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• Efficient L-Histidine-based Schiff base derivatives (HKA-1,2 and 3) were synthesized and characterized by spectroscopic techniques like FTIR, 1H NMR, 13C NMR, HRMS, and circular dichroism. • The compounds had potential Microbial-HO enzyme inhibitory activity and were confirmed to be non-competitive inhibitors of microbial-HO's by Lineweaver-Burk plot. • The compounds were found to have antimicrobial activity against the microorganisms tested. • The compounds were confirmed to be non-haemolytic in human erythrocyte model. • The molecular docking studies revealed good G-Score values that support enzyme inhibition study. Amino acid-derived Schiff base complexes had been well explored as antimicrobial agents and the imidazole-based Heme oxygenase (HO) inhibitors were proposed as novel antimicrobial agents with a novel mechanism of action i.e. , inhibition of microbial-HO, an enzyme essential for microbial survival in the human host. In line with this, we have synthesized and characterized three novel L-Histidine-based Schiff base derivatives (HKA-1,2 and 3) as inhibitors of microbial-HO. All the compounds were confirmed to be non-hemolytic and possess microbial-HO inhibitory activity against the microbial-HO's tested. HKA-1 showed good antimicrobial activity against Bacillus subtilis (6.25 µM), Escherichia coli (0.78 µM), Candida albicans (3.125 µM), and Saccharomyces cerevisiae (0.78 µM) whereas HKA-2 and HKA-3 showed good antimicrobial activity against Pseudomonas aeruginosa (3.125 µM) and Staphylococcus aureus (0.78 µM) respectively. According to molecular docking analysis, the HKA-1 with quinoline moiety showed better interaction with all the microbial HO's tested with a Glide Score extending from -9.71 to -5.51 Kcal/Mol whereas HKA-2 and HKA-3 with bi-phenyl moiety showed interaction with certain microbial-HO's with a Glide Score extending from -7.9 to -2.22 Kcal/Mol and -8.49 to -3.14 Kcal/Mol respectively. The formation of hydrogen bonds between ligand-protein interactions confirmed the stability of the complexes and the compounds reported in the present study could be used to treat drug-resistant pathogens. [Display omitted] [ABSTRACT FROM AUTHOR]

• L-Histidine nitrate, Crystal Structure using single crystal X-ray and neutron diffraction. • CSD to retrieve crystal structure of L-histidinium nitrate monohydrate, L-Histidinium dinitrate & DL-histidinium nitrate. • Conformation of L-histindine in L-histidinium nitrate monohydrate is gauche(+) different from other three. • Hirshfeld surface & interaction energies of the structures showed L-histidine nitrate monohydrate has maximum total energy. • Hyperpolarizabilities calculated using MOPAC2009 showed that L-histidine nitrate monohydrate has maximum average β. L-histidine crystallizes in three different crystal structure with nitric acid, i.e. L-histidinium nitrate, L-histidinium nitrate monohydrate and L-Histidinium dinitrate. Also there is DL-histidinium dinitrate. Though the structural aspects of histidinium nitrate monohydrate, L-Histidinium dinitrate and DL -histidinium nitrate are well studied, the structural studies on L-histidinium nitrate is not dealt in detail. Here we have tried to discuss in detail the crystal structure of L-histidinium nitrate using both single crystal X-ray and neutron diffraction. The crystal structure consists one L-histidine molecule which has the amino and imino groups protonated, but the carboxylic acid group is deprotonated. The nitrate ion is in anionic state ie NO3−. The conformation of histidine (N1-C2-C3-C4=64.99°) is gauche (-). Also a comparison of the structure of L-histidinium nitrate with other three available crystal structures retrieved using CSD have been carried out. It was found that L-histidine in L-histidinium nitrate monohydrate adopts gauche (+) conformation and in other three structure it is gauche (-), and L-histidinium nitrate has the lowest volume. Hirshfeld surface and interaction energies analysis of all the above structures were carried out using the x-ray data. L-histidinium nitrate monohydrate shows maximum globuarity. Interaction energy obtained from energy framework showed that L-histidinium nitrate monohydrate has maximum total energy of -41.5(kJ/Mole). The asphericity of our structure L-histidinium nitrate is 0.252 indicating prolate nature unlike the other three complexes. The percentage of H...H contacts is maximum in L-histidinium nitrate which is 27.3%. A comparison of various contacts of histidine between the x-ray and neutron structure of ours shows that the maximum change is reflected in the C...H and H...H contacts with C...H having a higher percentage and H...H having a lower percentage in the neutron structure indicating that the neutron diffraction maps shows the hydrogen bond interaction more accurately. The three complexes, except DL Histidinium dinitrate crystallizes in a non-centrosymmetric space group and hence could exhibit second-order optical non-linear properties, attempts were made to calculate heats of formation, dipole moments (D), polarizabilities (α) and first hyperpolarizabilities (β) using the semi empirical method at the PM6 level using MOPAC2009 and the packing energy as implemented in MERCURY. It was found that the average β of L-histidinium nitrate monohydrate was the highest amongst the three showing that it is more suitable for NLO material. Histidine with nitric acid in different stoichimetric ratio in presence of water crystallizes in above four crystal structures. [Display omitted] [ABSTRACT FROM AUTHOR]

Highlights: [•] A novel double-metal polymer of La(III) and Mo(VI) has been synthesized. [•] L-Histidine was transformed into oxalate via in situ reaction. [•] This polymer exhibits a photoluminescence emission at room temperature. [ABSTRACT FROM AUTHOR]

Abstract: Cu(amino acid) complexes were immobilised on silica gel by covalent anchoring. The amino acids were l-histidine and l-tyrosine and their BOC—(tert-butoxycarbonyl) or methyl ester protected derivatives. To gain control over the synthesis the appropriately protected amino acid was reacted with chloropropylated silica gel first. This modified material as is, or after deprotecting the anchored amino acids, was used in further steps of building the immobilised Cu(II) complex. The covalently grafted complexes were studied by FT-IR spectroscopy and computer modelling. Materials containing protected histidine ligands showed catalase activity (decomposition of H2O2), those containing protected or unprotected tyrosine ligands displayed tyrosinase activity (the decomposed H2O2 oxidised the tyrosine skeleton to a quinoidal structure). [Copyright &y& Elsevier]

Co(II), Ni(II), Cu(II) and Zn(II) complexes of Schiff base ligand (thio-L-his) derived from thiophene-2-carboxaldehyde (thio) with l -histidine (L-his) were synthesised. The thio-L-his and its metal complexes have been optimized and quantum chemical parameters are calculated using density functional theory. Despite several donor sites in the synthesised thio-L-his, the coordination with metal ion occurred through azomethine nitrogen and carboxylate oxygen as evidenced by elemental analyses, fourier transform infrared, mass and nuclear magnetic resonance spectral analysis. The electronic spectral data together with magnetic measurements suggest tetrahedral for Co(II) and Zn(II)-(thio-L-his) and square planar geometries for Ni(II) and Cu(II)-(thio-L-his) complexes, respectively. Molecular docking has been performed to predict the binding energy between thio-L-his and complexes with Epidermal Growth Factor and Cyclooxygenase-2 receptors. The efficiency of metal complexes as promising candidates for the photodegradation of methylene blue has been established in the present study. The comparative in vitro antimicrobial activities against various pathogens with reference to known antibiotics and antioxidant activity against standard control at variable concentrations revealed that the metal complexes show enhanced antimicrobial and free radical scavenging activities as compared to free thio-L-his. In vitro anticancer activity of the Cu(II)-(thio-L-his) was assayed against human ovarian cancer cells, showed that the complex exhibited promising anticancer activity on PA1 cell line. Image 1 • Metal complexes derived from thiophene-2-carboxaldehyde and l -histidine. • NBO confirms ligand to metal electron donation in complexes. • Docking results show the best binding affinity towards EGFR and COX-2 receptor. • Cu(II) complex was found to be most promising anticancer candidate against PA1 cell lines. [ABSTRACT FROM AUTHOR]