K. Anitha

DNA interaction, antimicrobial, antioxidant and anticancer studies on Cu(II) complexes of Luotonin A

Luotonin A (L), a novel natural cytotoxic and anti-inflammatory alkaloid, chelated with copper(II) to improve its cytotoxic effect against the cancer cells. The complexes [Cu(L)H2OCl]Cl (1) and [Cu(L)2]Cl2 (2) are prepared by using copper(II) chloride and L with ligand/metal molar ratio of 1:1 and 2:1 respectively. A solution of complexes 1 &2 are characterized by physical spectroscopic methods using Ultraviolet-visible (UV-Vis) spectrophotometer, Fourier Transform-Infra red (FT-IR) spectroscopy, Electron Para magnetic Resonance Spectroscopy (EPR) and by electrochemical methods. The interaction of these complexes 1 &2 with calf thymus (CT-DNA) have been investigated by physical methods to propose the modes of DNA binding with the complexes 1 &2. Absorption spectral titration studies of complex 1 with CT-DNA shows a red-shift of 5nm with the DNA binding affinity of Kb, 8.65×103M-1, but complex 2does not show any red-shift with binding constant Kb, 7.32×103M-1 reveals that the complex 1 binding with DNA strongly than complex 2 and the binding occurs in between the base pairs of DNA as intercalation. Strong interactions of the two complexes 1 & 2 with CT-DNA have also been confirmed by fluorescence spectral titration studies. The evaluated values of KSV and Kass shows that, the complexes 1 &2 interact with DNA through the intercalation, coincide with other partial intercalators strongly than the free ligand L. Complex 1 exhibits potent antioxidant activity with SC50 value of 23.9±0.69μM is evaluated by DPPH radical scavenging assay and which has potent antimicrobial activity against pathogens than 2 and L. The anticancer activity of L, complexes 1 &2 against human breast cancer cell line (MCF-7) and cervical cancer cell line (HeLa) has also been studied by using fluorescence staining method. The IC50 values of L, complexes 1&2 against MCF-7 and HeLa cell lines with the incubation time intervals of 24hrs are 1 (5.0±0.25, 12.0±0.30μM)<2 (6.5±0.27, 15.0±0.30μM)<L (7.0±0.15, 25.0±0.35μM) respectively. Interestingly, complex 1 exhibits anticancer activity more potent than L against both MCF-7 and HeLa cell lines. The result of anticancer activity studies show that the cytotoxic activity of L against MCF-7 and HeLa cells is increased, when chelated with Cu(II).

Natural alkaloid Luotonin A and its affixed acceptor molecules: Serum albumin binding studies

Effective interaction of natural alkaloid Luotonin A (L) and its affixed acceptor molecules 1 and 2 with donor molecule as Bovine serum albumin (BSA) at various pH (4.0, 7.4 and 10.0) medium have been demonstrated using various conventional spectroscopic techniques. These analyses provide some valuable features on the interaction between BSA and acceptor molecules (L, 1 and 2). From the absorption and fluorescence spectral titration studies, the formation of ground-state complexes between the acceptor molecules (L, 1 and 2) and the BSA have been confirmed. The results of the afore titrations analysis reveal that, the strong binding of receptor 1 with BSA (Kapp 5.68×104M-1; KSV 1.86×106Lmol-1; Ka 6.42×105Lmol-1; Kass 8.09×106M-1; ΔG -33.35kJ/mol) at physiological pH medium (7.4) than other receptor molecules 2 and L. The Förster resonance energy transfer (FRET) efficiency between the tryptophan (Trp) residues of BSA and acceptor molecules L, 1 and 2 during the interaction, are 28.85, 85.24 and 53.25 % respectively. The superior binding efficacy of acceptor 1 at physiological pH condition has been further confirmed by FT-IR and Raman spectral analysis methods. Moreover, theoretical docking studies of acceptors L, 1 and 2 towards HSA have been demonstrated to differentiate their binding behaviours. It reveals that, acceptor 1 has the strongest binding ability with HSA through two hydrogen bonding and the Atomic contact energy (ACE) value of -483.96kcal/mol.

Structural investigation and molecular docking studies of 2-amino-1H-benzimidazolium 2-hydroxybenzoate and 2-amino-1H-benzimidazolium pyridine 2-carboxylate single crystal

The molecular complexes of 2-amino-1H-benzimidazolium 2-hydroxybenzoate (2ABHB) and 2-amino-1H-benzimidazolium pyridine 2-carboxylate (2ABP2C) were synthesised from a donor 2-aminobenzimidazole (2AB), and acceptors, 2-hydroxybenzoate (2HB) and pyridine 2-carboxylic acid (P2C) respectively. The brown colour single crystals were successfully grown by slow evaporation solution growth technique. The densities of grown crystals 2ABHB and 2ABP2C were measured by floatation method using carbon tetrachloride and xylene as solvents. The single crystal X-ray diffraction reveals the molecular structures of compounds 2ABHB and 2ABP2C. Both the structures contain positively charged 2-aminobenzimidazolium cation, 2ABHB contains negatively charged 2-hydroxybenzoate anion and 2ABP2C contains pyridine 2 carboxylic acid anions. 1H and 13C NMR spectral analyses were used to predict the presence of proton and carbon in the title compounds. The FTIR and Raman spectra have been recorded to detect the vibrational modes of functional groups present in the 2ABHB and 2ABP2C compounds. The proton transfer between the cation and anion was confirmed by UV-Vis spectra of both compounds. For both the compounds, thermal behaviour and stability of the crystals were studied using thermogravimetric and differential thermal analyses technique respectively. Further, the anti-bacterial activity of 2ABHB and 2ABP2C complex against Staphylococcus aureus, Klebsiella pneumonia, Pseudomonas eruginos and E. coli pathogens were investigated.

Synthesis, crystal growth and characterization of bioactive material: 2-amino-1H-benzo[d]imidazol-3-ium salicylate single crystal-a proton transfer molecular complex

The 1:1 molecular adducts 2-aminobenzimidazolium salicylate (ABIS) single crystal was synthesized and grown from 2-aminobenzimidazole (ABI) as a donor and salicylic acid (SA) as an acceptor. The cell parameter was determined using single crystal X-Ray diffraction method and the complex ABIS belongs to monoclinic system. The spectroscopic studies showed that ABIS crystal was an ion pair complex. The FTIR and Raman spectra showed that the presence of O-H, C=N, C=O vibration which confirms the proton transfer from SA to ABI. The UV-Vis spectrum exhibited a visible band at 359nm for ABIS due to the salicylate anion of the molecule. Further the antimicrobial activity of ABIS complex against Staphylococcus aureus, klebsiella pneumonia, Pseudomonas eruginos and E.coli pathogens was investigated. So the complex molecule inhibits both Gram positive and Gram negative bacterial. It is found that benzimidazole with aminogroup at position 2 increases the general antimicrobial activities of ABIS crystal.

Growth and characterization of organic 2, 4, 6-triaminopyrimidinium 4-nitrophenolate single crystal

2, 4, 6-Triaminopyrimidinium 4-Nitrophenolate (2, 4, 6-TAPNP) was grown by slow evaporation technique at ambient temperature. The crystal was subjected to single crystal XRD analysis and it was found that the grown crystal has triclinic system. The functional groups present in the (2,4,6-TAPNP) crystal was identified by FT-IR and FT Raman analysis. The optical absorption spectrum shows the absence of absorption between 470 nm and 800 nm. It confirms the suitability of the crystal for NLO applications.

Synthesis and structural study of 4-(2-chlorophenyl)-2-ethoxy-5,6,7,8,9,10-hexahydrocycloocta[B]pyridine-3-carbonitrile

The novel organic material C20H21ClN2O was synthesized by One-Pot synthesis method and the single crystals were grown by slow evaporation solution growth technique. The crystal structure was elucidated by subjecting the grown crystals to the single crystal x-ray diffraction analysis and was refined by full matrix least-squares method to R=0.039 for 2746 reflections. Crystal system of the grown crystal was found to be monoclinic with the space group P21/a and a=9.196(4) A, b=13.449(4) A, c=14.818(4) A, β= 101.542(3)°, V=1795.6(11) A3 and Z=4. In this crystal structure, cyclooctanone prefers to reside in a chair-boat conformation. The structure is stabilized by attractive molecular force such as CH/π interaction called hydrophobic interaction.