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.     

The antiplasmodial activity of norcantharidin analogs

The antiplasmodial activities of sixty norcantharidin analogs were tested in vitro against a chloroquine sensitive (D6, Sierra Leone) and chloroquine resistant (W2) strains of Plasmodium falciparum. Forty analogs returned IC(50) values <500 μM against at least one of the P. falciparum strains examined. The ring open compound 24 ((1S,4R)-3-(allylcarbamoyl)-7-oxabicyclo[2.2.1]heptane-2-carboxylic acid) is the most active aliphatic analog (D6 IC(50)=3.0±0.0 and W2 IC(50)=3.0±0.8 μM) with a 20-fold enhancement relative to norcantharidin. Surprisingly, seven norcantharimides also displayed good antiplasmodial activity with the most potent, 5 returning D6=8.9±0.9 and W2 IC(50)=12.5±2.2 μM, representing a fivefold enhancement over norcantharidin.     

Design, synthesis and biological evaluation of pyrazolyl-thiazolinone derivatives as potential EGFR and HER-2 kinase inhibitors

A series of pyrazolyl-thiazolinone derivatives (E1-E36) have been designed and synthesized and their biological activities were also evaluated as potential EGFR and HER-2 kinase inhibitors. Thirty-four of the 36 compounds were reported for the first time. Among them, compound 2-(5-(4-bromophenyl)-3-p-tolyl-4,5-dihydro-1H-pyrazol-1-yl)thiazol-4(5H)-one (E28) displayed the most potent inhibitory activity (IC(50)=0.24μM for EGFR and IC(50)=1.07μM for HER-2). Antiproliferative assay results indicated that compound E28 owned high antiproliferative activity against MCF-7, B16-F10 and HCT-116 in vitro, with IC(50) value of 0.30, 0.54, and 0.70μM, respectively. Docking simulation was further performed to position compound E28 into the EGFR active site to determine the probable binding model. Based on the preliminary results, compound E28 with potent inhibitory activity in tumor growth would be a potential anticancer agent.     

Design, synthesis and anticancer activity of novel dihydrobenzofuro[4,5-b][1,8]naphthyridin-6-one derivatives

On the basis of the chemical structures of psorospermin with a xanthone template and acronycine derivatives with an acridone template, rac-1 and rac-2 constructed on an 1,2-dihydrobenzofuro[4,5-b][1,8]naphthyridin-6(11H)-one scaffold were designed and synthesized as potential anticancer agents. Their anticancer activities were evaluated against five human cancer cell lines. Rac-2 showed similar anticancer activity to doxorubicin and rac-1 exhibited even higher anticancer activity against LNCaP (IC(50)=0.14 μM), DU145 (IC(50)=0.15 μM), PC3 (IC(50)=0.30 μM) and MCF-7 (IC(50)=0.26 μM) cancer lines than doxorubicin and rac-2. Also, rac-1 revealed very potent anticancer activity (IC(50)=0.15 μM) against MCF-7/ADR cell (doxorubicin-resistant breast cancer cell) lines and induced G2/M phase arrest of the cell cycle in MCF-7/ADR cells.     

Synthesis, biological evaluation, and molecular docking of N-{3-[3-(9-methyl-9H-carbazol-3-yl)-acryloyl]-phenyl}-benzamide/amide derivatives as xanthine oxidase and tyrosinase inhibitors

Claisen-Schmidt condensation of 3-formyl-9-methylcarbazole with various amides of 3-aminoacetophenone afforded N-{3-[3-(9-methyl-9H-carbazol-3-yl)-acryloyl]-phenyl}-benzamide/amide derivatives. All compounds were investigated for their in vitro xanthine oxidase (XO), tyrosinase and melanin production inhibitory activity. Most of the target compounds had more potent XO inhibitory activity than the standard drug (IC(50)=4.3-5.6μM). Interestingly, compound 7q bearing cyclopropyl ring was found to be the most potent inhibitor of XO (IC(50)=4.3μM). Molecular modelling study gave an insight into its binding modes with XO. Compounds 7a, 7d, 7e, 7g, and 7k were found to be potent inhibitors of tyrosinase (IC(50)=14.01-17.52μM). These results suggest the possible use of these compounds for the design and development of novel XO and tyrosinase inhibitors.     

2-Alkynoic fatty acids inhibit topoisomerase IB from Leishmania donovani

2-Alkynoic fatty acids display antimycobacterial, antifungal, and pesticidal activities but their antiprotozoal activity has received little attention. In this work we synthesized the 2-octadecynoic acid (2-ODA), 2-hexadecynoic acid (2-HDA), and 2-tetradecynoic acid (2-TDA) and show that 2-ODA is the best inhibitor of the Leishmania donovani DNA topoisomerase IB enzyme (LdTopIB) with an EC(50)=5.3±0.7μM. The potency of LdTopIB inhibition follows the trend 2-ODA>2-HDA>2-TDA, indicating that the effectiveness of inhibition depends on the fatty acid carbon chain length. All of the studied 2-alkynoic fatty acids were less potent inhibitors of the human topoisomerase IB enzyme (hTopIB) as compared to LdTopIB. 2-ODA also displayed in vitro activity against Leishmania donovani (IC(50)=11.0μM), but it was less effective against other protozoa, Trypanosoma cruzi (IC(50)=48.1μM) and Trypanosoma brucei rhodesiense (IC(50)=64.5μM). The antiprotozoal activity of the 2-alkynoic fatty acids, in general, followed the trend 2-ODA>2-HDA>2-TDA. The experimental information gathered so far indicates that 2-ODA is a promising antileishmanial compound.     

Design and synthesis of small molecular dual inhibitor of falcipain-2 and dihydrofolate reductase as antimalarial agent

Resistance of malaria parasites has quickly developed to almost all used antimalarial drugs. Accordingly, the discovery of new effective drugs to counter the spread of malaria parasites that are resistant to existing agents, especially acting on multi-targets, is an urgent need. The cysteine protease falcipain-2 (FP-2) and dihydrofolate reductase (DHFR) play crucial roles in the Plasmodium life cycle. In this study, a series of first-gereration small molecular dual inhibitor of FP-2 and DHFR have been designed and synthesized based on the lead compound 1, which was randomly identified by screening FP-2 inhibitors in our laboratory. Six compounds (2f-g, 2j, and 2m-o) showed improved dual inhibitory activities against FP-2 (IC(50)=2.7-13.2μM) and DHFR (IC(50)=1.8-19.8μM), and the inhibitory capability of compound 2o against FP-2 and DHFR were increased ～8 and ～6 times than that of compound 1, respectively. Moreover, compound 2o exhibited moderate in vivo antimalarial activity in a dose dependent fashion, its safety and survival rate were slightly better than that of positive drug. The preliminary SAR was obtained, meanwhile, molecular modeling result provided the key structural information to maintain the dual inhibitory activity, and was helpful for future dual inhibitors design.     

Discovery of nitroheterocycles active against African trypanosomes. In vitro screening and preliminary SAR studies

A selection of 76 nitroheterocycles and related compounds from our in-house compound library was screened in vitro against the parasite Trypanosoma brucei rhodesiense, causative agent of human African trypanosomiasis (HAT). The unspecific cytotoxicity of the compounds was also evaluated against rat myoblast L6-cells to measure the selectivity of the compounds towards the parasite. This screening revealed some preliminary structure-activity relationships (SAR) among the series, and six hit compounds showing interesting activity (IC(50)≤10μM) and fair selectivity (SI>17). The 7-nitroquinoxalin-2-one and 5-nitroindazole scaffold derivatives 58 and 35, respectively, are particularly interesting because of their established oral bioavailability in mice. These hits represent interesting starting points for a medicinal project aimed at identifying the SAR behind this class of compounds.     

Synthesis, biological evaluation, and molecular docking studies of N,1,3-triphenyl-1H-pyrazole-4-carboxamide derivatives as anticancer agents

A series of N,1,3-triphenyl-1H-pyrazole-4-carboxamide derivatives have been designed, synthesized and evaluated for their potential antiproliferation activity and Aurora-A kinase inhibitory activity. Among all the compounds, compound 10e possessed the most potent biological activity against HCT116 and MCF-7 cell lines with IC(50) values of 0.39±0.06μM and 0.46±0.04 μM, respectively, which were comparable to the positive control. Compound 10e also exhibited significant Aurora-A kinase inhibitory activity (IC(50)=0.16±0.03 μM). Docking simulation was performed to position compound 10e into the active site of Aurora-A kinase, in order to get the probable binding model for further study. The results of Western-blot assay demonstrated that compound 10e possessed good Aurora-A kinase inhibitory activity against HCT116. Based on the preliminary results, it is deduced that compound 10e with potent Aurora-A kinase inhibitory activity may be a potential anticancer agent.     

Synthesis and antimalarial activity of new haemanthamine-type derivatives

Thirty one derivatives were prepared from the natural alkaloids haemanthamine (1), haemanthidine (2) and 11-hydroxyvittatine (3). They were evaluated for their in vitro antimalarial activity against chloroquine-sensitive strains of Plasmodium falciparum and some structure-activity relationships were outlined. For haemanthamine derivatives having a methoxy group at C-3, the presence of a free hydroxyl group at C-11 is important for the activity. The double bond at C-1-C-2 plays also an important role to achieve good inhibitory activity. Compound 35 with two nicotinate groups at C-3 and at C-11 was the most active compound with a IC(50)=0.8±0.06μM.     

II. Novel HCV NS5B polymerase inhibitors: discovery of indole C2 acyl sulfonamides

Development of SAR at the C2 position of indole lead 1, a palm site inhibitor of HCV NS5B polymerase (NS5B IC(50)=0.053μM, replicon EC(50)=4.8μM), is described. Initial screening identified an acyl sulfonamide moiety as an isostere for the C2 carboxylic acid group. Further SAR investigation resulted in identification of acyl sufonamide analog 7q (NS5B IC(50)=0.039μM, replicon EC(50)=0.011μM) with >100-fold improved replicon activity.     

Polyamine conjugates of stigmasterol

Three new polyamine conjugates with stigmasterol [(3β,22E)-stigmasta-5,22-dien-3-ol] were synthesized and subjected to basic antimicrobial and cytotoxic tests. The conjugate derived from spermine, (3β,22E)-stigmasta-5,22-dien-3-yl 4(12-amino-4,9-diaza-dodecylamino)-4-oxobutanoate (5c), displayed considerable antimicrobial activity on Staphylococcus aureus at low concentration (50μgmL(-1)). The cytotoxic activity was tested on cells of human T-lymfoblastic leukemia (IC(50)=35.8±10.3μM (5c) and IC(50)=35.9±5.7μM (5b)) and normal human fibroblasts (IC(50)=38.0±2.8μM (5c) and IC(50)=45.5±1.9μM (5b)). Conjugate 5a displayed no activity in both tests.     

Trimethoxy-chalcone derivatives inhibit growth of Leishmania braziliensis: synthesis, biological evaluation, molecular modeling and structure-activity relationship (SAR)

In this work we described the synthesis, the antileishmanial activity and the molecular modeling and structure-activity relationship (SAR) evaluations of a series of chalcone derivatives. Among these compounds, the methoxychalcones 2h, 2i, 2j, 2k and 2l showed significant antileishmanial activity (IC(50)<10 μM). Interestingly 2i (IC(50)=2.7 μM), 2j (IC(50)=3.9 μM) and 2k (IC(50)=4.6 μM) derivatives presented better antileishmanial activity than the control drug pentamidine (IC(50)=6.0 μM). Our SAR study showed the importance of methoxy di-ortho substitution at phenyl ring A and the relationship between the frontier orbital HOMO coefficients distribution of these molecules and their activity. The most active compounds 2h, 2i, 2j, 2k, and 2l fulfilled the Lipinski rule-of-five which theoretically is important for good drug absorption and permeation through biological membranes. The potential profile of 2j (IC(50)=3.9 μM and CC(50)=216 μM) pointed this chalcone derivative as a hit compound to be further explored in antileishmanial drug design.     

Depigmenting activity of new kojic acid derivative obtained as a side product in the synthesis of cinnamate of kojic acid

We synthesized cinnamate derivatives of kojic acid for use as depigmenting agents by various esterification methods. The cinnamate of 5-position of kojic acid (6) was obtained by EDC coupling, DCC coupling, acid chloride, and mixed anhydride methods. To obtain the cinnamate of the 2-position of kojic acid (7), we carried out the nucleophilic addition of the potassium salt of cinnamic acid to kojyl chloride. In this reaction, we discovered the occurrence of a side reaction and identified the structure of the side product thus formed. We evaluated the depigmenting activities of both the side product and the cinnamate derivatives of kojic acid. Interestingly, the side product (11) showed more potent depigmenting activity (IC(50)=23.51μM) than compound 7 (IC(50)>100μM) which is the mother compound of the side product. However, it has no tyrosinase inhibitory activity. Compound 6, the cinnamate of 5-position of kojic acid, also showed moderate depigmenting activity (IC(50)=46.64μM) without tyrosinase inhibitory activity. Production of this side product (11) may have originated from the proton exchange between the potassium salt of cinnamic acid and kojyl chloride. We then efficiently reduced the yield of the side product by controlling the equilibrium of the potassium salt of cinnamic acid. The addition of cinnamic acid greatly reduced the amount of the side product produced.     

Synthesis, cytotoxic and antioxidant evaluations of amino derivatives from perezone

A series of eight amino derivatives (3a-h) from perezone 1 were prepared by nucleophilic addition of bioactive amines v.gr. melatonin, acetyl tryptamine, tryptophan and other amino acids esters (valine, leucine and methionine). Their structures were elucidated by spectroscopy data. The cytotoxic evaluation against four human tumor cell lines PC-3, K-562, HCT-15 and SKLU-1 was performed as well as the TBARS assay for antioxidant activity. The results suggest that 1 and its isomer 4 were highly active against all cell lines, 4 was twice as potent than 1 against PC-3 and HCT-15. The derivative 3a (IC(50)=7.5±0.3μM) was more active than 1 against HCT-15 whereas 3h was selective against K-562 with IC(50)=4.5±0.4μM. The TBARS assay has shown that 3c with IC(50)=5.564±0.24μM is a potent antioxidant with superior effect comparing to α-tocopherol and moreover was more active than the precursor molecule 1.     

Oxadiazole derivatives containing 1,4-benzodioxan as potential immunosuppressive agents against RAW264.7 cells

A series of oxadiazole derivatives containing 1,4-benzodioxan (4a-4s) have been first synthesized for their potential immunosuppressive activity. Among the compounds, compound 4i showed the most potent biological activity against RAW264.7 cells (inhibition=37.66±2.34% for NO overproduction and IC(50)=0.05μM for iNOS). Docking simulation was performed to position compound 4i into the iNOS structure active site to determine the probable binding model. RT-PCR experiment results demonstrated that some of these compounds possessed good immunosuppressive activity against iNOS, especially for compound 4i. Therefore, compound 4i with potent inhibitory activity may be a potential agent.     

Development of 2-substituted-N-(naphth-1-ylmethyl) and N-benzhydrylpyrimidin-4-amines as dual cholinesterase and Aβ-aggregation inhibitors: Synthesis and biological evaluation

A group of 2-substituted N-(naphth-1-ylmethyl)pyrimidin-4-amines (6a-k) and N-benzhydrylpyrimidin-4-amines (7a-k) in conjunction with varying steric and electronic properties at the C-2 position were designed, synthesized and evaluated as dual cholinesterase and amyloid-β (Aβ)-aggregation inhibitors. The naphth-1-ylmethyl compound 6f (2-(4-cyclohexylpiperazin-1-yl)-N-(naphth-1-ylmethyl)pyrimidin-4-amine) exhibited optimum dual ChE (AChE IC(50)=8.0 μM, BuChE IC(50)=3.9 μM) and hAChE-promoted Aβ-aggregation inhibition (30.8% at 100 μM), whereas in the N-benzhydryl series, compound 7f (N-benzhydryl-2-(4-cyclohexylpiperazin-1-yl)pyrimidin-4-amine) exhibited optimum combination of dual ChE (AChE IC(50)=10.0 μM, BuChE IC(50)=7.6μM) and hAChE-promoted Aβ-aggregation inhibition (32% at 100 μM). These results demonstrate that a 2,4-disubstituted pyrimidine ring serves as a suitable template to target multiple pathological routes in AD, with a C-2 cyclohexylpiperazine substituent providing dual ChE inhibition and potency whereas a C-4 diphenylmethane substituent provides Aβ-aggregation inhibition.     

Synthesis and antimalarial evaluation of novel isocryptolepine derivatives

A series of mono- and di-substituted analogues of isocryptolepine have been synthesized and evaluated for in vitro antimalarial activity against chloroquine sensitive (3D7) and resistant (W2mef) Plasmodium falciparum and for cytotoxicity (3T3 cells). Di-halogenated compounds were the most potent derivatives and 8-bromo-2-chloroisocryptolepine displayed the highest selectivity index (106; the ratio of cytotoxicity (IC(50)=9005 nM) to antimalarial activity (IC(50)=85 nM)). Our evaluation of novel isocryptolepine compounds has demonstrated that di-halogenated derivatives are promising antimalarial lead compounds.     

Novel bis(indolyl)hydrazide-hydrazones as potent cytotoxic agents

A series of bis(indolyl) hydrazide-hydrazones 5a-n were synthesized and evaluated for their cytotoxicity against selected human cancer cell lines. The reaction of indole-3-carboxaldehyde 2 with indole-3-carbohydrazide 4 in presence of catalytic amount of acetic acid afforded 5a-n in good yields. Among the synthesized bis(indolyl)hydrazide-hydrazones, the compound 5b with N-(p-chlorobenzyl) and bromo substituents was found to be the most potent against multiple cancer cell lines (IC(50)=1.0 μM, MDA-MB-231). The compound 5k exhibited selective cytotoxicity against breast cancer cell line MCF7 (IC(50)=3.1 μM).