Usnic acid enantiomers restore cognitive deficits and neurochemical alterations induced by Aβ1-42 in mice

Neuroprotective properties of Betulin, Betulinic acid, and Ursolic acid as triterpenoids derivatives: a comprehensive review of mechanistic studies

Cognitive deficits are the main outcome of neurological disorders whose occurrence has risen over the past three decades. Although there are some pharmacologic approaches approved for managing neurological disorders, it remains largely ineffective. Hence, exploring novel nature-based nutraceuticals is a pressing need to alleviate the results of neurodegenerative diseases, such as Alzheimer's disease (AD) and other neurodegenerative disorders. Some triterpenoids and their derivates can be considered potential therapeutics against neurological disorders due to their neuroprotective and cognitive-improving effects. Betulin (B), betulinic acid (BA), and ursolic acid (UA) are pentacyclic triterpenoid compounds with a variety of biological activities, including antioxidative, neuroprotective and anti-inflammatory properties. This review focuses on the therapeutic efficacy and probable molecular mechanisms of triterpenoids in damage prevention to neurons and restoring cognition in neurodegenerative diseases. Considering few studies on this concept, the precise mechanisms that mediate the effect of these compounds in neurodegenerative disorders have remained unknown. The findings can provide sufficient information about the advantages of these compounds against neurodegenerative diseases.

Effect of Human Milk Oligosaccharides on Learning and Memory in Mice with Alzheimer's Disease

Alzheimer's disease (AD) is distinguished by cognitive dysfunction and neuroinflammation in the brain. 2'-Fucosyllactose (2'-FL) is a major human milk oligosaccharide (HMO) that is abundantly present in breast milk and has been demonstrated to exhibit immunomodulatory effects. However, the role of 2'-FL and HMO in gut microbiota modulation in relation to AD remains insufficiently investigated. This study aimed to elucidate the preventive effect of the 2'-FL and HMO impact of AD and the relevant mechanism involved. Here, the behavioral results showed that 2'-FL and HMO intervention decreased the expression of Tau phosphorylation and amyloid-β (Aβ), inhibited neuroinflammation, and restored cognitive impairment in AD mice. The metagenomic analysis proved that 2'-FL and HMO intervention restored the dysbiosis of the gut microbiota in AD. Notably, 2'-FL and HMO intervention significantly enhanced the relative abundance of Clostridium and Akkermansia. The metabolomics results showed that 2'-FL and HMO enhanced the oleoyl-l-carnitine metabolism as potential drivers. More importantly, the levels of oleoyl-l-carnitine were positively correlated with the abundances of Clostridium and Akkermansia. These results indicated that 2'-FL and HMO had therapeutic potential to prevent AD-induced cognitive impairment, which is of great significance for the treatment of AD.

Neuroprotective Profile of Triazole Grandisin Analogue against Amyloid-Beta Oligomer-Induced Cognitive Impairment

Alzheimer's disease (AD) is a neurodegenerative disorder caused by accumulation of amyloid-β oligomers (AβO) in the brain, neuroinflammation, oxidative stress, and cognitive decline. Grandisin, a tetrahydrofuran neolignan, exhibits relevant anti-inflammatory and antioxidant properties. Interestingly, grandisin-based compounds were shown to prevent AβO-induced neuronal death in vitro. However, no study has assessed the effect of these compounds on the AD animal model. This study focuses on a triazole grandisin analogue (TGA) synthesized using simplification and bioisosteric drug design, which resulted in improved potency and solubility compared with the parent compound. This study aimed to investigate the possible in vivo effects of TGA against AβO-induced AD. Male C57/Bl6 mice underwent stereotaxic intracerebroventricular AβO (90 μM) or vehicle injections. 24 h after surgery, animals received intraperitoneal treatment with TGA (1 mg/kg) or vehicle, administered on a 14 day schedule. One day after treatment completion, a novel object recognition task (NORT) was performed. Memantine (10 mg/kg) was administered as a positive control. NORT retention sessions were performed on days 8 and 16 after AβO injection. Immediately after retention sessions, animals were euthanized for cortex and hippocampus collection. Specimens were subjected to oxidative stress and cytokine analyses. TGA reduced the level of cortex/hippocampus lipoperoxidation and prevented cognitive impairment in AβO-injected mice. Additionally, TGA reduced tumor necrosis factor (TNF) and interferon-γ (IFN-γ) levels in the hippocampus. By contrast, memantine failed to prevent cortex/hippocampus lipid peroxidation, recognition memory decline, and AβO-induced increases in TNF and IFN-γ levels in the hippocampus. Thus, memantine was unable to avoid the AβO-induced persistent cognitive impairment. The results showed that TGA may prevent memory impairment by exerting antioxidant and anti-inflammatory effects in AβO-injected mice. Moreover, TGA exhibited a persistent neuroprotective effect compared to memantine, reflecting an innovative profile of this promising agent against neurodegenerative diseases, such as AD.

Intranasal in situ gelling liquid crystal for delivery of resveratrol ameliorates memory and neuroinflammation in Alzheimer's disease

Alzheimer's disease (AD) is an illness that affects people aged 65 or older and affects around 6.5 million in the United States. Resveratrol is a chemical obtained from natural products and it exhibits biological activity based on inhibiting the formation, depolymerization of the amyloid, and decreasing neuroinflammation. Due to the insolubility of this compound; its incorporation in surfactant-based systems was proposed to design an intranasal formulation. A range of systems has been produced by mixing oleic acid, CETETH-20 and water. Polarised light microscopy (PLM), small angle x-ray scattering (SAXS) and transmission electron microscopy (TEM) confirm the initial liquid formulation (F) presented as microemulsion (ME). After dilution, the gelled systems were characterized as hexagonal mesophase and they showed feasibility proprieties. Pharmacological assays performed after intranasal administration showed the ability to improve learning and memory in animals, as well as remission of neuroinflammation via inhibition of interleukin.

Critical Assessment of the Anti-Inflammatory Potential of Usnic Acid and Its Derivatives-A Review

Inflammation is a response of the organism to an external factor that disrupts its natural homeostasis, and it helps to eliminate the cause of tissue injury. However, sometimes the body's response is highly inadequate and the inflammation may become chronic. Thus, the search for novel anti-inflammatory agents is still needed. One of the groups of natural compounds that attract interest in this context is lichen metabolites, with usnic acid (UA) as the most promising candidate. The compound reveals a broad spectrum of pharmacological properties, among which anti-inflammatory properties have been studied both in vitro and in vivo. The aim of this review was to gather and critically evaluate the results of the so-far published data on the anti-inflammatory properties of UA. Despite some limitations and shortcomings of the studies included in this review, it can be concluded that UA has interesting anti-inflammatory potential. Further research should be directed at the (i) elucidation of the molecular mechanism of UA; (ii) verification of its safety; (iii) comparison of the efficacy and toxicity of UA enantiomers; (iv) design of UA derivatives with improved physicochemical properties and pharmacological activity; and (v) use of certain forms or delivery carriers of UA, especially in its topical application.

Nature's Toolbox Against Tau Aggregation: An Updated Review of Current Research

Tau aggregation is a hallmark of several neurodegenerative disorders, such as Alzheimer's disease (AD), frontotemporal dementia, and progressive supranuclear palsy. Hyperphosphorylated tau is believed to contribute to the degeneration of neurons and the development of these complex diseases. Therefore, one potential treatment for these illnesses is to prevent or counteract tau aggregation. In recent years, interest has been increasing in developing nature-derived tau aggregation inhibitors as a potential treatment for neurodegenerative disorders. Researchers have become increasingly interested in natural compounds with multifunctional features, such as flavonoids, alkaloids, resveratrol, and curcumin, since these molecules can interact simultaneously with the various targets of AD. Recent studies have demonstrated that several natural compounds can inhibit tau aggregation and promote the disassembly of pre-formed tau aggregates. Nature-derived tau aggregation inhibitors hold promise as a potential treatment for neurodegenerative disorders. However, it is important to note that more research is needed to fully understand the mechanisms by which these compounds exert their effects and their safety and efficacy in preclinical and clinical studies. Nature-derived inhibitors of tau aggregation are a promising new direction in the research of neurodegenerative complexities. This review focuses on the natural products that have proven to be a rich supply for inhibitors in tau aggregation and their uses in neurodegenerative complexities, including AD.

Phytochemical composition, antimicrobial activities, and cholinesterase inhibitory properties of the lichen Usnea diffracta Vain

Lichens are important sources of versatile bioactive compounds. Two new dibenzofurans (1-2), a multi-substituted single benzene ring (3), and two organic acid compounds (4-5) along with 25 known compounds (6-30) were isolated from the lichen Usnea diffracta Vain. Their structures were identified by physicochemical properties and spectral analyses. Compounds 1-30 were tested for inhibitory activities against Staphylococcus aureus, Escherichia coli, and Candida albicans by the disk diffusion method and microdilution assay respectively. Compound 3 showed moderate inhibitory activities against S. aureus and E. coli with the inhibition zone (IZ) of 6.2 mm and 6.3 mm, respectively. Depside 10 exhibited good activity against S.aureus and C. albicans with 6.6 mm and 32 μg/ml, respectively. The acetylcholinesterase inhibitory activities of compounds 1, 2, and 6-8 with the characteristic dibenzofuran scaffold were evaluated var anti-AChE assay and a molecular docking study. Compound 2 could better inhibit AChE at the concentration of 0.3 μmol/ml with a value of 61.07 ± 0.85%. The molecular docking study also demonstrated that compound 2 had the strongest binding affinity among the five dibenzofurans, and the "-CDOCKER Energy" value was 14.4513 kcal/mol.

Development of a Low-Molecular-Weight Aβ42 Detection System Using a Enzyme-Linked Peptide Assay

Alzheimer’s disease (AD) is a degenerative brain disease that is the most common cause of dementia. The incidence of AD is rapidly rising because of the aging of the world population. Because AD is presently incurable, early diagnosis is very important. The disease is characterized by pathological changes such as deposition of senile plaques and decreased concentration of the amyloid-beta 42 (Aβ42) peptide in the cerebrospinal fluid (CSF). The concentration of Aβ42 in the CSF is a well-studied AD biomarker. The specific peptide probe was screened through four rounds of biopanning, which included the phage display process. The screened peptide showed strong binding affinity in the micromolar range, and the enzyme-linked peptide assay was optimized using the peptide we developed. This diagnostic method showed specificity toward Aβ42 in the presence of other proteins. The peptide-binding site was also estimated using molecular docking analysis. Finally, the diagnostic method we developed could significantly distinguish patients who were classified based on amyloid PET images.

The Natural Compound Hydrophobic Usnic Acid and Hydrophilic Potassium Usnate Derivative: Applications and Comparisons

Usnic acid is the best-studied lichen metabolite, presenting several biological activities, such as antibacterial, immunostimulating, antiviral, antifungal, anti-inflammatory, and antiparasitic agents; despite these relevant properties, it is a hydrophobic and toxic molecule. In this context, scientific research has driven the development of innovative alternatives, considering usnic acid as a source of raw material in obtaining new molecules, allowing structural modifications (syntheses) from it. The purpose is to optimize biological activities and toxicity, with less concentration and/or response time. This work presents a literature review with an analogy of the hydrophobic molecule of usnic acid with its hydrophilic derivative of potassium usnate, emphasizing the elucidation and structural characteristics, biological activities, and toxicological aspects of both molecules, and the advantages of using the promising derivative hydrophilic in different in vitro and in vivo assays when compared to usnic acid.

Sublethal concentrations of usnic acid potassium salt impairs physiological parameters of Biomphalaria glabrata (Say, 1818) (Pulmonata: Planorbidae) infected and not infected with Schistosoma mansoni

Schistosomiasis is a public health problem in many developing countries. The mollusc Biomphalaria glabrata is the most important vector of Schistosoma mansoni in South America. The population control of this vector to prevent the spread of schistosomiasis is currently done with the application of highly toxic molluscicide to the environment. The screening of substances in sublethal concentrations that have deleterious effects on physiological parameters is very relevant for the control of schistosomiasis, since the effectiveness of disease prevention increases if it acts on population control of the vector and on reproduction and elimination in S. mansoni cercariae. The objective of this study was to evaluate the reproductive parameters (fecundity and fertility), intra-mollusk effect (sporocysts I (72 h) and II (14 days after)) on the development of cercariae of S. mansoni and the immune cell profile of B. glabrata exposed to sublethal concentrations (LC₂₅ - 0.5 µg/mL and LC₅₀ - 0.92 µg/mL) of the usnic acid potassium salt (potassium usnate). LC ₂₅ and LC ₅₀ significantly reduced (p < 0.05) the fecundity of B. glabrata when treated infected and/or not exposed to infection, while unviable embryos were not observed in sporocyst stage I, being only significant (p < 0.05) for mollusks infected and treated with LC₅₀ on sporocyst II. LC₂₅ and LC₅₀ of the potassium usnate caused significant reductions (p < 0.05) in the production and cercarial shedding when evaluated on sporocysts I and II. In addition, the mortality of infected and treated B. glabrata in the sporocyst II phase was quite marked after the 9th week of infection. Regarding the immunological cell profile of uninfected B. glabrata, both concentrations led to immunomodulatory responses, with significant morphological changes predominant of hemocytes that entered programmed cell death (apoptosis). It was concluded that the application of LC₂₅ and LC₅₀ from the potassium usnate could be useful in the population control of B. glabrata, since it interferes both in their biology and physiology and in the reproduction of the infectious agent of schistosomiasis mansoni.

Allicin ameliorates aluminium- and copper-induced cognitive dysfunction in Wistar rats: relevance to neuro-inflammation, neurotransmitters and Aβ(1-42) analysis

Alzheimer's disease (AD) is a multifactorial neurological disorder associated with neuropathological and neurobehavioral changes, like cognition and memory loss. Pathological hallmarks of AD comprise oxidative stress, formation of insoluble β-amyloid (Aβ) plaques, intracellular neurofibrillary tangles constituted by hyperphosphorylated tau protein (P-tau), neurotransmitters dysbalanced (DA, NE, 5-HT, GABA and Glutamate) and metal deposition. Chronic exposure to metals like aluminium and copper causes accumulation of Aβ plaques, promotes oxidative stress, neuro-inflammation, and degeneration of cholinergic neurons results in AD-like symptoms. In the present study, rats were administered with aluminium chloride (200 mg/kg p.o) and copper sulfate (0.5 mg/kg p.o) alone and in combination for 28 days. Allicin (10 and 20 mg/kg i.p) was administered from day 7 to day 28. Spatial and recognition memory impairment analysis was performed using Morris water maze, Probe trial, and Novel Object Recognition test. Animals were sacrificed on day 29, brain tissue was isolated, and its homogenate was used for biochemical (lipid peroxidation, nitrite, and glutathione), neuro-inflammatory (IL-1β, IL-6 and TNF- α), neurotransmitters (DA, NE, 5-HT, GABA and Glutamate), Aβ_(1-42) level, Al concentration estimation, and Na⁺/K⁺-ATPase activity. In the present study, aluminium chloride and copper sulfate administration increased oxidative stress, inflammatory cytokines release, imbalanced neurotransmitters' concentration, and promoted β-amyloid accumulation and Na⁺/K⁺-ATPase activity. Treatment with allicin dose-dependently attenuated these pathological events via restoration of antioxidants, neurotransmitters concentration, and inhibiting cytokine release and β-amyloid accumulation. Moreover, allicin exhibited the neuroprotective effect through antioxidant, anti-inflammatory, neurotransmitters restoration, attenuation of neuro-inflammation and β-amyloid-induced neurotoxicity.