Activity of Selected Group of Monoterpenes in Alzheimer's Disease Symptoms in Experimental Model Studies-A Non-Systematic Review

Neuroprotective effects of alpha-pinene against behavioral deficits in ketamine-induced mice model of schizophrenia: Focusing on oxidative stress status

Schizophrenia (SCZ) is a profound neurological disorder that affects approximately 1% of the global population. Alpha-pinene (α-pinene) is a natural and active monoterpene found in coniferous tree oil, primarily pine, with diverse pharmacological characteristics, including antioxidative, anxiolytic, and antidepressant properties. This research study delves into the neuroprotective effects of α-pinene on oxidative stress, memory deficits, and depressive and anxiety-like behaviors in a ketamine-induced mice model of SCZ using male mice. The mice were randomly divided into six groups: vehicle, control, positive control, ketamine, α-pinene at 50 mg/kg, and α-pinene at 100 mg/kg. Treatment of the ketamine-induced mice model of SCZ with α-pinene yielded significant improvements in depressive and anxiety-like behaviors and cognitive impairments. Furthermore, it significantly elevated glutathione (GSH) levels, total antioxidant capacity (TAC), dopamine levels, catalase (CAT), and superoxide dismutase (SOD) activities while markedly reducing malondialdehyde (MDA) levels. The current study establishes that α-pinene treatment effectively mitigates oxidative damage, cognitive deficits, and depressive and anxiogenic-like behaviors in the brains of ketamine-treated mice. Therefore, α-pinene treatment is an efficacious approach to forestall the neurobehavioral and neurobiochemical adverse effects of the ketamine-induced SCZ model of mice.

Anticholinesterases activity of Murraya koenigii (L.) Spreng. and Murraya paniculata (L.) Jacq. essential oils with GC/MS analysis and molecular docking

GC/MS analysis of Murraya koenigii (L.) Spreng. and Murraya paniculata (L.) Jacq. leaves revealed the identification of 73 components, with an evident greater contribution of monoterpenes hydrocarbons to their total volatiles. α-Pinene (37.5%) and β-caryophyllene (27.4%) were the most abundant compounds in M. koenigii leaves and β-phellandrene (40.7%) in M. paniculata leaves, using headspace. β-Phellandrene (33.7%) was the major constituent by M. koenigii leaves where germacrene D (23.8%), and δ-elemene (22.0%) were predominant in M. paniculata leaves, using steam distillation. M. koenigii leaves oil showed quite remarkable cholinesterase inhibitory activity, where oil of M. paniculata leaves showed strong inhibitory activity against AChE (IC50=13.2 ± 0.9 µg/mL) and BChE (IC50=5.1 ± 0.3 µg/mL). Germacrene D, α-zingiberene, and δ-elemene showed higher affinity to BChE than AChE as revealed from docking scores (S = -5.65 to -6.03 Kcal/mol) for BChE and (S = -5.56 to -6.25 Kcal/mol) for AChE.

Therapeutic potential of the linalool against cadmium-induced testicular tissue damage

Cadmium (Cd) is a heavy metal that has harmful effects and is one of the contaminants found in the environment. Cd exposure causes important pathophysiological processes, such as reproductive toxicity. Linalool (Lnl) is a monoterpene, a component of essential oils known to be produced synthetically. Additionally, Lnl has many important beneficial effects, such as anti-inflammatory and antioxidant effects. The objective of this study is to determine whether Lnl has a healing impact in opposition to testicular tissue damage due to Cd exposure. In the study, 28 male rats were divided at random into four equal groups (n = 7). No treatment was applied to the control group. CdCl2 was applied intraperitoneally to the Cd group at a dose of 3 mg/kg for the first 7 days of the trial. For the Cd + Lnl group, 3 mg/kg CdCl2 was applied intraperitoneally for the first 7 days of the trial, and 100 mg/kg/day Lnl was applied. Upon completion of all applications, the rats were sacrificed and blood samples and testicular tissue were taken. Cd exposure caused histopathological changes, oxidative stress, inflammation, and an increase in apoptotic cells in testicular tissue. However, Cd altered endocrine hormones in the hypothalamic-pituitary-gonad axis. However, Lnl application against Cd exposure was able to regulate the negativity caused by Cd in both testicular tissue and endocrine hormone levels. In conclusion, Lnl may be a potential therapeutic strategy against Cd-induced reproductive toxicity. We believe that Lnl has a high potential for further studies to determine its detailed mechanisms of action and cellular signaling pathways.

Prophylactic and therapeutic inhalation of two essential oils ameliorates scopolamine-induced cognitive impairment in mice

Clover and lemongrass essential oils of contrasting composition, at three concentration levels (1%, 5%, 10%), were administrated via prophylactic and therapeutic inhalation to scopolamine-treated mice. Chemical analysis showed that clover oil was dominant in eugenol (47.69%) and lemongrass free of eugenol but mainly containing monoterpenoids of comparable proportions. Animal behavioural and brain biochemical tests showed that injection of scopolamine caused memory and learning deficit in mice while prophylactic and therapeutic inhalation of two oils at moderate to high concentrations all obviously reversed the cognitive impairment via inhibiting acetylcholinesterase activities, oxidation and inflammation. Lemongrass essential oil with diverse monoterpenoids can be as effective as or a little bit more potent than eugenol-rich clover essential oil possibly due to the synergistic effect of various monoterpenoids. These findings implied that sniffing of such aroma recipes could be a promising complementary approach for the mitigation of Alzheimer's disease-related cognitive impairment.

A comprehensive review of the botany, phytochemistry, pharmacology, and toxicology of Murrayae Folium et Cacumen

Ethnopharmacological relevance: Murrayae Folium et Cacumen (MFC) is a plant considered to be a traditional Chinese medicine with culinary value as well. The dry leaves and twigs of Murraya paniculata and M. exotica are used to treat stomach aches, rheumatism, toothaches, swelling, and insect and snake bites. They are also used to prepare spicy chicken dishes. Aim of the review: This review comprehensively summarizes the available information on the botanical characterization, phytochemistry, pharmacological activities, pharmacodynamics, pharmacokinetics, and toxicity of MFC. Methods: Relevant scientific literature up to August 2023 was included in the study. Chinese and English studies on MFC were collected from databases, including PubMed, Elsevier, Web of Science, Springer, Science Direct, Wiley, ACS, and CNKI (Chinese). Doctoral and Master's dissertations were also included. Results: In total, 720 compounds have been identified and reported in the literature, including flavonoids, coumarins, alkaloids, sterols, phenylpropenols, organic acids, spirocyclopentenones, and volatile oils. Flavonoids and coumarins are the two most important bioactive compounds responsible for these pharmacological activities. MFC has anti-inflammatory, anti-bacterial, anti-microbial, anti-diabetic, anti-tumor, anti-oxidant, anti-depressant, potential anti-Alzheimer's disease, chondroprotective, and analgesic properties. The pharmacological effects include interrupting the STAT3/NF-κB/COX-2 and EGFR signaling pathways, downregulating EpCAM expression, inhibiting NF-κB and ERK signals, inhibiting the EP/cAMP/PKA signaling pathway and miR-29a/Wnt/β-catenin signaling activity, and upregulating Foxo3a expression. Conclusion: This review demonstrates that the chemical constituents, pharmacological activities, pharmacodynamics, pharmacokinetics, and toxicity of MFC support its use in traditional Chinese botanical medicines. MFC contains a wide range of chemical compounds. Flavonoids and coumarins promote strong pharmacological activity and, are low-toxicity natural phytomedicines that are widely used in medicine, food, ornamentation, and cosmetics, making MFC a promising compound for development and use in the treatment of several medical conditions.

Essential Oils in Cervical Cancer: Narrative Review on Current Insights and Future Prospects

Cervical cancer is a prevalent and often devastating disease affecting women worldwide. Traditional treatment modalities such as surgery, chemotherapy, and radiation therapy have significantly improved survival rates, but they are often accompanied by side effects and challenges that can impact a patient's quality of life. In recent years, the integration of essential oils into the management of cervical cancer has gained attention. This review provides an in-depth exploration of the role of various essential oils in cervical cancer, offering insights into their potential benefits and the existing body of research. The review also delves into future directions and challenges in this emerging field, emphasizing promising research areas and advanced delivery systems. The encapsulation of essential oils with solid lipid nanoparticles, nanoemulsification of essential oils, or the combination of essential oils with conventional treatments showed promising results by increasing the anticancer properties of essential oils. As the use of essential oils in cervical cancer treatment or management evolves, this review aims to provide a comprehensive perspective, balancing the potential of these natural remedies with the challenges and considerations that need to be addressed.

Chemo- and bio-informatics insight into anti-cholinesterase potentials of berries and leaves of Myrtus communis L., Myrtaceae: an in vitro/in silico study

BACKGROUND

Myrtus communis L. (MC) has been used in Mesopotamian medicine. Here, the cholinesterase (ChE) inhibitory potential of its methyl alcohol extracts has been investigated and computationally dissected.

METHOD

The ChE inhibition has been measured based on usual Ellman's colorimetric method compared to a canonical ChE inhibitor, eserine. Through a deep text mining, the structures of phytocompounds (= ligands) of MC were curated from ChemSpider, PubChem, and ZINC databases and docked into protein targets, AChE (PDB 1EVE) and BChE (PDB 1P0I) after initial in silico preparedness and binding affinity (BA; kcal/mol) reported as an endpoint. The calculation of ADMET (absorption, distribution, metabolism, excretion, and toxicity) features of phytocompounds were retrieved from SwissADME ( http://www.swissadme.ch/ ) and admetSAR software to predict the drug-likeness or lead-likeness fitness. The Toxtree v2.5.1, software platforms ( http://toxtree.sourceforge.net/ ) have been used to predict the class of toxicity of phytocompounds. The STITCH platform ( http://stitch.embl.de ) has been employed to predict ChE-chemicals interactions.

RESULTS

The possible inhibitory activities of AChE of extracts of leaves and berries were 37.33 and 70.00%, respectively as compared to that of eserine while inhibitory BChE activities of extracts of leaves and berries of MC were 19.00 and 50.67%, respectively as compared to that of eserine. Phytochemicals of MC had BA towards AChE ranging from -7.1 (carvacrol) to -9.9 (ellagic acid) kcal/mol. In this regard, alpha-bulnesene, (Z)-gamma-Bisabolene, and beta-bourbonene were top-listed low toxic binders of AChE, and (Z)-gamma-bisabolene was a more specific AChE binder. Alpha-cadinol, estragole, humulene epoxide II, (a)esculin, ellagic acid, patuletin, juniper camphor, linalyl anthranilate, and spathulenol were high class (Class III) toxic substances which among others, patuletin and alpha-cadinol were more specific AChE binders. Among intermediate class (Class II) toxic substances, beta-chamigrene was a more specific AChE binder while semimyrtucommulone and myrtucommulone A were more specific BChE binders.

CONCLUSION

In sum, the AChE binders derived from MC were categorized mostly as antiinsectants (e.g., patuletin and alpha-cardinal) due to their predicted toxic classes. It seems that structural amendment and stereoselective synthesis like adding sulphonate or sulphamate groups to these phytocompounds may make them more suitable candidates for considering in preclinical investigations of Alzheimer's disease.

Citronellal as a Promising Candidate for Alzheimer's Disease Treatment: A Comprehensive Study on In Silico and In Vivo Anti-Acetylcholine Esterase Activity

One of the primary therapeutic approaches for managing Alzheimer's disease (AD) involves the modulation of Acetylcholine esterase (AChE) activity to elevate acetylcholine (ACh) levels inside the brain. The current study employed computational chemistry approaches to evaluate the inhibitory effects of CTN on AChE. The docking results showed that Citronellal (CTN) and standard Donepezil (DON) have a binding affinity of -6.5 and -9.2 Kcal/mol, respectively, towards AChE. Further studies using molecular dynamics (MD) simulations were carried out on these two compounds. Binding free energy calculations and ligand-protein binding patterns suggested that CTN has a binding affinity of -12.2078. In contrast, DON has a much stronger binding relationship of -47.9969, indicating that the standard DON has a much higher binding affinity than CTN for AChE. In an in vivo study, Alzheimer-type dementia was induced in mice by scopolamine (1.5 mg/kg/day i.p) for 14 days. CTN was administered (25 and 50 mg/kg. i.p) along with scopolamine (SCO) administration. DON (0.5 mg/kg orally) was used as a reference drug. CTN administration significantly improved the mice's behavior as evaluated by the Morris water maze test, evident from decreased escape latency to 65.4%, and in the CPS test, apparent from reduced escape latency to 69.8% compared to the positive control mice. Moreover, CTN significantly increased the activities of antioxidant enzymes such as catalase and superoxide dismutase (SOD) compared to SCO. Furthermore, CTN administration significantly decreased SCO-induced elevated AChE levels in mice. These results were supported by histopathological and in silico molecular docking studies. CTN may be a potential antioxidant and neuroprotective supplement.

Therapeutic Potential of Myrtenal and Its Derivatives-A Review

The investigation of monoterpenes as natural products has gained significant attention in the search for new pharmacological agents due to their ability to exhibit a wide range in biological activities, including antifungal, antibacterial, antioxidant, anticancer, antispasmodic, hypotensive, and vasodilating properties. In vitro and in vivo studies reveal their antidepressant, anxiolytic, and memory-enhancing effects in experimental dementia and Parkinson's disease. Chemical modification of natural substances by conjugation with various synthetic components is a modern method of obtaining new biologically active compounds. The discovery of new potential drugs among monoterpene derivatives is a progressive avenue within experimental pharmacology, offering a promising approach for the therapy of diverse pathological conditions. Biologically active substances such as monoterpenes, for example, borneol, camphor, geraniol, pinene, and thymol, are used to synthesize compounds with analgesic, anti-inflammatory, anticonvulsive, antidepressant, anti-Alzheimer's, antiparkinsonian, antiviral and antibacterial (antituberculosis) properties. Myrtenal is a perspective monoterpenoid with therapeutic potential in various fields of medicine. Its chemical modifications often lead to new or more pronounced biological effects. As an example, the conjugation of myrtenal with the established pharmacophore adamantane enables the augmentation of several of its pivotal properties. Myrtenal-adamantane derivatives exhibited a variety of beneficial characteristics, such as antimicrobial, antifungal, antiviral, anticancer, anxiolytic, and neuroprotective properties, which are worth examining in more detail and at length.

Alpha-pinene moderates memory impairment induced by kainic acid via improving the BDNF/TrkB/CREB signaling pathway in rat hippocampus

Introduction

The potential benefits of natural ingredients in the alleviation of neurodegenerative disorders are of great interest. Alpha-pinene (APN) is an essential oil belonging to monoterpenes with multiple beneficial effects. In this study, the possible improving effects of alpha-pinene on memory impairment induced by kainic acid and the underlying molecular mechanisms were examined.

Methods

Memory impairment was induced by i.c.v. injection of kainic acid (KA) in male Wistar rats. Alpha-pinene (50 mg/kg/day, i.p.) was injected for 21 days, including 14 days before the KA injection and seven days afterward. Spatial working memory and inhibitory avoidance (IA) memory performance were assessed five and even days following KA injection, respectively. The hippocampal protein levels of brain-derived neurotrophic factor (BDNF), tropomyosin-like receptor kinase B (TrkB), cAMP response element binding protein (CREB), and neuronal loss in the CA1 region were also examined.

Results

Results revealed that the i.c.v. injection of KA triggered memory impairment, which was notably diminished by alpha-pinene pre-and post-treatment. Histopathological evaluation revealed that alpha-pinene significantly moderated the attenuation in CA1 alive neurons induced by KA injection. Western blotting analysis confirmed that alpha-pinene pre-and post-treatment significantly reversed the KA-induced decreases in the hippocampal levels of BDNF, TrkB, phosphorylated TrkB, CREB, and phosphorylated CREB.

Discussion

These findings suggest that alpha-pinene pre-and post-treatment moderate memory impairment induced by KA by restoring the BDNF/TrkB/CREB signaling pathway in the rat hippocampus.

Predictions of the Biological Effects of Several Acyclic Monoterpenes as Chemical Constituents of Essential Oils Extracted from Plants

Acyclic terpenes are biologically active natural products having applicability in medicine, pharmacy, cosmetics and other practices. Consequently, humans are exposed to these chemicals, and it is necessary to assess their pharmacokinetics profiles and possible toxicity. The present study considers a computational approach to predict both the biological and toxicological effects of nine acyclic monoterpenes: beta-myrcene, beta-ocimene, citronellal, citrolellol, citronellyl acetate, geranial, geraniol, linalool and linalyl acetate. The outcomes of the study emphasize that the investigated compounds are usually safe for humans, they do not lead to hepatotoxicity, cardiotoxicity, mutagenicity, carcinogenicity and endocrine disruption, and usually do not have an inhibitory potential against the cytochromes involved in the metabolism of xenobiotics, excepting CYP2B6. The inhibition of CYP2B6 should be further analyzed as this enzyme is involved in both the metabolism of several common drugs and in the activation of some procarcinogens. Skin and eye irritation, toxicity through respiration and skin-sensitization potential are the possible harmful effects revealed by the investigated compounds. These outcomes underline the necessity of in vivo studies regarding the pharmacokinetics and toxicological properties of acyclic monoterpenes so as to better establish the clinical relevance of their use.

Computational Studies Applied to Linalool and Citronellal Derivatives Against Alzheimer's and Parkinson's Disorders: A Review with Experimental Approach

Alzheimer's and Parkinson's are neurodegenerative disorders that affect a great number of people around the world, seriously compromising the quality of life of individuals, due to motor and cognitive damage. In these diseases, pharmacological treatment is used only to alleviate symptoms. This emphasizes the need to discover alternative molecules for use in prevention. Using Molecular Docking, this review aimed to evaluate the anti-Alzheimer's and anti-Parkinson's activity of linalool and citronellal, as well as their derivatives. Before performing Molecular Docking simulations, the compounds' pharmacokinetic characteristics were evaluated. For Molecular Docking, 7 chemical compounds derived from citronellal, and 10 compounds derived from linalool, and molecular targets involved in Alzheimer's and Parkinson's pathophysiology were selected. According to the Lipinski rules, the compounds under study presented good oral absorption and bioavailability. For toxicity, some tissue irritability was observed. For Parkinson-related targets, the citronellal and linalool derived compounds revealed excellent energetic affinity for α-Synuclein, Adenosine Receptors, Monoamine Oxidase (MAO), and Dopamine D1 receptor proteins. For Alzheimer disease targets, only linalool and its derivatives presented promise against BACE enzyme activity. The compounds studied presented high probability of modulatory activity against the disease targets under study, and are potential candidates for future drugs.

Rosiridin Attenuates Scopolamine-Induced Cognitive Impairments in Rats via Inhibition of Oxidative and Nitrative Stress Leaded Caspase-3/9 and TNF-α Signaling Pathways

AIM

A monoterpene and bioactive component of the plant Rhodiola rosea (R. rosea), rosiridin has beneficial effects on the human central nervous system and enhances brain function. The goal of this scientific study was to determine if rosiridin might shield rats from neurocognitive problems induced by scopolamine.

METHODS

To track the potential toxicities in rats, the acute toxicity in rats was clarified. Rosiridin at a dose of 10 mg/kg was tested in rats for 14 days. At the conclusion of the investigation, behavioral parameters that were used to identify the rats' cognitive and motor abilities were evaluated. Several biochemical parameters were estimated using the prepared homogenate, including acetylcholine esterase (AChE), choline acetyltransferase (ChAT), radical scavengers produced by the body (Catalase-CAT, superoxide dismutase-SOD, and reduced glutathione-GSH), indicators of oxidative and nitrative burnout, pro-inflammatory (Interleukins- IL-1β, IL-6, interferon gamma IFN-ꝩ, and tumor necrosis factor-TNF-α), and cell apoptosis caspases 3 and 9.

RESULTS AND CONCLUSION

A significant behavioral parameter restoration was seen in the rosiridin-treated group, including reduction in latency time during acquisition and retention trial in the Morris water maze test, and percentage of spontaneous alterations in the y-maze test, when compared to the disease control group that received scopolamine; rosiridin also altered the oxidative stress and neuroinflammatory markers, as well as restoring Ach and ChAT activities and normalizing GSH, SOD, MDA, TNF-α, nitrate, IL-1β, IL-6, IFN-ꝩ, caspases 3 and 9 levels. The results imply that rosiridin limits the effect of scopolamine on rat cognitive function.

Neuroprotective potential of terpenoid-rich extracts from orange juice by-products obtained by pressurized liquid extraction

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Orange juice by-products valorized by green PLE process.

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Terpenoid-rich PLE extract with enhanced in-vitro neuroprotective activity.

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Molecular docking between terpenoids and active sites of the target enzymes.

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Selected PLE extracts show human cell-based neuroprotection capacity.

Pressurized liquid extraction (PLE) conditions were optimized to improve the recovery of orange (Citrus sinensis) by-products terpenoids. The neuroprotective potential of the PLE extracts were tested against a set of in-vitro assay (antioxidant (ABTS), reactive oxygen/nitrogen species (ROS/RNS)) as well as enzymatic tests (acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and lipoxygenase (LOX)). Gas chromatography coupled to high-resolution mass spectrometry (GC-q-TOF-MS) analysis revealed a higher enrichment in mono- and sesquiterpenoids of the PLE extracts with the highest neuroprotection capacity. In-silico molecular docking analysis showed the specific interaction of representative terpenoids with enzymes active sites. The results demonstrate that the selected extract at 100 °C and 30 minutes possesses high antioxidant (ABTSIC50 = 13.5 μg mL⁻¹; ROSIC50 = 4.4 μg mL⁻¹), anti-cholinesterase (AChEIC50 = 137.1 vg  L⁻¹; BChEIC50 = 147.0 μg mL⁻¹) and anti-inflammatory properties (against IL-6 and LOXIC50 = 76.1 μg mL⁻¹), with low cytotoxicity and protection against L-glutamic acid in cell models.

Toxicity of Selected Monoterpenes and Essential Oils Rich in These Compounds

Monoterpenes make up the largest group of plant secondary metabolites. They can be found in numerous plants, among others, the Lamiaceae family. The compounds demonstrate antioxidative, antibacterial, sedative and anti-inflammatory activity, hence, they are often employed in medicine and pharmaceuticals. Additionally, their fragrant character is often made use of, notably in the food and cosmetic industries. Nevertheless, long-lasting studies have revealed their toxic properties. This fact has led to a detailed analysis of the compounds towards their side effects on the human organism. Although most are safe for human food and medical applications, there are monoterpene compounds that, in certain amounts or under particular circumstances (e.g., pregnancy), can cause serious disorders. The presented review characterises in vitro and in vivo, the toxic character of selected monoterpenes (α-terpinene, camphor, citral, limonene, pulegone, thujone), as well as that of their original plant sources and their essential oils. The selected monoterpenes reveal various toxic properties among which are embryotoxic, neurotoxic, allergenic and genotoxic. It is also known that the essential oils of popular plants can also reveal toxic characteristics that many people are unaware of.

Non-Alkaloid Cholinesterase Inhibitory Compounds from Natural Sources

Alzheimer’s disease (AD) is a severe neurodegenerative disorder of different brain regions accompanied by distresses and affecting more than 25 million people in the world. This progressive brain deterioration affects the central nervous system and has negative impacts on a patient’s daily activities such as memory impairment. The most important challenge concerning AD is the development of new drugs for long-term treatment or prevention, with lesser side effects and greater efficiency as cholinesterases inhibitors and the ability to remove amyloid-beta(Aβ) deposits and other related AD neuropathologies. Natural sources provide promising alternatives to synthetic cholinesterase inhibitors and many have been reported for alkaloids while neglecting other classes with potential cholinesterase inhibition. This review summarizes information about the therapeutic potential of small natural molecules from medicinal herbs, belonging to terpenoids, coumarins, and phenolic compounds, and others, which have gained special attention due to their specific modes of action and their advantages of low toxicity and high efficiency in the treatment of AD. Some show superior drug-like features in comparison to synthetic cholinesterase inhibitors. We expect that the listed phytoconstituents in this review will serve as promising tools and chemical scaffolds for the discovery of new potent therapeutic leads for the amelioration and treatment of Alzheimer’s disease.