Effects of Essential Oil from Thymus vulgaris on Viability and Inflammation in Zebrafish Embryos

Evaluation of the Anti-Inflammatory and Antioxidant Potential of Cymbopogon citratus Essential Oil in Zebrafish

This study explored the protective capacity of the essential oil (EO) of Cymbopogon citratus against oxidative stress induced by hydrogen peroxide (H2O2) and the inflammatory potential in zebrafish. Using five concentrations of EO (0.39, 0.78, 1.56, 3.12, and 6.25 μg/mL) in the presence of 7.5 mM H2O2, we analyzed the effects on neutrophil migration, caudal fin regeneration, cellular apoptosis, production of reactive oxygen species (ROS), and activities of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferase (GST) after 96 h of exposure. A significant decrease in neutrophil migration was observed in all EO treatments compared to the control. Higher concentrations of EO (3.12 and 6.25 μg/mL) resulted in a significant decrease in caudal fin regeneration compared to the control. SOD activity was reduced at all EO concentrations, CAT activity significantly decreased at 3.12 μg/mL, and GST activity increased at 0.78 μg/mL and 1.56 μg/mL, compared to the control group. No significant changes in ROS production were detected. A reduction in cellular apoptosis was evident at all EO concentrations, suggesting that C. citratus EO exhibits anti-inflammatory properties, influences regenerative processes, and protects against oxidative stress and apoptosis.

Essential Oils Produce Developmental Toxicity in Zebrafish Embryos and Cause Behavior Changes in Zebrafish Larvae

Essential oils have gained significant popularity in various industries due to their biological properties, but their potential toxic effects on living organisms have been poorly investigated. This study aimed to evaluate the effects of lemongrass, thyme, and oregano essential oils on zebrafish embryos and larvae as animal models. Embryos were exposed to different concentrations of essential oils, and various endpoints were assessed, including epiboly, mortality (LC50), morphometry, and behavioral changes. All three essential oils reduced epiboly, affecting embryonic development. LC50 values were calculated for lemongrass (3.7 µg/mL), thyme (14.4 µg/mL), and oregano (5.3 µg/mL) oils. Larvae exposed to these oils displayed morphological defects, including growth reduction, spinal deformation, pericardial edema, eye size reduction, and reduced swim-bladder inflation. Morphometric analysis confirmed reduced larval length at higher oil concentrations. Essential-oil exposure altered zebrafish larval swimming behavior, with lemongrass oil reducing dark-cycle activity and oregano oil increasing light-cycle activity, suggesting neurodevelopmental toxicity. These findings illustrate the adverse effects of these oils on zebrafish embryos and larvae and reveal essential-oil toxicity, indicating careful use should be considered, particularly during pregnancy.

Mesosphaerum suaveolens Essential Oil Attenuates Inflammatory Response and Oxidative Stress in LPS-Stimulated RAW 264.7 Macrophages by Regulating NF-κB Signaling Pathway

Mesosphaerum suaveolens (L.) Kuntze (Syn. Hyptis suaveolens (L.) Poit.) is a wild essential-oil-bearing plant having multiple uses in traditional medicine, perfumery, food, agriculture, and pharmaceutical industries. The present paper is the first report on the in vitro anti-inflammatory effects of the leaf essential oil of M. suaveolens (MSLEO) and unravels its molecular mechanism in LPS-stimulated RAW 264.7 macrophage cells. GC-MS analysis of the essential oil (EO) isolated from the leaves by hydro-distillation led to the identification of 48 constituents, accounting for 90.55% of the total oil, and β-caryophyllene (16.17%), phyllocladene (11.85%), abietatriene (11.46%), and spathulenol (7.89%) were found to be the major components. MSLEO treatment had no effect on the viability of RAW 264.7 cells up to a concentration of 100 μg/mL, and the EO was responsible for a reduction in proinflammatory cytokines like IL-6, IL-1β, and TNF-α, a decrease in intracellular ROS production, and the restoration of oxidative damage by elevating the levels of endogenous antioxidative enzymes like CAT, SOD, GPx, and GSH. RT-qPCR analysis indicated that MSLEO reduced the mRNA expression levels of iNOS and COX-2 as compared to the LPS-induced group. In addition, a confocal microscopy analysis showed that MSLEO inhibited the translocation of NF-κB from the cytosol to the nucleus. The results of this experiment demonstrate that MSLEO possesses significant anti-inflammatory potential by preventing the activation of NF-κB, which, in turn, inhibits the downstream expression of other inflammatory mediators associated with the activation of the NF-κB pathway in LPS-induced RAW 264.7 cells. Thus, the leaf essential oil of M. suaveolens may prove to be a promising therapeutic agent for the treatment of inflammation, and targeting the NF-κB signaling pathway may be considered as an attractive approach for anti-inflammatory therapies.

Anti-Inflammatory, Anti-Oxidative and Anti-Apoptotic Effects of Thymol and 24-Epibrassinolide in Zebrafish Larvae

Thymol (THY) and 24-epibrassinolide (24-EPI) are two examples of plant-based products with promising therapeutic effects. In this study, we investigated the anti-inflammatory, antioxidant and anti-apoptotic effects of the THY and 24-EPI. We used zebrafish (Danio rerio) larvae transgenic line (Tg(mpxGFP)ⁱ¹¹⁴) to evaluate the recruitment of neutrophils as an inflammatory marker to the site of injury after tail fin amputation. In another experiment, wild-type AB larvae were exposed to a well known pro-inflammatory substance, copper (CuSO4), and then exposed for 4 h to THY, 24-EPI or diclofenac (DIC), a known anti-inflammatory drug. In this model, the antioxidant (levels of reactive oxygen species-ROS) and anti-apoptotic (cell death) effects were evaluated in vivo, as well as biochemical parameters such as the activity of antioxidant enzymes (superoxide dismutase, catalase and glutathione peroxidase), the biotransformation activity of glutathione-S-transferase, the levels of glutathione reduced and oxidated, lipid peroxidation, acetylcholinesterase activity, lactate dehydrogenase activity, and levels of nitric acid (NO). Both compounds decreased the recruitment of neutrophils in Tg(mpxGFP)ⁱ¹¹⁴, as well as showed in vivo antioxidant effects by reducing ROS production and anti-apoptotic effects in addition to a decrease in NO compared to CuSO4. The observed data substantiate the potential of the natural compounds THY and 24-EPI as anti-inflammatory and antioxidant agents in this species. These results support the need for further research to understand the molecular pathways involved, particularly their effect on NO.

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

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

Essential Oils from Zingiber striolatum Diels Attenuate Inflammatory Response and Oxidative Stress through Regulation of MAPK and NF-κB Signaling Pathways

Zingiber striolatum Diels (Z. striolatum), a widely popular vegetable in China, is famous for its medicinal and nutritional values. However, the anti-inflammatory effects of essential oil from Z. striolatum (EOZS) remain unclear. In this study, EOZS from seven regions in China were extracted and analyzed by GC–MS. LPS-induced RAW264.7 cells and 12-O-Tetradecanoylphorbol 13-acetate (TPA)-stimulated mice were used to evaluate the anti-inflammatory effects of EOZS. Results show that 116 compounds were identified in EOZS from seven locations. Samples 2, 4 and 5 showed the best capability on DPPH radical scavenging and NO inhibition. They also significantly reduced the production of ROS, pro-inflammatory cytokines, macrophage morphological changes, migration and phagocytic capability. Transcriptomics revealed MAPK and NF-κB signaling pathways may be involved in the anti-inflammatory mechanism, and the predictions were proven by Western blotting. In TPA-induced mice, EOZS reduced the degree of ear swelling and local immune cell infiltration by blocking the activation of MAPK and NF-κB signaling pathways, which was consistent with the in vitro experimental results. Our research unveils the antioxidant capability and potential molecular mechanism of EOZS in regulating inflammatory response, and suggests the application of EOZS as a natural antioxidant and anti-inflammatory agent in the pharmaceutical and functional food industries.

Composition, Anti-MRSA Activity and Toxicity of Essential Oils from Cymbopogon Species

Many of the essential oils obtained from medicinal plants possess proven antimicrobial activity and are suitable for medicinal purposes and applications in the food industry. The aim of the present work was the chemical analysis of 19 essential oils (EOs) from seven different Cymbopogon species (C. nardus, C. citratus, C winterianus, C. flexuosus, C. schoenanthus, C. martinii, C. giganteus). Five different chemotypes were established by GC/MS and TLC assay. The EOs, as well as some reference compounds, i.e., citronellol, geraniol and citral (neral + geranial), were also tested for their antimicrobial and antibiofilm activity against methicillin-resistant Staphylococcus aureus (MRSA) by the microdilution method and direct bioautography. The toxicity of EOs was evaluated by Danio rerio ‘Zebrafish’ model assay. All examined EOs showed moderate to high activity against MRSA, with the highest activity noted for C. flexuosus—lemongrass essential oil, both in microdilution and direct autobiography method. Significant difference in the toxicity of the examined EOs was also detected.

Toxicological Parameters of a Formulation Containing Cinnamaldehyde for Use in Treatment of Oral Fungal Infections: An In Vivo Study

OBJECTIVE

We aimed to define the safety and toxicity of both isolated and embedded cinnamaldehyde using a pharmaceutical formulation for the treatment of oral fungal infections in an in vivo study.

MATERIALS AND METHODS

Acute toxicity was assessed in studies with Galleria mellonella larvae and Danio rerio embryos (zebrafish), and genotoxicity was assessed in a mouse model. The pharmaceutical formulation (orabase ointment) containing cinnamaldehyde was evaluated for verification of both in vitro antifungal activity and toxicity in keratinized oral rat mucosa.

RESULTS

In Galleria mellonella larvae, cinnamaldehyde was not toxic up to the highest dose tested (20 mg/kg) and presented no genotoxicity up to the dose of 4 mg/kg in the model using mice. However, it was found to be toxic in zebrafish embryos up to a concentration of 0.035 μg/mL; LC50 0.311; EC50 0.097 (egg hatching delay); and 0.105 (Pericardial edema). In the orabase antifungal susceptibility test, cinnamaldehyde exhibited activity in concentrations greater than 200 μg/mL. As for safety in the animal model with rats, the orabase ointment proved to be safe for use on keratinized mucosa up to the maximum concentration tested (700 μg/mL).

CONCLUSIONS

At the concentrations tested, cinnamaldehyde was not toxic in vertebrate and invertebrate animal models and did not exhibit genotoxic activity. In addition, when used in the form of an ointment in orabase, having already recognized antifungal activity, it was shown to be safe up to the highest concentration tested.

Modeling Inflammation in Zebrafish for the Development of Anti-inflammatory Drugs

Dysregulation of the inflammatory response in humans can lead to various inflammatory diseases, like asthma and rheumatoid arthritis. The innate branch of the immune system, including macrophage and neutrophil functions, plays a critical role in all inflammatory diseases. This part of the immune system is well-conserved between humans and the zebrafish, which has emerged as a powerful animal model for inflammation, because it offers the possibility to image and study inflammatory responses in vivo at the early life stages. This review focuses on different inflammation models established in zebrafish, and how they are being used for the development of novel anti-inflammatory drugs. The most commonly used model is the tail fin amputation model, in which part of the tail fin of a zebrafish larva is clipped. This model has been used to study fundamental aspects of the inflammatory response, like the role of specific signaling pathways, the migration of leukocytes, and the interaction between different immune cells, and has also been used to screen libraries of natural compounds, approved drugs, and well-characterized pathway inhibitors. In other models the inflammation is induced by chemical treatment, such as lipopolysaccharide (LPS), leukotriene B4 (LTB4), and copper, and some chemical-induced models, such as treatment with trinitrobenzene sulfonic acid (TNBS), specifically model inflammation in the gastro-intestinal tract. Two mutant zebrafish lines, carrying a mutation in the hepatocyte growth factor activator inhibitor 1a gene (hai1a) and the cdp-diacylglycerolinositol 3-phosphatidyltransferase (cdipt) gene, show an inflammatory phenotype, and they provide interesting model systems for studying inflammation. These zebrafish inflammation models are often used to study the anti-inflammatory effects of glucocorticoids, to increase our understanding of the mechanism of action of this class of drugs and to develop novel glucocorticoid drugs. In this review, an overview is provided of the available inflammation models in zebrafish, and how they are used to unravel molecular mechanisms underlying the inflammatory response and to screen for novel anti-inflammatory drugs.

Comparative Evaluation of Essential Oils from Medicinal-Aromatic Plants of Greece: Chemical Composition, Antioxidant Capacity and Antimicrobial Activity against Bacterial Fish Pathogens

The administration of antibiotics in aquaculture has raised concern about the impact of their overuse in marine ecosystems, seafood safety and consumers' health. This "green consumerism" has forced researchers to find new alternatives against fish pathogens. The present study focused on 12 Mediterranean medicinal-aromatic plants as potential antimicrobials and antioxidant agents that could be used in fish aquaculture. In vitro assays showed that the essential oils (EOs) from all studied plants had anti-bacterial and antioxidant properties, with their efficacy being dependent on their chemical composition. More specifically, EOs rich in carvacrol, p-cymene and γ-terpinene exhibited not only the strongest inhibitory activity against the growth of bacterial pathogens (inhibitory concentration: 26-88 μg mL-1), but also the greatest total antioxidant capacity (ABTS: 2591-5879 μmole mL-1; CUPRAC: 931-2733 μmole mL-1). These compounds were mainly found in the EOs from Greek oregano (Origanum vulgare subsp. hirtum), Spanish oregano (Thymbra capitata) and savoury (Satureja thymbra) collected from cultivations in Greece. The specific EOs stand out as promising candidates for the treatment of bacterial diseases and oxidative stress in farmed fish. Further in vivo experiments are needed to fully understand the effects of EO dietary supplementation on fish farming processes.

Chemical Composition and in Vitro Cytotoxic Screening of Sixteen Commercial Essential Oils on Five Cancer Cell Lines

The in vitro cytotoxic activity on human cancer cell lines of sixteen commercial EOs such as Aloysia citriodora, Boswellia sacra, Boswellia serrata, Cinnamomum zeylanicum, Cistus ladanifer, Citrus × aurantium, Citrus limon, Citrus sinensis, Cymbopogon citratus, Foeniculum vulgare, Illicium verum, Litsea cubeba, Satureja montana, Syzygium aromaticum, Thymus capitatus and Thymus vulgaris was performed using the MTT reduction assay. The screening was carried out on human cancer cells of breast adenocarcinoma (MCF7, T47D and MDA-MB-231), chronic myelogenous erythroleukemia (K562) and neuroblastoma cell lines (SH-SY5Y). C. zeylanicum and L. cubeba EOs were the most active on almost all the cell lines studied and thus could be promising as an anticancer agent. These two species showed a difference in their composition even though they belong to the Lauraceae family. Almost 57 % of the true cinnamon composition was made of (E)-cinnamaldehyde, while L. cubeba showed citral as the major compound (68.9 %). The K562 cells were the most sensitive to these oils with an IC₅₀ ranging from 5.2 parts-per million (ppm) (C. zeylanicum) to 11.1 ppm (L. cubeba). The latter oil also showed an important cytotoxicity on MDA-MB-231 (13.4 ppm).

Effects of the Essential Oil from Pistacia lentiscus Var. chia on the Lateral Line System and the Gene Expression Profile of Zebrafish (Danio rerio)

Mastic essential oil exhibits anti-bacterial, anti-inflammatory, and anti-oxidant properties. With the growing interest of the use of mastic oil in the food and pharmaceutical industry, systematic in vivo studies are needed to address controlled usage and safety issues. In the present work we evaluated the safety of mastic oil using as a model the zebrafish lateral line system. In addition, we studied the gene expression profile of zebrafish fed with mastic oil-supplemented diet using microarray analysis. Our results showed that the hair cells of lateral line neuromasts are functional upon exposure of zebrafish larvae up to 20 ppm of mastic essential oil, while treatment with higher concentrations, 100 and 200 ppm, resulted in increased larvae mortality. Dietary supplementation of zebrafish with mastic essential oil led to differential expression of interferon response-related genes as well as the immune responsive gene 1 (irg1) that links cellular metabolism with immune defense. Notably, mucin 5.2, a constituent of the mucus hydrogel that protects the host against invading pathogens, was up-regulated. Our in vivo work provides information concerning the safety of mastic essential oil use and suggests dietary effects on gene expression related with the physical and immunochemical properties of the gastrointestinal system.

Prolonged mosquitocidal activity of Siparuna guianensis essential oil encapsulated in chitosan nanoparticles

Background

The use of synthetic insecticides is one of the most common strategies for controlling disease vectors such as mosquitos. However, their overuse can result in serious risks to human health, to the environment, as well as to the selection of insecticidal resistant insect strains. The development of efficient and eco-friendly insect control is urgent, and essential oils have been presented as potential alternatives to synthetic insecticides. Moreover, nanoencapsulation techniques can enhance their efficiency by protecting from degradation and providing a controlled release rate.

Results

We assessed the potential of chitosan nanoparticles in encapsulating Siparuna guianensis essential oil, and maintaining its efficiency and prolonging its activity for the control of Aedes aegypti larvae. The encapsulation was characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA), with an encapsulation efficiency ranging from 84.8% to 88.0%. Toxicity studies have demonstrated efficacy against mosquito larvae over 50% for 19 days with 100% mortality during the first week. This persistent action is presumably due to the enhanced contact and slow and maintained release conferred by chitosan nanoparticles. Furthermore, the exposure of aquatic non-target organisms (e.g. embryos and small adult fishes) revealed adequate selectivity of these nanoparticles.

Conclusions

The encapsulation of S. guianensis essential oil in chitosan nanoparticles showed promising potential as a larvicide control alternative and should be considered within strategies for fighting Ae. aegypti.

Numerous outbreaks of infectious diseases such as dengue, zika, and chikungunya in tropical countries have occurred where the mosquito Aedes aegypti is the transmitting vector. In Brazil, these infections are responsible for deaths and severe sequelae. Thus, many efforts have been made by governmental and research groups to control these outbreaks. However, complete success in this control has so far remained unachieved. Parallel to the need to develop new technologies that contribute to the control of insects that transmit diseases, there is a growing societal awareness regarding the risks associated with the use of synthetic insecticides, which has led to a search for natural alternatives such as essential oils from plants. Thus, our group conducted experiments to evaluate the application of nanotechnology in obtaining an efficient prolonged release system to combat Ae. aegypti larvae using the essential oil of a plant native to the Cerrado and Amazonian forests. These results demonstrate that using a simple and easily scalable encapsulation technique; it is possible to keep the low toxicity against non-target organism and prolong the activity of an essential oil in water and maintain larval mortality at a significant level for more than a week with a single application.

In Vitro Activity of Essential Oils against Saprolegnia parasitica

Saprolegnia spp. water molds severely impact fish health in aquaculture, fish farms and hobby fish tanks colonizing mature and immature stages of fishes, as well as eggs. Considering that there are no drugs licensed for treating and/or control the organism, efficient and environmental low-impact methods to control these oomycetes in aquaculture are needed. The aim of the present report was to evaluate the in vitro sensitivity of Saprolegnia parasitica to essential oils (EOs) from Citrus aurantium L., Citrus bergamia Risso et Poiteau, Citrus limon Burm. f., Citrus paradisi Macfad, Citrussinensis Osbeck, Cinnamomum zeylanicum Blume, Cymbopogon flexuosum (Nees ex Steud.) Watson, Foeniculum vulgare Mill., Illicium verum Hook.f., Litsea cubeba (Lour.) Pers., Origanum majorana L., Origanum vulgare L., Pelargonium graveolens L’Hér., Syzygium aromaticum Merr. & L.M.Perry, and Thymus vulgaris L., by microdilution test. The most effective EOs assayed were T. vulgaris and O. vulgare, followed by C. flexuosum, L. cubeba and C. bergamia. These EOs could be of interest for controlling Saprolegnia infections. Nevertheless, further safety studies are necessary to evaluate if these products could be dispersed in tank waters, or if their use should be limited to aquaculture supplies.