In vitro biological effects of two anti-diabetic medicinal plants used in Benin as folk medicine.

BACKGROUND: Extracts from Polygonum senegalensis (Polygonaceae) and Pseudocedrela kotschyi (Meliaceae) are two important traditionally used medicinal plants in rural Benin to treat many diseases and notably type 2 diabetes. The aim of the study was to investigate the α-glucosidase inhibition, antioxidant and antibacterial activities of those plants extract: Polygonum senegalensis leaves, and Pseudocedrela kotschyi root. METHODS: Hydro-alcoholic (50%) extracts were analyzed for their phytochemical content and tested for their inhibition potency on α-glucosidase from Saccharomyces cerevisiae. Antioxidant activities were assessed using the DPPH, ORAC, FRAP and DCFH-DA (cell based) assay. Finally, the antibacterial activity was evaluated using MIC determination on four Gram-positive cocci (Bacillus subtilis, Clostridium difficile, Enterococcus faecalis, Staphylococcus aureus), three Gram-negative bacilli (Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae), and the yeast Candida albicans. RESULTS: Each extract presented significant α-glucosidase inhibition and antioxidant activities. Polygonum senegalensis leaf extracts were the most active in each in vitro assay with an IC50 = 1.5 µg/ml for α-glucosidase inhibition and an IC50 = 6.8 µg/ml for DPPH scavenging, - 4.5 µmol Fe II/g of dry matter - 9366 µmol Trolox / g DW - for FRAP and ORAC values, respectively. IC50 = 2.3 µg GA / ml for DCFH-DA assay. Concerning its antibacterial activity, a growth inhibitory effect was observed only against three Gram negative bacilli: B. subtilis, E. faecalis, S. aureus and the yeast C. albicans at high concentration. CONCLUSION: The results showed that the semi alcoholic extract of the two studied plants possess α-glucosidase inhibitory activity, antioxidant potency, and low antibacterial effect.

Imidazonaphthyridine systems (part 2): Functionalization of the phenyl ring linked to the pyridine pharmacophore and its replacement by a pyridinone ring produces intriguing differences in cytocidal activity.

We recently discovered that five- and pseudo-five-fused-ring derivatives in an imidazonaphthyridine series were promising hit compounds for the development of new DNA-intercalators. In this study, novel (dihydro)imidazo[1,6] and [1,7]naphthyridi(no)nes were prepared including pseudo-pentacycles. All the compounds synthesized were screened against four tumor cell lines. Compounds 3(b-d) showed significant in vitro cytotoxicity, and DNA intercalation properties were demonstrated at 25 µM. Imidazonaphthyridinones exhibited no DNA binding affinity despite significant growth inhibition activity. Interestingly, when a pyridinone pharmacophore was linked to the imidazo[1,2-a]pyridine scaffold, the geometric orientation of the link had a strong impact on the growth inhibition activity. From these results we conclude that the moderate cytotoxicity observed for these compounds is independent of their DNA-binding and topoisomerase inhibition activities.

Design and preparation of aza-analogues of benzo[c]phenanthridine framework with cytotoxic and antiplasmodial activities.

Benzo[c]phenanthridine alkaloids represent interesting lead for the discovery of new potential antiplasmodial and/or anticancer drugs. In this field, a novel library of aza-analogs of benzo[c]phenanthroline framework derivatives was designed and prepared. Although these compounds did not have specific antiplasmodial activities, some of them displayed specific in vitro activity against two cancer lines especially compound 24 with an IC(50) against the MCF7 line of 0.6 microM.

Synthesis and antiviral activity of an imidazo[1,2-a]pyrrolo[2,3-c]pyridine series against the bovine viral diarrhea virus.

A series of imidazo[1,2-a]pyrrolo[2,3-c]pyridines has been prepared and evaluated for their anti-BVDV activities in MDBK cells. From the synthesized analogues bearing modifications of the substituents at positions 2, 3, 7 and 8, compounds 10a, b, 16, 24, 25 and 26 exhibited significant anti-BVDV activities.

A pyrazolotriazolopyrimidinamine inhibitor of bovine viral diarrhea virus replication that targets the viral RNA-dependent RNA polymerase.

[7-[3-(1,3-Benzodioxol-5-yl)propyl]-2-(2-furyl)-7H-pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidin-5-amine] (LZ37) was identified as a selective inhibitor of in vitro bovine viral diarrhea virus (BVDV) replication. The EC(50) values for inhibition of BVDV-induced cytopathic effect (CPE) formation, viral RNA synthesis and production of infectious virus were 4.3+/-0.7microM, 12.9+/-1microM and 5.8+/-0.6microM, respectively. LZ37 proved inactive against the hepatitis C virus and the flavivirus yellow fever. LZ37 inhibits BVDV replication at a time point that coincides with the onset of intracellular viral RNA synthesis. Drug-resistant mutants carried the F224Y mutation in the viral RNA-dependent RNA polymerase (RdRp). LZ37 showed cross-resistance with the imidazopyrrolopyridine AG110 [which selects for the E291G drug resistance mutation] as well as with the imidazopyridine BPIP [which selects for the F224S drug-resistant mutation]. LZ37 did not inhibit the in vitro activity of purified recombinant BVDV RdRp. Molecular modelling revealed that F224 is located near the tip of the finger domain of the RdRp. Docking of LZ37 in the crystal structure of the BVDV RdRp revealed several potential contacts including: (i) hydrophobic contacts of LZ37 with A221, A222, G223, F224 and A392; (ii) a stacking interaction between F224 side chain and the ring system of LZ37 and (iii) a hydrogen bond between the amino function of LZ37 and the O backbone atom of A392. It is concluded that LZ37 interacts with the same binding site as BPIP or VP32947 at the top of the finger domain of the polymerase that is a "hot spot" for inhibition of pestivirus replication.

Synthesis and antituberculosis activity of new hydrazide derivatives.

The increasing clinical importance of drug-resistant mycobacterial pathogens, especially Mycobacterium tuberculosis, has lent additional urgency to microbiological research and new antimycobacterial compound development. For this purpose, new hydrazide derivatives of imidazo[1,2-a]pyridine were synthesized and evaluated for antituberculosis activity. The reaction of 2-[(2-carboxyimidazo[1,2-a]pyridine-3-yl)sulfanyl]acetic acid hydrazide with various benzaldehydes gave N-(arylidene)-2-[(2-carboxyimidazo[1,2-a]pyridine-3-yl)sulfanyl]acetic acid hydrazide derivatives. The chemical structures of the compounds were elucidated by IR,(1)H-NMR, FAB-MS spectral data and elemental analysis. Antituberculosis activities of the synthesized compounds were determined by broth microdilution assay, the Microplate Alamar Blue Assay in BACTEC 12B medium. The results were screened in vitro, using the BACTEC 460 Radiometric System against Mycobacterium tuberculosis H37Rv (ATCC 27294) at 6.25 microg/mL; the tested compounds showed significant inhibition.

New opportunities with the Duff reaction.

The Duff reaction (HMTA, AcOH or TFA) was studied on substituted [6 + 5] heterocyclic compounds. This reaction provides a useful route to aldehydes for compounds bearing sensitive amide functions. It gives also access to tricyclic lactams of potential biological interest. The formation of an aminomethyl intermediate in the Duff reaction mechanism is unequivocally demonstrated.

Design, synthesis, and biological activities of conformationally restricted analogs of primaquine with a 1,10-phenanthroline framework.

A series of primaquine analogs was prepared, according to a conformationally restricted conformation of primaquine. In vitro antiplasmodial activities were evaluated and showed that all compounds were active on different strains of Plasmodium falciparum. In particular compounds 5 and 15 possessing a methoxy group were more active than was primaquine. Furthermore, analog 5 displayed good in vitro gametocytocidal activity. In addition selectivity indexes were calculated in respect with cytotoxic activities on Vero cell lines.

Design, synthesis and preliminary biological evaluation of acridine compounds as potential agents for a combined targeted chemo-radionuclide therapy approach to melanoma.

Various iodo-acridone and acridine carboxamides have been prepared and evaluated as agents for targeted radionuclide and/or chemotherapy for melanoma, due to their structural similarity to benzamides which are known to possess specific affinity for melanin. Three of these carboxamides selected for their in vitro cytotoxic properties were radioiodinated with [(125)I]NaI at high specific activity. Biodistribution studies carried out in B16F0 murine melanoma tumour-bearing mice highlighted that acridone 8f and acridine 9d, presented high, long-lasting tumour concentrations together with an in vivo kinetic profile favourable to application in targeted radionuclide therapy.

Evaluation of radiolabeled (hetero)aromatic analogues of N-(2-diethylaminoethyl)-4-iodobenzamide for imaging and targeted radionuclide therapy of melanoma.

Targeted radionuclide therapy using radioiodinated compounds with a specific affinity for melanoma tissue is a promising treatment for disseminated melanoma, but the candidate with the ideal kinetic profile remains to be discovered. Targeted radionuclide therapy concentrates the effects on tumor cells, thereby increasing the efficacy and decreasing the morbidity of radiotherapy. In this context, analogues of N-(2-diethylaminoethyl)-4-iodobenzamide (BZA) are of interest. Various (hetero)aromatic analogues 5 of BZA were synthesized and radioiodinated with (125)I, and their biodistribution in melanoma-bearing mice was studied after i.v. administration. Most [ (125)I] 5-labeled compounds appeared to bind specifically and with moderate-to-high affinity to melanoma tumor. Two compounds, 5h and 5k, stood out with high specific and long-lasting uptake in the tumor, with a 7- and 16-fold higher value than BZA at 72 h, respectively, and kinetic profiles that makes them promising agents for internal targeted radionuclide therapy of melanoma.

Novel imidazo[1,2-a]naphthyridinic systems (part 1): synthesis, antiproliferative and DNA-intercalating activities.

Novel imidazo[1,2-a]naphthyridinic systems 6a-15a and 6b-15b were obtained from Friedländer's reaction in imidazo[1,2-a]pyridine series. Most of the compounds were evaluated for their antitumor activity in the NCIs in vitro human tumor cell line screening panel. Among them, pentacyclic derivatives 13b and 14a exhibited in vitro activity comparable to anticancer agent such as amsacrine. Their mechanism of cytotoxicity action was unrelated to poisoning or inhibiting abilities against topo1. On the contrary, we highlighted a direct intercalation of the drugs into DNA by electrophoresis on agarose gel.

Synthesis and biological evaluation of indoloquinolines and pyridocarbazoles: a new example of unexpected photoreduction accompanying photocyclization.

Indoloquinoline alkaloid cryptolepine and pyridocarbazole alkaloid ellipticine are of great interest because in vitro and in vivo studies revealed their good cytotoxic properties. In order to obtain some biologically active analogs of these compounds, we developed a synthesis based on the photocyclization of tertiary N-substituted enaminones derived from 1,3-cyclohexandione and 3 or 6-aminoquinoline. The angular cyclized compounds thus obtained were tested in vitro on K 562 cells and A 2780 doxorubicin sensitive and resistant cells. All compounds were less effective than doxorubicin in sensitive cells but their activity wasn't decreased by MDR resistance.

The imidazopyrrolopyridine analogue AG110 is a novel, highly selective inhibitor of pestiviruses that targets the viral RNA-dependent RNA polymerase at a hot spot for inhibition of viral replication.

Ethyl 2-methylimidazo[1,2-a]pyrrolo[2,3-c]pyridin-8-carboxylate (AG110) was identified as a potent inhibitor of pestivirus replication. The 50% effective concentration values for inhibition of bovine viral diarrhea virus (BVDV)-induced cytopathic effect, viral RNA synthesis, and production of infectious virus were 1.2 +/- 0.5 microM, 5 +/- 1 microM, and 2.3 +/- 0.3 microM, respectively. AG110 proved inactive against the hepatitis C virus and a flavivirus. AG110 inhibits BVDV replication at a time point that coincides with the onset of intracellular viral RNA synthesis. Drug-resistant mutants carry the E291G mutation in the viral RNA-dependent RNA polymerase (RdRp). AG110-resistant virus is cross-resistant to the cyclic urea compound 1453 which also selects for the E291G drug resistance mutation. Moreover, BVDV that carries the F224S mutation (because of resistance to the imidazopyridine 5-[(4-bromophenyl)methyl]-2-phenyl-5H-imidazo[4,5-c]pyridine [BPIP]and VP32947) is also resistant to AG110. AG110 did not inhibit the in vitro activity of recombinant BVDV RdRp but inhibited the activity of BVDV replication complexes (RCs). Molecular modeling revealed that E291 is located in a small cavity near the tip of the finger domain of the RdRp about 7 A away from F224. Docking of AG110 in the crystal structure of the BVDV RdRp revealed several potential contacts including with Y257. The E291G mutation might enable the free rotation of Y257, which might in turn destabilize the backbone of the loop formed by residues 223 to 226, rendering more mobility to F224 and, hence, reducing the affinity for BPIP and VP32947. It is concluded that a single drug-binding pocket exists within the finger domain region of the BVDV RdRp that consists of two separate but potentially overlapping binding sites rather than two distinct drug-binding pockets.

N-Phenyl-N'-(2-chloroethyl)urea analogues of combretastatin A-4: Is the N-phenyl-N'-(2-chloroethyl)urea pharmacophore mimicking the trimethoxy phenyl moiety?

A series of novel N-phenyl-N'-(2-chloroethyl)urea derivatives potentially mimicking the structure of combretastatin A-4 were synthesized and tested for their cell growth inhibition and their binding to the colchicine-binding site of beta-tubulin. Compounds 2a, 3a, and 3b were found to inhibit cell growth at the micromolar level on four human tumor cell lines. Flow cytometric analysis indicates that the new compounds act as antimitotics and arrest the cell cycle in G(2)/M phase. Covalent binding of 2a, 3a, and 3b to the colchicine-binding site of beta-tubulin was confirmed also using SDS-PAGE and competition assays.

In vitro and in vivo antimalarial activity of derivatives of 1,10-phenanthroline framework.

A series of trisubstituted 1,10-phenanthrolines was prepared. These compounds exhibited mild to high biological activities in vitro both toward chloroquino-resistant FcB1-Columbia and FcM29-Cameron strains and Nigerian chloroquino-sensitive strain of Plasmodium falciparum. Cytotoxicity of the most active compounds was estimated showing that one compound (10) exhibited a selective activity against malaria parasite (selectivity indexes of 52 and 144). Antiplasmodial activity of this derivative was optimized by N-10 alkylation and the phenanthrolinium salt (15) submitted to an in vivo study using mice infected by P. vinckei petteri showing an ED50 of 7.86 mg/kg/day.

A photochemical approach to pyridopyrroloquinoline derivatives as new potential anticancer agents.

Indoloquinoline alkaloid cryptolepine and pyridocarbazole alkaloid ellipticine are of great interest because in vitro and in vivo studies revealed their good cytotoxic properties. In order to obtain some biologically active analogs of these compounds, we developped a synthesis based on the photocyclisation of tertiary N-methylated enaminones derived from cyclopentane-1,3-dione and 3 or 6-aminoquinoline. The angular cyclised compounds thus obtained were submitted to Beckmann rearrangement, preceded by the formation of a Z oxime. Finally, the delta-lactame ring was oxidized using 10% palladium/carbon in diphenylether and pyridopyrroloquinolines were obtained. These compounds and the intermediate lactams and cyclopentanopyrroloquinolines were tested in vitro on K 562 cells and A 2780 doxorubicine sensitive and resistant cells. All compounds were less effective than doxorubicine in sensitive cells but their activity wasn't decreased by MDR resistance.