Genotoxic effect of Lippia alba (Mill.) N. E. Brown essential oil on fish (Oreochromis niloticus) and mammal (Mus musculus)

Chemical composition and biological activities of the essential oils from Lippia alba and Lippia origanoides

There is an increasing interest in essential oils extracted from Verbenaceae plant species as potential sources of biologically active compounds that could provide a starting point for designing novel phyto-pharmaceuticals in aquaculture. The present study was aimed to investigate the chemical composition, antioxidant activity, acute toxicity and antimicrobial effects against Vibrio parahaemolyticus of essential oils extracted from Lippia alba and L. origanoides. Approximately 23 components were identified and quantified by gas chromatography-mass spectrometry and flame ionization detection in each species' essential oil. The most predominant compounds were geranial (23.0%), limonene (17.0%) and neral (15.5%) in L. alba, and thymol (47.2%), p-cymene (16.0%) and E-caryophyllene (11.3%) in L. origanoides. The essential oils have antibacterial activity against Vibrio parahaemolyticus presenting Minimum Inhibitory Concentration (MIC) and Bactericidal Concentration (MBC) values between 156-625 µg mL-1. The essential oils also show antioxidant potential estimated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging assays, presenting IC50 of 60.16 mg mL-1 and 0.22 mg mL-1 for L. alba and L. origanoides EO, respectively. Both oils were classified as toxic to Artemia salina nauplii. Therefore, these essential oils may be useful for controlling pathogenic bacteria important to the aquaculture industry.

Pharmacological Screening of Species from the Lippia genus, Content in Terpenes and Phenylpropanoids, and their Vasorelaxing Effects on Human Umbilical Artery

BACKGROUND

Naturally occurring bioactive compounds have a plethora of biological effects.

OBJECTIVE

In this study, we examined a pharmacological screening of natural products on the human umbilical artery (HUA).

METHODS

HUA preparations were used to follow contractions by KCl (60 mM) and tested at different concentrations (1-5000 μg/mL and μM) of the Lippia alba (EOLa) and Lippia origanoides (EOLo) essential oils, terpenes (citral, limonene perilic alcohol) and phenylpropanoids (eugenol, methyl eugenol). Discussion/Results: The reduction corresponded to approximately 100%, except for limonene (80±1.2 %). When evaluating the concentration of the natural product that promotes 50 % relaxation of the HUA contracted by KCL, EC50 values were: 424.3 μg/mL (EOLa); 468.7±6.7 μg/mL (EOLo); 264.2 ± 8.2 μM (citral); 677.8±5.4 μM (limonene); 186.3±6.4 μM (peryl alcohol); 986.4±7.9 μM (eugenol); and 279.1±4.4 μM (methyl-eugenol). Perillyl alcohol had a lower EC50 (consequently it has a higher pharmacological potency).

CONCLUSION

The plant extracts have a promising vasorelaxing effect in HUAs, paving the way for future investigations: as applications in diseases related to these vessels, such as preeclampsia.

Effect of Lippia alba (Mill.) N.E. Brown Essential Oil on the Human Umbilical Artery

Lippia alba is popularly known as lemon balm, with its essential oil (EO) cited for displaying antimicrobial, sedative, and vasorelaxant effects. Yet, its action on isolated human vessels has not been described in the literature. Thus, we evaluated the vasorelaxant effect of essential oil of L. alba (EOLa) on human umbilical arteries (HUA) isolated in organ baths. HUA rings were isolated, subjected to contractions induced by potassium chloride (KCl), serotonin (5-HT), or histamine (HIST) to record the isometric tension, and then treated with EOLa (30-1000 µg/mL). The EOLa showed a more prominent inhibitory effect on the pharmacomechanical coupling contraction via HIST with an EC₅₀ value of 277.1 ± 8.5 µg/mL and maximum relaxant effect at 600 µg/mL. The addition of tetraethylammonium (TEA) or 4-aminopyridine (4-AP) in HUA preparations did not inhibit EOLa total relaxant effect at 1000 µg/mL. In the presence of gliblenclamide (GLI), the oil relaxed the HUA rings by 90.8% at maximum concentration. The EOLa was also investigated for its effects on voltage-operated calcium channels (VOCCs), where the HUA preincubation with this oil at 1000 μg/mL inhibited BaCl₂ (0.1-30 mM)-induced contractions. This study demonstrates for the first time that EOla has a vasorelaxant effect on HUA and its particular blockade of VOCCs.

Physiological Response of Atlantic Salmon (Salmo salar) to Long-Term Exposure to an Anesthetic Obtained from Heterosigma akashiwo

Despite the invaluable role of anesthetics as a tool for ensuring animal welfare in stressful situations, there is currently a lack of anesthetic drugs that meet the requirements of intensive aquaculture. In response to the growing interest in anesthetic substances of natural origin, this study evaluated the physiological and health impact of an anesthetic based on an extract of the microalga Heterosigma akashiwo on juvenile salmon (Salmo salar) exposed for a period of 72 h. To simulate a condition closer to reality where fish are subjected to stimuli (e.g., transport), the animals were exposed to 50 mg L⁻¹ of algal extract and to physical stress. Functional, physiological, and histological parameters were evaluated in blood and tissues at different sampling periods (0, 24, and 72 h). There was no mortality and the induction and recovery times observed were within the established criteria for anesthetic efficacy. The anesthetic extract did not induce any side effects, such as stress or metabolic damage, indicating that this extract is a viable option for supporting fish welfare during deleterious events. This study provides information to support that the anesthetic extract tested, derived from H. akashiwo, is a promising candidate drug for operations requiring sedation (e.g., Salmonid transport).

Insecticidal activity of a chemotype VI essential oil from Lippia alba leaves collected at Caatinga and the major compound (1,8-cineole) against Nasutitermes corniger and Sitophilus zeamais

Lippia alba is an aromatic shrub known to produce a diversity of essential oils, which can be classified into chemotypes. This study reports on the insecticidal activity of essential oil from L. alba leaves collected at Caatinga and its major compound against termite Nasutitermes corniger and maize weevil Sitophilus zeamais. The chromatographic analysis revealed the presence of 19 compounds, with 1,8-cineole being the most common (70.01%). When ingested, the oil promoted the mortality of N. corniger (LC₅₀: 18.25 and 8.4 nL/g for workers and soldiers, respectively). The compound 1,8-cineole was also termiticidal for workers (LC₅₀: 13.7 nL/g). The oil inhibited the activity of N. corniger exoglucanase, xylanase, and proteases. Toxicity by ingestion to S. zeamais was detected for the oil (LC₅₀: 0.297 μL/g) but not for 1,8-cineole; however, both the oil and 1,8-cineole showed anti-nutritional effects. Fumigant effects of the oil and 1,8-cineole against S. zeamais (LC₅₀ of 78.0 and 13.64 μL/L in air, respectively) were detected. This is the first record of a chemotype VI oil from L. alba collected at Caatinga and the first report of the insecticidal activity of a chemotype VI oil. Our study demonstrates that essential oil from L. alba and 1,8 cineole have the potential for the development of natural insecticides.

Biofilm inhibition by biocompatible poly(ε-caprolactone) nanocapsules loaded with essential oils and their cyto/genotoxicity to human keratinocyte cell line

Essential oils (EOs) of Thymus capitatus (Th) carvacrol chemotype and Origanum vulgare (Or) thymol and carvacrol chemotype were encapsulated in biocompatible poly(ε-caprolactone) nanocapsules (NCs). These nanosystems exhibited antibacterial, antifungal, and antibiofilm activities against Staphylococcus aureus, Escherichia coli, and Candida albicans. Th-NCs and Or-NCs were more effective against all tested strains than pure EOs and at the same time were not cytotoxic on HaCaT (T0020001) human keratinocyte cell line. The genotoxic effects of EO-NCs and EOs on HaCaT were evaluated using an alkaline comet assay for the first time, revealing that Th-NCs and Or-NCs did not induce DNA damage compared with untreated control HaCaT cells in vitro after 24 h. The cells morphological changes were assessed by label-free live cell Raman imaging. This study demonstrate the ability of poly(ε-caprolactone) nanocapsules loaded with thyme and oregano EOs to reduce microbial and biofilm growth and could be an ecological alternative in the development of new antimicrobial strategies.

The effectiveness of surfactants applied with essential oil of Lippia alba in the anesthesia of Nile tilapia (Oreochromis niloticus) and their toxicity assessment for fish and mammals

The Lippia alba essential oil (EO) is a fish anesthetic immiscible in water and commonly used diluted in ethanol. We evaluated the effectiveness of surfactant use with Lippia alba EO in the anesthesia of Oreochromis niloticus, as well as its toxicity in fish and mammals. The EO was extracted by hydrodistillation and the fish were exposed to anesthesia at the concentration of 250 μL/L for 10 min with the surfactants polysorbate 20 (T20), polysorbate 80 (T80), polyethylene glycol (PEG), and ethanol. We also evaluated fish recovery and anesthetic safety margin after exposure for 10, 20, and 30 min. To assess the surfactants' toxicity in mammals, Mus musculus (mice) received the same treatments by gavage. The main constituents of the Lippia alba EO were linalool (42.36%), geraniol (12.46%), neral (10.7%), and limonene (7.45%). Deeper anesthesia was faster in the T20 (60 ± 2.9 s) and T80 (272 ± 21 s) treatment groups, while recovery time for T80 was longer (596 ± 47 s). All treatments showed a good safety margin, without mortality. The genotoxic effects caused by surfactants in mammals and fish were at similar levels to those found in the ethanol treatment. Therefore, this study demonstrated that the use of surfactants T20 and T80 in Oreochromis niloticus anesthesia presented neither a reduction nor a considerable increase of the toxicity when compared to the commonly used ethanol; however, an increase in anesthetic effectiveness was observed throughout the experiment.

Toxicity of polystyrene nanoplastics in Ctenopharyngodon idella juveniles: A genotoxic, mutagenic and cytotoxic perspective

The increased contamination of surface water with plastic waste is proportional to the increased consumption of products that use them as raw material. However, the impact of these residues on aquatic biota remains limited, mainly when it comes to nanoplastics (NPs). Thus, the aim of the current study is to test the hypothesis that the exposure of Ctenopharyngodon idella juveniles to polystyrene nanoplastics (PS NPs) at low concentrations (0.04 ng/L, 34 ng/L and 34 μg/L), for 20 days, leads to DNA damage and has mutagenic and cytotoxic effects on their erythrocytes. Comet assay enabled observing that DNA damage (inferred from the greater tail length, DNA percentage in the tail and Olive tail moment) induced by PS NPs has increased as the pollutant concentrations have increased, as well as that the formation of micronuclei and other nuclear abnormalities was equitable in animals exposed to this pollutant. On the other hand, there were significant changes in erythrocyte shape and size, oxidative stress generation (NO levels, lipid peroxidation, hydrogen peroxide), antioxidant system inhibition (mediated by total hepatic glutathione) and PS NPs accumulation in the liver and brain of animals exposed to higher concentrations of it. Therefore, the current study has confirmed the initial hypothesis and enhanced the knowledge about the genotoxic, mutagenic and cytotoxic potential of PS NPs in freshwater fish at early developmental stage, relating these effects to biochemical changes and significant accumulation of these nanomaterials. Besides, it is a warning about the (eco) toxicological risk represented by these nanopollutants in aquatic environments. CAPSULE: Polystyrene nanoplastics are capable of inducing DNA damage, mutagenic and cytotoxicity changes in fish.

Trophic transfer of carbon nanofibers among eisenia fetida, danio rerio and oreochromis niloticus and their toxicity at upper trophic level

Although the toxicity of carbon-based nanomaterials has already been demonstrated in several studies, their transfer in the food chain and impact on the upper trophic level remain unexplored. Thus, based on the experimental food chain "Eisenia fetida → Danio rerio → Oreochromis niloticus", the current study tested the hypothesis that carbon nanofibers (CNFs) accumulated in animals are transferred to the upper trophic level and cause mutagenic and cytotoxic changes. E. fetida individuals were exposed to CNFs and offered to D. rerio, which were later used to feed O. niloticus. The quantification of total organic carbon provided evidence of CNFs accumulation at all evaluated trophic levels. Such accumulation was associated with higher frequency of erythrocyte nuclear abnormalities such as constricted erythrocyte nuclei, vacuole, blebbed, kidney-shaped and micronucleated erythrocytes in Nile tilapia exposed to CNFs via food chain. The cytotoxic effect was inferred based on the smaller size of the erythrocyte nuclei and on the lower "nuclear/cytoplasmic" area ratio in tilapia exposed to CNFs via food chain. Our study provided pioneering evidence about CNFs accumulation at trophic levels of the experimental chain, as well as about the mutagenic and cytotoxic effect of these materials on O. niloticus.

Histopathological, genotoxic, and behavioral damages induced by manganese (II) in adult zebrafish

Manganese is a metal often found as an environmental pollutant and very associated with neurological disorders when in high concentrations. However, little is known about the effects that this contaminant can cause when in environmentally relevant concentrations and occurrence, that is, much lower than those commonly studied. So, the aim of the study was to evaluate the effects that environmentally relevant concentrations of this metal would cause in different zebrafish organs (brain, liver, and blood). Acute 96-h and chronic 30-day exposures were performed using the manganese chloride salt as a pollutant. Behavioral alterations of anxiogenic type were observed in the animals after chronic exposures to 4.0 mg L^-1 MnCl₂, which traveled a greater distance at the bottom of the aquarium. This may be associated with neuronal damages in the telencephalic region responsible for motor and cognitive activity of the fish, observed in animals from the same exposure. In addition, hepatic histopathological damage as vacuolization of hepatocytes and genotoxic damage, identified by comet assay and micronucleus test, was also observed after acute and chronic exposure, especially at the highest pollutant concentrations (8.0 and 16.0 mg L^-1 in acute exposure, and 4.0 mg L^-1 in chronic exposure. The study reinforces the risk that environmental pollutants pose to the ecosystem, even in low concentrations.

Nanospheres as a technological alternative to suppress hepatic cellular damage and impaired bioenergetics caused by nerolidol in Nile tilapia (Oreochromis niloticus)

Nerolidol is a sesquiterpene found in essential oils of several plant species. It is found commonly in human and animal diets and is approved by the US Food and Drug Administration as a flavoring agent. Nevertheless, recent studies have suggested that nerolidol has potent hepatotoxic effects. Because use of plant-based products in human and animal food has expanded considerably, it is essential to develop approaches such as nanotechnology to avoid or reduce hepatic toxic effects. Therefore, the aim of the study was to determine whether nerolidol dietary supplementation elicited hepatic damage associated with impairment of energy homeostasis, as well as whether supplementation with nerolidol-loaded in nanospheres prevented hepatotoxic effects in Nile tilapia (Oreochromis niloticus). Nile tilapia were divided into five groups (A-E, n = 10 per group) with four replicates each, as follows: group A received basal feed (without supplementation); group B received feed containing 0.5 mL free nerolidol/kg; group C received feed containing 1.0 mL free nerolidol/kg; group D received feed containing 0.5 mL nanospheres nerolidol/kg; and group E received feed containing 1.0 mL nanospheres nerolidol/kg. All groups received experimental feed once a day (10% total biomass) at 2 p.m. for 60 consecutive days. Hepatic liver weight and relative liver weight were significantly lower in fish fed 1.0 mL free nerolidol/kg feed than in fish given basal diet (control group). Hepatic pyruvate kinase (1.0 mL free nerolidol/kg) and adenylate kinase (0.5 and 1.0 mL free nerolidol/kg) activities were significantly lower than in the control group, while hepatic reactive oxygen species and lipid damage levels were significantly higher. Finally, the comet assay revealed significant increases in the frequency of damage and the damage index in fish given 0.5 and 1.0 mL free nerolidol/kg in a dose-dependent manner. Nerolidol-loaded in nanospheres prevented all alterations elicited by free nerolidol. Based on these data, we concluded that dietary supplementation with free nerolidol elicited severe impairment of hepatic bioenergetics homeostasis that appeared to be mediated by excessive ROS production and lipid damage, contributing to a genotoxic effect. Dietary supplementation with nerolidol-loaded in nanospheres did not elicit hepatic damage, and therefore, should be considered as a replacement so as to limit toxicity, permitting its continued use as a dietary supplement.

An insight on the mutagenicity and cytotoxicity of zinc oxide nanoparticles in Gallus gallus domesticus (Phasianidae)

Although the toxicity of zinc oxide (ZnO) nanoparticles (NPs) is known in several experimental models, little is known about their effects on bird representatives. Therefore, the aim of the current study is to evaluate the mutagenic and cytotoxic potential of ZnO NPs in chicks belonging to species Gallus gallus domesticus, as well as to analyze the role played by nuclear and erythrocyte morphological changes as biomarkers of the toxicity of these nanopollutants. Two doses of ZnO NPs (0.245 mg k^-1 and 245.26 mg kg^-1) were herein tested; they were determined based on the predictive environmental concentration of these NPs (760 μg L-1), on the body biomass of the analyzed animals and on the mean daily water intake/bird. Birds were subjected to two intraperitoneal applications (one per day) of solution containing ZnO NPs; they were euthanized 48 h after the first application. The herein collected data have shown that NPs were capable of inducing the formation of different types of erythrocyte nuclear abnormalities, such as micronucleus, binucleate erythrocytes, blebbed, reniform and multilobulated nuclei, as well as symmetric and asymmetric constriction. In addition, changes in the size and shape of erythrocytes were observed in birds exposed to ZnO NPs. Zn bioaccumulation analysis conducted in brain tissues confirmed the association between these changes and animal exposure to ZnO NPs. Thus, besides confirming the toxicological potential of ZnO NPs, to the best of our knowledge, the current study is the first report on the mutagenic and cytotoxic effects of these NPs on bird representatives.