Β-secretase Inhibitory Activity Research Articles

Design and synthesis of novel anti-Alzheimer’s agents: Acridine-chromenone and quinoline-chromenone hybrids

A novel series of acridine-chromenone and quinoline-chromenone hybrids were designed, synthesized, and evaluated as anti-Alzheimer’s agents. All synthesized compounds were evaluated as cholinesterases (ChEs) inhibitors and among them, 7-(4-(6-chloro-2,3-dihydro-1H-cyclopenta[b]quinolin-9-ylamino)phenoxy)-4-methyl-2H-chromen-2-one (8e) exhibited the most potent anti-acetylcholinesterase (AChE) inhibitory activity (IC50=16.17μM) comparing with rivastigmine (IC50=11.07μM) as the reference drug. Also, compound 8e was assessed for its β-secretase (BACE1) inhibitory and neuroprotective activities which demonstrated satisfactory results. It should be noted that both kinetic study on the inhibition of AChE and molecular modeling revealed that compound 8e interacted simultaneously with both the catalytic active site (CAS) and peripheral anionic site (PAS) of AChE.

Multifunctional activity of polyphenolic compounds associated with a potential for Alzheimer's disease therapy from Ecklonia cava.

Five polyphenols were isolated and purified from a brown alga Ecklonia cava. These compounds showed diverse biological activities such as antioxidative, antiinflammatory, and enzyme inhibitory activities. This led us to investigate the potential of these compounds as Alzheimer's disease drugs. All of the compounds showed moderate acetylcholinesterase inhibitory activity in a micromolar range (IC50 from 16.0 to 96.3 μM). For butyrylcholinesterase, a new target for the treatment of Alzheimer's disease, phlorofucofuroeckol-A (PFF-A), showed a particularly potent inhibitory activity (IC50 0.95 μM), which is over 100-fold greater than for acetylcholinesterase. These compounds inhibited glycogen synthase kinase 3 beta, which is related to the formation of hyperphosphorylated tau and generation Aβ. Bieckol and PFF-A inhibited amyloid precursor protein biosynthesis. PFF-A also showed very strong β-secretase inhibitory activity with IC50 of submicromole. These results render these compounds as interesting potential drug candidates for Alzheimer's disease.

Molecular structure, FT-IR, vibrational assignments, HOMO–LUMO, MEP, NBO analysis and molecular docking study of ethyl-6-(4-chlorophenyl)-4-(4-fluorophenyl)-2-oxocyclohex-3-ene-1-carboxylate

The optimized molecular structure, vibrational frequencies, corresponding vibrational assignments of ethyl-6-(4-chlorophenyl)-4-(4-fluoro-phenyl)-2-oxocyclohex-3-ene-1-carboxylate have been investigated experimentally and theoretically using Gaussian09 software. The title compound was optimized using the HF and DFT levels of theory. The geometrical parameters are in agreement with the XRD data. The stability of the molecule has been analyzed by NBO analysis. The HOMO and LUMO analysis is used to determine the charge transfer within the molecule. Molecular electrostatic potential was performed by the DFT method. As can be seen from the MEP map of the title compound, regions having the negative potential are over the electro negative atoms, the region having the positive potential are over the phenyl rings and the remaining species are surrounded by zero potential. First hyperpolarizability is calculated in order to find its role in non linear optics. The title compound binds at the active sites of both CypD and β-secretase and the molecular docking results draw the conclusion that the compound might exhibit β-secretase inhibitory activity which could be utilized for development of new anti-alzheimeric drugs with mild CypD inhibitory activity.

Characterization of β-secretase inhibitory peptide purified from skate skin protein hydrolysate

The objective of this study was to purify and characterize the β-secretase inhibitor from enzymatic hydrolysates of skate skin, for the development of a novel antidementia agent that may be utilized in the drug or functional food industries. β-secretase inhibitory peptide was purified from various enzymatic hydrolysates of skate skin. Among six enzymatic hydrolysates, the Neutrase hydrolysate showed the highest β-secretase inhibitory activity. Consecutive purification of the skate skin hydrolysate using Sephadex G-25 column chromatography and octadecylsilane C18 reversed phase HPLC techniques was used to isolate a potent β-secretase inhibitory peptide composed of 12 amino acids, Gln–Gly–Try–Arg–Pro–Leu–Arg–Gly–Pro–Glu–Phe–Leu (MW: 1,391 Da). The purified peptide had strong β-secretase inhibitory activity, with IC50 value of 24.26 μM, and displayed a non-competitive mode of inhibition. Among the synthesized β-secretase inhibitory peptides, the tetrapeptide Pro–Glu–Phe–Leu had the highest β-secretase inhibitory activity. The result of this study suggests that the β-secretase inhibitory peptide derived from skate skin could be potential candidates to develop nutraceuticals and pharmaceuticals.

In Vitro BACE1 Inhibitory Activity of Geraniin and Corilagin from Geranium thunbergii

Generation of amyloid β peptide through the proteolytic process of amyloid precursor protein by β-secretase and γ-secretase is a main casual factor of Alzheimer's disease, since amyloid β peptide is a major and crucial component of senile plaques in Alzheimer's disease brains. In the process of searching for β-secretase inhibitors from natural resources, the EtOAc soluble fraction of Geranium thunbergii exhibited significant β-secretase inhibitory activity. Two compounds, geraniin and corilagin, isolated from the most active EtOAc fraction of G. thunbergii, exhibited predominant inhibition against β-secretase with IC₅₀ values of 4.0 × 10⁻⁶ M and 3.4 × 10⁻⁵ M, respectively. Dixon plot of geraniin and corilagin demonstrated that the β-secretase inhibition was noncompetitive with the substrate, thus clearly suggesting that these compounds might bind either to the β-secretase subsites or to another regulatory domain with Ki values of 2.8 × 10⁻⁶ M and 7.9 × 10⁻⁵ M, respectively. Both compounds exhibited no significant inhibition against α-secretase and other serine proteases including trypsin and chymotrypsin, showing that they were relatively specific and selective inhibitors of β-secretase. These novel findings suggest that geraniin and corilagin from G. thunbergii may be effective therapeutic agents for further drug development in Alzheimer's disease.

The green tea polyphenol (2)-epigallocatechin-3-gallate (EGCG) is not a β-secretase inhibitor

(2)-Epigallocatechin-3-gallate (EGCG) is a major polyphenolic component of green tea. A number of studies have demonstrated EGCG has the possibility for delaying the onset or retarding the progression of Alzheimer's disease (AD) and indicated EGCG possess inhibition of β-secretase activity. We utilized homogeneous time-resolved fluorescence assay with a substrate Eu-CEVNLDAEFK-Qsy7 to screen β-secretase inhibitor in a cell-free system and AlphaLISA assay in cell system. The results first showed that EGCG had significant inhibition of β-secretase activity with IC(50) value of 7.57 × 10(-7)M in screening assay, but then we found EGCG had significant fluorescence-quenching effect in confirming assay, this indicates EGCG has the false positive β-secretase inhibitory activity. Furthermore, the followed AlphaLISA assay based on cell showed EGCG did not reduce the β-amyloid 1-40 secretion in HuAPPswe/HuBACE1 Chinese hamster ovary cell without affecting cell viability. Therefore our findings indicate EGCG do not inhibit β-secretase cleavage activity. Overall this study illustrates that EGCG is not a β-secretase inhibitor based on the compelling data. This provides further support that the choice of complementary assay format or technology is a critical factor in molecular screening and drug development for improving the hit-finding capability and efficiency.

Microbial reduction of coumarin, psoralen, and xanthyletin by Glomerella cingulata

Microbial transformation of coumarin, psoralen, and xanthyletin was performed with the fungus Glomerella cingulata. The main reaction pathways involved reduction at α,β-unsaturated δ-lactone ring on coumarin analogue. Coumarin was metabolized by G. cingulata to give the corresponding reduced acid, hydrocoumaric acid. In the biotransformation of psoralen, two reduced metabolites, 6,7-furano-hydrocoumaric acid, and 6,7-furano- o-hydrocoumaryl alcohol were isolated from the incubation of psoralen. Xanthyletin was converted to reduced products 9,9-dimethyl-6,7-pyrano-hydrocoumaric acid and 9,9-dimethyl-6,7-pyrano-o-hydrocoumaryl alcohol by G. cingulata. The structures of the new compounds were characterized using spectroscopic techniques. In addition, all of compounds including methyl ester derivatives of the metabolites were tested for the β-secretase (BACE1) inhibitory activity in vitro. 6,7-Furano-hydrocoumaric acid methyl ester was shown to possess BACE1 inhibitory activity, and an IC 50 value was 0.84 ± 0.06 mM.

Biotransformation of isoimperatorin and imperatorin by Glomerella cingulata and β-secretase inhibitory activity

Biotransformation studies conducted on the furanocoumarins isoimperatorin ( 1) and imperatorin ( 3) have revealed that 1 was metabolized by Glomerella cingulata to give the corresponding reduced acid, 6,7-furano-5-prenyloxy hydrocoumaric acid ( 2), and 3 was transformed by G. cingulata to give the dealkylated metabolite, xanthotoxol ( 4) in high yields (83% and 81%), respectively. The structures of the new compound 2 have been established on the basis of spectral data. The metabolites 2 and 4 were tested for the β-secretase (BACE1) inhibitory activity in vitro, and metabolite 2 slightly inhibited the β-secretase activity with an IC 50 value of 185.6 ± 6.8 μM. The metabolite 4 was less potent activity than compounds 1 – 3. In addition, methyl ester ( 2Me), methyl ether ( 2a) and methyl ester and ether ( 2aMe) of 2 were synthesized, and investigated for the ability to inhibit β-secretase. Compound 2aMe exhibited the best β-secretase inhibitory activity at the IC 50 value 16.2 ± 1.2 μM and found to be the 2aMe showed competitive mode of inhibition against β-secretase with K i value 11.3 ± 2.8 μM.

Screening and Optimal Extraction of a New Antidementia β-Secretase Inhibitor-Containing Mushroom

To produce a potent antidementia β-secretase inhibitor from a mushroom, the β-secretase inhibitory activities of various mushroom extracts were determined. Methanol extracts of Lentinula edodes exhibited the highest inhibitory activity (40.1%). The inhibitor was maximally extracted when a fruiting body of L. edodes was treated with 50% methanol at 40°C for 24 h.

BACE1 inhibitory effects of lavandulyl flavanones from Sophora flavescens

In order to access β-secretase (BACE1), and enzyme strongly implicated in the cause of Alzheimer’s disease, inhibitors must possess sufficient lipophilicity to traverse two lipid bilayers. Current drug candidates, which are almost totally peptide-derived, are thus inefficient because cell permeability presents a serious limiting factor. In this study, lipophilic alkylated (C 10–C 5) flavanones from Sophora flavescens were examined for their inhibitory effects against β-secretase. Lavandulyl flavanones ( 1, 2, 5, 6, and 8) showed potent β-secretase inhibitory activities with IC 50s of 5.2, 3.3, 8.4, 2.6, and 6.7 μM, respectively, while no significant activity was observed in the corresponding hydrated lavandulyl flavanones ( 4 and 7) and prenylated flavanone ( 3). As we expected, lavandulyl flavanones reduced Aβ secretion dose-dependently in transfected human embryonic kidney (HEK-293) cells. In kinetic studies, all compounds screened were shown to be noncompetitive inhibitor.

Chitooligosaccharides as a novel β-secretase inhibitor

Nine kinds of hetero-chitooligosaccharides (hetero-COSs) with different degrees of deacetylation and molecular weights were prepared using an ultrafiltration (UF) membrane reactor system. In addition, their sulfated derivatives were also synthesized by a method using trimethylamine-sulfur trioxide to investigate the functional group of COSs on β-secretase inhibitory activity. 90-MMWCOSs-I, which are 90% deacetylated COSs passed through the 5 kDa membrane but not passed through the 3 kDa membrane, exhibited the highest β-secretase inhibitory activity (25–42 μM) based on molecular weight of 3 and 5 kDa. The inhibition pattern of the inhibitor was found to be a non-competitive by Dixon plot, and K i of 90-MMWCOSs-I was 3.87–6.47 μM. Therefore, the data of this research suggest that 90-MMWCOSs-I is a good candidate target molecule to inhibit β-secretase.

Design of β-Secretase Inhibitors by Introduction of a Mandelyl Moiety in DAPT Analogues

We report the synthesis of two series of compounds with 3,5-difluoromandelyl-alanyl or 3,5-difluorophenylacetyl-alanyl backbones coupled to various heterocyclic or peptidic moieties. These two series of compounds were evaluated for their inhibitory properties on β-secretase (BACE-1) enzymatic assay, a target enzyme for Alzheimer’s disease (AD) pathology. We found that both diastereomers obtained from the racemic mixture 7 of the coumarin derivative bearing a mandelyl moiety were the most potent BACE-1 inhibitors studied in this work (IC50 = 1 × 10−6 M). Analysis of the obtained results led to the hypothesis that introduction of a difluoromandelyl residue in place of a difluorophenylacetyl moiety may induce β-secretase inhibitory activity.