Swagatika Das

The cytotoxic properties and preferential toxicity to tumour cells displayed by some 2,4-bis(benzylidene)-8-methyl-8-azabicyclo[3.2.1] octan-3-ones and 3,5-bis(benzylidene)-1-methyl-4-piperidones

This study demonstrated that replacement of the axial protons on the C2 and C6 atoms of various 1-methyl-3,5-bis(benzylidene)-4-piperidones 3 by a dimethylene bridge leading to series 2 lowered cytotoxic potencies. Four compounds 2a and 3a-c emerged as lead molecules based on their toxicity towards different neoplasms and their selective toxicity for malignant rather than normal cells. Some possible reasons for the disparity between the IC(50) values in the two series of compounds are presented based on molecular modeling, logP values and respiration in rat liver mitochondria.

N-Aroyl-3,5-bis(benzylidene)-4-piperidones: a novel class of antimycobacterial agents.

A number of 3,5-bis(benzylidene)-4-piperidones 1 and some N-4-(2-aminoethoxy)phenylcarbonyl analogs 3-6 display excellent in vitro antimycobacterial properties. In particular, 1c and 6d are potent antimycobacterials which are well tolerated in mice and are identified as important lead molecules. The nature of both the benzylidene aryl rings and the terminal basic groups which affect the antimycobacterial potencies and the absence of neurotoxic side effects were identified. Several representative compounds stimulated respiration in mitochondria isolated from rat liver and this effect was not caused by the swelling of these organelles. Various guidelines for the creation of further related novel antimycobacterial agents are provided.

3,5-Bis(benzylidene)-4-oxo-1-phosphonopiperidines and related diethyl esters: Potent cytotoxins with multi-drug-resistance reverting properties.

A series of 3,5‐bis(benzylidene)‐4‐piperidones 3 were converted into the corresponding 3,5‐bis(benzylidene)‐1‐phosphono‐4‐piperidones 5 via diethyl esters 4. The analogues in series 4 and 5 displayed marked growth inhibitory properties toward human Molt 4/C8 and CEM T‐lymphocytes as well as murine leukemia L1210 cells. In general, the N‐phosphono compounds 5, which are more hydrophilic than the analogues in series 3 and 4, were the most potent cluster of cytotoxins, and, in particular, 3,5‐bis‐(2‐nitrobenzylidene)‐1‐phosphono‐4‐piperidone 5 g had an average IC50 value of 34 nM toward the two T‐lymphocyte cell lines. Four of the compounds displayed potent cytotoxicity toward a panel of nearly 60 human tumor cell lines, and nanomolar IC50 values were observed in a number of cases. The mode of action of 5 g includes the induction of apoptosis and inhibition of cellular respiration. Most of the members of series 4 as well as several analogues in series 5 are potent multi‐drug resistance (MDR) reverting compounds. Various correlations were noted between certain molecular features of series 4 and 5 and cytotoxic properties, affording some guidelines in expanding this study.

E,E-2-Benzylidene-6-(nitrobenzylidene)cyclohexanones: Syntheses, cytotoxicity and an examination of some of their electronic, steric, and hydrophobic properties

Three series of structurally isomeric 2-benzylidene-6-(nitrobenzylidene) cyclohexanones 1-3 were prepared and evaluated against human Molt/C8 and CEM T-lymphocytes as well as murine L1210 cells. The IC(50) values of the majority of compounds are less than 10microM and in some assays, the figures for 1d and 1e are submicromolar. Correlations were discerned between cytotoxic potencies and the atomic charges on one of the olefinic carbon atoms, the torsion angles between an aryl ring, and the adjacent unsaturated group as well as logP values. Three representative compounds were examined for their effect on respiration in rat liver mitochondria.

Novel 3,5-bis(arylidene)-4-piperidone dimers: Potent cytotoxins against colon cancer cells

Two novel series of dimeric 3,5-bis(arylidene)-4-piperidones 7 and 8 were prepared as cytotoxic agents. A specific objective of this study was the discovery of novel compounds displaying potent anti-proliferative activities against colon cancers. Most of the compounds demonstrate potent cytotoxicity against HCT116 and HT29 colon cancer cell lines in which the IC50 values range from low micromolar to nanomolar values. In general, the majority of the compounds showed greater cytotoxicity and some degree of selectivity toward HCT116 cells compared to HT29 cells. Compound 9 in which the amidic carbonyl groups were excised was substantially less potent than 8a in both cell lines suggested that the amide groups are important components of the molecules for exhibiting cytotoxicity. Virtually all the compounds were more potent than a reference drug 5-fluorouracil which is used in treating colon cancers as well as a related enone curcumin. QSAR studies were undertaken and some guidelines for amplification of the project have been formulated. Flow cytometry analysis of a representative potent compound 7f revealed that it induces apoptosis in HCT116 cells.

Bis[3,5‐bis(benzylidene)‐4‐oxo‐1‐piperidinyl]amides: A Novel Class of Potent Cytotoxins

The principal objective of this study was the examination of the theory of cytotoxic synergism. In this exploratory study, we tested the hypothesis that doubling the number of sites available for thiol alkylation in a series of candidate cytotoxins increases potency more than two‐fold. This concept was verified in one‐third of our comparisons using human Molt 4/C8 and CEM T‐lymphocytes and murine L1210 cells. In addition, the significant potencies of various members of our compound series justified further studies. Molecular modeling revealed that relative locations of the amidic groups correlate with cytotoxicity. A potent cytotoxic compound, 1,2‐bis(3,5‐dibenzylidene‐4‐oxo‐piperidin‐1‐yl)ethane‐1,2‐dione (1 a) inhibited the growth of a large number of human tumor cell lines and displayed greater toxicity toward certain non‐adherent cells than toward adherent neoplasms or fibroblasts. The mode of action of 1 a includes induction of apoptosis and necrosis.

E-2-[3-(3,4-dichlorophenyl)-1-oxo-2-propenyl]-3-methylquinoxaline-1,4-dioxide: a lead antitubercular agent which alters mitochondrial respiration in rat liver.

A series of 2-(3-aryl-1-oxo-2-propenyl)-3-methylquinoxaline-1,4-dioxides 1a-l and 2-acetyl-3-methylquinoxaline-1,4-dioxide 2 were evaluated against Mycobacterium tuberculosis H(37)Rv. With the exception of the 4-nitro analog 1k, significant antitubercular potencies were observed in series 1 and 2 which have IC(50) values in the range of 1-23 microM. Negative correlations were noted between the IC(50) values of 1a-j, l towards M. tuberculosis and both the sigma and pi constants of the substituents in the benzylidene aryl ring. In particular, 1h emerged as a lead compound having IC(50) and IC(90) figures of 1.03 microM and 1.53 microM, respectively. This molecule affected respiration in rat liver mitochondria which is likely one way that 1h and the bioactive analogs exert their antitubercular properties. The quinoxaline 2, which lacks an alpha,beta-unsaturated group, has no effect on mitochondrial respiration using concentrations which inhibit the growth of M. tuberculosis.

Tumor-selective Cytotoxicity of a Novel Pentadiene Analogue on Human Leukemia/lymphoma Cells

BACKGROUND A novel series of structurally divergent 1,5-diaryl-3-oxo-1,4-pentadiene analogues 1-10 displayed marked cytotoxic potencies towards a number of human leukemia/lymphoma cells. OBJECTIVE To identify novel selective cytotoxic compounds that induce apoptosis. METHODS The Differential Nuclear Staining (DNS) screening protocol was utilized to measure the cytotoxicity of all experimental dienones on several cancerous cells. Additionally, the selective cytotoxicity index was calculated by comparing the dienones cytotoxicity between leukemia/lymphoma cells vs. non-cancerous cells. Furthermore, to discern whether a selected dienone induced cell death via apoptosis or necrosis on T-lymphocyte leukemia cells, diverse approaches were utilized to detect individual biochemical facets of apoptosis. RESULTS The dienones were tested for their anti-neoplastic efficiency on human leukemia/lymphoma-derived cell lines. Special emphasis was applied on dienone 1, on the basis of its sub-micromolar cytotoxicity (CC50=0.43+0.02 μM) and high selective cytotoxicity index (11.1) exerted on T-leukemia cells. In general, dienone 1 showed the most potent cytotoxic properties as compared to other dienones and a related reference cytotoxin curcumin as well as the EF-24 curcumin analogue. Dienone 1 caused cell death by apoptosis in Jurkat cells as evidenced by inducing phosphatidylserine externalization, mitochondrial depolarization and caspase-3/7. These effects were mainly attributed to the induction of apoptotic pathways. CONCLUSION The novel dienone 1 was found to exhibit potent anti-leukemia activity by inducing programmed cell death/apoptosis. Consequently, dionone 1 should be developed further to examine its potential efficacy to combat malignancies in a pre-clinical animal model.

3,5-Bis(3-dimethylaminomethyl-4-hydroxybenzylidene)-4-piperidone and related compounds induce glutathione oxidation and mitochondria-mediated cell death in HCT-116 colon cancer cells

This study aims at investigating the cytotoxicity and some of the modes of action of 3,5-bis(3-dimethylamino-4-hydroxybenzylidene)-4-piperidone trihydrochloride 3 and two related compounds 2 (which lacks the dimethylaminomethyl groups) and 4 (which has an additional dimethylaminoethyl substituent in both aryl rings) in order to ascertain the contribution of dimethylaminoethyl substituent to bioactivity. The bioactivities of 2-4 were compared with curcumin 5. Both 2 and 3 displayed submicromolar GI50 values towards HCT-116 cells and were significantly more potent than 4, 5 and 5-fluorouracil (5-FU). All of the compounds displayed greater toxicity towards HCT-116 cells than human CRL-1790 non-malignant colon cells. In HCT-116 cells, the compounds 2, 3 and 5 increased the ratio of oxidised to reduced glutathione and destabilized the mitochondrial membrane potential. Both 2 and 5 produced an increase in mitochondrial superoxide and a burst in intracellular reactive oxygen species in HCT 116 cells. In addition, 2 and 4 stimulated respiration in rat liver mitochondria while 2 and 5 induced mitochondrial swelling. The results suggest that 2 and 5 cause oxidation or cross-linking of the thiols which control the mitochondrial permeability transition.

Novel conjugated unsaturated ketones with submicromolar potencies towards some leukemic and colon cancer cells

BACKGROUND Cancer continues to be the major health burden worldwide. There is an urgent need for the development of novel antineoplastic compounds to treat this devastating condition. Various alkylating anticancer drugs have been employed in the clinic for treating cancers. Unsaturated conjugated ketones are a group of alkylators which are of significant interest as potent antineoplastic agents. OBJECTIVE The goal of this study is to discover unsaturated conjugated ketones which are novel potent cytotoxins displaying growth-inhibitory properties towards neoplasms and also to serve as cytotoxic warheads in drug development. METHODS A variety of 3,5-bis (benzylidene)-4-piperidones 2a-n were synthesized and evaluated against a number of neoplastic cell lines. The short-term neurotoxicity of 2a-k, n was evaluated in mice by i.p. administration using doses level of 30, 100 and 300 mg/kg. Statistical correlations for determining structure-activity relationships were performed using an SPSS software. RESULTS A number of compounds display cytotoxic potencies in the region of 10-7 to 10-8 M and some of the structural features contributing to the cytotoxicity were identified. Compounds 2a-d, 2h demonstrated substantially higher cytotoxic potencies compared to melphalan and 5- fluorouracil against a panel of leukemic and colon cancer cell lines. These lead cytotoxins comply with drug-likeness properties. In general, the antineoplastics 2 are well tolerated in mice using a short-term neurotoxicity screening. CONCLUSION In general, this group of compounds comprises excellent cytotoxic agents, which warrant their further development as cytotoxic warheads.