Eucalyptol induces hyperexcitability and epileptiform activity in snail neurons by inhibiting potassium channels

1,8-cineole (eucalyptol): A versatile phytochemical with therapeutic applications across multiple diseases

1,8-cineole (Eucalyptol), a naturally occurring compound derived from botanical sources such as eucalyptus, rosemary, and camphor laurel, has a long history of use in traditional medicine and exhibits an array of biological properties, including anti-inflammatory, antioxidant, antimicrobial, bronchodilatory, analgesic, and pro-apoptotic effects. Recent evidence has also indicated its potential role in managing conditions such as Alzheimer's disease, neuropathic pain, and cancer. This review spotlights the health advantages of 1,8-cineole, as demonstrated in clinical trials involving patients with respiratory disorders, including chronic obstructive pulmonary disease, asthma, bronchitis, and rhinosinusitis. In addition, we shed light on potential therapeutic applications of 1,8-cineole in various conditions, such as depression, epilepsy, peptic ulcer disease, diarrhea, cardiac-related heart diseases, and diabetes mellitus. A comprehensive understanding of 1,8-cineole's pharmacodynamics and safety aspects as well as developing effective formulations, might help to leverage its therapeutic value. This thorough review sets the stage for future research on diverse health benefits and potential uses of 1,8-cineole in tackling complex medical conditions.

Chemical Analysis of Various Tea Samples Concerning Volatile Compounds, Fatty Acids, Minerals and Assessment of Their Thermal Behavior

Tea is the most consumed drink worldwide due to its pleasant taste and various beneficial effects on human health. This paper assesses the physicochemical analysis of different varieties of tea (leaves, flowers, and instant) after prior drying and fine grinding. The thermal decomposition behavior of the tea components shows that the tea has three stages of decomposition, depending on temperature. The first stage was attributed to the volatilization of water, while the second stage involved the degradation of volatiles, polyphenols, and fatty acids. The degradation of cellulose, hemicellulose, and lignin content occurs at the highest temperature of 400 °C in the third stage. A total of 66 volatile compounds, divided into eight classes, were identified in the tea samples. The volatile compounds were classified into nine odor classes: floral, fruity, green, sweet, chemical, woody, citrus, roasted, and alcohol. In all flower and leaf tea samples, monounsaturated (MUFAs), polyunsaturated (PUFAs), and saturated fatty acids (SFAs) were identified. A high content of omega-6 was quantified in acacia, Saint John's Wort, rose, and yarrow, while omega-3 was found in mint, Saint John's Wort, green, blueberry, and lavender samples. The flower and leaf tea samples studied could be a good dietary source of polyphenolic compounds, essential elements. In instant tea samples, a low quantity of polyphenols and major elements were identified. The physicochemical analysis demonstrated that both flower and leaf teas have high-quality properties when compared to instant tea.

Metal-organic framework on porous TiO2 thin film-coated alumina beads for fractional distillation of plant essential oils

Fractionation of essential oils is technically challenging due to enormous scaffold diversities and structural complexities as well as difficulties in the implementation of the fractionation in the gas phase. Packing beads with multi-dimensional hierarchical nanostructures have been developed herein to pack fractional columns for atmospheric distillations. Activated alumina beads were coated with a porous TiO₂ thin film. Growth of Cu-BTC (benzene-1,3,5-tricarboxylate) crystals in resultant porous surfaces leads to the generation of new nanopores and increased metal centers for differential coordination with diverse components of essential oils. The TiO₂ thin film is not only an integral part of the composites but also induces the oriented growth of Cu-BTC metal organic framework (MOF) crystals through coordinative interactions. These Al₂O₃@TiO₂@Cu-BTC MOF beads show very strong absorptive capability for major components of essential oils, except for a single cyclic ether eucalyptol with steric hindrances. The eucalyptol was fractionated by using the column packed with those modified alumina beads from raw materials of Artemisia argyi, and Rosmarinus officinalis with high purities up to 96% and 93%, respectively.

Essential oil related seizures (EORS): A multi-center prospective study on essential oils and seizures in adults

OBJECTIVE

Essential oils (EOs) like eucalyptus and camphor have pro-convulsant properties. These EOs are present in many over- the- counter balms and oils. The effect of exposure to these EOs and occurrence of seizure is not systematically studied. The aim of this study was to evaluate the relationship between essential oils and the first episode of seizure and breakthrough seizures in known epileptic patients.

METHODS

This was a multi-center prospective study, conducted in four hospitals over four years. Every person presenting with the first episode of seizure or breakthrough seizure was asked about exposure to EOs, mode of exposure, time to onset of a seizure in relationship to exposure, duration of seizure, type of seizure, and antiepileptic drug therapy.

RESULTS

During the four-year period there were 55 patients with essential oil-related seizure (EORS). 22(40 %) had essential oil-induced seizures (EOIS) and 33(60 %) had essential oil-provoked seizures (EOPS). The female: male ratio was 1:1.1, the age of the patients ranged from 8 months to 77 years. In the EOIS group, 95 % had generalized tonic-clonic seizures and 5% had focal impaired awareness seizures. In the EOPS group, 42.4 % had focal impaired awareness seizures, 27.3 % generalized tonic-clonic seizures, 15 % focal to bilateral tonic-clonic seizures, and 15 % focal aware motor seizures. EOs implicated were preparations containing eucalyptus and camphor.

CONCLUSION

Exposure to essential oils of eucalyptus and camphor is an under-recognized cause of the first and breakthrough seizure. Identifying the true causative factor will prevent unnecessary antiepileptic drug therapy and future recurrence.

Eucalyptus Oil-Induced Seizures in Children: A Single-Center Prospective Study

Objective

Eucalyptus oil (EO) is known to have proconvulsant properties. EO is present in many over-the-counter preparations and used orally or topically to treat many ailments. In this study, we seek to describe clinical features, neuroimaging, and electroencephalographic findings and follow up outcome in children with eucalyptus oil-induced seizures (EOIS).

Materials and methods

This was a single-center prospective observational study, conducted at a tertiary care hospital from South India over a period of two years. Children (up to 18 years of age) with a first afebrile seizure or breakthrough seizures with preexisting epilepsy and with a recent exposure to EO were included. Data from all the children including demographic data, exposure to EO, mode of exposure, time to onset of seizures in relation to exposure, duration of seizure, type of seizure, investigations, and antiepileptic drug therapy were noted. All the patients were followed up for recurrence of seizures for six to nine months. 

Results

During the study period of two years, a total of 17 children met the inclusion criteria, with a median (range) age of 3.75 years (23 - 150 months) and 10 (59%) were male. Only one patient had breakthrough seizures and all other 16 children had a first episode of seizure. All the children had generalized tonic-clonic seizures with median duration of three minutes (30 sec - 30 minutes). The median (range) interval between EO exposure and the onset of seizures was 20 minutes (10 - 120 minutes). All the children had taken EO drops orally mixed in either water or milk in different amounts. All the patients' brain neuroimaging was normal. All the patients had normal electroencephalography except for four children. Only five patients were treated with antiepileptic drugs for two weeks and one patient with preexisting epilepsy was continued on the same antiepileptic drug. None of the patients had a recurrence of seizures during the follow-up period of six to nine months.

Conclusion 

EOIS is an underrecognized and rare entity of seizures in children. EOIS can occur as first seizures or as breakthrough seizures in preexisting epilepsy patients. Despite the previous case reports in the literature quoting the seizurogenic potential of EO, this awareness is lacking in both clinicians and parents. We also recommend clinicians inquire about exposure to EO while approaching a child with first afebrile seizures or breakthrough seizures, which can prevent unnecessary investigations and long-term antiepileptic drug therapy.

Herbal Medicine-Induced Seizures in Children: Single-Center Experience Over 18 Months

Many common household herbal preparations may have seizurogenic ingredients. We report 15 children with seizures following exposure to such compounds: oral ingestion of liquid preparation in 13, and local application of balm and Eucalyptus oil ingestion in one each. All children, except one, had generalized seizures. This study highlights the need to address this history during evaluation of first seizure, and increase awareness of seizurogenic potential of such preparations.

Network pharmacology-based therapeutic mechanism of Kuanxiong aerosol for angina pectoris

ETHNOPHARMACOLOGICAL RELEVANCE

Kuanxiong aerosol has been reported to be an effective and safe clinical treatment for angina pectoris (AP).

AIM OF THE STUDY

To explore the potential pharmacological mechanism of Kuanxiong aerosol by combined methods of network pharmacology prediction and experimental verification.

MATERIALS AND METHODS

Networks of Kuanxiong aerosol-associated targets and AP-related genes were constructed through STRING database. Potential targets and pathway enrichment analysis related to the therapeutic efficacy of Kuanxiong aerosol were identified using Cytoscape and Database for Annotation, Visualization and Integrated Discovery (DAVID). To explore the mechanism of action of Kuanxiong aerosol, its in vitro effects on myocardial hypoxia, inflammatory cytokines, and oxidative injury, and its in vivo pharmacological effects on myocardial ischemia and cardiac fibrosis were studied in rat models.

RESULTS

Network pharmacology analysis revealed that the potential targets mainly include the Fas ligand (FASLG), interleukin 4 (IL4), and catalase (CAT), which mediated the processes of apoptosis, and cellular responses to hypoxia, lipopolysaccharide (LPS), reactive oxygen species (ROS), and mechanical stimulus. Multiple pathways, such as the hypoxia-inducible factor 1 (HIF1) and tumor necrosis factor (TNF) pathways were found to be closely related to the pharmacological protective mechanism of Kuanxiong aerosol against AP. In addition, Kuanxiong aerosol suppressed the hypoxia, LPS, and hydrogen peroxide (H₂O₂)-induced injuries of H9c2 cardiomyocytes through the regulation of HIF1A, suppressed expression of IL6 and TNF, and antioxidant property. In the rat model of myocardial ischemia, Kuanxiong aerosol was found to lower the creatine kinase (CK), creatine kinase-myocardial band (CK-MB), and lactate dehydrogenase (LDH) levels, without altering the hemodynamic function. Kuanxiong aerosol was capable of attenuating cardiac fibrosis and improving cardiac function in a cardiac fibrosis rat model.

CONCLUSIONS

This study revealed that the pharmacological mechanisms of Kuanxiong aerosol for AP therapy were related to anti-myocardial ischemia, anti-inflammation, and anti-oxidation via a non-hemodynamic manner, indicating that Kuanxiong aerosol is a preferable drug clinically for AP treatment due to its both preventive and protective effects.

Essential oil-related status epilepticus: A small case series study

OBJECTIVE

Essential oils are plant-derived oils and are widely used as an over-the-counter remedy for common ailments. Many essential oils are found to have proconvulsant effects. Here we report a small case series of 3 adults with eseential oil-related status epilepticus.

METHODS

This was an observational study conducted in a tertiary care hospital in south India from January 2018 to December 2019. We collected the demographic, clinical, and imaging features of all cases of status epilepticus resulting from exposure to essential oils. Cases of status epilepticus secondary to all other causes were excluded.

RESULTS

There were 3 young adults with essential oil-related status epilepticus. Two had de novo generalized tonic-clonic status epilepticus, and 1 with posttraumatic occipital lobe epilepsy had focal-impaired awareness status epilepticus. The first 2 cases presented with histories of ingestion of eucalyptus oil. The third case had focal-impaired awareness status epilepticus after topical application of various balms containing eucalyptus and camphor.

CONCLUSIONS

Proconvulsant essential oils of eucalyptus and camphor can cause both generalized and focal status epilepticus. Physicians dealing with patients of status epilepticus should enquire about the exposure to proconvulsant essential oils.

Thymol provokes burst of action potentials in neurons of snail Caucasotachea atrolabiata

Thymol, a phenolic monoterpene, is well known for its antimicrobial, antifungal and antioxidant properties. In spite of wide use in oral care products, pharmaceutical and cosmetic preparation and in food industry, the effects of thymol on the neuronal activity and intrinsic properties have not been well studied. We studied the effects of thymol on the spontaneous activity and action potential properties of central neurons of snail Caucasotachea atrolabiata. Thymol (1 mM) altered action potentials characteristics and provoked epileptiform burst firing in snail neurons, which were partially reversible after washout. Before burst firing, action potentials had lower amplitude and maximum rising slope, while the threshold voltage was raised. These results suggest the inhibition of ion channels underlying action potential initiation and upstroke. The maximum falling slope and afterhyperpolarization were also considerably reduced, suggesting the inhibition of potassium channels. Thymol (0.5 mM) that was not able to induce burst firing in snail neurons, synergistically acted with potassium channel blocker, tetraethyl ammonium, to induce burst firing, which also supports the importance of potassium channel inhibition, especially delayed rectifier potassium channels, to the thymol-induced alteration of firing pattern. The thymol-induced burst firing seems to be dependent on both sodium and calcium currents. Our findings provide evidences for the ability of thymol in altering the firing mode of central neurons of snail, which apparently involves the inhibition of calcium and potassium currents. These results further support the interaction of thymol with ion channels and emphasize on the vulnerability of nervous system to this compound.

Effects of phosphorus sources on volatile organic compound emissions from Microcystis flos-aquae and their toxic effects on Chlamydomonas reinhardtii

There is diverse phosphorus (P) in eutrophicated waters, but it is considered as a crucial nutrient for cyanobacteria growth due to its easy precipitation as insoluble salts. To uncover the effects of complex P nutrients on the emission of volatile organic compounds (VOCs) from cyanobacteria and their toxic effects on other algae, the VOCs from Microcystis flos-aquae supplied with different types and amount of P nutrients were analyzed, and the effects of VOCs and their two main compounds on Chlamydomonas reinhardtii growth were investigated. When M. flos-aquae cells were supplied with K₂HPO₄, sodium pyrophosphate and sodium hexametaphosphate as the sole P source, 27, 23 and 29 compounds were found, respectively, including furans, sulfocompounds, terpenoids, benzenes, aldehydes, hydrocarbons and esters. With K₂HPO₄ as the sole P source, the VOC emission increased with reducing P amount, and the maximum emission was found under Non-P condition. In the treatments of M. flos-aquae VOCs under Non-P condition and two main terpenoids (eucalyptol and limonene) in the VOCs, remarkable decreases were found in C. reinhardtii cell growth, photosynthetic pigment content and photosynthetic abilities. Therefore, we deduce that multiple P nutrients in eutrophicated waters induce different VOC emissions from cyanobacteria, and P amount reduction caused by natural precipitation and algal massive growth results in more VOC emissions. These VOCs play toxic roles in cyanobacteria becoming dominant species, and eucalyptol and limonene are two toxic agents.

Essential Oils and Their Constituents Targeting the GABAergic System and Sodium Channels as Treatment of Neurological Diseases

Essential oils and the constituents in them exhibit different pharmacological activities, such as antinociceptive, anxiolytic-like, and anticonvulsant effects. They are widely applied as a complementary therapy for people with anxiety, insomnia, convulsion, pain, and cognitive deficit symptoms through inhalation, oral administration, and aromatherapy. Recent studies show that essential oils are emerging as a promising source for modulation of the GABAergic system and sodium ion channels. This review summarizes the recent findings regarding the pharmacological properties of essential oils and compounds from the oils and the mechanisms underlying their effects. Specifically, the review focuses on the essential oils and their constituents targeting the GABAergic system and sodium channels, and their antinociceptive, anxiolytic, and anticonvulsant properties. Some constituents target transient receptor potential (TRP) channels to exert analgesic effects. Some components could interact with multiple therapeutic target proteins, for example, inhibit the function of sodium channels and, at the same time, activate GABA_A receptors. The review concentrates on perspective compounds that could be better candidates for new drug development in the control of pain and anxiety syndromes.

The effects of linalool on the excitability of central neurons of snail Caucasotachea atrolabiata

Linalool is a major constituent of the essential oil of several plant species and possesses several biological activities. In this work, we studied the effects of linalool on excitability of central neurons of land snail Caucasotachea atrolabiata and tried to elucidate the underlying mechanisms. The lower concentration of linalool (0.1mM) showed suppressive action on spontaneous activity and pentylenetetrazole-induced epileptiform activity. These effects were associated with elevation of the action potential threshold and reduction of action potential rising phase, supporting the inhibitory action of linalool on Na⁺ channels. At this concentration it also prolonged the post stimulus inhibitory period that can take part in its antiepileptic effect and apparently results from increased action potential duration and indirect augmentation of Ca²⁺-activated K⁺ currents. At higher concentration, however, linalool (0.4mM) increased the neuronal excitability and induced epileptiform activity. The modulatory effects on action potential waveform during preconvulsive period suggest that the recent effect is mainly dependent on the suppression of outward potassium currents underlying repolarization phase and afterhyperpolarization. The linalool-induced epileptiform activity was abolished by Ca2⁺ channel blockers, nifedipine and nickel chloride, and selective inhibitor of protein kinase C, chelerythrine, suggesting that Ca2⁺ inward currents and protein kinase C (PKC) activity are required for linalool-induced epileptiform activity. Our results support the antiepileptic activity of linalool at lower dose, but it shows epileptogenic activity when applied directly on snail neurons at higher dose. Linalool may also be a potential therapeutic agent for activating PKC.

Volatile organic compounds released from Microcystis flos-aquae under nitrogen sources and their toxic effects on Chlorella vulgaris

Eutrophication promotes massive growth of cyanobacteria and algal blooms, which can poison other algae and reduce biodiversity. To investigate the differences in multiple nitrogen (N) sources in eutrophicated water on the emission of volatile organic compounds (VOCs) from cyanobacteria, and their toxic effects on other algal growth, we analyzed VOCs emitted from Microcystis flos-aquae with different types and concentrations of nitrogen, and determined the effects under Normal-N and Non-N conditions on Chlorella vulgaris. M. flos-aquae released 27, 22, 20, 27, 19, 25 and 17 compounds, respectively, with NaNO₃, NaNO₂, NH₄Cl, urea, Ser, Lys and Arg as the sole N source. With the reduction in N amount, the emission of VOCs was increased markedly, and the most VOCs were found under Non-N condition. C. vulgaris cell propagation, photosynthetic pigment and Fv/Fm declined significantly following exposure to M. flos-aquae VOCs under Non-N condition, but not under Normal-N condition. When C. vulgaris cells were treated with two terpenoids, eucalyptol and limonene, the inhibitory effects were enhanced with increasing concentrations. Therefore, multiple N sources in eutrophicated water induce different VOC emissions from cyanobacteria, and reduction in N can cause nutrient competition, which can result in emissions of more VOCs. Those VOCs released from M. flos-aquae cells under Non-N for nutrient competition can inhibit other algal growth. Among those VOCs, eucalyptol and limonene are the major toxic agents.

Dual effects of eugenol on the neuronal excitability: An in vitro study

Besides its well-known actions on sensory afferents, eugenol also affects general excitability of the nervous system, but the mechanisms involved in the recent effect, especially through modulation of ion channels, have received much less attention. In this study, we studied the effects of eugenol on the excitability of central neurons of land snail Caucasotachea atrolabiata and tried to elucidate the underlying ionic mechanisms. The lower concentration of eugenol (0.5mM) reversibly reduced the frequency of spontaneous action potentials that was associated with elevation of threshold, reduction of maximum slope of rising phase and prolongation of actin potentials. These effects were mimicked by riluzole, suggesting that they might be mediated by inhibition of Na⁺ channels. Eugenol also prolonged the single-spike afterhyperpolarization and post stimulus inhibitory period, but these effects seemed to be consequent to action potential prolongation that indirectly augment Ca²⁺ inward currents and Ca²⁺-activated K⁺ currents. This concentration of eugenol was also able to prevent or abolish pentylenetetrazole-induced epileptiform activity. On the other hand, a higher concentration of eugenol (2mM) reversibly increased the frequency of action potentials and then induced epileptiform activity in majority of treated neurons. Several criteria suggest that the inhibition of K⁺ channels by higher concentration of eugenol and indirect augmentation of Ca²⁺ currents are central to the hyperexcitability and epileptiform activity induced by eugenol. Our findings indicate that while low concentration of eugenol could have antiepileptic properties, at higher concentration it induces epileptiform activity. It seems that does dependent inhibition of the ionic currents underlying rising and falling phases of action potential is relevant to the eugenol suppressant and excitatory actions, respectively.