Potent inhibition of acetylcholinesterase by sargachromanol I from Sargassum siliquastrum and by selected natural compounds

Phytochemical composition of aerial parts and roots of Pfaffia glomerata (Spreng.) Pedersen and anticholinesterase, antioxidant, and antiglycation activities

The Pfaffia glomerata, a plant popularly called Brazilian ginseng, is widely used in Brazil for the treatment of various pathologies, including those associated with the Central Nervous System. 20-hydroxyecdysone (20E), a phytosteroid present in this plant, can promote adaptogenic effects in the organism, providing greater body resistance to stressors. This study aimed to evaluate the phytochemical composition and the anticholinesterase, antioxidant, and antiglycation effects of extracts and fractions of aerial parts and roots of P. glomerata, also analyzing their possible cytotoxic effects. The fractions were obtained by partitioning methanol extracts from the aerial part and roots of P. glomerata with hexane, dichloromethane, ethyl acetate, n-butanol, and water. The samples were initially tested in anticholinesterase, antioxidant, and antiglycation assays, and the most promising samples were submitted for cytotoxicity and chromatographic analyses. Mass spectrometry and chromatography methods revealed that 20E was the main compound in the dichloromethane fractions, there being 35% more 20E in the aerial part (APD) than in the roots (RD). Added to the higher concentration of 20E, the APD fraction also presented more promising results than the RD fraction in anticholinesterase and antioxidant analyses, indicating that their effects may be related to the concentration of 20E. These same fractions showed no hemolytic effects but were cytotoxic in high concentrations. These new findings contribute to scientific information about P. glomerata and open more perspectives for the understanding of its therapeutic properties, allowing the association of biological activity with the presence of 20E.

Naturally Occurring Cholinesterase Inhibitors from Plants, Fungi, Algae, and Animals: A Review of the Most Effective Inhibitors Reported in 2012-2022

Since the development of the "cholinergic hypothesis" as an important therapeutic approach in the treatment of Alzheimer's disease (AD), the scientific community has made a remarkable effort to discover new and effective molecules with the ability to inhibit the enzyme acetylcholinesterase (AChE). The natural function of this enzyme is to catalyze the hydrolysis of the neurotransmitter acetylcholine in the brain. Thus, its inhibition increases the levels of this neurochemical and improves the cholinergic functions in patients with AD alleviating the symptoms of this neurological disorder. In recent years, attention has also been focused on the role of another enzyme, butyrylcholinesterase (BChE), mainly in the advanced stages of AD, transforming this enzyme into another target of interest in the search for new anticholinesterase agents. Over the past decades, Nature has proven to be a rich source of bioactive compounds relevant to the discovery of new molecules with potential applications in AD therapy. Bioprospecting of new cholinesterase inhibitors among natural products has led to the discovery of an important number of new AChE and BChE inhibitors that became potential lead compounds for the development of anti-AD drugs. This review summarizes a total of 260 active compounds from 142 studies which correspond to the most relevant (IC50 ≤ 15 μM) research work published during 2012-2022 on plant-derived anticholinesterase compounds, as well as several potent inhibitors obtained from other sources like fungi, algae, and animals.

Sargassum horneri Extract Attenuates Depressive-like Behaviors in Mice Treated with Stress Hormone

Sargassum horneri, a brown seaweed, is known for its various health benefits; however, there are no reports on its effects on depression. This study aimed to investigate the antidepressant effects of S. horneri ethanol extract (SHE) in mice injected with corticosterone (CORT) and to elucidate the underlying molecular mechanisms. Behavioral tests were conducted, and corticotropin-releasing hormone (CRH), adrenocorticotropic hormone (ACTH), and CORT levels were measured. A fluorometric monoamine oxidase (MAO) enzyme inhibition assay was performed. Neurotransmitters like serotonin, dopamine, and norepinephrine levels were determined. Moreover, the ERK-CREB-BDNF signaling pathway in the prefrontal cortex and hippocampus was evaluated. Behavioral tests revealed that SHE has antidepressant effects by reducing immobility time and increasing time spent in open arms. Serum CRH, ACTH, and CORT levels decreased in the mice treated with SHE, as did the glucocorticoid-receptor expression in their brain tissues. SHE inhibited MAO-A and MAO-B activities. In addition, SHE increased levels of neurotransmitters. Furthermore, SHE activated the ERK-CREB-BDNF pathway in the prefrontal cortex and hippocampus. These findings suggest that SHE has antidepressant effects in CORT-injected mice, via the regulation of the hypothalamic-pituitary-adrenal axis and monoaminergic pathway, and through activation of the ERK-CREB-BDNF signaling pathway. Thus, our study suggests that SHE may act as a natural antidepressant.

Screening the Extract of Laportea bulbifera (Sieb. et Zucc.) Wedd. Based on Active Component Content, Its Antioxidant Capacity and Exploration of Hepatoprotective Activity in Rats

Laportea bulbifera (Sieb. et Zucc.) Wedd., a plant with a long history of medicinal use, possesses uncertainly defined medicament portions while its antioxidant capacity remains largely unexplored. To gain a better understanding of its medicinal value, this study focused on investigating the Laportea bulbifera aboveground part (LBAP) and the Laportea bulbifera root (LBR). Through an assessment of the bioactive compound content, a significant finding emerged: the LBR exhibited notably higher levels of these bioactive phytochemicals compared to the LBAP. This observation was further reinforced by the antioxidant assays, which demonstrated the superiority of the LBR's antioxidant capacity. The experimental results unequivocally indicate that the root is the optimal medicament portion for Laportea bulbifera. Furthermore, it was discovered that the presence of alcohol in the extraction solvent significantly enhanced the extraction of active ingredients, with the methanol extract of LBR performing the best among the extracts tested. Consequently, this extract was selected for further research. Leveraging cutting-edge UHPLC-ESI-Q-TOF-MS technology, the methanol extract of LBR was meticulously analyzed, revealing the presence of 41 compounds, primarily belonging to the phenolics and fatty acids. Remarkably, stability experiments demonstrated that the phenolics in the methanol extract maintained their stability across various pH values and during in vitro simulations of the human digestive system, albeit showing gradual degradation under high temperatures. Furthermore, the oxidative stability tests conducted on oils revealed the potential of the methanol extract as a stabilizer for olive oil and sunflower oil. Moreover, oral acute toxicity studies confirmed the low toxicity of the methanol extract, further supporting its safe use for medicinal purposes. Of particular note, histopathological examination and biochemical analysis affirmed the remarkable protective effects of the methanol extract against d-galactosamine-induced liver damage. These findings underscore the therapeutic potential of the methanol extract from the LBR in the treatment of diseases associated with oxidative imbalance.

The Anti-Inflammatory Effect of Low Molecular Weight Fucoidan from Sargassum siliquastrum in Lipopolysaccharide-Stimulated RAW 264.7 Macrophages via Inhibiting NF-κB/MAPK Signaling Pathways

Brown seaweed is a rich source of fucoidan, which exhibits a variety of biological activities. The present study discloses the protective effect of low molecular weight fucoidan (FSSQ) isolated from an edible brown alga, Sargassum siliquastrum, on lipopolysaccharide (LPS)-stimulated inflammatory responses in RAW 264.7 macrophages. The findings of the study revealed that FSSQ increases cell viability while decreasing intracellular reactive oxygen species production in LPS-stimulated RAW 264.7 macrophages dose-dependently. FSSQ reduced the iNOS and COX-2 expression, inhibiting the NO and prostaglandin E2 production. Furthermore, mRNA expression of IL-1β, IL-6, and TNF-α was downregulated by FSSQ via modulating MAPK and NF-κB signaling. The NLRP3 inflammasome protein complex, including NLRP3, ASC, and caspase-1, as well as the subsequent release of pro-inflammatory cytokines, such as IL-1β and IL-18, release in LPS-stimulated RAW 264.7 macrophages was inhibited by FSSQ. The cytoprotective effect of FSSQ is indicated via Nrf2/HO-1 signaling activation, which is considerably reduced upon suppression of HO-1 activity by ZnPP. Collectively, the study revealed the therapeutic potential of FSSQ against inflammatory responses in LPS-stimulated RAW 264.7 macrophages. Moreover, the study suggests further investigations on commercially viable methods for fucoidan isolation.

Anti-Neuroinflammatory Meroterpenoids from a Chinese Collection of the Brown Alga Sargassum siliquastrum

Nine new chromane-type meroterpenoids, including the rare nor-meroterpenoid sargasilol A (1) and the eight meroditerpenoids sargasilols B-I (2-9), were isolated from a China Sea collection of the brown alga Sargassum siliquastrum, together with six known analogues (10-15). The structures of the new chromanes were identified by extensive spectroscopic analysis and by comparison with previously reported data. Compounds 1-3 and 6-15 exhibited inhibition against LPS-induced NO production in BV-2 microglial cells, and 1, with a shorter carbon chain, was the most active one. Compound 1 was established as an anti-neuroinflammatory agent through targeting the IKK/IκB/NF-κB signaling pathway. As such, the chromanes from brown algae could provide promising anti-neuroinflammatory lead compounds for further structural modification.

Natural Inhibitors of Cholinesterases: Chemistry, Structure-Activity and Methods of Their Analysis

This article aims to provide an updated description and comparison of the data currently available in the literature (from the last 15 years) on the studied natural inhibitors of cholinesterases (IChEs), namely, acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). These data also apply to the likely impact of the structures of the compounds on the therapeutic effects of available and potential cholinesterase inhibitors. IChEs are hitherto known compounds with various structures, activities and origins. Additionally, multiple different methods of analysis are used to determine the cholinesterase inhibitor potency. This summary indicates that natural sources are still suitable for the discovery of new compounds with prominent pharmacological activity. It also emphasizes that further studies are needed regarding the mechanisms of action or the structure-activity correlation to discuss the issue of cholinesterase inhibitors and their medical application.

Dynamic Kinetic Resolution of β-Substituted α-Diketones via Asymmetric Transfer Hydrogenation

Developing innovative dynamic kinetic resolution (DKR) modes and achieving the highly regio- and enantioselective semihydrogenation of unsymmetrical α-diketones are two formidable challenges in the field of contemporary asymmetric (transfer) hydrogenation. In this work, we report the highly regio- and stereoselective asymmetric semi-transfer hydrogenation of unsymmetrical α-diketones through a unique DKR mode, which features the reduction of the carbonyl group distal from the labile stereocenter, while the proximal carbonyl remains untouched. Moreover, the protocol affords a variety of enantioenriched acyclic ketones with α-hydroxy-α'-C(sp²)-functional groups, which represent a new product class that has not been furnished in known arts. The utilities of the products have been demonstrated in a series of further transformations including the rapid synthesis of drug molecules. Density functional theory calculations and plenty of control experiments have also been conducted to gain more mechanistic insights into the highly selective semihydrogenation.

Medicarpin and Homopterocarpin Isolated from Canavalia lineata as Potent and Competitive Reversible Inhibitors of Human Monoamine Oxidase-B

Thirteen compounds were isolated from the Canavalia lineata pods and their inhibitory activities against human monoamine oxidase-A (hMAO-A) and -B (hMAO-B) were evaluated. Among them, compounds 8 (medicarpin) and 13 (homopterocarpin) showed potent inhibitory activity against hMAO-B (IC₅₀ = 0.45 and 0.72 µM, respectively) with selectivity index (SI) values of 44.2 and 2.07, respectively. Most of the compounds weakly inhibited MAO-A, except 9 (prunetin) and 13. Compounds 8 and 13 were reversible competitive inhibitors against hMAO-B (K_i = 0.27 and 0.21 µM, respectively). Structurally, the 3-OH group at A-ring of 8 showed higher hMAO-B inhibitory activity than 3-OCH3 group at the A-ring of 13. However, the 9-OCH3 group at B-ring of 13 showed higher hMAO-B inhibitory activity than 8,9-methylenedioxygroup at the B-ring of 12 (pterocarpin). In cytotoxicity study, 8 and 13 showed non-toxicity to the normal (MDCK) and cancer (HL-60) cells and moderate toxicity to neuroblastoma (SH-SY5Y) cell. Molecular docking simulation revealed that the binding affinities of 8 and 13 for hMAO-B (-8.7 and -7.7 kcal/mol, respectively) were higher than those for hMAO-A (-3.4 and -7.1 kcal/mol, respectively). These findings suggest that compounds 8 and 13 be considered potent reversible hMAO-B inhibitors to be used for the treatment of neurological disorders.

Maternal exposure to glyphosate-based herbicide promotes changes in the muscle structure of C57BL/6 mice offspring

Glyphosate (GBH) is a worldwide consumption pesticide and is used in the formulation of Roundup®, one of the most commercialized herbicides in the world. Maternal exposure to this herbicide can promote changes and adaptations in the offspring; however, the effects on skeletal muscle are poorly understood. In this sense, the present study sought to evaluate the effect of exposure to GBH on the characteristics of the soleus (SOL) and extensor digitorum longus (EDL) muscles. C57BL/6 pregnant female mice were divided into two groups: control (CTL) receiving water and glyphosate (GBH; n = 6) receiving 0.5% glyphosate. Male puppies were designated according to the group to which the mothers belonged, such as CTL-F1 and GBH-F1 and then euthanized at 150 days of age. There was a reduction in body weight and nasoanal length of animals exposed to GBH, while there was an increase in EDL weight, reduction in the proportion of fibers and number of nuclei, and an increase in the connective tissue of the SOL. The animals exposed to GBH presented higher values of body characteristics, mainly adiposity gain, while they presented a reduction in neuromuscular junctions (NMJ), and an increase in fibrosis in the SOL muscle, while there was a reduction in the number of nuclei, and an increase in the weight of the EDL muscle. These findings indicate that glyphosate can promote changes in the offspring's body growth, the deposition of adipose panicles and its effects on muscle can lead to changes in the structure and functioning of this tissue.

Inhibition of Cholinesterases by Benzothiazolone Derivatives

Thirteen benzothiazolone derivatives (M1–M13) were synthesized and evaluated for their inhibitory activity against cholinesterases (ChEs) and monoamine oxidases (MAOs). All the compounds inhibited ChEs more effectively than MAOs. In addition, most of the compounds showed higher inhibitory activities against butyrylcholinesterase (BChE) than acetylcholinesterase (AChE). Compound M13 most potently inhibited BChE with an IC50 value of 1.21 μM, followed by M2 (IC50 = 1.38 μM). Compound M2 had a higher selectivity index (SI) value for BChE over AChE (28.99) than M13 (4.16). The 6-methoxy indole group of M13 was expected to have a greater effect on BChE inhibitory activity than the other groups. Kinetics and reversibility tests showed that M13 was a reversible noncompetitive BChE inhibitor with a Ki value of 1.14 ± 0.21 μM. In a docking simulation, M13 is predicted to form a hydrogen bond with the backbone carbonyl group of Ser287 of BChE through its methoxy indole moiety and π−π interactions between its benzothiazolone group and the side chain of Trp82 with the five-membered pyrrole ring and with the six-membered benzene ring. From these results, it is suggested that M13 is a BChE inhibitor and a potential candidate agent for the treatment of Alzheimer’s disease.

Development of Halogenated-Chalcones Bearing with Dimethoxy Phenyl Head as Monoamine Oxidase-B Inhibitors

Two series of dimethoxy-halogenated chalcones (DM1−DM20) were synthesized and tested for their ability to inhibit monoamine oxidase (MAOs). Compound DM2 exhibited the most significant inhibition against MAO-B with an IC50 value of 0.067 µM, followed by compound DM18 (IC50 = 0.118 µM), with selectivity index (SI) values of 93.88 and >338.98, respectively. However, none of the substances successfully inhibited MAO-A. The MAO-B inhibitors DM2 and DM18 were competitive and reversible, with Ki values of 0.032 ± 0.004 and 0.045 ± 0.001 µM, respectively. DM2 was non-toxic below 100 µg/mL in the cytotoxic test using the Vero epithelial cell line by the MTT method. According to molecular docking studies, DM2 and DM18 formed very similar conformations within the MAO-B binding pocket, with the ortho-chlorine and ortho-fluorine aromatic rings sandwiched between F168 and Y326. These conformations were predicted to show better interactions with the targeted MAO-B than MAO-A. In particular, the induced-fit docking of the dimethoxy phenyl ring of DM2 facing the hydrophobic pocket made up of FAD, Y398, and Y435 had an impact on F168 in the docking pocket. Taken together, DM2 and DM18 may be suitable candidates for treating neurodegenerative conditions such as Parkinson’s disease.

BChE inhibitors from marine organisms - A review

Acetylcholine is a key neurotransmitter for brain and muscle function, that has its levels decreased in the brain of people with Alzheimer's Disease (AD). Cholinesterase inhibitors are medicines that decrease the breakdown of acetylcholine, through the inhibition of acetyl- and butyrylcholinesterase enzymes. Despite the fact that butyrylcholinesterase activity rises with the disease, while acetylcholinesterase activity declines, the cholinesterase inhibitors that are currently commercialized inhibit either acetylcholinesterase or both enzymes. The development of selective butyrylcholinesterase inhibitors is a promising strategy in the search for new drugs acting against AD. The marine environment is a rich source of molecules with therapeutic potential, which can provide compounds more easily than traditional methods, with reduced toxicity risks compared to synthetic molecules. This review comprises articles from 2003 to 2020, that assessed the butyrylcholinesterase inhibitory activities from marine organisms, considering their crude extracts and isolated compounds. Part of the articles reported a multi-target activity, inhibiting also other AD-related enzymes. Some of the marine compounds reported here have shown an excellent potential for butyrylcholinesterase inhibition compared to standard inhibitors. Further studies of some compounds reported here may lead to the development of a new treatment for AD.

Synthesis of 4-substituted benzyl-2-triazole-linked-tryptamine-paeonol derivatives and evaluation of their selective inhibitions against butyrylcholinesterase and monoamine oxidase-B

Cholinesterase (ChE) and monoamine oxidase (MAO) inhibitors are being used and developed to treat Alzheimer's disease (AD), a major type of dementia patients. Fifteen 4-substituted benzyl-2-triazole-linked-tryptamine-paeonol derivatives were synthesized and evaluated for their inhibitory activities against acetylcholinesterase (AChE), butyrylcholinesterase (BChE), monoamine oxidase-A (MAO-A), and B (MAO-B). Compound 896 was the most potent BChE inhibitor (IC₅₀ = 0.13 μM) with the selectivity index (SI) value of >769.23 for BChE over AChE. Compound 897 was the most potent selective MAO-B inhibitor (IC₅₀ = 0.73 μM; SI = 20.45 for MAO-B over MAO-A). The meta-CF₃ substituent of 896 increased BChE inhibitory activity and the para-CF₃ substituent of 897 increased MAO-B inhibitory activity. Compound 896 was a reversible noncompetitive BChE inhibitor (K_i = 0.171 μM) and 897 was a reversible competitive MAO-B inhibitor (K_i = 0.237 μM). Compound 896 had a lower binding energy (-13.75 kcal/mol) to BChE than 897 (-11.29 kcal/mol), and 897 had a lower binding energy to MAO-B (-11.31 kcal/mol) than that to MAO-A (-6.72 kcal/mol). Little cytotoxicity was observed for 896 and 897 to normal cells (MDCK) and human neuroblastoma cells (SH-SY5Y). This study suggested that 896 and 897 are therapeutic candidates for various neurodegenerative disorders such as AD.

Role of Natural Compounds and Target Enzymes in the Treatment of Alzheimer’s Disease

Alzheimer’s disease (AD) is a progressive neurological condition. The rising prevalence of AD necessitates the rapid development of efficient therapy options. Despite substantial study, only a few medications are capable of delaying the disease. Several substances with pharmacological activity, derived from plants, have been shown to have positive benefits for the treatment of AD by targeting various enzymes, such as acetylcholinesterase (AChE), butyrylcholinesterase (BuChE), β-secretase, γ-secretase, and monoamine oxidases (MAOs), which are discussed as potential targets. Medicinal plants have already contributed a number of lead molecules to medicine development, with many of them currently undergoing clinical trials. A variety of medicinal plants have been shown to diminish the degenerative symptoms associated with AD, either in their raw form or as isolated compounds. The aim of this review was to provide a brief summary of AD and its current therapies, followed by a discussion of the natural compounds examined as therapeutic agents and the processes underlying the positive effects, particularly the management of AD.

Development of a Novel Class of Pyridazinone Derivatives as Selective MAO-B Inhibitors

Sixteen compounds (TR1-TR16) were synthesized and evaluated for their inhibitory activities against monoamine oxidase A and B (MAOs). Most of the derivatives showed potent and highly selective MAO-B inhibition. Compound TR16 was the most potent inhibitor against MAO-B with an IC₅₀ value of 0.17 μM, followed by TR2 (IC₅₀ = 0.27 μM). TR2 and TR16 selectivity index (SI) values for MAO-B versus MAO-A were 84.96 and higher than 235.29, respectively. Compared to the basic structures, the para-chloro substituent in TR2 and TR16 increased the inhibitory activity of MAO-B. TR2 and TR16 were reversible MAO-B inhibitors that were competitive, with K_i values of 0.230 ± 0.004 and 0.149 ± 0.016 µM, respectively. The PAMPA method indicated that compounds TR2 and TR16 had the tendency to traverse the blood-brain barrier. Docking investigations revealed that lead compounds were beneficial for MAO-B inhibition via association with key as well as selective E84 or Y326 residues, but not for MAO-A inhibition via interaction primarily driven by hydrophobic contacts. In conclusion, TR2 and TR16 are therapeutic prospects for the management of multiple neurodegenerative diseases.

Determination of Anti-Alzheimer's Disease Activity of Selected Plant Ingredients

Neurodegenerative diseases, among which one of the more common is Alzheimer’s disease, are the one of the biggest global public health challenges facing our generation because of the increasing elderly population in most countries. With the growing burden of these diseases, it is essential to discover and develop new treatment options capable of preventing and treating them. Neurodegenerative diseases, among which one of the most common is Alzheimer’s disease, are a multifactorial disease and therefore demand multiple therapeutic approaches. One of the most important therapeutic strategies is controlling the level of acetylcholine—a neurotransmitter in cholinergic synapses—by blocking the degradation of acetylcholine using acetylcholinesterase inhibitors such as tacrine, galantamine, donepezil and rivastigmine. However, these drugs can cause some adverse side effects, such as hepatotoxicity and gastrointestinal disorder. Thus, the search for new, more effective drugs is very important. In the last few years, different active constituents from plants have been tested as potential drugs in neurodegenerative disease therapy. The availability, lower price and less toxic effects of herbal medicines compared with synthetic agents make them a simple and excellent choice in the treatment of neurodegenerative diseases. The empirical approach to discovering new drugs from the systematic screening of plant extracts or plant-derived compounds is still an important strategy when it comes to finding new biologically active substances. The aim of this review is to identify new, safe and effective compounds that are potential candidates for further in vivo and clinical tests from which more effective drugs for the treatment of Alzheimer’s disease could be selected. We reviewed the methods used to determine anti-Alzheimer’s disease activity. Here, we have discussed the relevance of plant-derived compounds with in vitro activity. Various plants and phytochemical compounds have shown different activity that could be beneficial in the treatment of Alzheimer’s disorders. Most often, medicinal plants and their active components have been investigated as acetylcholinesterase and/or butyrylcholinesterase activity inhibitors, modifiers of β-amyloid processing and antioxidant agents. This study also aims to highlight species with assessed efficacy, usable plant parts and the most active plant components in order to identify species and compounds of interest for further study. Future research directions are suggested and recommendations made to expand the use of medicinal plants, their formulations and plant-derived active compounds to prevent, mitigate and treat Alzheimer’s disease.

Evaluation of Inhibitory Activities of Sophora flavescens and Angelica gigas Nakai Root Extracts against Monoamine Oxidases, Cholinesterases, and β-Secretase

In this study, Sophora flavescens (SF) from Yeongcheon (YSF) and Mt. Jiri (JiSF), and Angelica gias (AG) from Yeongcheon (YAG), Mt. Jiri (JiAG), and Jecheon (JeAG) were extracted using three concentrations of ethanol, 95% (95Et), 70% (70Et), and 50% (50Et), and hot water (DW) to evaluate the inhibitions of monoamine oxidases (MAOs; MAO-A and B), cholinesterases (ChEs; AChE and BChE) and β-secretase (BACE1) for targeting depression and neurodegenerative diseases. There were no significant differences in constituent compounds depending on herbal origins, except that YSF-95Et and JiSF-95Et showed a distinct non-polar spot upper maackiain position, and JiAG and JeAG showed a higher amount of decursin than YAG. Ethanolic YAG and JeAG extracts showed the highest MAO-A inhibition, and YSF-95Et mostly inhibited MAO-B. JiSF-95Et showed the highest AChE inhibition and YSF-70Et, JiSF-95Et, and -70Et showed the highest BChE inhibition. Interestingly, ethanolic AG extracts showed extremely potent BACE1 inhibition, especially for JiAG-95Et and JeAG-50Et, whereas there have been no reports about BACE1 inhibition of decursin, the major compound, or AG extracts in other studies. All extracts were nontoxic to MDCK and SH-SY5Y with a low toxicity to HL-60. The results showed a different pattern of inhibitory activities of the extracts toward target enzymes depending on the origins, and multi-target abilities, especially for MAO-B and BChE by YSF-95Et, for AChE and BChE by JiSF-95Et, and for MAO-B and BACE1 by JiAG-95Et. It is suggested that those extracts are potential candidates for finding novel compounds with multi-target inhibitory activities, and herbal origin is an important factor to be considered in selection of the plants.

Conjugated Dienones from Differently Substituted Cinnamaldehyde as Highly Potent Monoamine Oxidase-B Inhibitors: Synthesis, Biochemistry, and Computational Chemistry

Fifteen multiconjugated dienones (MK1-MK15) were synthesized and evaluated to determine their inhibitory activities against monoamine oxidases (MAOs) A and B. All derivatives were found to be potent and highly selective MAO-B inhibitors. Compound MK6, with an IC₅₀ value of 2.82 nM, most effectively inhibited MAO-B, like MK12 (IC₅₀ = 3.22 nM), followed by MK5, MK13, and MK14 (IC₅₀ = 4.02, 4.24, and 4.89 nM, respectively). The selectivity index values of MK6 and MK12 for MAO-B over MAO-A were 7361.5 and 1780.5, respectively. Compounds MK6 and MK12 were competitive reversible inhibitors of MAO-B, with K _i values of 1.10 ± 0.20 and 3.0 ± 0.27 nM, respectively. Cytotoxic studies showed that MK5, MK6, MK12, and MK14 exhibited low toxicities on Vero cells, with IC₅₀ values of 218.4, 149.1, 99.96, and 162.3 μg/mL, respectively, which were much higher than those for their effective nanomolar-level concentrations. Also, MK5, MK6, MK12, and MK14 decreased cell damage in H₂O₂-induced cells via a significant scavenging effect of reactive oxygen species. Molecular modeling was performed to rationalize the potential inhibitory activities of MK5, MK6, MK12, and MK14 toward MAO-B and their possible binding mechanisms, showing high-affinity binding pocket interactions and conformation perturbations of the compounds with MAO-B, which were interpreted as the conformational dynamics of MAO-B. This study concluded that all the compounds tested were more potent MAO-B inhibitors than the reference drugs, and leading compounds could be further explored for their effectiveness in various kinds of neurodegenerative disorders.

(S)-5-Methylmellein Isolated from an Endogenous Lichen Fungus Rosellinia corticium as a Potent Inhibitor of Human Monoamine Oxidase A

In this study, the inhibitory activities against human monoamine oxidases (hMAOs) were evaluated using a library of 195 endogenous lichen fungi from Ukraine. Among them, the extract ELF68 of the endogenous fungus Rosellinia corticium from the lichen Pseudevernia furfuracea (L.) Zopf. exhibited the strongest inhibitory activity against hMAO-A. Using the activity-guided method, (S)-5-methylmellein (5MM) was isolated from the extract and had an IC50 value of 5.31 µM for hMAO-A with a lower potency for hMAO-B (IC50 = 9.15 µM). Compound 5MM also moderately inhibited acetylcholinesterase (IC50 = 27.07 µM) but very weakly inhibited butyrylcholinesterase and β-secretase. Compound 5MM had a Ki value of 2.45 μM and was a reversible competitive inhibitor of hMAO-A. A molecular docking study predicted that (S)-5MM showed higher binding affinity for hMAO-A (−6.8 kcal/mol) than hMAO-B (−6.4 kcal/mol). Its isomer, (R)-5MM, exhibited lower binding affinities for hMAO-A (−6.6 kcal/mol) and hMAO-B (−5.2 kcal/mol), compared to (S)-5MM. The S-form interacted with hMAO-A through hydrogen bonding with the Phe208 residue (distance: 1.972 Å), while the R-form interacted with the Asn181 residue (2.375 Å). The results of an in silico pharmacokinetic analysis indicated that 5MM did not violate Lipinski’s five rules and showed high gastrointestinal absorption and blood–brain barrier permeability. These results suggest that 5MM can be considered a candidate in the treatment of neuropsychiatric disorders, such as depression and cardiovascular disease.

Halogenated Coumarin-Chalcones as Multifunctional Monoamine Oxidase-B and Butyrylcholinesterase Inhibitors

A series of halogenated coumarin-chalcones were synthesized, characterized, and their inhibitory activities against monoamine oxidases (MAOs), acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and β-site amyloid precursor protein cleaving enzyme 1 (BACE-1) were evaluated. Compound CC2 most potently inhibited MAO-B with an IC₅₀ value of 0.51 μM, followed by CC1 (IC₅₀ = 0.69 μM), with a selectivity index (SI) of >78.4 and >58.0, respectively, over MAO-A. However, none of the compounds effectively inhibited MAO-A, AChE, and BChE, except for CC2 and CC3 inhibiting BChE with IC₅₀ values of 7.00 (SI > 5.73 over AChE) and 11.8 μM, respectively. CC1 and CC2 were found to be reversible and competitive inhibitors of MAO-B, with K _i values of 0.50 ± 0.06 and 0.53 ± 0.04 μM, respectively, and CC2 was also a reversible and competitive inhibitor of BChE, with a K _i value of 2.84 ± 0.09 μM. The parallel artificial membrane permeability assay (PAMPA) method showed that lead candidates can cross the blood-brain barrier (BBB). The in vitro toxicity analysis on the Vero cell line (Normal African green monkey kidney epithelial cells) by MTT confirmed that both CC1 and CC2 were nontoxic up to 100 μg/mL, which is almost equivalent to 100 times of their effective concentration used in biological studies. In addition, CC1 and CC2 attenuated H₂O₂-induced cellular damage via their reactive oxygen species (ROS) scavenging effect. These results suggest that CC1 and CC2 are selective and competitive inhibitors of MAO-B, and that CC2 is a selective and competitive inhibitor of BChE. Molecular docking studies of lead compounds provided the possible type of interactions in the targeted enzymes. Based on the findings, both compounds, CC1 and CC2, can be considered plausible drug candidates against neurodegenerative disorders.

Potent and Selective Inhibitors of Human Monoamine Oxidase A from an Endogenous Lichen Fungus Diaporthe mahothocarpus

Using 126 endogenous lichen fungus (ELF) extracts, inhibitory activities against monoamine oxidases (MAOs) and cholinesterases (ChEs) were evaluated. Among them, extract ELF29 of the endogenous fungus Diaporthe mahothocarpus of the lichen Cladonia symphycarpia showed the highest inhibitory activity against hMAO-A. Compounds alternariol (AT), 5′-hydroxy-alternariol (HAT), and mycoepoxydiene (MED), isolated from the extract, had potent inhibitory activities against hMAO-A with IC₅₀ values of 0.020, 0.31, and 8.68 µM, respectively. AT, HAT, and MED are reversible competitive inhibitors of hMAO-A with K_i values of 0.0075, 0.116, and 3.76 µM, respectively. The molecular docking studies suggested that AT, HAT, and MED had higher binding affinities for hMAO-A (−9.1, −6.9, and −5.6 kcal/mol, respectively) than for hMAO-B (−6.3, −5.2, and −3.7 kcal/mol, respectively). The relative tight binding might result from a hydrogen bond interaction of the three compounds with a Tyr444 residue in hMAO-A, whereas no hydrogen bond interaction was proposed in hMAO-B. In silico pharmacokinetics, the three compounds showed high gastrointestinal absorption without violating Lipinski’s five rules, but only MED showed high probability to cross the blood–brain barrier. These results suggest that AT, HAT, and MED are candidates for treating neuropsychiatric disorders, such as depression and cardiovascular disease.

Selected Class of Enamides Bearing Nitro Functionality as Dual-Acting with Highly Selective Monoamine Oxidase-B and BACE1 Inhibitors

A small series of nitro group-bearing enamides was designed, synthesized (NEA1–NEA5), and evaluated for their inhibitory profiles of monoamine oxidases (MAOs) and β-site amyloid precursor protein cleaving enzyme 1 (β-secretase, BACE1). Compounds NEA3 and NEA1 exhibited a more potent MAO-B inhibition (IC₅₀ value = 0.0092 and 0.016 µM, respectively) than the standards (IC₅₀ value = 0.11 and 0.14 µM, respectively, for lazabemide and pargyline). Moreover, NEA3 and NEA1 showed greater selectivity index (SI) values toward MAO-B over MAO-A (SI of >1652.2 and >2500.0, respectively). The inhibition and kinetics studies suggested that NEA3 and NEA1 are reversible and competitive inhibitors with K_i values of 0.013 ± 0.005 and 0.0049 ± 0.0002 µM, respectively, for MAO-B. In addition, both NEA3 and NEA1 showed efficient BACE1 inhibitions with IC₅₀ values of 8.02 ± 0.13 and 8.21 ± 0.03 µM better than the standard quercetin value (13.40 ± 0.04 µM). The parallel artificial membrane permeability assay (PAMPA) method demonstrated that all the synthesized derivatives can cross the blood–brain barrier (BBB) successfully. Docking analyses were performed by employing an induced-fit docking approach in the GLIDE module of Schrodinger, and the results were in agreement with their in vitro inhibitory activities. The present study resulted in the discovery of potent dual inhibitors toward MAO-B and BACE1, and these lead compounds can be fruitfully explored for the generation of newer, clinically active agents for the treatment of neurodegenerative disorders.

Piperazine-substituted chalcones: a new class of MAO-B, AChE, and BACE-1 inhibitors for the treatment of neurological disorders

Eleven piperazine-containing 1,3-diphenylprop-2-en-1-one derivatives (PC1-PC11) were evaluated for their inhibitory activities against monoamine oxidases (MAOs), cholinesterases (ChEs), and β-site amyloid precursor protein cleaving enzyme 1 (BACE-1) with a view toward developing new treatments for neurological disorders. Compounds PC10 and PC11 remarkably inhibited MAO-B with IC₅₀ values of 0.65 and 0.71 μM, respectively. Ten of the eleven compounds weakly inhibited AChE and BChE with > 50% of residual activities at 10 μM, although PC4 inhibited AChE by 56.6% (IC₅₀ = 8.77 μM). Compound PC3 effectively inhibited BACE-1 (IC₅₀ = 6.72 μM), and PC10 and PC11 moderately inhibited BACE-1 (IC₅₀ =14.9 and 15.3 μM, respectively). Reversibility and kinetic studies showed that PC10 and PC11 were reversible and competitive inhibitors of MAO-B with K_i values of 0.63 ± 0.13 and 0.53 ± 0.068 μM, respectively. ADME predictions for lead compounds revealed that PC10 and PC11 have central nervous system (CNS) drug-likeness. Molecular docking simulations showed that fluorine atom and trifluoromethyl group on PC10 and PC11, respectively, interacted with the substrate cavity of the MAO-B active site. Our results suggested that PC10 and PC11 can be considered potential candidates for the treatment of neurological disorders such as Alzheimer's disease and Parkinson's disease.

Molecular Characterization of Novel Family IV and VIII Esterases from a Compost Metagenomic Library

Two novel esterase genes, est8L and est13L, were isolated and identified from a compost metagenomic library. The encoded Est8L and Est13L had molecular masses of 33,181 and 44,913 Da consisting of 314 and 411 amino acids, respectively, without signal peptides. Est8L showed the highest identity (32.9%) to a hyper-thermophilic carboxylesterase AFEST from Archaeoglobus fulgidus compared to other esterases reported and was classified to be a novel member of family IV esterases with conserved regions such as HGGG, DY, GXSXG, DPL, and GXIH. Est13L showed the highest identity (98.5%) to the family VIII esterase Est7K from the metagenome library. Est8L and Est13L had the highest activities for p-nitrophenyl butyrate (C4) and p-nitrophenyl caproate (C6), respectively, and Est13L showed a broad substrate specificity for p-nitrophenyl substrates. Est8L and Est13L effectively hydrolyzed glyceryl tributyrate. The optimum temperatures for activities of Est8L and Est13L were identical (40 °C), and the optimum pH values were 9.0 and 10.0, respectively. Est13L showed higher thermostability than Est8L. Sephacryl S-200 HR chromatography showed that the native form of Est8L was a dimer. Interestingly, Est13L was found to be a tetramer, contrary to other family VIII esterases reported. Est8L was inhibited by 30% isopropanol, methanol, and acetonitrile; however, Est13L was activated to 182.9% and 356.1%, respectively, by 30% isopropanol and methanol. Est8L showed enantioselectivity for the S-form, but Est13L showed no enantioselectivity. These results show that intracellular Est8L and/or Est13L are oligomeric in terms of native forms and can be used for pharmaceutical and industrial applications with organic solvents under alkaline conditions.

Chromenone Derivatives as Monoamine Oxidase Inhibitors from Marine-Derived MAR4 Clade Streptomyces sp. CNQ-031

Three compounds were isolated from marine-derived Streptomyces sp. CNQ-031, and their inhibitory activities against monoamine oxidases (MAOs), acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and β-secretase (BACE-1) were evaluated. Compound 1 (5,7-dihydroxy-2-isopropyl-4H-chromen-4-one) was a potent and selective inhibitor of MAO-A, with a 50% inhibitory concentration (IC₅₀) of 2.70 μM and a selectivity index (SI) of 10.0 versus MAO-B. Compound 2 [5,7-dihydroxy-2-(1-methylpropyl)-4H-chromen-4-one] was a potent and low-selective inhibitor of MAO-B, with an IC₅₀ of 3.42 μM and an SI value of 2.02 versus MAO-A. Compound 3 (1-methoxyphenazine) did not inhibit MAO-A or MAO-B. All three compounds showed little inhibitory activity against AChE, BChE, and BACE-1. The K_i value of compound 1 for MAO-A was 0.94 ± 0.28 μM, and the K_i values of compound 2 for MAO-A and MAO-B were 3.57 ± 0.60 and 1.89 ± 0.014 μM, respectively, with competitive inhibition. The 1-methylpropyl group in compound 2 increased the MAO-B inhibitory activity compared with the isopropyl group in compound 1. Inhibition of MAO-A and MAO-B by compounds 1 and 2 was recovered by dialysis experiments. These results suggest that compounds 1 and 2 are reversible, competitive inhibitors of MAOs and can be considered potential therapies for neurological disorders such as depression and Alzheimer's disease.

Acetylcholinesterase and monoamine oxidase-B inhibitory activities by ellagic acid derivatives isolated from Castanopsis cuspidata var. sieboldii

Among 276 herbal extracts, a methanol extract of Castanopsis cuspidata var. sieboldii stems was selected as an experimental source for novel acetylcholinesterase (AChE) inhibitors. Five compounds were isolated from the extract by activity-guided screening, and their inhibitory activities against butyrylcholinesterase (BChE), monoamine oxidases (MAOs), and β-site amyloid precursor protein cleaving enzyme 1 (BACE-1) were also evaluated. Of these compounds, 4'-O-(α-L-rhamnopyranosyl)-3,3',4-tri-O-methylellagic acid (3) and 3,3',4-tri-O-methylellagic acid (4) effectively inhibited AChE with IC₅₀ values of 10.1 and 10.7 µM, respectively. Ellagic acid (5) inhibited AChE (IC₅₀ = 41.7 µM) less than 3 and 4. In addition, 3 effectively inhibited MAO-B (IC₅₀ = 7.27 µM) followed by 5 (IC₅₀ = 9.21 µM). All five compounds weakly inhibited BChE and BACE-1. Compounds 3, 4, and 5 reversibly and competitively inhibited AChE, and were slightly or non-toxic to MDCK cells. The binding energies of 3 and 4 (- 8.5 and - 9.2 kcal/mol, respectively) for AChE were greater than that of 5 (- 8.3 kcal/mol), and 3 and 4 formed a hydrogen bond with Tyr124 in AChE. These results suggest 3 is a dual-targeting inhibitor of AChE and MAO-B, and that these compounds should be viewed as potential therapeutics for the treatment of Alzheimer's disease.

Characterization of a Novel Family IV Esterase Containing a Predicted CzcO Domain and a Family V Esterase with Broad Substrate Specificity from an Oil-Polluted Mud Flat Metagenomic Library

Two novel esterase genes, est2L and est4L, were identified from a previously constructed metagenomic library derived from an oil-polluted mud flat sample. The encoded Est2L and Est4L were composed of 839 and 267 amino acids, respectively, without signal peptides. Est2L was a unique fusion type of protein composed of two domains: a domain of the CzcO superfamily, associated with a cationic diffusion promoter with CzcD, and a domain of the acetylesterase superfamily, belonging to family IV with conserved motifs, such as HGG, GXSAG, and GXPP. Est2L was the first fused esterase with a CzcO domain. Est4L belonged to family V with GXS, GXSMGG, and PTL motifs. Native Est2L and Est4L were found to be in dimeric and tetrameric forms, respectively. Est2L and Est4L showed the highest activities at 60 °C and 50 °C, respectively, and at a pH of 10.0. Est2L preferred short length substrates, especially p-nitrophenyl (pNP)-acetate, with moderate butyrylcholinesterase activity, whereas Est4L showed the highest activity with pNP-decanoate and had broad specificity. Significant effects were not observed in Est2L from Co2+ and Zn2+, although Est2L contains the domain CzcD. Est2L and Est4L showed high stabilities in 30% methanol and 1% Triton X-100. These enzymes could be used for a variety of applications, such as detergent and mining processing under alkaline conditions.

Morpholine-based chalcones as dual-acting monoamine oxidase-B and acetylcholinesterase inhibitors: synthesis and biochemical investigations

Nine compounds (MO1–MO9) containing the morpholine moiety were assessed for their inhibitory activities against monoamine oxidases (MAOs) and acetylcholinesterase (AChE). Most of the compounds potently inhibited MAO-B; MO1 most potently inhibited with an IC₅₀ value of 0.030 µM, followed by MO7 (0.25 µM). MO5 most potently inhibited AChE (IC₅₀ = 6.1 µM), followed by MO9 (IC₅₀ = 12.01 µM) and MO7 most potently inhibited MAO-A (IC₅₀ = 7.1 µM). MO1 was a reversible mixed-type inhibitor of MAO-B (K_i = 0.018 µM); MO5 reversibly competitively inhibited AChE (K_i = 2.52 µM); and MO9 reversibly noncompetitively inhibited AChE (K_i = 7.04 µM). MO1, MO5 and MO9 crossed the blood–brain barrier, and were non-toxic to normal VERO cells. These results show that MO1 is a selective inhibitor of MAO-B and that MO5 is a dual-acting inhibitor of AChE and MAO-B, and that both should be considered candidates for the treatment of Alzheimer’s disease.

Selective Inhibition of Human Monoamine Oxidase B by 5-hydroxy-2-methyl-chroman-4-one Isolated from an Endogenous Lichen Fungus Daldinia fissa

Inhibitory activities against monoamine oxidases (MAOs) and cholinesterases (ChEs) and antioxidant activity were evaluated for 195 extracts from Ukraine-derived endogenous lichen fungi (ELF). Among them, an ELF13 (identified as Daldinia fissa) extract showed the highest inhibitory activity against MAO-B, and 5-hydroxy-2-methyl-chroman-4-one (HMC) was isolated as a ~ 4-fold selective inhibitor of MAO-B (IC₅₀ = 3.23 µM) compared to MAO-A (IC₅₀ = 13.97 µM). HMC is a reversible competitive inhibitor with a K_i value of 0.896 µM. No cytotoxicity was observed in normal and cancer cells at 50 µM of HMC. HMC showed blood–brain barrier permeability and high gastrointestinal absorption in silico pharmacokinetics. The docking simulation results showed that the binding affinity of HMC for MAO-B (−7.3 kcal/mol) was higher than that of MAO-A (−6.1 kcal/mol) and that HMC formed a hydrogen bond interaction with Cys172 of MAO-B (distance: 3.656 Å), whereas no hydrogen bonding was predicted with MAO-A. These results suggest that HMC can be considered a candidate for the treatment of neurodegenerative diseases, such as Alzheimer’s disease and Parkinson’s disease.

Acetylcholinesterase and butyrylcholinesterase inhibitory activities of khellactone coumarin derivatives isolated from Peucedanum japonicum Thurnberg

Cholinesterase (ChE) and monoamine oxidase (MAO) inhibitors have been attracted as candidate treatments for Alzheimer's disease (AD). Fifteen khellactone-type coumarins from the roots of Peucedanum japonicum Thunberg were tested for acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and MAO inhibitory activities. Compound 3′-angeloyl-4′-(2-methylbutyryl)khellactone (PJ13) most potently inhibited AChE (IC₅₀ = 9.28 µM), followed by 3′-isovaleryl-4′-(2-methylbutyroyl)khellactone (PJ15) (IC₅₀ = 10.0 μM). Compound senecioyl-4′-angeloyl-khellactone (PJ5) most potently inhibited BChE (IC₅₀ = 7.22 μM) and had the highest selectivity index (> 5.54), followed by 3′-senecioyl-4′-(2-methylbutyryl)khellactone (PJ10) and 3′,4′-disenecioylkhellactone (PJ4) (IC₅₀ = 10.2 and 10.7 μM, respectively). Compounds PJ13, PJ15, and PJ5 showed reversible and mixed-types of inhibition with K_i values of 5.98, 10.4 (for AChE), and 4.16 µM (for BChE), respectively. However, all 15 compounds weakly inhibited MAO-A and MAO-B. Molecular docking simulation revealed that PJ13 had a higher binding affinity (− 9.3 kcal/mol) with AChE than PJ15 (− 7.8 kcal/mol) or PJ5 (− 5.4 kcal/mol), due to the formation of a hydrogen bond with Tyr121 (distance: 2.52 Å). On the other hand, the binding affinity of PJ5 (− 10.0 kcal/mol) with BChE was higher than for PJ13 (− 7.7 kcal/mol) or PJ15 (− 8.1 kcal/mol), due to the formation of a hydrogen bond with Ser198 (distance: 2.05 Å). These results suggest that PJ13 and PJ5 are potential reversible selective inhibitors of AChE and BChE, respectively, for the treatment of AD.

Antidepressant-Like Effects of Ethanol Extract of Ziziphus jujuba Mill Seeds in Mice

The antidepressant-like activity of ethanol extract of Ziziphus jujuba Mill var. spinosa seeds (Semen Ziziphi Spinosae, SZS) was investigated by behavioral tests, such as a forced swimming test (FST), a tail-suspension test (TST), and an open field test (OFT), using mice exposed to chronic unpredictable mild stress (CUMS). In the TST, immobility times of the extract-treated groups E100 and E300 (CUMS + 100 and 300 mg/kg extract, respectively) were significantly decreased in a dose-dependent manner compared with the negative control (CUMS; p < 0.01, though those of E100 and E300 were higher than those of the positive control (CUMS + 15 mg/kg fluoxetine). In the FST, immobility times of E100 and E300 were decreased compared to the normal control. In the OFT, total and zone distances of E100 and E300 were significantly higher than those of negative controls (p < 0.01) with a dose dependency. In liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis after behavioral tests, norepinephrine (NE) and 5-hydroxytryptamine (5-HT) levels in the hippocampus tissues of E100 and E300 were significantly higher than those of negative controls. Brain-derived neurotrophic factor (BDNF) levels in the hippocampus tissues of E100 and E300 were higher than those of negative controls. From these results, the SZS ethanol extract exhibited significant antidepressant-like effects via immobility decrease, distance increase, hippocampal NE and 5-HT increase, and BDNF expression. These results suggest that the extract could be a potential antidepressant agent.

Selected 1,3-Benzodioxine-Containing Chalcones as Multipotent Oxidase and Acetylcholinesterase Inhibitors

Chalcones are considered effective templates for the development of monoamine oxidase (MAO) and cholinesterase (ChE) inhibitors. The present work describes the syntheses of selected 1,3-benzodioxine-containing chalcones (CD3, CD8 and CD10), and their inhibitory activities against MAO-A, MAO-B, acetylcholinesterase (AChE), and butyrylcholinesterase (BChE). Compound CD8 most potently inhibited MAO-B with an IC₅₀ value of 0.026 μM, followed by CD10 and CD3 (1.54 and 1.68 μM, respectively). CD8 potently and non-selectively inhibited MAO-A (IC₅₀ value of 0.023 μM). On the other hand, CD10 and CD8 inhibited AChE with IC₅₀ values of 5.40 and 9.57 μM, respectively. Kinetics and reversibility experiments showed that all synthesized molecules were competitive and reversible inhibitors, and the K_i values of CD8 for MAO-A and MAO-B were 0.018 and 0.0019 μM, respectively. By in vitro and in silico analyses, all compounds were found to have high passive human gastrointestinal absorptions, blood-brain barrier permeabilities, and non-toxicities. Molecular docking simulations revealed that docking affinity of each compound for MAO-B was higher than that for MAO-A. The results indicate that CD8 is a potent non-selective MAO inhibitor, and CD10 is an effective selective MAO-B inhibitor, and both possess AChE inhibitory activity. Therefore, we suggest that CD8 and CD10 be considered potential dual-targeting inhibitors of MAO and AChE for the treatment of various neurodegenerative disorders.

Inhibition of Butyrylcholinesterase and Human Monoamine Oxidase-B by the Coumarin Glycyrol and Liquiritigenin Isolated from Glycyrrhiza uralensis

Eight compounds were isolated from the roots of Glycyrrhiza uralensis and tested for cholinesterase (ChE) and monoamine oxidase (MAO) inhibitory activities. The coumarin glycyrol (GC) effectively inhibited butyrylcholinesterase (BChE) and acetylcholinesterase (AChE) with IC₅₀ values of 7.22 and 14.77 µM, respectively, and also moderately inhibited MAO-B (29.48 µM). Six of the other seven compounds only weakly inhibited AChE and BChE, whereas liquiritin apioside moderately inhibited AChE (IC₅₀ = 36.68 µM). Liquiritigenin (LG) potently inhibited MAO-B (IC₅₀ = 0.098 µM) and MAO-A (IC₅₀ = 0.27 µM), and liquiritin, a glycoside of LG, weakly inhibited MAO-B (>40 µM). GC was a reversible, noncompetitive inhibitor of BChE with a K_i value of 4.47 µM, and LG was a reversible competitive inhibitor of MAO-B with a K_i value of 0.024 µM. Docking simulations showed that the binding affinity of GC for BChE (−7.8 kcal/mol) was greater than its affinity for AChE (−7.1 kcal/mol), and suggested that GC interacted with BChE at Thr284 and Val288 by hydrogen bonds (distances: 2.42 and 1.92 Å, respectively) beyond the ligand binding site of BChE, but that GC did not form hydrogen bond with AChE. The binding affinity of LG for MAO-B (−8.8 kcal/mol) was greater than its affinity for MAO-A (−7.9 kcal/mol). These findings suggest GC and LG should be considered promising compounds for the treatment of Alzheimer’s disease with multi-targeting activities.

Calycosin and 8-O-methylretusin isolated from Maackia amurensis as potent and selective reversible inhibitors of human monoamine oxidase-B

Nineteen compounds were isolated from the stems of Maackia amurensis by activity-guided screening for new human monoamine oxidase-B (hMAO-B) inhibitors. Among the compounds isolated, flavonoids calycosin (5) and 8-O-methylretusin (6) were found to potently and selectively inhibit hMAO-B (IC₅₀ = 0.24 and 0.23 μM, respectively) but not hMAO-A with high selectivity index (SI) values (SI = 293.8 and 81.3, respectively). In addition, 5 and 6 reversibly and competitively inhibited hMAO-B with K_i values of 0.057 and 0.054 μM, respectively. A pterocarpan (-)-medicarpin (18) was also observed to strongly inhibit hMAO-B (IC₅₀ = 0.30 μM). Most of the compounds weakly inhibited AChE, except isolupalbigenin (13) (IC₅₀ = 20.6 μM), which suggested 13 be considered a potential dual function inhibitor of MAO-B and AChE. Molecular docking simulation revealed that the binding affinities of 5 and 6 for hMAO-B (both -9.3 kcal/mol) were higher than those for hMAO-A (-7.4 and -7.2 kcal/mol, respectively). Compound 5 was found to interact by hydrogen bonding with hMAO-B at Cys172 residue (distance: 3.250 Å); no hydrogen bonding was predicted between 5 and hMAO-A. These findings suggest that compounds 5 and 6 be considered novel potent, selective, and reversible hMAO-B inhibitors and candidates for the treatment of neurological disorders.

The Effects of Storage on Quality and Nutritional Values of Ehrenberg's Snapper Muscles (Lutjanus Ehrenbergi): Evaluation of Natural Antioxidants Effect on the Denaturation of Proteins

Protein denaturation in frozen minced fillets (Ehrenberg’s Snapper), stored at −25 °C was studied; 50.0 mg biomass/50g mince fillets treated with cinnamon, cumin, turmeric, garlic, ginger and 25.0 mg of vitamin C were used to slow protein denaturation. FT-IR stretching vibration of Amide-A (νNH) at 3300 cm⁻¹; Amide-I stretching (νC=O) between 1600−1690 cm⁻¹ and Amide-II stretching (νCN) and bending (δNH) between 1480 and 1575cm⁻¹ were used as marker peaks. Garlic was the most significant (p ≤ 0.01) in controlling the rate of protein denaturation when νNH was used as a marker peak. DSC analysis showed that turmeric presented the highest effect on delaying the denaturation of sarcoplasmic proteins with a ΔH0=73.7J/g  followed by garlic-treated mince fillets ΔH0=70.1J/g. All spices used were efficient in stopping the denaturation of myosin with the highest ΔH0=769.3 J/g registered for cinnamon-treated mince fillets. Actin was less vulnerable to denaturation in comparison to myosin and sarcoplasmic proteins.