Synthesis of indole analogs as potent β-glucuronidase inhibitors

Natural products are the main source of motivation to design and synthesize new molecules for drug development. Designing new molecules against β-glucuronidase inhibitory is utmost essential. In this study indole analogs (1–35) were synthesized, characterized using various spectroscopic techniques including ¹H NMR and EI-MS and evaluated for their β-glucuronidase inhibitory activity. Most compounds were identified as potent inhibitors for the enzyme with IC₅₀ values ranging between 0.50 and 53.40 μM, with reference to standard d-saccharic acid 1,4-lactone (IC₅₀ = 48.4 ± 1.25 μM). Structure-activity relationship had been also established. The results obtained from docking studies for the most active compound 10 showed that hydrogen bond donor features as well as hydrogen bonding with (Oε1) of nucleophilic residue Glu540 is believed to be the most importance interaction in the inhibition activity. It was also observed that hydroxyl at fourth position of benzylidene ring acts as a hydrogen bond donor and interacts with hydroxyl (OH) on the side chain of catalysis residue Tyr508. The enzyme-ligand complexed were being stabilized through electrostatic π-anion interaction with acid-base catalyst Glu451 (3.96 Å) and thus preventing Glu451 from functioning as proton donor residue.     

Synthesis of citrate–ciprofloxacin conjugates

Two regioisomeric citrate-functionalized ciprofloxacin conjugates have been synthesized and their antimicrobial activities against a panel of clinically-relevant bacteria have been determined. Cellular uptake mechanisms were investigated using wild-type and ompF deletion strains of Escherichia coli K-12.     

Synthesis of fluorescent nucleoside analogs as probes for 2′-deoxyribonucleoside kinases

We are reporting on the synthesis of fluorescent nucleoside analogs with modified sugar moieties (e.g., sugars other than ribose and 2′-deoxyribose). Four novel derivatives of the fluorescent thymidine analog 6-methyl-3-(β-D-2′-deoxyribofuranosyl) furano-[2,3-d]pyrimidin-2-one were synthesized via Sonogashira reaction and subsequent copper-catalyzed cycloaddition. These compounds represent promising tools for studying nucleoside metabolism inside living cells, as well as for screening directed evolution libraries of 2′-deoxyribonucleoside kinases with new and improved activity for the corresponding nucleoside analogs.     

Synthesis of 4β-acyloxypodophyllotoxin analogs modified in the C and E rings as insecticidal agents against Mythimna separata Walker

To discover the new natural-product-based insecticidal agents, four series of sixty novel 4β-acyloxypodophyllotoxin analogs modified in the C and E rings were prepared, and their insecticidal activity was tested against the pre-third-instar larvae of oriental armyworm, Mythimna separata (Walker) in vivo at the concentration of 1 mg/mL. It demonstrated that the position of the dioxo group on the E-ring of 4′-demethylepipodophyllotoxin was regioselectively controlled by the chlorine atom at its C-2′ position when 2′-chloro-4′-demethylepipodophyllotoxin was oxidized by sodium periodate. Among all the derivatives, IIIi exhibited the best potent insecticidal activity with the final mortality rate of 63.3%. To alkylacyloxy series, the proper length of the side chain at the C-4 position of Ia–g, IIa–g and IIIa–g was important for their insecticidal activity.     

Synthesis and biological evaluation of new pyrazolone–pyridazine conjugates as anti-inflammatory and analgesic agents

A new series of pyrazolone–pyridazine conjugates 3 and 4a–l were synthesized and characterized by spectroscopic means and elemental analyses. All compounds were tested in vivo for their anti-inflammatory and analgesic properties against diclofenac, as reference compound. The synthesized compounds were also evaluated for their ability to inhibit the production of certain inflammatory cytokines such as TNF-α and IL-6 in serum samples. The ulcerogenic potential of the synthesized compounds was also determined. IC₅₀ values for inhibition of COX-1 and COX-2 enzymes were investigated in vitro for the most active candidates. Molecular docking was performed on the active site of COX-2 to predict their mode of binding to the amino acids. Among the synthesized derivatives, compounds 4c and 4e showed good analgesic and anti-inflammatory activities with lower ulcer index than the reference drug.     

Synthesis of chlorophyll–amino acid conjugates as models for modification of proteins with chromo/fluorophores

A chlorophyll-a derivative bonded directly with epoxide at the peripheral position of the chlorin π-system was reacted with N-urethane and C-ester protected amino acids bearing an alcoholic or phenolic hydroxy group as well as a carboxy group at the residue to give chlorophyll–amino acid conjugates. The carboxy residues of N,C-protected aspartic and glutamic acids were esterified with the epoxide in high yields. The synthetic conjugates in dichloromethane had absorption bands throughout the visible region including intense red-side Qy and blue-side Soret bands. By their excitation at the visible bands, strong and efficient fluorescence emission was observed up to the near-infrared region. The chromo/fluorophores are promising for preparation of functional peptides and modification of proteins.     

Synthesis of 4β-carbamoyl epipodophyllotoxins as potential antitumour agents

A series of new 4β-carbamoyl epipodophyllotoxin analogues have been synthesized and evaluated for their anticancer activity against eleven cancer cell lines including Zr-75-1, MCF7, KB, Gurav, DWD, Colo 205, A-549, Hop62, PC3, SiHa and A-2780. Most of the compounds exhibited better growth-inhibition activities against tested cell lines than that of etoposide. Further, compounds 6g and 6i are also evaluated for their DNA topoisomerase-II (topo-II) inhibition activity and they exhibited significant inhibition of topo-II catalytic activity comparable to etoposide.     

Synthesis and bioevaluation of ω-N-amino analogs of B13

Novel ω-N-amino analogs of B13 (Class E) were designed, synthesized and tested as inhibitors of acid ceramidase (ACDase) and potential anticancer agents deprived of unwanted lysosomal destabilization and ACDase proteolytic degradation properties of LCL204 [Szulc, Z. M.; Mayroo, N.; Bai, A.; Bielawski, J.; Liu, X.; Norris, J. S.; Hannun, Y. A.; Bielawska, A. Bioorg. Med. Chem. 2008, 16, 1015].Representative analog LCL464, (1R,2R)-2-N-(12′-N,N-dimethylaminododecanoyl amino)-1-(4″-nitrophenyl)-1,3-propandiol, inhibited ACDase activity in vitro, with a similar potency as B13 but higher than LCL204. LCL464 caused an early inhibition of this enzyme at a cellular level corresponding to decrease of sphingosine and specific increase of C₁₄- and C₁₆-ceramide. LCL464 did not induce lysosomal destabilization nor degradation of ACDase, showed increased cell death demonstrating inherent anticancer activity in a wide range of different cancer cell lines, and induction of apoptosis via executioner caspases activation. LCL464 represents a novel structural lead as chemotherapeutic agent acting via the inhibition of ACDase.     

Synthesis and antibacterial activity of catecholate–ciprofloxacin conjugates

The development of an efficient route to obtain artificial siderophore–antibiotic conjugates active against Gram-negative bacteria is crucial. Herein, a practical access to triscatecholate enterobactin analogues linked to the ciprofloxacin along with their antibacterial evaluation are described. Two series of conjugates were obtained with and without a piperazine linker which is known to improve the pharmacokinetics profile of a drug. A monocatecholate–ciprofloxacin conjugate was also synthesized and evaluated. The antibacterial activities against Pseudomonas aeruginosa for some conjugates are related to the iron concentration in the culture medium and seem to depend on the bacterial iron uptake systems.     

Syntheses of p-aminophenyl 1-thio-α- and -β-d-idopyranosides as analogs of glycosidase substrates

The p-nitrophenyl and p-aminophenyl 1-thio-α- and -β-d-idopyranosides were synthesized for use in structure-activity studies of glycosidases. Zinc chloride-catalyzed fusion of α-d-idopyranose pentaacetate with p-nitrobenzenethiol gave p-nitrophenyl 2,3,4,6-tetra-O-acetyl-1-thio-α-d-idopyranoside as an amorphous glass in 67% yield, and the crystalline β anomer in 13% yield. Deacetylation with catalytic amounts of sodium methoxide in methanol, followed by hydrogenation under pressure over palladium-on-barium sulfate catalyst, afforded p-aminophenyl 1-thio-α- and -β-d-idopyranosides.     

Synthesis and structure–activity relationships of novel furazan-3,4-diamide analogs as potent anti-cancer agents

This study describes the synthesis and structure–activity relationships of a series of furazan-3,4-diamide analogs. 1,2,5-Oxadiazole ring and electron-withdrawing substituent on the phenyl ring are proposed to be the important elements which contribute to a significant extent maximal potency of anti-proliferation effect.     

Synthesis and biological evaluation of novel biotin–iminoalditol conjugates

Biotin–iminosugar conjugates of different configuration such as d-gluco, d-galacto, l-ido as well as a furanoid representative in the d-manno configuration have been synthesised and exhibit powerful inhibition of β-glucosidase from Agrobacterium sp. with K_i values in the range of the respective parent compounds. Such molecular probes have potential for activity-based protein profiling taking advantage of the biotin–(strept)avidin interaction.     

Synthesis and radical scavenging activity of phenol–imidazole conjugates

Novel hydroxylated benzylideneamino imidazole derivatives were synthesized and their radical scavenging activity was assessed against DPPH and hydroxyl radicals. In the DPPH assay, most of the synthesized compounds showed an IC₅₀ in the range 3.2 μM ⩽ IC₅₀ ⩽ 8.4 μM, lower than the reference compound trolox (IC₅₀ = 9.5 μM) or the parent aldehydes (5.4 μM ⩽ IC₅₀ ⩽ 11.6 μM). The activity depends mainly on the phenolic subunit (number and position of the hydroxyl groups) and the extent of conjugation with the imidazole ring. In the deoxyribose assay, all the compounds, including parent imidazoles and aldehydes, showed high activity against the hydroxyl radical and the ability to chelate iron ions. At 5 μM concentration, the compounds protected the deoxyribose from degradation by hydroxyl radical between 62% and 38%.     

Synthesis and biological evaluation of imidazopyridinyl-1,3,4-oxadiazole conjugates as apoptosis inducers and topoisomerase IIα inhibitors

A series of imidazopyridinyl-1,3,4-oxadiazole conjugates were synthesized and investigated for their cytotoxic activity and some compounds showed promising cytotoxic activity. Compound 8q (NSC: 763639) exhibited notable growth inhibition that satisfies threshold criteria at single dose (10 μM) on all human cancer cell lines. This compound was further evaluated at five dose levels (0.01, 0.1, 1, 10 and 100 μM) to obtain GI₅₀ values ranging from 1.30 to 5.64 μM. Flow cytometric analysis revealed that compound 8q arrests the A549 cells in sub G1 phase followed by induction of apoptosis which was further confirmed by Annexin-V-FITC, Hoechst nuclear staining, caspase 3 activation, measurement of mitochondrial membrane potential and ROS generation. Topo II mediated DNA relaxation assay results showed that conjugate 8q could significantly inhibit the activity of topo II. Moreover, molecular docking studies also indicated binding to the topoisomerase enzyme (PDBID 1ZXN).     

Synthesis and evaluation of the antioxidative potential of minoxidil–polyamine conjugates

A series of conjugates (MNX–CO–PA) of minoxidil (MNX) with the polyamines (PAs) putrescine (PUT), spermidine (SPD) and spermine (SPM) as well as dopamine were produced through activation of MNX with N,N′-carbonyldiimidazole, followed by reaction with dopamine or selectively protected PAs and acid-mediated deprotection. These conjugates together with conjugates of the general type MNX–PA or PA–MNX–PA, readily produced using literature protocols, were tested as antioxidants. The most potent inhibitors of lipid peroxidation were the conjugates MNX–SPM (2, 94%), SPM–MNX–SPM (4, 94%) and MNX–N⁴-SPD (7, 91%) and MNX (91%). The most powerful lipoxygenase (LOX) inhibitors were MNX (IC₅₀ = 20 μM) and the conjugates MNX–N⁸-SPD (9, IC₅₀ = 22.1 μM), MNX–CO–dopamine (11, IC₅₀ = 28 μM) and MNX–N¹-SPD (8, IC₅₀ = 30 μM). The most interesting conjugates 2, MNX–CO–PUT (5), 8 and 11 as well as MNX were generally found to exhibit weaker (22–36.5%) or no (conjugate 8) anti-inflammatory activity than indomethacin (47%) with the exception of MNX which showed almost equal potency (49%) to indomethacin. The cytocompatibility of conjugates and MNX at the highest concentration of 100 μM showed a survival percentage of 87–107%, with the exception of conjugates with SPM (compound 2) and MNX–CO–SPM (6), which showed considerable cytotoxicity (survival percentage 8–14%). Molecular docking studies were carried on conjugate 9 and the parent compound MNX and were found to be in accordance with our experimental biological results.     

Synthesis and antibacterial activity evaluation of metronidazole–triazole conjugates

Synthesis and antibacterial activity of metronidazole–triazole conjugates are reported. Total 21 hybrid compounds have been synthesized with different substitution pattern on the triazole ring in order to study their influence on the antibacterial activity. These compounds demonstrated potent to weak antibacterial activity against Gram-positive, and Gram-negative bacteria. Six compounds have shown equal or better antibacterial activity against Gram-negative strains than the reference compound.     

Synthesis and antibacterial evaluation of amino acid–antibiotic conjugates

Amino acid conjugates of quinolone, metronidazole and sulfadiazine antibiotics were synthesized in good yields using benzotriazole methodology. All the conjugates were screened for their antibacterial activity using methods adapted from the Clinical and Laboratory Standards Institute. Antibiotic conjugates were tested for activity in four medically relevant organisms; Staphylococcus aureus (RN4220), Escherichia coli (DH5α), Pseudomonas aeruginosa (PAO1), and Bacillus subtilis (168). Several antibiotic conjugates show promising results against several of the strains screened.     

Synthesis and antitumor activities of novel rhein α-aminophosphonates conjugates

Several rhein α-aminophosphonates conjugates (5a–5q) were synthesized and evaluated for in vitro cytotoxicity against HepG-2, CNE, Spca-2, Hela and Hct-116 cell lines. Some compounds showed relatively high cytotoxicity. Especially, compound 5i exhibited the strongest cytotoxicity against Hct-116 cells (IC₅₀ was 5.32 μM). All the synthesized compounds exhibited low cytotoxicity against HUVEC cells. The mechanism of compound 5i was preliminarily investigated by Hoechst 33258 staining, JC-1 mitochondrial membrane potential staining and flow cytometry, which indicated that the compound 5i induced apoptosis in Hct-116 cancer cells. Cell cycle analysis showed that these compound 5i mainly arrested Hct-116 cells in G1 stage. The effects of 5i on the activation of caspases expression indicated that 5i might induce apoptosis via the membrane death receptor pathways. In addition, the binding properties of a model analog 5i to DNA were investigated by methods (UV–vis, fluorescence, CD spectroscopy and FRET-melting) in compare with that of rhein. Results indicated that 5i showed moderate ability to interact ct-DNA.     

Synthesis and cellular studies of polyamine conjugates of a mercaptomethyl–carboranylporphyrin

Seven polyamine conjugates of a tri(p-carboranylmethylthio)tetrafluorophenylporphyrin were prepared in high yields by sequential substitution of the p-phenyl fluoride of tetrakis(pentafluorophenyl)porphyrin (TPPF), and investigated as boron delivery agents for boron neutron capture therapy (BNCT). The polyamines used were derivatives of the natural-occurring spermine with different lengths of the carbon chains, terminal primary amine groups and, in two of the conjugates, additional aminoethyl moieties. A tri(polyethylene glycol) conjugate was also synthesized for comparison purposes. The polyamine conjugates showed low dark cytotoxicity (IC₅₀ >400 μM) and low phototoxicity (IC₅₀ >40 μM at 1.5 J/cm²). All polyamine conjugates, with one exception, showed higher uptake into human glioma T98G cells (up to 12-fold) than the PEG conjugate, and localized preferentially in the cell ER, Golgi and the lysosomes. Our results show that spermine derivatives can serve as effective carriers of boronated porphyrins for the BNCT of tumors.