transmitter release. Thus, the EO blocks synaptic transmission, largely due to citral, and this likely contributes to its behavioral effects.

Differentiation of key biomarkers in tea infusions using a target/nontarget gas chromatography/mass spectrometry workflow

Climatic conditions affect the chemical composition of edible crops, which can impact flavor, nutrition and overall consumer preferences. To understand these effects new data analysis software capable of tracking hundreds of compounds across years of samples under various environmental conditions is needed. Our recently developed mass spectral (MS) subtraction algorithms have been used with spectral deconvolution to efficiently analyze complex samples by 2-dimensional gas chromatography/mass spectrometry (GC-GC/MS). In this paper, we address the accuracy of identifying target and nontarget compounds by GC/MS. Findings indicate that Yunnan tea contains higher concentrations of floral compounds. In contrast, Fujian tea contains higher concentrations of compounds that exhibit fruity characteristics, but contains much less monoterpenes. Principal components analysis shows that seasonal changes in climate impact tea plants similarly despite location differences. For example, spring teas contained more of the sweet, floral and fruity compounds compared to summer teas, which had higher concentrations of green, woody, herbal compounds.

Effect of different operating conditions in cloud point assisted extraction of thymol from Ajwain (Trachyspermum Ammi L.) seeds and recovery using solvent

Cloud point assisted extraction of thymol from water extract of Ajwain (Trachyspermum Ammi L.) seeds has been reported. Effects of different operating conditions, i.e., concentration of surfactant, heating time and temperature in extraction efficiency were investigated. It was observed that maximum extraction efficiency of thymol was achieved with 30% (v/v) of SPAN 80 surfactant, 45 min of heating at 65 °C. Recovery of thymol from the surfactant complex was optimal at 1:3 coacervate phase to solvent (acetone) volume ratio. A semi-empirical correlation was proposed at the optimum time to predict the concentration of surfactant and temperature required for a desired yield.

Lack of postexposure analgesic efficacy of low concentrations of eugenol in zebrafish

OBJECTIVE

To test the postexposure analgesic efficacy of low doses of eugenol in zebrafish.

STUDY DESIGN

Prospective experimental study.

ANIMALS

A total of 76 large adult zebrafish (Danio rerio).

METHODS

Fish swimming behavior (median velocity, freeze time, high-speed swimming and distance moved in the vertical direction) was recorded in a 1.6 L video arena before and after exposure to eugenol (0, 1, 2, 5, 10 and 20 mg L^-1). In a second experiment, fish were anesthetized with 2-phenoxy-ethanol and treated with an injection of 5% acetic acid (noxious stimulus), and then exposed to 0, 1, 2 and 5 mg L^-1 eugenol. The fish swimming behavior was also recorded.

RESULTS

The higher doses (10 and 20 mg L^-1) reduced the median velocity, high-speed swimming and distance moved in the vertical direction, and increased the freeze time. Zebrafish behavior was not altered by eugenol (1, 2 and 5 mg L^-1) after noxious stimulation.

CONCLUSIONS AND CLINICAL RELEVANCE

The change in the behavior of zebrafish associated with a noxious stimulus can be monitored and is a good model for studying analgesia in fish. Eugenol (10 and 20 mg L^-1) induced zebrafish sedation. The response after a noxious stimulus was not affected by postexposure to lower doses, and thus we cannot recommend its use as an analgesic.

Anesthetic Agents of Plant Origin: A Review of Phytochemicals with Anesthetic Activity

The majority of currently used anesthetic agents are derived from or associated with natural products, especially plants, as evidenced by cocaine that was isolated from coca (Erythroxylum coca, Erythroxylaceae) and became a prototype of modern local anesthetics and by thymol and eugenol contained in thyme (Thymus vulgaris, Lamiaceae) and clove (Syzygium aromaticum, Myrtaceae), respectively, both of which are structurally and mechanistically similar to intravenous phenolic anesthetics. This paper reviews different classes of phytochemicals with the anesthetic activity and their characteristic molecular structures that could be lead compounds for anesthetics and anesthesia-related drugs. Phytochemicals in research papers published between 1996 and 2016 were retrieved from the point of view of well-known modes of anesthetic action, that is, the mechanistic interactions with Na⁺ channels, γ-aminobutyric acid type A receptors, N-methyl-d-aspartate receptors and lipid membranes. The searched phytochemicals include terpenoids, alkaloids and flavonoids because they have been frequently reported to possess local anesthetic, general anesthetic, antinociceptive, analgesic or sedative property. Clinical applicability of phytochemicals to local and general anesthesia is discussed by referring to animal in vivo experiments and human pre-clinical trials. This review will give structural suggestions for novel anesthetic agents of plant origin.

Cellular and Molecular Targets of Menthol Actions

Menthol belongs to monoterpene class of a structurally diverse group of phytochemicals found in plant-derived essential oils. Menthol is widely used in pharmaceuticals, confectionary, oral hygiene products, pesticides, cosmetics, and as a flavoring agent. In addition, menthol is known to have antioxidant, anti-inflammatory, and analgesic effects. Recently, there has been renewed awareness in comprehending the biological and pharmacological effects of menthol. TRP channels have been demonstrated to mediate the cooling actions of menthol. There has been new evidence demonstrating that menthol can significantly influence the functional characteristics of a number of different kinds of ligand and voltage-gated ion channels, indicating that at least some of the biological and pharmacological effects of menthol can be mediated by alterations in cellular excitability. In this article, we examine the results of earlier studies on the actions of menthol with voltage and ligand-gated ion channels.

Negative inotropism of terpenes on guinea pig left atrium: structure-activity relationships

The aim of this work was to evaluate the pharmacological effect of seven structurally related terpenes on the contractility of cardiac muscle. The effect of terpenes was studied on isolated electrically driven guinea pig left atrium. From concentration-response curves for inotropic effect were determined the EC₅₀ and relative potency of such terpenes. Our results revealed that all terpenes, except phytol, showed ability to reduce the contractile response of guinea pig left atrium. Further, relative potency was directly related to the number of isoprene units and to the lipophilicity of the compounds. For example, sesquiterpenes farnesol and nerolidol showed higher relative potency when compared with the monoterpenes citronellol, geraniol and nerol. We can conclude that most of the evaluated terpenes showed a promising negative inotropism on the atrial muscle. Future studies are necessary to investigate their action mechanism.

Global transcriptional response of Escherichia coli MG1655 cells exposed to the oxygenated monoterpenes citral and carvacrol

DNA microarrays were used to study the mechanism of bacterial inactivation by carvacrol and citral. After 10-min treatments of Escherichia coli MG1655 cells with 100 and 50ppm of carvacrol and citral, 76 and 156 genes demonstrated significant transcriptional differences (p≤0.05), respectively. Among the up-regulated genes after carvacrol treatment, we found gene coding for multidrug efflux pumps (acrA, mdtM), genes related to phage shock response (pspA, pspB, pspC, pspD, pspF and pspG), biosynthesis of arginine (argC, argG, artJ), and purine nucleotides (purC, purM). In citral-treated cells, transcription of purH and pyrB and pyrI was 2 times higher. Deletion of several differentially expressed genes confirmed the role of ygaV, yjbO, pspC, sdhA, yejG and ygaV in the mechanisms of E. coli inactivation by carvacrol and citral. These results would indicate that citral and carvacrol treatments cause membrane damage and activate metabolism through the production of nucleotides required for DNA and RNA synthesis and metabolic processes. Comparative transcriptomics of the response of E. coli to a heat treatment, which caused a significant change of the transcription of 1422 genes, revealed a much weaker response to both individual constituents of essential oils (ICs).·Thus, inactivation by citral or carvacrol was not multitarget in nature.

Essential Oils of Oregano: Biological Activity beyond Their Antimicrobial Properties

Essential oils of oregano are widely recognized for their antimicrobial activity, as well as their antiviral and antifungal properties. Nevertheless, recent investigations have demonstrated that these compounds are also potent antioxidant, anti-inflammatory, antidiabetic and cancer suppressor agents. These properties of oregano essential oils are of potential interest to the food, cosmetic and pharmaceutical industries. The aim of this manuscript is to review the latest evidence regarding essential oils of oregano and their beneficial effects on health.

Thujone inhibits the function of α7-nicotinic acetylcholine receptors and impairs nicotine-induced memory enhancement in one-trial passive avoidance paradigm

Effects of thujone, a major ingredient of absinthe, wormwood oil and some herbal medicines, were tested on the function of α₇ subunit of the human nicotinic acetylcholine (α₇ nACh) receptor expressed in Xenopus oocytes using the two-electrode voltage-clamp technique. Thujone reversibly inhibited ACh (100μM)-induced currents with an IC₅₀ value of 24.7μM. The effect of thujone was not dependent on the membrane potential and did not involve Ca²⁺-dependent Cl^- channels expressed endogenously in oocytes. Inhibition by thujone was not reversed by increasing ACh concentrations. Moreover, specific binding of [¹²⁵I] α-bungarotoxin was not altered by thujone. Further experiments in SH-EP1 cells expressing human α₇ nACh receptor indicated that thujone suppressed choline induced Ca²⁺ transients in a concentration-dependent manner. In rat hippocampal CA3-dentate gyrus synapses, nicotine-induced enhancement of long-term potentiation was also inhibited by thujone. Furthermore, the results observed in in-vivo one-trial passive avoidance paradigm show that thujone (1.25mg/kg, i.p.) significantly impaired nicotine-induced enhancement of learning and memory in Wistar rats. Collectively, our results indicate that thujone inhibits the function of the α7-nACh receptor and impairs cellular and behavioral correlates of cholinergic modulation of learning and memory.

Terpenoids with Special Pharmacological Significance: A Review

Terpenoids are a very prominent class of natural compounds produced in diverse genera of plants, fungi, algae and sponges. They gained significant pharmaceutical value since prehistoric times, due to their broad spectrum of medical applications. The fragrant leaves of Eucalyptus trees are a rich source of terpenoids. Therefore this review starts by summarizing the main terpenoid compounds present in Eucalyptus globulus, E. citriodora, E. radiata and E. resinifera and describing their biosynthetic pathways. Of the enormous number of pharmaceutically important terpenoids, this paper also reviews some well established and recently discovered examples and discusses their medical applications. In this context, the synthetic processes for (–)-menthol, (–)- cis-carveol, (+)-artemisinine, (+)-merrilactone A and (–)-sclareol are presented. The tricyclic sesquiterpene (–)-englerin A isolated from the stem bark of the Phyllanthus engleri plant ( Euphorbiaceae) is highly active against certain renal cancer cell lines. In addition, recent studies showed that englerin A is also a potent and selective activator of TRPC4 and TRPC5 calcium channels. These important findings were the motivation for several renowned research labs to achieve a total synthesis of (–)-englerin A. Two prominent examples – Christmann and Metz – are compared and discussed in detail.