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 ß-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.

Evaluation of Selective COX-2 Inhibition and In Silico Study of Kuwanon Derivatives Isolated from Morus alba.

Six kuwanon derivatives (A/B/C/E/H/J) extracted from the roots of Morus alba L. were evaluated to determine their cyclooxygenase (COX)-1 and 2 inhibitory effects. Cyclooxygenase (COX) is known as the target enzyme of nonsteroidal anti-inflammatory drugs (NSAIDs), which are the most widely used therapeutic agents for pain and inflammation. Among six kuwanon derivatives, kuwanon A showed selective COX-2 inhibitory activity, almost equivalent to that of celecoxib, a known COX inhibitor. Kuwanon A showed high COX-2 inhibitory activity (IC50 = 14 µM) and a selectivity index (SI) range of >7.1, comparable to celecoxib (SI > 6.3). To understand the mechanisms underlying this effect, we performed docking simulations, fragment molecular orbital (FMO) calculations, and pair interaction energy decomposition analysis (PIEDA) at the quantum-mechanical level. As a result, kuwanon A had the strongest interaction with Arg120 and Tyr355 at the gate of the COX active site (-7.044 kcal/mol) and with Val89 in the membrane-binding domain (-6.599 kcal/mol). In addition, kuwanon A closely bound to Val89, His90, and Ser119, which are residues at the entrance and exit routes of the COX active site (4.329 Å). FMO calculations and PIEDA well supported the COX-2 selective inhibitory action of kuwanon A. It showed that the simulation and modeling results and experimental evidence were consistent.

Lycorine, a non-nucleoside RNA dependent RNA polymerase inhibitor, as potential treatment for emerging coronavirus infections.

BACKGROUND: Highly effective novel treatments need to be developed to suppress emerging coronavirus (CoV) infections such as COVID-19. The RNA dependent RNA polymerase (RdRp) among the viral proteins is known as an effective antiviral target. Lycorine is a phenanthridine Amaryllidaceae alkaloid isolated from the bulbs of Lycoris radiata (L'Hér.) Herb. and has various pharmacological bioactivities including antiviral function. PURPOSE: We investigated the direct-inhibiting action of lycorine on CoV's RdRp, as potential treatment for emerging CoV infections. METHODS: We examined the inhibitory effect of lycorine on MERS-CoV, SARS-CoV, and SARS-CoV-2 infections, and then quantitatively measured the inhibitory effect of lycorine on MERS-CoV RdRp activity using a cell-based reporter assay. Finally, we performed the docking simulation with lycorine and SARS-CoV-2 RdRp. RESULTS: Lycorine efficiently inhibited these CoVs with IC50 values of 2.123 ± 0.053, 1.021 ± 0.025, and 0.878 ± 0.022 µM, respectively, comparable with anti-CoV effects of remdesivir. Lycorine directly inhibited MERS-CoV RdRp activity with an IC50 of 1.406 ± 0.260 µM, compared with remdesivir's IC50 value of 6.335 ± 0.731 µM. In addition, docking simulation showed that lycorine interacts with SARS-CoV-2 RdRp at the Asp623, Asn691, and Ser759 residues through hydrogen bonding, at which the binding affinities of lycorine (-6.2 kcal/mol) were higher than those of remdesivir (-4.7 kcal/mol). CONCLUSIONS: Lycorine is a potent non-nucleoside direct-acting antiviral against emerging coronavirus infections and acts by inhibiting viral RdRp activity; therefore, lycorine may be a candidate against the current COVID-19 pandemic.

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 Ki 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.

Adaptive cellular stress pathways as therapeutic targets of dietary phytochemicals: focus on the nervous system.

During the past 5 decades, it has been widely promulgated that the chemicals in plants that are good for health act as direct scavengers of free radicals. Here we review evidence that favors a different hypothesis for the health benefits of plant consumption, namely, that some phytochemicals exert disease-preventive and therapeutic actions by engaging one or more adaptive cellular response pathways in cells. The evolutionary basis for the latter mechanism is grounded in the fact that plants produce natural antifeedant/noxious chemicals that discourage insects and other organisms from eating them. However, in the amounts typically consumed by humans, the phytochemicals activate one or more conserved adaptive cellular stress response pathways and thereby enhance the ability of cells to resist injury and disease. Examplesof such pathways include those involving the transcription factors nuclear factor erythroid 2-related factor 2, nuclear factor-κB, hypoxia-inducible factor 1α, peroxisome proliferator-activated receptor γ, and forkhead box subgroup O, as well as the production and action of trophic factors and hormones. Translational research to develop interventions that target these pathways may lead to new classes of therapeutic agents that act by stimulating adaptive stress response pathways to bolster endogenous defenses against tissue injury and disease. Because neurons are particularly sensitive to potentially noxious phytochemicals, we focus on the nervous system but also include findings from other cell types in which actions of phytochemicals on specific signal transduction pathways have been more thoroughly studied.

Ginsenoside Rc modulates Akt/FoxO1 pathways and suppresses oxidative stress.

Ginsenoside Rc (Rc), a protopanaxadiol type ginsenoside, is the active component mainly responsible for the therapeutic and pharmacologic properties of ginseng, which are derived from its suppression of superoxide-induced free radicals. Forkhead box O (FoxO1) regulates various genes involved in cellular metabolism related to cell death and response to oxidative stress, and Rc is known to prevent FoxO1 phosphorylation by activation of PI3K/Akt and subsequent inhibition of AMP-activated protein kinase (AMPK) in cells exposed to tert-butylhydroperoxide (t-BHP). In the current study, we attempted the mechanism of increased catalase expression by Rc through inhibition of FoxO1 activation resulting from t-BHP-induced production of reactive species (RS). We found that overexpression of catalase induced by Rc resulted in suppression of RS production in kidney human embryo kidney 293T cells (HEK293T) cells, and that oxidative stress induced activation of PI3K/Akt and inhibition of the AMPK pathway and FoxO1 phosphorylation, leading to down-regulation of catalase, a FoxO1-targeting gene. In addition, treatment of HEK293T cells with Rc resulted in cAMP-response element-binding protein (CREB)-binding protein (CBP) regulated FoxO1 acetylation. Our results suggest that Rc modulates FoxO1 phosphorylation through activation of PI3K/Akt and inhibition of AMPK and FoxO1 acetylation through interaction with CBP and SIRT1, and that this leads to upregulation of catalase under conditions of oxidative stress.

Synthesis and biological activity of hydroxy substituted phenyl-benzo[d]thiazole analogues for antityrosinase activity in B16 cells.

In this study, we synthesized hydroxy and/or alkoxy substituted phenyl-benzo[d]thiazole derivatives using substituted benzaldehydes and 2-aminothiophenol in MeOH. The structures of these compounds were established by (1)H and (13)CNMR and mass spectral analyzes. All synthesized compounds were evaluated for their mushroom tyrosinase inhibition activity. Out the 12 generated compounds, 2a and 2d exhibited much higher tyrosinase inhibition activity (45.36-73.07% and 49.94-94.17% at 0.01-20 µM, respectively) than kojic acid (9.29-50.80% at 1.25-20 µM), a positive control. The cytotoxicity of 2a and 2d was evaluated using B16 cells and the compounds were found to be nontoxic. Compounds 2a and 2d were also demonstrated to be potent mushroom tyrosinase inhibitors, displaying IC(50) values of 1.14±0.48 and 0.01±0.0002 µM, respectively, compared with kojic acid, which has an IC(50) value of 18.45±0.17 µM. We also predicted the tertiary structure of tyrosinase, simulated the docking with compounds 2a and 2d and confirmed that the compounds strongly interact with mushroom tyrosinase residues. Kinetic plots showed that 2a and 2d are competitive tyrosinase inhibitors. Substitutions with a hydroxy group at R(3) or both R(3) and R(1) of the phenyl ring indicated that these groups play a major role in the high binding affinity to tyrosinase. We further found that compounds 2a and 2d inhibit melanin production and tyrosinase activity in B16 cells. These results may assist in the development of new potent tyrosinase inhibitors against hyperpigmentation.