Polyphenols based on isoflavones as inhibitors of Helicobacter pylori urease

Twenty polyphenols were synthesized and evaluated for their effect on Helicobacter pylori urease. Among these compounds, 4-(p-hydroxyphenethyl)pyrogallol (15) (IC(50)=0.03 mM) and 7,8,4'-trihydroxyisoflavone (19) (IC(50)=0.14 mM) showed potent inhibitory activities, and inhibited Helicobacter pylori urease in a time-dependent manner. The structure-activity relationship of these polyphenols revealed: the two ortho hydroxyl groups were essential for inhibitory activity of polyphenol. When the C-ring of isoflavone was broken, the inhibitory activity markedly decreased. As for deoxybenzoin, the carboxyl group was clearly detrimental.     

6-Nitrobenzimidazole derivatives: potential phosphodiesterase inhibitors: synthesis and structure-activity relationship

6-Nitrobenzimidazole derivatives (1-30) synthesized and their phosphodiesterase inhibitory activities determined. Out of thirty tested compounds, ten showed a varying degrees of phosphodiesterase inhibition with IC(50) values between 1.5±0.043 and 294.0±16.7 μM. Compounds 30 (IC(50)=1.5±0.043 μM), 1 (IC(50)=2.4±0.049 μM), 11 (IC(50)=5.7±0.113 μM), 13 (IC(50)=6.4±0.148 μM), 14 (IC(50)=10.5±0.51 μM), 9 (IC(50)=11.49±0.08 μM), 3 (IC(50)=63.1±1.48 μM), 10 (IC(50)=120.0±4.47 μM), and 6 (IC(50)=153.2±5.6 μM) showed excellent phosphodiesterase inhibitory activity, much superior to the standard EDTA (IC(50)=274±0.007 μM), and thus are potential molecules for the development of a new class of phosphodiesterase inhibitors. A structure-activity relationship is evaluated. All compounds are characterized by spectroscopic parameters.     

Synthesis and evaluation of 2',4',6'-trihydroxychalcones as a new class of tyrosinase inhibitors

In this study, we synthesized a series of hydroxychalcones and examined their tyrosinase inhibitory activity. The results showed that 2',4',6'-trihydroxychalcone (1), 2,2',3,4',6'-pentahydroxychalcone (4), 2',3,4,4',5,6'-hexahydroxychalcone (5), 2',4',6'-trihydroxy- 3,4-dimethoxychalcone (9) and 2,2',4,4',6'-pentahydroxychalcone (15) exhibited high inhibitory effects on tyrosinase with respect to l-tyrosine as a substrate. By the structure-activity relationship study, it was suggested that the 2',4',6'-trihydroxyl substructure in the chalcone skeleton were efficacious for the inhibition of tyrosinase activity. And also, the catechol structure on B-ring of chalcones was not advantageous for the inhibitory potency. Furthermore, 15 (IC(50)=1microM) was found to show the highest activity out of a set of 15 hydroxychalcones, even better than both 2,2',4,4'-tetrahydroxychalcone (13, IC(50)=5microM) and kojic acid (16, IC(50)=12microM), which were known as potent tyrosinase inhibitors. Kinetic study revealed that 15 acts as a competitive inhibitor of tyrosinase with K(i) value of 3.1microM.     

Novel tacrine derivatives that block neuronal calcium channels

A new series of tacrine (9-amino-1,2,3,4-tetrahydroacridine) derivatives were synthesized and their effects on 45Ca(2+) entry into bovine adrenal chromaffin cells stimulated with dimethylphenylpiperazinium (DMPP) or K(+), studied. At 3 microM, compound 1 did not affect (45)Ca(2+) uptake evoked by DMPP. Compounds 14, 15 and 17 inhibited the effects of DMPP by 30%. Compounds 3, 9 and tacrine blocked the DMPP signal by about 50%. Compounds 5 and 12 were the most potent blockers of DMPP-stimulated 45Ca(2+) entry (90%); the rest of the compounds inhibited the effects of DMPP by 70-80%. Compounds 1, 3, 4, 8, 10, 11, 13, 16, 17 and tacrine inhibited 45Ca(2+) uptake induced by K(+) about 20%. Compounds 6, 14 and 15 inhibited the K(+) effects by 10% or less. Compounds 7, 9, 12 and 18 blocked the K(+) signal by 30% and, finally, compounds 2 and 5 inhibited the K(+)-induced 45Ca(2+) entry by 50%. None of the new compounds was as effective as diltiazem (IC(50)=0.03 microM) in causing relaxation of the rat aorta precontracted with 35 mM K(+); the most potent was compound 7 (IC(50)=0.3 microM). Compounds 5, 6, 8, 9, 10 and 13 had IC(50)s around 10 microM and compounds 3, 4, 11 and 12 around 20 microM. Blockade of Ca(2+) entry through neuronal voltage-dependent Ca(2+) channels, without concomitant blockade of vascular Ca(2+) channels, suggests that some of these compounds might exhibit neuroprotectant effects but not undesirable hemodynamic effects.     

Design of N-acetyl-6-sulfo-beta-d-glucosaminide-based inhibitors of influenza virus sialidase

Biological activity of N-acetyl-6-sulfo-beta-d-glucosaminides (6-sulfo-GlcNAc 1) having a structural homology to N-acetylneuraminic acid (Neu5Ac 2) and 2-deoxy-2,3-dehydro-N-acetylneuraminic acid (Neu5Ac2en 3) was examined in terms of inhibitory activity against influenza virus sialidase (influenza, A/Memphis/1/71 H3N2). pNP 6-Sulfo-GlcNAc 1a was proved to show substantial activity to inhibit the virus sialidase (IC(50)=2.8 mM), though p-nitrophenyl (pNP) GlcNAc without 6-sulfo group and pNP 6-sulfo-GlcNH(3)(+) 1b without 2-NHAc showed little activity (IC(50) >50 mM). The activity was enhanced nearly 100-fold when the pNP group of 1a was converted to p-acetamidophenyl one 5 (IC(50)=30 microM) or replaced with 1-naphthyl 6 (IC(50)=10 microM) or n-propyl one 8 (IC(50)=11 microM).     

Urease inhibitory activity of simple alpha,beta-unsaturated ketones

A variety of alpha,beta-unsaturated ketones were evaluated for their effect on the jack bean urease. Of 35 compounds tested, 2-cyclohepten-1-one (1), 2-cyclohexen-1-one (2), 2-cyclopenten-1-one (3), and 5,6-dihydro-2H-pyran-2-one (4) showed potent inhibitory activities against the enzyme. The most potent compound (1) (IC50=0.16 mM) showed similar inhibitory potency to hydroxyurea (IC50=0.095 mM). The inhibitory effects of 1, 2, 3, and 4 were significantly reduced by 2-mercaptoethanol or dithiothreitol. These data suggest that alpha,beta-unsaturated ketones inhibited the urease activity, possibly by a Michael-like addition of a protein SH group to the double bond of the alpha,beta-unsaturated carbonyl group.     

Synthesis, structural elucidation, DNA-PK inhibition, homology modelling and anti-platelet activity of morpholino-substituted-1,3-naphth-oxazines

A number of new angular 2-morpholino-(substituted)-naphth-1,3-oxazines (compound 10b), linear 2-morpholino-(substituted)-naphth-1,3-oxazines (compounds 13b-c), linear 6, 7 and 9-O-substituted-2-morpholino-(substituted)-naphth-1,3-oxazines (compounds 17-22, 24, and 25) and angular compounds 14-16 and 23 were synthesised. The O-substituent was pyridin-2yl-methyl (15, 18, and 21) pyridin-3yl-methyl (16, 19, and 22) and 4-methylpipreazin-1-yl-ethoxy (23-25). Twelve compounds were tested for their inhibitory effect on collagen induced platelet aggregation and it was found that the most active compounds were compounds 19 and 22 with IC(50)=55±4 and 85±4 μM, respectively. Furthermore, the compounds were also assayed for their ability to inhibit DNA-dependent protein kinase (DNA-PK) activity. The most active compounds were 18 IC(50)=0.091 μM, 24 IC(50)=0.191 μM, and 22 IC(50)=0.331 μM. Homology modelling was used to build a 3D model of DNA-PK based on the X-ray structure of phosphatidylinositol 3-kinases (PI3Ks). Docking of synthesised compounds within the binding pocket and structure-activity relationships (SAR) analyses of the poses were performed and results agreed well with observed activity.     

Purification and properties of Arabidopsis thaliana type 1 protein phosphatase (PP1).

The Arabidopsis thaliana type 1 protein phosphatase (PP1) catalytic subunit was released from its endogenous regulatory subunits by ethanol precipitation and purified by anion exchange and microcystin affinity chromatography. The enzyme was identified by MALDI-TOF mass spectrometry from a tryptic digest of the purified protein as a mixture of PP1 isoforms (TOPP 1-6) indicating that at least 4-6 of the eight known PP1 proteins are expressed in sufficient quantities for purification from A. thaliana suspension cells. The enzyme had a final specific activity of 8950 mU/mg using glycogen phosphorylase a as substrate, had a subunit molecular mass of 35 kDa as determined by SDS-PAGE and behaved as a monomeric protein of approx. 39 kDa on Superose 12 gel filtration chromatography. Similar to the mammalian type 1 protein phosphatases, the A. thaliana enzyme was potently inhibited by Inhibitor-2 (IC(50)=0.65 nM), tautomycin (IC(50)=0.06 nM), microcystin-LR (IC(50)=0.01 nM), nodularin (IC(50)=0.035 nM), calyculin A (IC(50)=0.09 nM), okadaic acid (IC(50)=20 nM) and cantharidin (IC(50)=60 nM). The enzyme was also inhibited by fostriecin (IC(50)=22 microM), NaF (IC(50)=2.1 mM), Pi (IC(50)=9.5 mM), and PPi (IC(50)=0.07 mM). Purification of the free catalytic subunit allowed it to be used to probe protein phosphatase holoenzyme complexes that were enriched on Q-Sepharose and a microcystin-Sepharose affinity matrix and confirmed several proteins to be PP1 targeting subunits.     

Synthesis and antitumor activity of 1-substituted-2-methyl-5-nitrobenzimidazoles

Different substituents were introduced in position 1 of 2-methyl-5(6)-nitro-1H-benzimidazole (2) in order to obtain different side chains having different heterocyclic compounds, for example, thiadiazoles (5-7), tetrazoles (8, 9a, b), triazoles (11-13), thiazoles (14a-e), triazines (10, 16, 17), and imidazoles (18a-c). The antitumor effect of compounds 1, 2, 2a, 4, 5, 7, 8, 9a, 10, 13, 14a, 15, 16, and 18c was studied against breast cancer (MCF7) and compounds 2 [IC(50)=4.52 microg] and 7 [IC(50)=8.29 microg] were found to be active.     

ent-Kaurene diterpenoids from Isodon oresbius

Three new ent-kaurene diterpenoids, oreskaurins A-C (1-3), together with ten known ent-kaurene diterpenoids, enmenin monoacetate (4), effusanin E (5), adenolin B (6), maoecrystal G (7), enmelol (8), trichokaurin (9), sodoponin (10), trichorabdal A (11), nodosin (12), enmein (13), and a flavonoid, vitexin (14), were isolated from Isodon oresbius. Their structures were determined by spectroscopic means. Compound 12 showed inhibitory activity toward K562 cells with IC(50)=1.43 microg/ml.     

Structure-activity relationship of aza-steroids as PI-PLC inhibitors

A number of aza-steroids were synthesized as potent phosphatidylinositol phospholipase C (PI-PLC) inhibitors. The epimeric mixtures 22,25-diazacholesterol (8a) and 3beta-hydroxy-22,25-diazacholestane (8b) were among the most active of these inhibitors, with IC(50) values of 7.4 and 7.5 microM, respectively. The 20alpha epimer, 8a2 (IC(50)=0.64 microM), whose stereochemistry at C-20 coincides with that of cholesterol, was found 50 times more potent than the 20beta epimer, 8a1 (IC(50)=32.2 microM). In diaza-estrone derivatives, the 3-methoxy group on the aromatic A-ring of 23 exhibited moderate PI-PLC inhibitory activity (IC(50)=19.7 microM), while compound with a free hydroxyl group (21) was inactive. However, in diaza-pregnane derivatives, epimers with a 3-hydroxyl group (8a, IC(50)=7.4 microM) exhibited more potent PI-PLC inhibitory activity than their counterparts with 3-methoxyl group on the non-aromatic A-ring (26, IC(50)=17.4 microM). We have illustrated in our previous publication that 3-hydroxyl-6-aza steroids are potent PI-PLC inhibitors.(3) However, simultaneous presence of the 6-aza and 22,25-diaza moieties in one molecule as in 13, led to loss of activity. Epimeric mixture 8a showed selective growth inhibition effects in the NCI in vitro tumor cell screen with a mean GI(50) value (MG-MID) of 5.75 microM for 54 tumors.     

Modified norcantharidins; synthesis, protein phosphatases 1 and 2A inhibition, and anticancer activity

Fourteen modified norcantharidin analogues have been synthesised and screened for their ability to inhibit the serine/threonine protein phosphatases 1 and 2A. The most potent compounds found were 10 (PP1 IC(50)=13+/-5 microM; PP2A IC(50)=7+/-3 microM) and 16 (PP1 IC(50)=18+/-8 microM; PP2A IC(50)=3.2+/-0.4 microM). Overall, only analogues possessing at least one acidic residue at the former anhydride warhead displayed any PP1 or PP2A inhibitory action. The ability of these analogues to inhibit PP1 and PP2A correlates well with their observed anti-cancer activity against a panel of five cancer cell lines: A2780 (human ovarian carcinoma), G401 (human kidney carcinoma), HT29 (human colorectal carcinoma), H460 (human lung carcinoma) and L1210 (murine leukemia).     

Cytotoxic isoprenylated xanthones from Cudrania tricuspidata

Eight new isoprenylated xanthones, cudratricusxanthones A-H (1-8), were isolated from the roots of Cudrania tricuspidata, together with ten known compounds, cudraxanthones H (9) and M (10), xanthone V(1a) (11), toxyloxanthone C (12), macluraxanthone B (13), 1-hydroxy-3, 6, 7-trimethoxyxanthone (14), cycloartocarpesin (15), artocarpesin (16), cudraflavone B (17), and kaempferol (18). Their structures were characterized by spectroscopic methods. Xanthones 5, 7, 10, and 12 showed inhibitory effects on four kinds of human digestive apparatus tumor cell lines (HCT-116, SMMC-7721, SGC-7901, and BGC-823) with IC(50) values of 1.6-11.8 microg/mL. Xanthones 2, 4, and 11 displayed significant cytotoxicity against HCT-116, SMMC-7721, and SGC-7901 (IC(50)=1.3-9.8 microg/mL). Flavonoids 15-17 were almost inactive.     

Sulfonamide chalcone as a new class of alpha-glucosidase inhibitors

Chalcones 1-20, a new class of glycosidase inhibitors, were synthesized, and their glycosidase inhibitory activities were investigated. Non-aminochalcones 1-12 had no inhibitory activity, however, aminochalcones 13-20 had strong glycosidase (alpha-glucosidase, alpha-amylase, and beta-amylase) inhibitory activities. In particular, sulfonamide chalcones 17-20 had more potent alpha-glucosidase inhibitory activity than aminated chalcone 13-16. 4'-(p-Toluenesulfonamide)-3,4-dihydroxy chalcone 20 (IC(50)=0.4microM) was the best inhibitor against alpha-glucosidase, and these sulfonamide chalcones showed non-competitive inhibition.     

Design, synthesis, and biological evaluation of novel (1-thioxo-1,2,3,4-tetrahydro-β-carbolin-9-yl)acetic acids as selective inhibitors for AKR1B1

New substituted (1-thioxo-1,2,3,4-tetrahydro-β-carbolin-9-yl)acetic acids were designed as the inhibitor of AKR1B1 based upon the structure of rhetsinine, a minor alkaloidal component of Evodia rutaecarpa, and twenty derivatives were synthesized and evaluated. The most active compound of the series was (2-benzyl-6-methoxy-1-thioxo-1,2,3,4-tetrahydro-β-carbolin-9-yl)acetic acid (7m), which showed comparable inhibitory activity for AKR1B1 (IC(50)=0.15μM) with clinically used epalrestat (IC(50)=0.1μM). In the view of activity and selectivity, the most potent compound was (2-benzyl-6-carboxy-1-thioxo-1,2,3,4-tetrahydro-β-carbolin-9-yl)acetic acid (7t), which showed strong inhibitory effect (IC(50)=0.17μM) and very high selectivity for AKR1B1 against AKR1A1 (311:1) and AKR1B10 (253:1) compared with epalrestat.     

Synthesis and urease enzyme inhibitory effects of some dicoumarols

Dicoumarols 1-10 with substituted phenyl residues at C-11 were synthesized and screened for their urease inhibition effects. All synthesized compounds showed varying degree of urease inhibitory activity ranging from IC50 = 74.30-91.35 microM.     

Novel azolyl-(phenylmethyl)]aryl/heteroarylamines: potent CYP26 inhibitors and enhancers of all-trans retinoic acid activity in neuroblastoma cells

The synthesis and potent inhibitory activity of novel 4-[(imidazol-1-yl and triazol-1-yl)(phenyl)methyl]aryl-and heteroaryl amines versus a MCF-7 CYP26A1 cell assay is described. Biaryl imidazole ([4-(imidazol-1-yl-phenyl-methyl)-phenyl]-naphthalen-2-yl-amine (8), IC(50)=0.5 microM; [4-(imidazol-1-yl-phenyl-methyl)-phenyl]-indan-5-yl-amine (9), IC(50)=1.0 microM) and heteroaryl imidazole derivatives ((1H-benzoimidazol-2-yl)-{4-[(5H-imidazol-1-yl)-phenyl-methyl]-phenyl}-amine (15), IC(50)=2.5 microM; benzooxazol-2-yl-{4-[(5H-imidazol-1-yl)-phenyl-methyl]-phenyl}-amine (16), IC(50)=0.9 microM; benzothiazol-2-yl-{4-[(5H-imidazol-1-yl)-phenyl-methyl]-phenyl}-amine (17), IC(50)=1.5 microM) were the most potent CYP26 inhibitors. Using a CYP26A1 homology model differences in activity were investigated. Incubation of SH-SY5Y human neuroblastoma cells with the imidazole aryl derivative 8, and the imidazole heteroaryl derivatives 16 and 17 potentiated the atRA-induced expression of CYP26B1. These data suggest that further structure-function studies leading to clinical development are warranted.     

Novel retinoic acid 4-hydroxylase (CYP26) inhibitors based on a 3-(1H-imidazol- and triazol-1-yl)-2,2-dimethyl-3-(4-(phenylamino)phenyl)propyl scaffold

Retinoic acid (RA), the biologically active metabolite of vitamin A, is used medicinally for the treatment of hyperproliferative diseases including dermatological conditions and cancer. The antiproliferative effects of RA have been well documented as well as the limitations owing to toxicity and the development of resistance to RA therapy. RA metabolism inhibitors (RAMBAs or CYP26 inhibitors) are attracting increasing interest as an alternative method for enhancing endogenous levels of retinoic acid in the treatment of hyperproliferative disease. Here the synthesis and inhibitory activity of novel 3-(1H-imidazol- and triazol-1-yl)-2,2-dimethyl-3-(4-(phenylamino)phenyl)propyl derivatives in a MCF-7 CYP26A1 microsomal assay are described. The most promising inhibitor methyl 2,2-dimethyl-3-(4-(phenylamino)phenyl)-3-(1H-1,2,4-triazol-1-yl)propanoate (6) exhibited an IC(50) of 13 nM (compared with standards Liarozole IC(50) 540 nM and R116010 IC(50) 10 nM) and was further evaluated for CYP selectivity using a panel of CYP with >100-fold selectivity for CYP26 compared with CYP1A2, 2C9 and 2D6 observed and 15-fold selectivity compared with CYP3A4. The results demonstrate the potential for further development of these potent inhibitors.     

Synthetic undecapeptide (NTX10–20) of noxiustoxin blocks completely the I A potassium currents of cerebellum granular cells

Native noxiustoxin (NTX) and synthetic peptides corresponding to its primary sequence, from positions 1-9, 1-14, 1-20, 10-20, 21-39 and 30 39, were prepared and assayed on the K+ currents of cerebellum granular cells, using the patch-clamp technique in the whole-cell configuration system. Native toxin has a reversible inhibitory effect (IC50 = 360 nM), whereas synthetic peptides NTXI-20 and NTX1-9 had a half-effective dose IC50 of approximately 2 and 10 microM, respectively, which correlates with their biological effects in vivo. Synthetic peptide NTX10-20 was quite remarkable in having a preference for the IA current, which was completely inhibited at high peptide concentration. The effects of the other peptides (NTXI 14, NTX21-39 and NTX30-39), although positive and reversible, required higher concentrations (50 200 microM) to block both currents, suggesting no affinity or, at least, much lower specificity for the channels responsible for the potassium currents in the granular cells studied.     

Design and synthesis of 2,6-diprenyl-4-iodophenol TX-1952 with a novel and potent anti-peroxidative activity

The structure-based elucidation of 2,4,6-tri-substituted phenols for their antioxidative and anti-peroxidative effects has been investigated using TX-1952 (2,6-diprenyl-4-iodophenol), TX-1961, TX-1980, BTBP and BHT. In the inhibition of mitochondrial lipid peroxidation, the inhibitory activity of 2,6-di-tert-butyl-4-bromophenol (BTBP) (IC(50)=0.17 microM) was twice as high as that of 2,6-di-tert-butyl-4-methylphenol (BHT) (IC(50)=0.31 microM). This result shows that the 4-halogen group increases inhibitory activity for mitochondrial lipid peroxidation. Besides, TX-1952 (IC(50)=0.60 microM) was the highest inhibitor among 2,6-diprenyl-4-halophenols, followed by TX-1961 (IC(50)=0.93 microM) and TX-1980 (IC(50)=1.2 microM). In 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging experiments, the activity of TX-1952 (IC(0.200)=53.1 microM) was lower than that of BHT (IC(0.200)=33.7 microM) and BTBP (IC(0.200)=16.0 microM), but TX-1952 and BHT showed the same HOMO energy (-8.991 eV). These results suggest that the two prenyl groups at ortho position hinder the phenolic hydrogen abstraction by DPPH radical. These findings demonstrated that TX-1952 was a novel and potent inhibitor for lipid peroxidation.