Durba Ganguly

Enhancement of anti-leukemic potential of 2-hydroxyphenyl-azo-2′-naphthol (HPAN) on MOLT-4 cells through conjugation with Cu(II)

A Cu(II) complex of 2-hydroxyphenyl-azo-2′-naphthol (HPAN) having the formula CuII(HPAN)2 was characterized by different techniques. When HPAN and CuII(HPAN)2 were incubated for 24 hours with human T-acute lymphoblastic leukemia (MOLT-4) cells, almost no activity was observed for HPAN while the complex was active. When incubated for 48 hours, HPAN showed cell death of ∼35% at a concentration of 40 μM while CuII(HPAN)2 was only slightly better than when incubated for 24 hours. Therefore, irrespective of incubation time, the anti-proliferative activity due to CuII(HPAN)2 was similar. However, increase in incubation time did show increased activity for HPAN. Anti-leukemic potential was confirmed by microscopic analysis of cell viability by trypan blue stain and MTT assay. The BrdU assay further confirmed proliferative effects of aqueous Cu(II)/HPAN and anti-proliferative effects of Cu(II)(HPAN)2. Propidium iodide staining of Cu(II)(HPAN)2-treated MOLT-4 cells confirmed apoptosis. Since amines formed as a consequence of reduction of the azo bond are reported to be cytotoxic, we performed an enzyme assay to understand the relative reduction of the azo bond in both compounds. Results suggest reduction of the azo bond was slightly higher for HPAN. DNA binding of CuII(HPAN)2 using fluorescence spectroscopy was compared with that of HPAN to determine the propensity of biological activity. The results being similar, binding of the compounds with DNA and the ease of reduction of the azo bond were not able to explain why CuII(HPAN)2 was better in preventing cell proliferation. The high anti-proliferative activity of CuII(HPAN)2 was attributed to increased cellular uptake. We designed experiments to support this hypothesis using independent approaches. In one, Cu(II) was identified in cell lysates using ferrocyanide, while, in another, CuII(HPAN)2 was detected using flow cytometry. We chose Cu(II) as the metal ion for this work because of its recognized involvement in cancer. Being essential for angiogenesis, it is found in increased levels in cancer cells. Interaction of Cu(II)(aq) with MOLT-4 cells confirmed this as a part of this study also. Hence, our objective was to see if molecules like HPAN that bind Cu(II) could lead to its role reversal, i.e. from supporting the growth of cancer cells to be able to destroy them as CuII(HPAN)2.

The Water Fraction of Calendula officinalis Hydroethanol Extract Stimulates In Vitro and In Vivo Proliferation of Dermal Fibroblasts in Wound Healing.

The active fraction and/or compounds of Calendula officinalis responsible for wound healing are not known yet. In this work we studied the molecular target of C. officinalis hydroethanol extract (CEE) and its active fraction (water fraction of hydroethanol extract, WCEE) on primary human dermal fibroblasts (HDF). In vivo, CEE or WCEE were topically applied on excisional wounds of BALB/c mice and the rate of wound contraction and immunohistological studies were carried out. We found that CEE and only its WCEE significantly stimulated the proliferation as well as the migration of HDF cells. Also they up‐regulate the expression of connective tissue growth factor (CTGF) and α‐smooth muscle actin (α‐SMA) in vitro. In vivo, CEE or WCEE treated mice groups showed faster wound healing and increased expression of CTGF and α‐SMA compared to placebo control group. The increased expression of both the proteins during granulation phase of wound repair demonstrated the potential role of C. officinalis in wound healing. In addition, HPLC‐ESI MS analysis of the active water fraction revealed the presence of two major compounds, rutin and quercetin‐3‐O‐glucoside. Thus, our results showed that C. officinalis potentiated wound healing by stimulating the expression of CTGF and α‐SMA and further we identified active compounds. Copyright

Synthesis and characterization of 5-amino-2-((3-hydroxy-4-((3-hydroxyphenyl) phenyl) diazenyl) phenol and its Cu(II) complex – a strategy toward developing azo complexes for reduction of cytotoxicity

A major drawback of azo compounds is their associated toxicity, often carcinogenic, which is related to the reduction of the azo bond. This study intends to re-investigate this behavior by studying 5-amino-2-((3-hydroxy-4-((3-hydroxyphenyl) phenyl) diazenyl) phenol (AHPD), a compound containing two azo bonds. Interaction of AHPD and its dimeric Cu(II) complex with bacterial strains Escherichia coli and Staphylococcus aureus revealed the complex was less toxic. Reductive cleavage of the azo bond in AHPD and the complex followed using cytochrome c reductase (a model azo-reductase) as well as azo-reductase enzymes obtained from bacterial cell extracts. Degradation of the azo bond was less in the complex allowing us to correlate the observed cytotoxicity. Cyclic voltammetry on AHPD and the complex support observations of enzyme assay experiments. These were particularly useful in realizing the formation of amines as an outcome of the reductive cleavage of azo bonds in AHPD that could not be identified through an enzyme assay. Results suggest that complex formation of azo compounds could be a means to control the formation of amines responsible for cytotoxicity. Studies carried out on bacterial cells for mere simplicity bear significance for multicellular organisms and could be important for human beings involved with the preparation and utilization of azo dyes.

Molecular diversity in several pyridyl based Cu(II) complexes: biophysical interaction and redox triggered fluorescence switch

Variation of pyridyl based receptors around a Cu(II) center results in structural diversity allowing redox triggered Cu(II)/Cu(I) fluorescence switch for intracellular Cu(I) imaging. Single crystal X-ray structures of 2-hydroxy-6-methylnicotinic acid (L1), its mono nuclear Cu(II) complex, viz. [Cu(L1)2(H2O)(SO4)]·2H2O (C1a), polymeric Cu(II) complex (C1b) and a dinuclear Cu(II) complex of 2-(naphthalen-2-ylmethylsulfanyl)-nicotinic acid (L4), viz. [Cu2(L4)4(H2O)2]·1.12H2O (C4) with a Cu–Cu distance of 2.6028(7) A are reported. Moreover, C1a interacts with calf thymus DNA, which is useful for disruption of normal DNA activity with plausible applications in biology (binding constant, K′ = 1.56 × 104). Chemical or electrochemical reduction of C1a generates a fluorescent Cu(I) complex. The lowest detection limit of L1 for Cu(I) is 50 μM. The association constant of L1 for Cu+ is 7.09 × 102. Quenching constants of Cu(II) for L1, L2, L3 and L4 are 4 × 105, 4.2 × 106, 8.9 × 105 and 4.4 × 106, respectively. The magnetic behavior of C1b indicates a ferromagnetic one-dimensional solid.

Synthesizing a CuII complex of tinidazole to tune the generation of the nitro radical anion in order to strike a balance between efficacy and toxic side effects

A monomeric complex of Cu(II) with tinidazole [Cu(tnz)2Cl2] was synthesized. The complex decreases the formation of the nitro-radical anion (NO2˙−), which was followed by an enzyme assay involving xanthine oxidase, a model nitro-reductase. It has a binding constant value with DNA comparable to that of tinidazole. In addition to the drug efficacy of the nitro radical anion, it also has neurotoxic side effects; so it is essential to control its formation to an optimum, sufficient for bringing about cytotoxic activity on disease causing microbes but avoiding excess that could make it neurotoxic. If this is achieved through modification of the 5-nitroimidazole moiety then too much NO2˙− would not be generated, implying that the chances of the drug causing any harm to the host due to toxic side effects could be reduced. However, with decreased NO2˙− formation, in an effort to decrease complications, a certain amount of therapeutic efficacy would be compromised. Therefore, the biological activity of tinidazole and its modified form, a monomeric complex, was investigated to see how the latter compares with tinidazole under comparable conditions. Studies revealed that, in spite of decreased NO2˙− formation, the complex showed similar activity to that of tinidazole on two bacterial strains and an amoeba strain, implying that it has other attributes, not known for 5-nitroimidazoles, that enable it to match the efficacy of tinidazole. The study suggests that there is a substantial decrease in NO2˙− due to the formation of the tinidazole complex, meaning that the toxic side effects are likely to be reduced which is an advantage as it would improve the therapeutic index.

Correction: The biological in vitro effect and selectivity shown by a CoII complex of 2-(2-hydroxyphenylazo)-indole-3′-acetic acid on three distinctly different cancer cells

A major intention of this study was to use the modified toxicity of the azo moiety in [2-(2-hydroxyphenylazo)-1H-indol-3-yl]-acetic acid (HPIA), achieved through complex formation with CoII on some cancer cell lines. This is important because the azo functional group has not been tried in cancer chemotherapy. Keeping in mind aspects of drug resistance of some of the common anticancer drugs, a serious problem and a major clinical challenge in cancer chemotherapy, it is essential that new molecules are identified with anticancer activity. Although cytotoxicity of azo compounds is established there are not many reports that utilize them in cancer treatment. Another important aspect is to prepare compounds having preferential activity on cancer cells over normal cells so that toxic side effects are a minimum. Enzyme assay on the reductive cleavage of the azo bond showed complex formation with CoII almost completely checked the generation of cytotoxic amines implying that the complex could be less cytotoxic which was actually observed in case of normal healthy cells. Even though the complex formed less cytotoxic amines and possessed an almost similar binding ability with DNA like that of HPIA surprisingly its activity on three cancer cell lines namely human colon carcinoma HCT116 cells, acute lymphoblastic leukemia MOLT-4 cells and MCF-7 breast cancer cells was much greater than HPIA. The difference in activity between HPIA and its CoII complex on cancer cells showed no correlation with DNA binding or amine formation like that observed for normal cells. The complex probably possesses multiple modes of action whereby it is able to inhibit one or more cellular processes or functioning of different enzymes involved in the cell cycle of cancer cells for which it was found more effective.

Modification of the toxicity of an azo compound through complex formation help target bacterial strains

The antibacterial efficacy of a Cu(II) complex of

A study on the formation of the nitro radical anion by ornidazole and its significant decrease in a structurally characterized binuclear Cu(II)-complex: impact in biology

\hbox {2-hydroxyphenyl-azo-2}^{\prime }\hbox {-naphthol}