Biological evaluation of 7-O-amide hesperetin derivatives as multitarget-directed ligands for the treatment of Alzheimer's disease

Recent advances in the natural product analogues for the treatment of neurodegenerative diseases

Neurodegenerative diseases (NDs) represent a hallmark of numerous incapacitating and untreatable conditions, the incidence of which is escalating swiftly, exemplified by Alzheimer's disease and Parkinson's disease. There is an urgent necessity to create pharmaceuticals that exhibit high efficacy and minimal toxicity in order to address these debilitating diseases. The structural complexity and diversity of natural products confer upon them a broad spectrum of biological activities, thereby significantly contributing to the history of drug discovery. Nevertheless, natural products present challenges in drug discovery, including time-consuming separation processes, low content, low bioavailability, and other related issues. To address these challenges, numerous analogs of natural products have been synthesized. This methodology enables the rapid synthesis of analogs of natural products with the potential to serve as lead compounds for drug development, thereby paving the way for the discovery of novel pharmaceuticals. This paper provides a summary of 127 synthetic analogues featuring various natural product structures, including flavonoids, alkaloids, coumarins, phenylpropanoids, terpenoids, polyphenols, and amides. The compounds are categorized based on their efficacy in treating various diseases. Furthermore, this article delves into the structure-activity relationship (SAR) of certain analogues, offering a thorough point of reference for the systematic development of pharmaceuticals aimed at addressing neurodegenerative conditions.

Discovery of novel deoxyvasicinone derivatives with benzenesulfonamide substituents as multifunctional agents against Alzheimer's disease

A series of deoxyvasicinone derivatives with benzenesulfonamide substituents were designed and synthesized to find a multifunctional anti-Alzheimer's disease (AD) drug. The results of the biological activity evaluation indicated that most compounds demonstrated selective inhibition of acetylcholinesterase (AChE). Among them, g17 exhibited the most potent inhibitory effect on AChE (IC50 = 0.24 ± 0.04 μM). Additionally, g17 exhibited promising properties as a metal chelator and inhibitor of amyloid β peptides self-aggregation (68.34 % ± 1.16 %). Research on oxidative stress has shown that g17 displays neuroprotective effects and effectively suppresses the intracellular accumulation of reactive oxygen species. Besides, g17 demonstrated remarkable anti-neuroinflammatory effects by significantly reducing the production of pro-inflammatory cytokines (such as NO, IL-1β, and TNF-α) and inhibiting the expression of inflammatory mediators iNOS and COX-2. In vivo studies showed that g17 significantly improved AD model mice's cognitive and memory abilities. Histological examination of mouse hippocampal tissue sections using hematoxylin and eosin staining revealed that g17 effectively mitigates neuronal damage. Considering the multifunctional properties of g17, it is regarded as a promising lead compound for treating AD.

Hesperetin attenuates cognitive dysfunction via SIRT6/NLRP3 pathway in scopolamine-induced mice

Neuroinflammation is a critical feature in the pathogenesis of neurodegenerative disorders such as Alzheimer's disease (AD). Hesperetin can exert anti-inflammatory, antioxidant and other neuroprotective effects. In this study, the scopolamine (SCOP)-induced cognitive dysfunction in mice model was used to evaluate the neuroprotective effects of hesperetin. Behavioral tests (Morris water maze, open field, and novel object recognition tests) were conducted to evaluate the effect of hesperetin on cognitive dysfunction behaviors. Nissl staining and Immunofluorescence were used to evaluate hippocampal neuronal damage and microglial activation in mice. The levels of proinflammatory factors, oxidant stress, and the cholinergic neurotransmitter were detected by real-time quantitative fluorescence PCR (RT-qPCR) or biochemical reagent kits. Western blotting was used to detect the relative protein expression of the sirtuin 6 (SIRT6) / NOD-like receptor thermal protein domain associated protein 3 (NLRP3) pathway. Results showed that hesperetin could ameliorate SCOP-induced cognitive impairment and neuronal damage, and regulate the levels of cholinergic neurotransmitters in the hippocampal of AD mice. Hesperetin could also enhance antioxidant defense by regulating the levels of reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT). Hesperetin exerted anti-neuroinflammation effects through inhibiting of microglia activation and down-regulating the mRNA transcript levels of inflammatory cytokines, such as tumor necrosis factor α (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β), cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS). Meanwhile, hesperetin could attenuate the expression of NLRP3, apoptosis-associated speck-like protein containing a CARD (ASC), thioredoxin-interacting protein (TXNIP), and caspase-1 p20 and upregulate the expression of SIRT6 in SCOP-induced mice. Overall, our study suggested that hesperetin might ameliorate SCOP-induced cognitive dysfunction by improving cholinergic system dysfunction and suppressing oxidative stress and attenuating neuroinflammation via SIRT6/NLRP3 pathway in mice.

Neuroprotective Potentials of Flavonoids: Experimental Studies and Mechanisms of Action

Neurological and neurodegenerative diseases, particularly those related to aging, are on the rise, but drug therapies are rarely curative. Functional disorders and the organic degeneration of nervous tissue often have complex causes, in which phenomena of oxidative stress, inflammation and cytotoxicity are intertwined. For these reasons, the search for natural substances that can slow down or counteract these pathologies has increased rapidly over the last two decades. In this paper, studies on the neuroprotective effects of flavonoids (especially the two most widely used, hesperidin and quercetin) on animal models of depression, neurotoxicity, Alzheimer's disease (AD) and Parkinson's disease are reviewed. The literature on these topics amounts to a few hundred publications on in vitro and in vivo models (notably in rodents) and provides us with a very detailed picture of the action mechanisms and targets of these substances. These include the decrease in enzymes that produce reactive oxygen and ferroptosis, the inhibition of mono-amine oxidases, the stimulation of the Nrf2/ARE system, the induction of brain-derived neurotrophic factor production and, in the case of AD, the prevention of amyloid-beta aggregation. The inhibition of neuroinflammatory processes has been documented as a decrease in cytokine formation (mainly TNF-alpha and IL-1beta) by microglia and astrocytes, by modulating a number of regulatory proteins such as Nf-kB and NLRP3/inflammasome. Although clinical trials on humans are still scarce, preclinical studies allow us to consider hesperidin, quercetin, and other flavonoids as very interesting and safe dietary molecules to be further investigated as complementary treatments in order to prevent neurodegenerative diseases or to moderate their deleterious effects.

Lipopolysaccharide-Induced Model of Neuroinflammation: Mechanisms of Action, Research Application and Future Directions for Its Use

Despite advances in antimicrobial and anti-inflammatory therapies, inflammation and its consequences still remain a significant problem in medicine. Acute inflammatory responses are responsible for directly life-threating conditions such as septic shock; on the other hand, chronic inflammation can cause degeneration of body tissues leading to severe impairment of their function. Neuroinflammation is defined as an inflammatory response in the central nervous system involving microglia, astrocytes, and cytokines including chemokines. It is considered an important cause of neurodegerative diseases, such as Alzheimer’s disease, Parkinson’s disease and amyotrophic lateral sclerosis. Lipopolysaccharide (LPS) is a strong immunogenic particle present in the outer membrane of Gram-negative bacteria. It is a major triggering factor for the inflammatory cascade in response to a Gram-negative bacteria infection. The use of LPS as a strong pro-inflammatory agent is a well-known model of inflammation applied in both in vivo and in vitro studies. This review offers a summary of the pathogenesis associated with LPS exposure, especially in the field of neuroinflammation. Moreover, we analyzed different in vivo LPS models utilized in the area of neuroscience. This paper presents recent knowledge and is focused on new insights in the LPS experimental model.

Potential of flavonoids as anti-Alzheimer's agents: bench to bedside

Developing therapies for neurodegenerative diseases are challenging because of the presence of blood-brain barrier and Alzheimer being one of the commonest and uprising neurodegenerative disorders possess the need for developing novel therapies. Alzheimer's is attributed to be the sixth leading cause of death in the USA and the number of cases is estimated to be increased from 58 million in 2021 to 88 million by 2050. Natural drugs have benefits of being cost-effective, widely available, fewer side effects, and immuno-booster can be useful in managing Alzheimer. Flavonoids can slow the neuronal degeneration as they have shown activity in central nervous system and are able to cross the blood-brain barrier. These can be easily extracted from fruits, vegetable, and plants. In Alzheimer disease, flavonoids scavenges the reactive oxygen species and reduces the production of amyloid beta protein. Agents from sub-classes of flavonoids such as flavanones, flavanols, flavones, flavonols, anthocyanins, and isoflavones having pharmacological action in treating Alzheimer disease are discussed in this review.

Design, synthesis and biological evaluation of naringenin carbamate derivatives as potential multifunctional agents for the treatment of Alzheimer's disease

A series of naringenin derivatives were designed and synthesized as multifunctional anti-Alzheimer's disease (AD) agents. The results showed that these derivatives displayed moderate-to-good acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitory activities at the micromolar range (IC₅₀, 12.91 ~ 62.52 μM for AChE and 0.094 ~ 13.72 μM for BuChE). Specifically, compound 1 showed the highest inhibitory activity against BuChE with the IC₅₀ value of (0.094 ± 0.0054) μM. A Lineweaver-Burk plot and molecular docking studies demonstrated that 1 targeted both the catalytically active site (CAS) and the peripheral anion site (PAS) of BuChE. Besides, all derivatives showed excellent hydroxyl free radicals (·OH) scavenging ability than vitamin C and cyclic voltammetry results displayed that 1 could effectively scavenge superoxide anion radical (·O₂^-). In addition, compound 1 displayed good metal chelating properties and had anti-Aβ aggregation activities. Therefore, compound 1 might be the potential anti-AD agent for further developments.

Discovery of 7-O-1, 2, 3-triazole hesperetin derivatives as multi-target-directed ligands against Alzheimer's disease

The development of multi-target-directed ligands (MTDLs) may improve complex central nervous system diseases such as Alzheimer's disease (AD). Here, a series of 7-O-1, 2, 3-triazole hesperetin derivatives was evaluated for their inhibition of cholinesterase, anti-neuroinflammatory, and neuroprotective activity. Among the hesperetin derivatives, compound a8 (7-O-((1-(3-chlorobenzyl)-1H-1,2,3-triazol-4-yl)methyl)hesperetin) possessed excellent anti-butyrylcholinesterase activity (IC50 = 3.08 ± 0.29 μM) and exhibited good anti-neuroinflammatory activity (IC50 = 2.91 ± 0.47 μM) against NO production through remarkably blocking the NF-κB signaling pathway and inhibiting the phosphorylation of P65. In addition, a8 showed a remarkable neuroprotective effect and lacked neurotoxicity up to 50 μM concentration. Furthermore, possessing significant self-mediated Aβ1-42 aggregation inhibitory activity, chelated biometals and reduced ROS production were found in compound a8. In the bi-directional transport assay, a8 exhibited a blood-brain barrier penetrating ability. In this study, the Morris water maze task showed that compound a8 significantly improved the learning and memory impairment of the scopolamine-induced AD mice model. Results highlighted the potential of compound a8 to be a potential MTDL for the development of anti-AD agents.