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).     

Potent antitumor activity of synthetic 1,2-Naphthoquinones and 1,4-Naphthoquinones

Rhinacanthone (1) and two 1,2-pyranonaphthoquinones (2,3) were synthesized and found to show very potent cytotoxicity against three cancer cell lines (KB, HeLa and HepG(2)) with IC(50) values of 0.92-9.63 microM, whereas the corresponding hydroxylated derivative 4 had reduced cytotoxicity (IC(50) values of 7.61-24.13 microM). Three 1,2-furanonaphthoquinone derivatives (5-7) were also synthesized with similar cytotoxicity as 1,2-pyranonaphthoquinones. In comparison to 1,2-naphthoquinones, six 1,4-naphthoquinones derivatives fused with pyran ring (8-10) and furan ring (11-13) were synthesized and they showed less cytotoxicity or inactive to the cancer cell lines. Moreover, compound 13 had significant cytotoxicity against HeLa cell line (IC(50) value of 9.25 microM) while it showed no toxic to vero cell.     

Anticancer and immunomodulatory activities of novel 1,8-naphthyridine derivatives

A number of 1,8-naphthyridine derivatives (22–62) have been synthesized and screened for their in vitro cytotoxicity against eight tumors and two non-tumor cell lines. Halogen substituted 1,8-naphthyridine-3-caboxamide derivatives showed potent activity with compound 47 having IC₅₀ of 0.41 and 0.77 μM on MIAPaCa and K-562 cancer cell lines, respectively while, compound 36 had IC₅₀ of 1.19 μM on PA-1 cancer cell line. However, one of the unsubstituted 1,8-naphthyridine-C-3’-heteroaryl derivative 29 showed potent cytotoxicity with IC₅₀ of 0.41 and 1.4 μM on PA-1 and SW620 cancer cell lines, respectively. These compounds were also evaluated for anti-inflammatory activity as suggested by downregulation of proinflammaotory cytokines.     

Heterocyclic substituted cantharidin and norcantharidin analogues--synthesis, protein phosphatase (1 and 2A) inhibition, and anti-cancer activity

Norcantharidin (3) is a potent PP1 (IC(50)=9.0+/-1.4 microM) and PP2A (IC(50)=3.0+/-0.4 microM) inhibitor with 3-fold PP2A selectivity and induces growth inhibition (GI(50) approximately 45 microM) across a range of human cancer cell lines including those of colorectal (HT29, SW480), breast (MCF-7), ovarian (A2780), lung (H460), skin (A431), prostate (DU145), neuroblastoma (BE2-C), and glioblastoma (SJ-G2) origin. Until now limited modifications to the parent compound have been tolerated. Surprisingly, simple heterocyclic half-acid norcantharidin analogues are more active than the original lead compound, with the morphilino-substituted (9) being a more potent (IC(50)=2.8+/-0.10 microM) and selective (4.6-fold) PP2A inhibitor with greater in vitro cytotoxicity (GI(50) approximately 9.6 microM) relative to norcantharidin. The analogous thiomorpholine-substituted (10) displays increased PP1 inhibition (IC(50)=3.2+/-0 microM) and reduced PP2A inhibition (IC(50)=5.1+/-0.41 microM), to norcantharidin. Synthesis of the analogous cantharidin analogue (19) with incorporation of the amine nitrogen into the heterocycle further increases PP1 (IC(50)=5.9+/-2.2 microM) and PP2A (IC(50)=0.79+/-0.1 microM) inhibition and cell cytotoxicity (GI(50) approximately 3.3 microM). These analogues represent the most potent cantharidin analogues thus reported.     

Synthesis of 6-chloroisoquinoline-5,8-diones and pyrido[3,4-b]phenazine-5,12-diones and evaluation of their cytotoxicity and DNA topoisomerase II inhibitory activity

The substituted chloroisoquinolinediones and pyrido[3,4-b]phenazinediones were synthesized, and the cytotoxic activity and topoisomerase II inhibitory activity of the prepared compounds were evaluated. Chloroisoquinolinediones have been prepared by the reported method employing 6,7-dichloroisoquinoline-5,8-dione. The cyclization to pyrido[3,4-b]phenazinediones was achieved by adding the aqueous sodium azide solution to the dimethylformamide solution of corresponding chloroisoquinoline-5,8-dione. The cytotoxicity of the synthesized compounds was evaluated by a SRB (Sulforhodamine B) assay against various cancer cell lines such as A549 (human lung cancer cell line), SNU-638 (human stomach cancer cell), Col2 (human colon cancer cell line), HT1080 (human fibrosarcoma cell line), and HL-60 (human leukemia cell line). Almost all the synthesized pyrido[3,4-b]phenazinediones showed greater cytotoxic potential than ellipticine (IC(50)=1.82-5.97 microM). In general, the cytotoxicity of the pyrido[3,4-b]phenazinediones was higher than that of the corresponding chloroisoquinolinediones. The caco-2 cell permeability of selected compounds was 0.62 x 10(-6)-35.3 x 10(-6)cm/s. The difference in cytotoxic activity among tested compounds was correlated with the difference in permeability to some degree. To further investigate the cytotoxic mechanism, the topoisomerase II inhibitory activity of the synthesized compounds was estimated by a plasmid cleavage assay. Most of compounds showed the topoisomerase II inhibitory activity (28-100%) at 200 microM. IC(50) values for the most active compound 6a were 0.082 microM. However, the compounds were inactive for DNA relaxation by topoisomerase I at 200 microM.     

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.     

Cysteine chloromethyl and diazomethyl ketone derivatives with potent anti-leukemic activity

A series of cysteine diazomethyl- and chloromethyl ketone derivatives has been synthesized and evaluated against human B-lineage (Nalm-6) and T-lineage (Molt-3) acute lymphoblastic leukemia cell lines. The chloromethyl ketone compounds showed potent cytotoxicity against these cell lines, with IC50 values in the low micromolar range. The best compounds were N-acetyl-S-dodecyl-Cys chloromethyl ketone (IC50 = 2.0 microM against Nalm-6, 2.3 microM against Molt-3) and N-acetyl-S-trans,trans-farnesyl-Cys chloromethyl ketone (IC50 = 3.0 microM against Nalm-6 and 1.4 microM against Molt-3).     

Synthesis, cytostatic and anti-HIV evaluations of the new unsaturated acyclic C-5 pyrimidine nucleoside analogues

A series of the novel C-5 alkynyl pyrimidine nucleoside analogues (1-14) in which the sugar moiety was replaced by the conformationally restricted Z- and E-2-butenyl spacer between the phthalimido and pyrimidine ring were synthesized by using Sonogashira cross-coupling reaction. Cytostatic activity evaluation of the novel compounds showed that E-isomers exhibited, in general, better cytostatic activities than the corresponding Z-isomers. E-isomer 14 exhibited the best cytostatic effect against all evaluated malignant cell lines, particularly against hepatocellular carcinoma (Hep G2, IC(50)=4.3microM). However, this compound was also cytotoxic to human normal fibroblasts (WI 38). Its Z-isomer 7 showed highly specific antiproliferative activity against Hep G2 (IC(50)=18microM) and no cytotoxicity to WI 38. Moreover, compounds 3, 4 and 14 expressed some marginal inhibitory activity against HIV-1 and HIV-2.     

Synthetic tyrosyl gallate derivatives as potent melanin formation inhibitors

Three tyrosyl gallate derivatives (1-3) with variable hydroxyl substituent at the aromatic ring of tyrosol were synthesized and evaluated as potent inhibitors on tyrosinase activity and melanin formation in melan-a cells. Among three tyrosyl gallate derivatives, 4-hydroxyphenethyl 3,4,5-trihydroxybenote (1) (IC(50)=4.93 microM), 3-hydroxyphenethyl 3,4,5-trihydroxybenote (2) (IC(50)=15.21 microM), and 2-hydroxyphenethyl 3,4,5-trihydroxybenote (3) (IC(50)=14.50 microM) exhibited significant inhibitory effect on tyrosinase activity. Compound 1 was the most active compound, though it did not show the inhibitory effect on melanin formation in melan-a cells. However, compounds 2 (IC(50)=8.94 microM) and 3 (IC(50)=13.67 microM) significantly suppressed the cellular melanin formation without cytotoxicity. This study shows that the position of hydroxyl substituent at the aromatic ring of tyrosol plays an important role in the intracellular regulation of melanin formation in cell-based assay system.     

Synthesis, cytotoxicity, and DNA topoisomerase II inhibitory activity of benzofuroquinolinediones

Benzofuroquinolinediones (7c and 7d) were synthesized by base-catalyzed condensation of dichloroquinolinediones with phenolic derivatives. Their dialkylaminoalkoxy derivatives (8i-8p) were prepared by reaction with various dialkylaminoalkyl chlorides. The cytotoxicity of the synthesized compounds was evaluated against eight types of human cancer cell lines, and their topoisomerase II inhibition was assessed. In general, the cytotoxicity of benzofuroquinolinediones (8i-8p) was similar or superior to that of doxorubicin and showed more potent inhibitory activity than naphthofurandiones (8a-8h). Also, most of the compounds exhibited excellent topoisomerase II inhibitory activity at a concentration of 5 microM and two compounds, 8d and 8i, showed IC50 values of 1.19 and 0.68 microM, respectively, and were much more potent than etoposide (IC50=78.4 microM), but similar to doxorubicin (IC50=2.67 microM). However their inhibitory activity on topoisomerase I was lower, and 8d and 8i showed IC50 values of 42.0 and 64.3 microM, respectively.     

Cytotoxicity of fungal metabolites to lepidopteran (Spodoptera frugiperda) cell line (SF-9)

The toxicity of sixteen fungal metabolites produced by some entomopathogenic fungi or biological control fungi agents was evaluated on lepidopteran Spodoptera frugiperda (SF-9) cell line by Trypan blue dye exclusion and MTT-colorimetric assay, after 48 h of incubation. No statistical difference was found between IC50values (50% Inhibiting Concentration) and CC50 values (50% Cytotoxicity Concentration) obtained by MTT test and Trypan blue dye exclusion for each fungal metabolite. By MTT assay, the cytotoxicity ranking was fusarenon X (IC50 0.3 microM) = diacetoxyscirpenol (IC50 0.5 microM) = beauvericin (IC50 2.5 microM) = nivalenol (IC50 5.3 microM) = enniatin (IC50 6.6 microM) > or = gliotoxin (IC50 7.5 microM) > zearalenone (IC50 17.5 microM) > deoxynivalenol (IC50 47.6 microM). By Trypan blue dye exclusion the cytotoxicity ranking was fusarenon X (CC50 0.4 microM) = diacetoxyscirpenol (CC50 1.1 microM) beauvericin = (CC50 3.0 microM)=gliotoxin (CC50 4.0 microM) = enniatin (CC50 6.7 microM) > or = nivalenol (CC50 9.5 microM) > zearalenone (CC50 18.3 microM) > deoxynivalenol (CC50 45.0 microM). The comparison with other bioassays showed that the SF-9 insect cell line could represent a further tool to screen for the toxic effects of fungal metabolites especially for beauvericin, gliotoxin, and zearalenone.     

Tryptamine derivatives as novel non-nucleosidic inhibitors against hepatitis B virus

A series of tryptamine derivatives were synthesized and evaluated for their anti-hepatitis B virus (HBV) activity and cytotoxicity in the HepG2.2.15 cell line. The preliminary SAR was discussed. Compounds 2e and 4a showed potent antiviral activity (IC(50)=0.4 and <1 μM, respectively) and low cytotoxicity (CC(50)=40.6 and >25 μM, respectively).     

Organic phenyl arsonic acid compounds with potent antileukemic activity

A series of 12 organic arsonic acid compounds has been synthesized and evaluated against human B-lineage (NALM-6) and T-lineage (MOLT-3) acute lymphoblastic leukemia (ALL) cell lines. The lead compounds 2-trichloromethyl-4-[4'-(4"-phenylazo)phenylarsonic acid]aminoquinazoline (compound 19, PHI-P518; IC(50)=1.1+/-0.5 microM against NALM-6 and 2.0+/-0.8 microM against MOLT-3) and 2-methylthio-4-(2'-phenylarsonic acid)aminopyrimidine (compound 15, PHI-P381; IC(50)=1.5+/-0.3 microM against NALM-6 and 2.3+/-0.5 microM against MOLT-3) exhibited potent antileukemic activity at low micromolar concentrations.     

Glycosidation of lupane-type triterpenoids as potent in vitro cytotoxic agents

The weak hydrosolubility of betulinic acid (3) hampers the clinical development of this natural anticancer agent. In order to circumvent this problem and to enhance the pharmacological properties of betulinic acid (3) and the lupane-type triterpenes lupeol (1), betulin (2), and methyl betulinate (7), glycosides (beta-D-glucosides, alpha-L-rhamnosides, and alpha-D-arabinosides) were synthesized and in vitro tested for cytotoxicity against three cancerous (A-549, DLD-1, and B16-F1) and one healthy (WS1) cell lines. The addition of a sugar moiety at the C-3 or C-28 position of betulin (2) resulted in a loss of cytotoxicity. In contrast, the 3-O-beta-D-glucosidation of lupeol (1) improved the activity by 7- to 12-fold (IC50 14-15.0 microM). Moreover, the results showed that cancer cell lines are 8- to 12-fold more sensitive to the 3-O-alpha-L-rhamnopyranoside derivative of betulinic acid (IC50 2.6-3.9 microM, 22) than the healthy cells (IC50 31 microM). Thus, this study indicates that 3-O-glycosides of lupane-type triterpenoids represent an interesting class of potent in vitro cytotoxic agents.     

Design, synthesis and cytotoxic activity of novel spin-labeled rotenone derivatives

Three series of novel spin-labeled rotenone derivatives were synthesized and evaluated for cytotoxicity against four tumor cell lines, A-549, DU-145, KB and KBvin. All of the derivatives showed promising in vitro cytotoxic activity against the tumor cell lines tested, with IC(50) values ranging from 0.075 to 0.738μg/mL. Remarkably, all of the compounds were more potent than paclitaxel against KBvin in vitro, and compounds 3a and 3d displayed the highest cytotoxicity against this cell line (IC(50) 0.075 and 0.092μg/mL, respectively). Based on the observed cytotoxicity, structure-activity relationships have been described.     

Synthesis of 4/5-deoxy-4/5-nucleobase derivatives of 3-O-methyl-D-chiro-inositol as potential antiviral agents

Using D-pinitol (= 3-O-methyl-D-chiro-inositol) as starting material, a concise synthesis of 4/5-deoxy-4/5-nucleobase derivatives 11-19 has been achieved. The key intermediate 9 was obtained in good yield via an epoxidation from mono-methanesulfonate of D-pinitol. The process of opening of the epoxide ring in 9 by nucleobases appeared to be regioselective in presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). All the synthesized carbocyclic nucleosides were assayed against several viruses and tumors such as HIV-1, HSV-1, and HSV-2, and lung and bladder cancer. However, only compounds 14b, 14a, 16a, 16b, and 19 showed mild inhibitory effect against human lung cancer cell lines (PG) with IC50 values ranging from 50 to 100 microM, and the other compounds did not exhibit any significant antiviral activity or cytotoxicity even at concentrations up to 200 microM.     

Application of multicomponent reactions to antimalarial drug discovery. Part 2: New antiplasmodial and antitrypanosomal 4-aminoquinoline gamma- and delta-lactams via a 'catch and release' protocol

A parallel synthesis of a new series of 4-aminoquinoline gamma- and delta-lactams synthesized via the Ugi 3-component 4-centre multicomponent reaction is described. The basicity of the quinoline nitrogen was exploited in the purification of compounds via a 'catch and release' protocol. Yields ranging from 60% to 77% and purities as high as 96% were obtained. Compound 29, the most active against a chloroquine-resistant W2 strain of Plasmodium falciparum with an IC(50) of 0.096 microM, also inhibited recombinant falcipain-2 in vitro (IC(50)= 17.6 microM). Compound 17 inhibited the growth of Trypanosoma brucei with an ED(50) of 1.44 microM whilst exhibiting a favourable therapeutic index of 409 against a human KB cell line.     

A macromolecular prodrug of doxorubicin conjugated to a biodegradable cyclotriphosphazene bearing a tetrapeptide

A new biodegradable water-soluble phosphazene trimer-doxorubicin conjugate was synthesized, in which equimolar hydrophilic methoxy-poly(ethylene glycol) with a molecular weight of 350 (MPEG350) and a tumor-specific tetrapeptide (Gly-Phe-Leu-Gly) were grafted to cyclotriphosphazene. The present conjugate exhibited cytotoxicity lower than that of free doxorubicin (IC50=0.10 microM) but a reasonably higher in vitro cytotoxicity (IC50=1.1 microM) against the leukemia L1210 cell line probably due to its enzymatically controlled release.     

Synthesis and anticancer evaluation of bis(benzimidazoles), bis(benzoxazoles), and benzothiazoles

Four classes of UK-1 analogues were synthesized and their cytotoxicity testing against human A-549, BFTC-905, RD, MES-SA, and HeLa carcinoma cell lines was determined. The results revealed that UK-1 and four of these analogues (15-18) are potent against the cancer cell lines. In particular, compound 16 is more potent than UK-1 against A-549 and HeLa cell lines, and compounds 15, 17, and 18 selectively exhibit potent cytotoxic activity against the BFTV-905 cells (IC50 9.6 microM), A-549 cells (IC50 6.6 microM), and MES-SA cells (IC50 9.2 microM), respectively.     

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.