Antioxidant and antiproliferative activity of curcumin semicarbazone

A new semicarbazone derivative of curcumin (CRSC) was synthesized and examined for its antioxidant, antiproliferative, and antiradical activity and compared with those of curcumin (CR). The antioxidant activity was tested by their ability to inhibit radiation induced lipid peroxidation in rat liver microsomes. The antiproliferative activity was tested by studying the in vitro activity of CRSC against estrogen dependant breast cancer cell line MCF-7. Kinetics of reaction of (2,2'-diphenyl-1-picrylhydrazide) DPPH, a stable hydrogen abstracting free radical was studied to measure the antiradical activity using stopped-flow spectrophotometer. Finally one-electron oxidized radicals of CRSC were generated and characterized by pulse radiolysis. The results suggest that the probable site of attack for CRSC is both the phenolic OH and the imine carbonyl position. CRSC shows efficient antioxidant and antiproliferative activity although its antiradical activity is less than that of CR.     

Evaluation of a new copper(II)-curcumin complex as superoxide dismutase mimic and its free radical reactions

A mononuclear (1:1) copper complex of curcumin, a phytochemical from turmeric, was synthesized and examined for its superoxide dismutase (SOD) activity. The complex was characterized by elemental analysis, IR, NMR, UV-VIS, EPR, mass spectroscopic methods and TG-DTA, from which it was found that a copper atom is coordinated through the keto-enol group of curcumin along with one acetate group and one water molecule. Cyclic voltammetric studies of the complex showed a reversible Cu(2+)/Cu(+) couple with a potential of 0.402 V vs NHE. The Cu(II)-curcumin complex is soluble in lipids and DMSO, and insoluble in water. It scavenges superoxide radicals with a rate constant of 1.97 x 10(5) M(-1) s(-1) in DMSO determined by stopped-flow spectrometer. Subsequent to the reaction with superoxide radicals, the complex was found to be regenerated completely, indicating catalytic activity in neutralizing superoxide radicals. Complete regeneration of the complex was observed, even when the stoichiometry of superoxide radicals was 10 times more than that of the complex. This was further confirmed by EPR monitoring of superoxide radicals. The SOD mimicking activity of the complex was determined by xanthine/xanthine oxidase assay, from which it has been found that 5 microg of the complex is equivalent to 1 unit of SOD. The complex inhibits radiation-induced lipid peroxidation and shows radical-scavenging ability. It reacts with DPPH radicals with rate constant 10 times less than that of curcumin. Pulse radiolysis-induced one-electron oxidation of the complex by azide radicals in TX-100 micellar solutions produced strongly absorbing ( approximately 500 nm) phenoxyl radicals, indicating that the phenolic moiety of curcumin remained intact on complexation with copper. The results confirm that the new Cu(II)-curcumin complex possesses SOD activity, free radical neutralizing ability, and antioxidant potential. Quantum chemical calculations with density functional theory have been performed to support the experimental observations.     

Antibacterial property of the antipsychotic agent prochlorperazine, and its synergism with methdilazine

The antipsychotic drug prochlorperazine was screened in vitro for possible antimicrobial property against 157 strains of bacteria, belonging to gram positive and gram negative genera. The minimum inhibitory concentration (MIC) of prochlorperazine was determined by agar dilution method, which ranged from 25 to 200 microg/ml with respect to most of the strains. Based on such findings, a further study was undertaken to determine whether the efficacy of this drug could be enhanced in the presence of an antihistaminic agent methdilazine, reported to have remarkable antimicrobial action. Four bacterial strains, sensitive to prochlorperazine as well as to three antibacterial chemotherapeutics, viz., methdilazine, fluphenazine and thioridazine were chosen. Disc diffusion tests with prochlorperazine and methdilazine revealed marked synergism between the combination, compared to their individual effects. The synergism was found to be statistically significant (p<0.01). To assess the degree of synergism, the checkerboard analysis was performed. The FIC index of this combination turned out to be 0.37, which confirmed synergism. Therefore, this synergistic drug combination might open a new therapeutic approach to combat drug-resistance in bacterial infections.     

Pathways in the degradation of hydrolyzed alcohols of butyl benzyl phthalate in metabolically diverse Gordonia sp. strain MTCC 4818

In the present study, the metabolic pathways involved in the degradation of benzyl alcohol and 1-butanol, the hydrolyzed products of butyl benzyl phthalate, were investigated by the Gordonia sp. strain MTCC 4818. The strain can utilize both benzyl alcohol and 1-butanol individually as sole carbon sources, where benzyl alcohol was found to be metabolized via benzaldehyde, benzoic acid and catechol, which was further degraded by ortho-cleavage dioxygenase to cis,cis-muconic acid and subsequently to muconolactone leading to tricarboxylic acid cycle. On the other hand, 1-butanol was metabolized via butyraldehyde and butyric acid, which was channeled into the tricarboxylic acid cycle via the beta-oxidation pathway. Numbers of dehydrogenases, both NAD+-dependent and NAD+-independent, were found to be involved in the degradation of benzyl alcohol and 1-butanol, where several dehydrogenases exhibited relaxed substrate specificity. Both 2,3- and 3,4-dihydroxybenzoic acids were utilized by the test organism for growth and metabolized by the ortho-cleavage pathway by the cell-free extract of benzoate-grown cells, similar to catechol, suggesting possible broad substrate specificity of the ring cleavage dioxygenase. Moreover, the test organism can utilize various primary and secondary alcohols, aliphatic aldehydes and acids in the C2-C5 range besides n-hexadecane, 1,4-butanediol and cyclohexanol individually as the sole carbon sources indicating metabolic diversity in the Gordonia sp. strain MTCC 4818.     

Degradation of Cdt1 during S phase is Skp2-independent and is required for efficient progression of mammalian cells through S phase

Previous reports have shown that the N terminus of Cdt1 is required for its degradation during S phase (Li, X., Zhao, Q., Liao, R., Sun, P., and Wu, X. (2003) J. Biol. Chem. 278, 30854-30858; Nishitani, H., Lygerou, Z., and Nishimoto, T. (2004) J. Biol. Chem. 279, 30807-30816). The stabilization was attributed to deletion of the cyclin binding motif (Cy motif), which is required for its phosphorylation by cyclin-dependent kinases. Phosphorylated Cdt1 is subsequently recognized by the F-box protein Skp2 and targeted for proteasomal mediated degradation. Using phosphopeptide mapping and mutagenesis studies, we found that threonine 29 within the N terminus of Cdt1 is phosphorylated by Cdk2 and required for interaction with Skp2. However, threonine 29 and the Cy motif are not necessary for proteolysis of Cdt1 during S phase. Mutants of Cdt1 that do not stably associate with Skp2 or cyclins are still degraded in S phase to the same extent as wild type Cdt1, indicating that other determinants within the N terminus of Cdt1 are required for degrading Cdt1. We localized the region necessary for Cdt1 degradation to the first 32 residues. Overexpression of stable forms of Cdt1 significantly delayed entry into and completion of S phase, suggesting that failure to degrade Cdt1 prevents normal progression through S phase. In contrast, Cdt1 mutants that fail to interact with Skp2 and cyclins progress through S phase with similar kinetics as wild type Cdt1 but stimulate the re-replication caused by overexpressing Cdt1. Therefore, a Skp2-independent pathway that requires the N-terminal 32 residues of Cdt1 is critical for the degradation of Cdt1 in S phase, and this degradation is necessary for the optimum progression of cells through S phase.     

Interaction and structural study of kinin peptide bradykinin and ganglioside monosialylated 1 micelle

Partitioning of small proteins and peptides from the aqueous to membrane phase is often coupled with folding. In this work we examine the binding and folding of the kinin peptide, bradykinin (BK), in the presence of the ganglioside monosialylated 1 (GM1) micelle. Using two-dimensional NMR techniques, we have shown that at low concentration, GM1 micelle is able to induce a turn conformation to BK. A pulsed-field gradient diffusion NMR study indicated that the peptide partitions into the GM1 micelle with a DeltaG(part) of -3.14 +/- 0.03 kcal/mol. A saturation transfer difference (STD) NMR study indicated that the binding is mostly through hydrophobic residues.     

Histology of vitamin A induced ectopic limbs and normal hind limbs in tadpoles of Polypedates maculatus

Marked histological similarities were observed between normal and vitamin A induced ectopic limb buds of P. maculatus. However, close association of nephric tubule and lateral plate mesoderm, as seen in normal hind limb bud does not seem to be essential for ectopic limb development. The ectopic limbs tend to develop in pairs.     

Dynamic influences on a high-affinity, high-specificity interaction involving the C-terminal SH3 domain of p67phox

An analysis of the backbone dynamics of the C-terminal Src homology 3 (SH3) domain of p67(phox), p67(phox)SH3(C), in complex with a 32-residue high-affinity (K(d) = 24 nM) peptide, Pf, from the C-terminal region of p47(phox) is presented. This paper represents the first detailed analysis of the backbone dynamics and the ligand-induced changes therein of a high-affinity, high-specificity interaction involving an SH3 domain. The dynamic features are compared with those in the high-affinity, highly specific interaction between the SH3 domain of C-terminal Src kinase (Csk-SH3) and a proline-rich peptide from proline-enriched phosphatase (PEP). Both systems share common dynamic features especially in the canonical PxxP motif recognition surface where slow micro- to millisecond time scale dynamics persist on complex formation especially in several residues that are implicated in ligand recognition and in stabilizing the SH3 fold. These residues are highly conserved in SH3 domains. Ile505, which lies outside the PxxP recognition motif on p67(phox)SH3(C) and is key in conferring high specificity to the p67(phox)SH3(C)/Pf interaction, becomes more disordered upon complex formation. This behavior is similar to that seen in the residues that constitute the specificity surface in Csk-SH3.