Kallikat N. Rajasekharan

Neuroprotective role of curcumin from Curcuma longa on ethanol‐induced brain damage

In the present study, curcumin from Curcuma longa was screened for neuroprotective activity using ethanol as a model of brain injury. Oral administration of curcumin to rats caused a significant reversal in lipid peroxidation, brain lipids and produced enhancement of glutathione, a non‐enzymic antioxidant in ethanol intoxicated rats, revealing that the antioxidative and hypolipidaemic action of curcumin isresponsible for its protective role against ethanol induced brain injury. Copyright

4-Amino-5-benzoyl-2-(4-methoxyphenylamino)thiazole (DAT1): a cytotoxic agent towards cancer cells and a probe for tubulin-microtubule system

1 Microtubule binding drugs are of special interest as they have important roles in the modulation of cellular functions and many of them act as anticancer agents. 4‐Amino‐5‐benzoyl‐2‐(4‐methoxyphenylamino)thiazole (DAT1) was identified as one of the active compounds from a series of diaminoketothiazoles in a cell‐based screening assay to discover cytotoxic compounds. 2 DAT1 shows cytotoxicity with GI50 values ranging from 0.05 to 1 μM in different malignant cell lines with an average value of 0.35 μM. It blocks mitosis in the prometaphase and metaphase stages. In HeLa cells, DAT1 blocks the spindle function by disturbing spindle microtubule and chromosome organization. 3 The drug also inhibits assembly of brain microtubules and binds tubulin specifically at a single site with induction of fluorescence. The dissociation constant of DAT1 binding to tubulin was determined as 2.9±1 μM at 24°C. The binding site of DAT1 on tubulin overlaps with that of the conventional colchicine‐binding site. 4 DAT1 can thus be considered as a lead compound of a new class of small molecules and this study can be used as a step to develop potent antimitotic agents for the control of cytoskeletal functions and cell proliferation. It would also be an interesting probe for the structure–function studies of tubulin–microtubule system.

Suppression of pro-inflammatory and proliferative pathways by diferuloylmethane (curcumin) and its analogues dibenzoylmethane, dibenzoylpropane, and dibenzylideneacetone: role of Michael acceptors and Michael donors

Curcumin, a diferuloylmethane, has been shown to exhibit anti-inflammatory and anti-proliferative activities. Whereas curcumin has both a Michael acceptor and a Michael donor units, its analogues dibenzoylmethane (DBM, a component of licorice) and dibenzoylpropane (DBP) have a Michael donor but not a Michael acceptor unit, and the analogue dibenzylideneacetone (DBA) has a Michael acceptor unit. In the current report, we investigated the potency of DBM, DBP, and DBA in relation to curcumin for their ability to suppress TNF-induced NF-κB activation, NF-κB-regulated gene products, and cell proliferation. We found that all four agents were active in suppressing NF-κB activation; curcumin was most active and DBM was least active. When examined for its ability to inhibit the direct DNA binding activity of p65, a subunit of NF-κB, only DBP inhibited the binding. For inhibition of TNF-induced IKK activation, DBA was most active. For suppression of TNF-induced expression of NF-κB-regulated gene products such as COX-2 (inflammation marker), cyclin D1 (proliferation marker), and VEGF (angiogenesis marker), DBA and curcumin were more active than DBM. Similarly for suppression of proliferation of leukemia (KBM-5), T cell leukemia (Jurkat), prostate (DU145), and breast (MDA-MB-231) cancer cells, curcumin and DBA were most active and DBP was least active. Overall, our results indicate that although curcumin and its analogues exhibit activities to suppress inflammatory pathways and cellular proliferation, a lack of Michael acceptor units in DBM and DBP can reduce their activities.

Curcumin is an inhibitor of calcium/calmodulin dependent protein kinase II

Calcium/calmodulin dependent protein kinase II (CaMKII) is involved in the mechanisms underlying higher order brain functions such as learning and memory. CaMKII participates in pathological glutamate signaling also, since it is activated by calcium influx through the N-methyl-d-aspartate type glutamate receptor (NMDAR). In our attempt to identify phytomodulators of CaMKII, we observed that curcumin, a constituent of turmeric and its analogs inhibit the Ca(2+)-dependent and independent kinase activities of CaMKII. We further report that a heterocyclic analog of curcumin I, (3,5-bis[β-(4-hydroxy-3-methoxyphenyl)ethenyl]pyrazole), named as pyrazole-curcumin, is a more potent inhibitor of CaMKII than curcumin. Microwave assisted, rapid synthesis of curcumin I and its heterocyclic analogues is also reported.

Upregulation of DR5 receptor by the diaminothiazole DAT1 [4-amino-5-benzoyl-2-(4-methoxy phenyl amino) thiazole] triggers an independent extrinsic pathway of apoptosis in colon cancer cells with compromised pro and antiapoptotic proteins

Mitochondria mediated signalling is the more common way of apoptosis induction exhibited by many chemotherapeutic agents in cancer cells. Death receptor mediated signalling for apoptosis in many cells also requires further amplification from the mitochondrial pathway activation through tBid. Thus the potential of most chemotherapeutic agents in tumours with intrinsic apoptosis resistance due to changes in molecules involved in the mitochondrial pathway is limited. Diaminothiazoles were shown earlier to bind to tubulin thereby exhibiting cytotoxicity towards different cancer cells. We observed that the lead diaminothiazole, DAT1 [4-amino-5-benzoyl-2-(4-methoxy phenyl amino) thiazole] could induce apoptosis in the colon cancer cell line HCT116 by both pathways. However, in contrast to many other chemotherapeutic agents, DAT1 triggered apoptosis where the intrinsic pathway was blocked by changing the pro and antiapoptotic proteins. An independent extrinsic pathway activation triggered by the upregulation of DR5 receptor accounted for that. The induction of DR5 occurred in the transcriptional level and the essential role of DR5 was confirmed by the fact that siRNA downregulation of DR5 significantly reduced DAT1 induced apoptosis. HCT116 cells were earlier shown to have a type II response for apoptosis induction where extrinsic pathway was connected to the intrinsic pathway via the mediator protein tBid. Our finding thus indicates that the signalling events in the manifestation of apoptosis depend not only on the cancer cell type, but also on the inducer. Our results also place diaminothiazoles in a promising position in the treatment of tumours with compromised apoptotic factors.

Mechanochemical synthesis of 2,2-difluoro-4, 6-bis(β-styryl)-1,3,2-dioxaborines and their use in cyanide ion sensing

Abstract The conversion of arylaldehydes to 1,7-diaryl-5-hydroxyhepta-1,4,6-trien-3-ones (curcuminoids) and the mechanochemical cyclization of these products to 2,2-difluoro-4,6-bis(β-styryl)-1,3,2-dioxaborines using BF3-Et2O are described. Investigation of the cyanide ion sensing ability of the 2,2-difluoro-4,6-bis(β-styryl)-1,3,2-dioxaborines, in relation to the substituent groups on the aryl ring, showed that a hydroxy susbstituent is required, preferably para to the intervening carbon bridge.

Effect of Curcumin and its Analogue on Lipids in Carbon Tetrachloride-Induced Hepatotoxicity: A Comparative Study

Abstract Curcumin and its analogue (bis.demethoxy curcumin analogue [BDMC-A]) were studied for their possible lipid-lowering properties in carbon tetrachloride (CCl4)-induced hepatotoxicity in rats. Carbon tetrachloride (3 ml kg−1 wk−1) administration to albino Wistar rats increased the levels of hepatic marker enzymes such as aspartate transaminase (AST), alkaline phosphatase (ALP), and γ.-glutamyl transferase (GGT) in the plasma. The levels of lipids cholesterol, triglycerides, and free fatty acids were also increased in plasma and tissues (liver, kidney, heart, and brain). Phospholipid levels increased in plasma, heart, and brain but decreased in liver and kidney. Curcumin (80 mg/kg) and BDMC-A (80 mg/kg) administration to CCl4-treated rats for a period of 3 months significantly decreased the lipid levels. The effect exerted by BDMC-A was more prominent than that of curcumin. Studies on the histopathology of the liver are also in line with the biochemical parameters studied. These observations show the lipid-lowering efficacy of curcumin and its analogue in CCl4-induced hepatotoxicity.

Diaminothiazoles Inhibit Angiogenesis Efficiently by Suppressing Akt Phosphorylation

The prevention of neovessel formation or angiogenesis is a recent popular strategy for limiting and curing cancer. Diaminothiazoles are a class of compounds that have been reported to show promise in the treatment of cancer by inhibiting cancer cell proliferation and inducing apoptosis, because of their effects on microtubules and as inhibitors of cyclin-dependent kinases. Many microtubule-targeting agents are being studied for their antiangiogenic activity, and a few have shown promising activity in the treatment of cancer. Here, we report that diaminothiazoles can be highly effective as antiangiogenic agents, as observed in the chick membrane assay. The lead compound, 4-amino-5-benzoyl-2-(4-methoxyphenylamino)thiazole (DAT1), inhibits endothelial cell processes such as invasion, migration, and tubule formation, which require a functional cytoskeleton. DAT1 also decreases the expression of cell adhesion markers. The antiangiogenic activities of DAT1 occur at concentrations that are not cytotoxic to the normal endothelium. Analysis of intracellular signaling pathways shows that DAT1 inhibits Akt phosphorylation, which is actively involved in the angiogenic process. The antiangiogenic properties of diaminothiazoles, in addition to their promising antimitotic and cytotoxic properties in cancer cell lines, give them an extra advantage in the treatment of cancer.

Synthesis of 2,4-diamino-5-(fur-2-oyl), (thien-2-oyl), and (pyrid-2-oyl)thiazoles

ABSTRACT The synthesis of 5-furoyl-, thienoyl- or pyridoyl-2,4-diaminothiazoles, as the thiazole analogs of the cytotoxic marine alkaloid dendrodoine, is reported. A preliminary study on a tandem bromination-heterocyclization approach, amenable for a combinatorial synthesis of 2,4-diaminothiazoles, is also described.

Mechanochemical Synthesis and Antioxidant Activity of Curcumin-Templated Azoles

A solvent‐free, mechanochemical method for the synthesis of curcumin (1) derived 3,5‐bis(styryl)pyrazoles and 3,5‐bis(styryl)isoxazole (2a–g) at room temperature, with very short reaction time, is reported. Such earlier structural modifications of curcumin, at its β‐diketone unit by transforming it into an isosteric pyrazole or isoxazole unit, required prolonged heating. The evaluation of the antioxidant activity of these compounds, based on DPPH, FRAP, and β‐carotene bleaching assays, showed that several of these azoles are better antioxidants than curcumin, with the isoxazole derivative 2g being overall the best. Typically, the inhibition of 2,2‐diphenyl‐1‐picrylhydrazyl (10−2 mmol), expressed as EC50 values, by curcumin (1), 3,5‐bis(4‐hydroxy‐3‐methoxystyryl)pyrazole (2a), and 3,5‐bis(4‐hydroxy‐3‐methoxystyryl)isoxazole (2g) are 40 ± 0.06, 14 ± 0.18, and 8 ± 0.11 μmol, respectively. Moreover, the reported method is useful in accessing 3,5‐bis(4‐hydroxy‐3‐methoxystyryl)‐1‐phenylpyrazole (2b), which is important in studies related to neuroprotection and Alzheimers disease, and 2a and 2g, which are inhibitors of protein kinases involved in neuronal excitotoxicity.