Dr. Khursheed Ahmad
@nitp.ac.in
Associate Professor Department of Chemistry
National Institute of Technology PATNA
RESEARCH INTERESTS
Coordination Chemistry, Bio-inorganic chemistry.
Scopus Publications
Scopus Publications
N. Noorussabah, Mukesh Choudhary, Achintya Jana, Neeladri Das, B. Mohan, K. Ahmad, S. Sangeeta, S. Bharti, M. K. Mishra, and S. R. Sharma
Informa UK Limited
Abstract In the present investigation, we report the synthesis and characterization of three novel nickel(II) [Ni(L)2] (1) and copper(II) [Cu(L)2] (2a) and [Cu(L)2] (2b) complexes, which are made through the coordination of (E)-1-(2-methoxybenzylidine)-4-phenylethiosemicarbazone (HL) as bidentate N,S-ligand. Several modern techniques including experimental electronic and fluorescence spectroscopy, single-crystal X-ray crystallography, molecular docking and BSA-binding are used to characterize the isolated coordination compounds. X-ray crystallography, FT-IR and UV–visible spectra agree with the observed crystal structures. The crystallographic and spectroscopic studies confirmed that these complexes display four-coordinate square-planar trans-[MN2S2] coordination geometry, whose central metal(II) atom lies on the center of symmetry. Complexes 1 and 2a crystallized in the orthorhombic system of the space group Pbca whereas 2b crystallized in the monoclinic system of P21/c. The binding affinity of complexes towards bovine serum albumin (BSA) was determined by UV–visible and fluorescence spectrophotometric methods. The cytotoxic/antiproliferative potential of the synthesized compounds on human cell lines was also investigated by MTT assay.
Sulakshna Bharti, Mukesh Choudhary, Bharti Mohan, S.P. Rawat, S.R. Sharma, and K. Ahmad
Elsevier BV
Abstract A series of new dimer complexes of copper (II) and nickel (II) were designed and synthesized using the Schiff base ligands which was formed by the condensation of 2-aminothiophenol with 2- methoxybenzaldehyde, 3-formylbenzonitrile and 3-bromo-2-hydroxy-5-nitrobenzaldehyde, respectively. The synthesized metallic complexes were characterized by using different physicochemical and spectroscopic methods. The most plausible geometry for the 1:2 complexes appeared to be distorted square-planar or tetrahedral environments. All the synthesized metal complexes are found to be binuclear and confirmed by elemental analyses, magnetic susceptibility measurements and ESR spectroscopy. The Schiff base ligands (HL1/HL2/H2L) were coordinated to the metal ions through the ONS/SNN and/or N, S donor atoms. In order to prevent the oxidation of the thiol group during the formation of Schiff bases and its complexes, all of the reactions were carried out under an inert atmosphere of argon. The X-ray structures of the Schiff base ligands showed that in the crystalline form the SH groups were oxidized to produce a disulfide Schiff bases as a new double Schiff base ligands (L1a/L2a/H2La). The L1b ligand is a bicyclic ring system of N, S-containing heterocyclic. The crystal structures of the double Schiff bases were determined by single crystal X-ray diffraction. The molar conductivity values of the complexes in DMSO implied the presence of non-electrolyte species. The SOD-like activity of Schiff bases and its complexes were investigated by NBT-DMSO assay and IC50 values were evaluated. Their biological properties have also been studied. These complexes were also tested for their in vitro antibacterial screening activities against three bacteria (Streptococcus aureus, Salmonella typhi, and Escherichia coli) comparing with the Schiff base ligands. Most of the complexes have higher antibacterial activities than those of the free Schiff bases, double Schiff bases and the control.
Sulakshna Bharti, Mukesh Choudhary, Bharti Mohan, S. R. Sharma, and K. Ahmad
Informa UK Limited
Abstract Ni (II) and Cu (II) complexes [Ni(L)2] (1) and [Cu(L)2].H2O (2) was synthesized using a Schiff base (HL) ligand which was formed by 5-bromosalicylaldehyde with 2-methoxybenzeneamine. The crystal structure of the ligand and its complexes were determined through crystal X-ray diffraction. The most plausible geometry for the 1:2 complexes appeared to be distorted octahedral. The TG–DTA analysis of complex (1) and (2) exhibits an exothermic peaks at around 367–393 °C. Their inhibition studies was performed on urease. Complex (1) and (2) can inhibit urease activity, with IC50 values of 2.10 ± 0.06 and 2.10 ± 0.10 µmol L−1, respectively. Their DFT study were also discussed.
S. Sangeeta, K. Ahmad, N. Noorussabah, S. Bharti, M.K. Mishra, S.R. Sharma, and M. Choudhary
Elsevier BV
Abstract [Ni(L)2] 1 and [Cu(L)2] 2 [HL = 2-((E)-(2-methoxyphenylimino)methyl)-4,6-dichlorophenol] Schiff base complexes have been successfully synthesized and were characterized by FT-IR, UV–Vis, fluorescence spectroscopy and thermogravimetric analysis. The crystal structures of the two complexes were determined through X-ray crystallography. Its inhibitory activity against Helicobacter pylori urease was evaluated in vitro and showed strong inhibitory activity against H. pylori urease compared with acetohydroxamic acid (IC50 = 42.12 μmolL−1), which is a positive reference. A docking analysis using the AutoDock 4.0 program could explain the inhibitory activity of the complex against urease.
Sulakshna Bharti, Mukesh Choudhary, Bharti Mohan, S.P. Rawat, S.R. Sharma, and Khursheed Ahmad
Elsevier BV
Abstract Three new copper (II) and nickel (II) complexes viz. [Cu(L)2](1a), [Cu(L)2](1b) and [Ni(L)2].DMF(2), where HL = 2-((E)-(2, 4-dibromophenylimino) methyl)-4-bromophenol, have been synthesized and characterized by using various physico-chemical and spectroscopic techniques. The crystal structures of Schiff base (HL) and their metal complexes (1a), (1b) and (2) were determined by single crystal X-ray diffraction. IR and UV–Vis spectra and magnetic susceptibility measurements agree with the observed crystal structures. The crystallographic and spectroscopic studies confirmed four coordinate environments around the metal (II) ions. The synthesized Schiff base ligand (HL) crystallizes in the orthorhombic system of the space group Pbca. Complex (1a) of HL was crystallized in the monoclinic system of the space group P21/c, a = 10.1712(9) A, b = 10.9299(10) A,c = 12.7684(11) A,α = 90,β = 104.649(2), γ = 90 and Z = 2 whereas complex (1b) and (2) crystallized in the triclinic system of the space group P-1, a = 11.499(5)A, b = 11.598(5)A, c = 12.211(5)A, α = 98.860(5), β = 115.653(5),γ = 100.906(5) and Z = 2 for (1b), a = 9.080(6) A, b = 9.545(8)A, c = 9.545(8)A, α = 101.43(4)o,β = 99.63(3), γ = 117.71(2)o and Z = 1 for (2). The synthesized ligand (HL) was behaved as monobasic bidentate Schiff base ligand having N and O donor sites. The electron paramagnetic resonance spectra indicate a dx2–y2ground state (g|| > g⊥> 2.0023) for (1a) and (1b). Copper (II) complexes display X-band EPR spectra in 100% DMSO and 77 K, giving indicating dx2–y2ground state. Superoxide dismutase-like activities of HL and its complexes were investigated by nitrobluetetrazolium chloride-DMSO assay and IC50 values were evaluated. These complexes were also tested for their in vitro antimicrobial activities against two bacteria (E. coli and Salmonella typhi) and two fungi (Pencillium, Aspergillus sp.) comparing with the Schiff base. The antimicrobial results showed that the complexes were more biologically active compounds to the Schiff base (HL).
S. Sangeeta, K. Ahmad, N. Noorussabah, S. Bharti, M.K. Mishra, S.R. Sharma, and M. Choudhary
Elsevier BV
Abstract Two new Schiff bases 2-((E)-(4-bromo-2-chlorophenylimino)methyl)-4-bromophenol(HL1) and1-((E)-(4-bromo-2-chlorophenylimino)methyl)naphthalene-2-ol (HL2) and their new nickel (II) complexes [Ni(L1)2]·DMF(1) and [Ni(L2)2] (2) have been synthesized and characterized by various physico- chemical and spectroscopic methods. The solid-state structures of synthesized compounds were determined by single crystal X-ray crystallography, which revealed square planar geometry around Ni (II) ion. Infrared spectra, UV–Vis, thermal analysis and magnetic susceptibility measurements agreed with the observed crystal structures. The ligand (HL1) crystallized in the Orthorhombic system of the space group Pbca,a = 7.5485(4)A, b = 11.5514(5) A, c = 30.1370(14)A, α = 90°, β = 90°, γ = 90°and Z = 8. Complex[Ni(L1)2]·DMF(1) crystallized in the Triclinic system of the space group P-1, a = 8.9954(3) A, b = 9.4593(4) A, c = 13.2657(5) A, α = 101.478°, β = 99.595°, γ = 117.651°and Z = 2, whereas complex [Ni(L2)2]·(2) crystallized in the Monoclinic system of the space group P21/c, a = 9.301(9)A, b = 12.149(8)A, c = 13.792(10)A, α = 90°, β = 106.35(4).°, γ = 90°and Z = 2. The Schiff bases (HL1and HL2) behaved as monobasic bidentate ligands possessing N and O donor atoms. The SOD activities of HL1 and its Ni (II) complex[Ni(L1)2]·DMF(1) have been measured using xanthine-xanthine oxidase as a source of superoxide radical and NBT assay as O2− scavenger. In vitro antimicrobial activities of the Ni(II) complexes (1) and (2)against Bacillus cereus and Staphylococcus aureus as Gram + ve and Salmonella typhi, Klebsiella pneumonia and Escherichia coli as Gram-ve species have been investigated comparing with the Schiff base ligands (HL1and HL2).
Siow-Ping Tan, Abdul Manaf Ali, Mohd Azlan Nafiah, Khalijah Awang, and Kartini Ahmad
Elsevier BV
Abstract Six new carbazole alkaloids, murrastanine-A (1), murrastinine-A, -B, -C (2–4), murrayatanine-A (5) and bismahanimboline (6), were isolated from the bark and leaves of Murraya koenigii (Linn.) Spreng along with 24 known carbazole alkaloids. The structure of these compounds were elucidated by extensive spectroscopic analysis. Murrastinine-C (4) and murrayatanine-A (5) exhibited cytotoxic activity against HL-60 and HeLa (CD50
Kartini Ahmad, Siow-Ping Tan, Hazrina Hazni, and Mohd Azlan Nafiah
Penerbit UTM Press
Murraya koenigii, locally known as "kari" tree, was selected for the phytochemical analysis. The extraction and isolation of the carbazole alkaloids from its n-hexane extract of the bark was carried out by using various chromatographic techniques. Three cyclic monoterpenoid pyranocarbazole alkaloids namely, murrayazolinol, murrayakoeninol and bicyclomahanimbine, were isolated. Their structures were determined on the basis of 1D-, 2D-NMR, IR, UV and mass spectrometry, and by comparison with the data from literature.
Mohamad Azmi, Mohd Din, Chin Kee, Munirah Suhaimi, Ang Ping, Kartini Ahmad, Mohd Nafiah, Noel Thomas, Khalit Mohamad, Leong Hoong,et al.
MDPI AG
Resveratrol, a natural stilbene found in grapes and wines exhibits a wide range of pharmacological properties. Resveratrol is also known as a good chemopreventive agent for inhibiting carcinogenesis processes that target kinases, cyclooxygenases, ribonucleotide reductase and DNA polymerases. A total of 19 analogues with an amide moiety were synthesized and the cytotoxic effects of the analogues on a series of human cancer cell lines are reported. Three compounds 6d, 6i and 6n showed potent cytotoxicity against prostate cancer DU-145 (IC50 = 16.68 μM), colon cancer HT-29 (IC50 = 7.51 μM) and breast cancer MCF-7 (IC50 = 21.24 μM), respectively, which are comparable with vinblastine. The resveratrol analogues were synthesized using the Heck method.
Hiroshi Morita, Kartini Ahmad, Yusuke Hirasawa, Alfarius Eko Nugroho, and A. Hamid A. Hadi
Japan Institute of Heterocyclic Chemistry
Yih Yih Kok, Lim Yang Mooi, Kartini Ahmad, Mohd Aspollah Sukari, Nashriyah Mat, Mawardi Rahmani, and Abdul Manaf Ali
MDPI AG
Girinimbine, a carbazole alkaloid isolated from the stem bark of Murraya koenigii was tested for the in vitro anti-tumour promoting and antioxidant activities. Anti-tumour promoting activity was determined by assaying the capability of this compound to inhibit the expression of early antigen of Epstein-Barr virus (EA-EBV) in Raji cells that was induced by the tumour promoter, phorbol 12-myristate 13-acetate. The concentration of this compound that gave an inhibition rate at fifty percent was 6.0 µg/mL and was not cytotoxic to the cells. Immunoblotting analysis of the expression of EA-EBV showed that girinimbine was able to suppress restricted early antigen (EA-R). However, diffused early antigen (EA-D) was partially suppressed when used at 32.0 µg/mL. Girinimbine exhibited a very strong antioxidant activity as compared to α-tocopherol and was able to inhibit superoxide generation in the 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced differentiated premyelocytic HL-60 cells more than 95%, when treated with the compound at 5.3 and 26.3 µg/mL, respectively. However girinimbine failed to scavenge the stable diphenyl picryl hydrazyl (DPPH)-free radical.
Mohd Azlan Nafiah, Mat Ropi Mukhtar, Hanita Omar, Kartini Ahmad, Hiroshi Morita, Marc Litaudon, Khalijah Awang, and A. Hamid A. Hadi
MDPI AG
A phytochemical study of the bark of Alseodaphne perakensis has yielded three aporphine alkaloids: the new compound N-cyanomethylnorboldine (1), and the two known alkaloids N-methyllaurotetanine (2) and norboldine (3). The isolation was achieved by chromatographic techniques and the structural elucidation was performed via spectral methods, notably 1D- and 2D-NMR, UV, IR, and HRFABMS. The vasorelaxation activity of compound 1 has been studied.
Kartini Ahmad, Noel F. Thomas, A. Hamid A. Hadi, Mat Ropi Mukhtar, Khalit Mohamad, Mohd Azlan Nafiah, Koichi Takeya, Hiroshi Morita, Marc Litaudon, Hiroko Arai,et al.
Pharmaceutical Society of Japan
A phytochemical study on the bark of Neisosperma oppositifolia (Apocynaceae) yielded two new beta-carboline indole alkaloids, oppositinines A (1) and B (2), together with five known alkaloids, isoreserpiline, isocarapanaubine, vobasine, 10-methoxydihydrocorynantheol-N-oxide, and ochropposinine oxindole. Structural elucidation of 1 and 2 was performed using 2D NMR methods. Oppositinines A (1) and B (2) showed potent vasorelaxant effects on the rat aorta.
Kartini Ahmad, Noel F. Thomas, Mohd Fadzli Din, Khalijah Awang, and Seik Weng Ng
International Union of Crystallography (IUCr)
In the title compound, C17H17NO2, the phenylene rings are nearly coplanar [dihedral angle 7.3 (1)°]. The acetamido group is twisted out of the plane of the aromatic ring in order to form an N–H...O hydrogen bond to the acetamido group of an adjacent molecule, generating a helical chain running along thebaxis.
Khalit Mohamad, Mahfizah Yusoff, Khalijah Awang, Kartini Ahmad, and Seik Weng Ng
International Union of Crystallography (IUCr)
In the molecule of pinnatane A, C30H48O3, isolated from the bark ofWalsura pinnataHassk, the four cyclohexane rings adopt chair conformations; the carboxyl and hydroxy substituents occupy axial positions. The cyclohexene ring is envelope-shaped. Adjacent molecules are linked by O—H...O hydrogen bonds into a chain running along thecaxis.
Kartini Ahmad, Noel F. Thomas, Mohd Azlan Nafiah, Khalijah Awang, and Seik Weng Ng
International Union of Crystallography (IUCr)
In the title compound, C17H17NO2, the phenylene rings are bent with respect to the carbon–carbon double bond [dihedral angle between rings = 39.6 (1)°]. The acetamido group is twisted out of the plane of the aromatic ring [dihedral angle = 44.2 (1)°] in order to form an N–H...O hydrogen bond to the acetamido group of an adjacent molecule, generating a zigzag chain running along thecaxis.
Kartini Ahmad, Khalijah Awang, Noel F. Thomas, Jean-Frederic Faizal Weber, and Seik Weng Ng
International Union of Crystallography (IUCr)
The C=C double bond in the title substituted stilbene, C18H17Cl2NO3, has a trans arrangement of the aryl substituents. The aromatic ring of the 2-acetylaminophenyl substituent is twisted by 39.9 (3)° with respect to the central C—C=C—C unit and that of the 2,6-dichloro-3,5-dimethoxyphenyl substitutent is twisted by 42.7 (3)°.
Kartini Ahmad, Noel F. Thomas, Mat Ropi Mukhtar, Ibrahim Noorbatcha, Jean-Frederic Faizal Weber, Mohd Azlan Nafiah, Saraswati S. Velu, Koichi Takeya, Hiroshi Morita, Chuan-Gee Lim,et al.
Elsevier BV
Abstract The FeCl3-promoted oxidative cyclization/coupling of acetamidostilbenes possessing 3-methoxy, 4-methoxy and 3,5-methoxy substitutions (21), (22) and (23) is described. Only 3,5-substitution gave rise to novel indolostilbenes, each possessing two stereogenic axes (axially chiral but racemic dimers (39) and (40)). The 4-methoxy substituted acetamidostilbenes, by contrast, yielded the bisindoline dimer (36).
Khalijah Awang, Kartini Ahmad, Noel F. Thomas, Yusuke Hirasawa, Koichi Takeya, Mat Ropi Mukhtar, Khalit Mohamad, and Hiroshi Morita
Japan Institute of Heterocyclic Chemistry
Study on chemical constituents from the leaves of Kopsia singapurensis (Apocynaceae) yielded a new indole alkaloid, singaporentine A (1) together with two known alkaloids, kopsifoline A (2) and kopsininic acid (3). The structure of 1 was elucidated by combination of various spectroscopic methods such as MS, UV, IR, 1D and 2D NMR. Singaporentine A exhibited cytotoxic activity against P388 murine leukemia cells.