Mino R. Caira

University of Cape Town, Kaapstad, Western Cape, South Africa

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Publications (294)543.72 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The phytoalexin trans-resveratrol, 5-[(1E)-2-(4-hydroxyphenyl)ethenyl]-1,3-benzenediol, is a well-known, potent antioxidant having a variety of possible biomedical applications. However, its adverse physicochemical properties (low stability, poor aqueous solubility) limit such applications and its inclusion in cyclodextrins (CDs) has potential for addressing these shortcomings. Here, various methods of the attempted synthesis of inclusion complexes between trans-resveratrol and three methylated cyclodextrins (permethylated α-CD, permethylated β-CD and 2,6-dimethylated β-CD) are described. Isolation of the corresponding crystalline 1:1 inclusion compounds enabled their full structure determination by X-ray analysis for the first time, revealing a variety of guest inclusion modes and unique supramolecular crystal packing motifs. The three crystalline inclusion complexes were also fully characterized by thermal analysis (hot stage microscopy, thermogravimetric analysis and differential scanning calorimetry). To complement the solid-state data, phase-solubility studies were conducted using a series of CDs (native and variously derivatised) to establish their effect on the aqueous solubility of trans-resveratrol and to estimate association constants for complex formation.
    Beilstein Journal of Organic Chemistry 12/2014; 10:3136-51. DOI:10.3762/bjoc.10.331 · 2.80 Impact Factor
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    ABSTRACT: 7,8,9,10-Tetrahydropyrrolo[2,1-a]isoquinolines were obtained by 1,3-dipolar cycloaddition reactions of their corresponding N-ylides with olefinic (acrylonitrile) and symmetrical or non-symmetrical acetylenic dipolarophiles (methyl/ethyl propiolate, dimethyl acetylenedicarboxylate). Also, stable 5,6,7,8-tetrahydroisoquinolinium dicyanomethylide was isolated and characterized by X-ray diffraction analysis.
    Tetrahedron Letters 10/2014; 55(41):5635–5638. · 2.39 Impact Factor
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    ABSTRACT: 3- and 4-Methylcyclohexanone have been isolated exclusively as their energetically disfavoured axial conformers in the host-guest complexes formed upon recrystallization of the novel optically pure host compound, (+)-(2R,3R)-1,1,4,4-tetraphenylbutane-1,2,3,4-tetraol (TETROL), from these cycloalkanones.
    Chemical Communications 09/2014; 50:13353-13355. DOI:10.1039/c4cc06826b · 6.72 Impact Factor
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    ABSTRACT: 7,8,9,10-Tetrahydropyrrolo[2,1-a]isoquinolines were obtained by 1,3-dipolar cycloaddition reactions of their corresponding N-ylides with olefinic (acrylonitrile) and symmetrical or non-symmetrical acetylenic dipolarophiles (methyl/ethyl propiolate, dimethyl acetylenedicarboxylate). Also, stable 5,6,7,8-tetrahydroisoquinolinium dicyanomethylide was isolated and characterized by X-ray diffraction analysis.
    Tetrahedron Letters 09/2014; 55(41):5635–5638. DOI:10.1016/j.tetlet.2014.08.054 · 2.39 Impact Factor
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    ABSTRACT: 3-(6-Methoxypyridin-3-yl)-5-(4-methylsulfonyl phenyl)-pyridin-2-amine (MMP) is a member of a novel class of orally active antimalarial drugs. This aminopyridine molecule has shown potent in vitro antiplasmodial activity and in vivo antimalarial activity in Plasmodium berghei-infected mice. The aqueous solubility of this molecule is, however, limited. Thus investigations aimed at improving the physicochemical properties, including solubility, of MMP were accordingly conducted. Five salts of MMP were formed with co-former molecules saccharin, salicylic acid, fumaric acid, oxalic acid and suberic acid, but a cocrystal was obtained when the co-former adipic acid was employed. All these new multicomponent systems have been fully characterised using X-ray diffraction and thermal methods. Semiquantitative, turbidimetric solubility tests in a phosphate-buffered saline solution at a pH of 7.4 were performed on the salts and the cocrystal of MMP. The saccharinate salt, fumarate salt and the cocrystal of MMP proved to have greater solubility than MMP itself. This work illustrates the importance of screening and modifying candidate drug compounds in their preliminary stages of development.
    CrystEngComm 06/2014; 2014(16):5781-5792. DOI:10.1039/C3CE41798K · 3.86 Impact Factor
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    ABSTRACT: In this article we present a detailed structural investigation of novel polycyclic pentacyclo[5.4.1.0(2,6).0(3,10).0(5,9)]undecane and adamantane propargylamine hybrid molecules. The structural characterization of these compounds was performed using MS, FT-IR and NMR spectroscopy in combination with X-ray diffraction analysis. The single crystal X-ray analyses of four synthons (6, 8-10) are presented; 8-(N)-propargylamino-8,11-oxapentacyclo-[5.4.1.0(2,6).0(3,10).0(5.9)]undecane (compound 6 crystallized in the monoclinic system, unit cell parameters: a = 20.737(2) angstrom; b = 8.127(1) angstrom; c = 12.606 (1) ; beta = 92.360(2)degrees; V = 2122.8(3) angstrom(3); Z = 8); 11-hydroxy-(N)-propargyl-8,11-azapentacyclo[5.4.1.0(2,6).0(3,10).0(5.9)]undecane (compound 8 crystallized in the monoclinic system, unit cell parameters: a = 7.9624(6) angstrom; b = 14.9332(6) angstrom; c = 9.6162(7) angstrom; beta = 109.029(3); V = 1080.9(2) angstrom(3); Z = 4); 1-methyl-11-hydroxy-(N)-propargyl-8,11-azapentacyclo[5.4.1.0(2,6).0(3,10).0(5.9)]undecane (compound 9 crystallized in the monoclinic system, unit cell parameters: a = 7.732(1) angstrom; b = 15.148(2) angstrom; c = 9.864(1) ; beta = 101.728(3)angstrom; V = 1131.3 (2) angstrom(3); Z = 4); and an adamantane derivative, N,N-dipropargyl-adamantan-1-amine (compound 10 crystallized in the orthorhombic system, unit cell parameters: a = 34.098(4) angstrom; b = 6.825(1) angstrom; c = 10.979(1) angstrom; V = 2555.0(5) angstrom(3); Z = 8). From the X-ray analyses it is clear that the polycyclic structures had different modes of intermolecular interaction and molecular stacking. Compound 9 exhibited a cis configuration between the OH and CH3 moieties as expected in view of potential steric hindrance and the electron density effects of the methyl moiety on the initial amination reaction. These hybrid molecules exhibited significant anti-apoptotic activity and could thus find application as neuroprotective agents.
    Journal of Chemical Crystallography 04/2014; 44(4). DOI:10.1007/s10870-014-0501-y · 0.48 Impact Factor
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    ABSTRACT: Thermogravimetric and differential scanning calorimetric traces were recorded for several crystalline hydrated cyclodextrin complexes containing drug substances (salts of diclofenac, meclofenamate sodium, (L)-menthol) as guests. It was possible to reconcile observed thermal events for complex dehydration with three dimensional hydration patterns deduced from available X-ray crystal structures of the complexes. For complexes containing drug salts, strong retention of water molecules is attributed to their coordination to metal ions.
    Journal of Thermal Analysis and Calorimetry 03/2014; 51(3):981-991. DOI:10.1007/BF03341478 · 2.21 Impact Factor
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    ABSTRACT: 7,8,9,10-Tetrahydropyrrolo[2,1-a]isoquinolines were obtained by 1,3-dipolar cycloaddition reactions of their corresponding N-ylides with olefinic (acrylonitrile) and symmetrical or non-symmetrical acetylenic dipolarophiles (methyl/ethyl propiolate, dimethyl acetylenedicarboxylate). Also, stable 5,6,7,8-tetrahydroisoquinolinium dicyanomethylide was isolated and characterized by X-ray diffraction analysis.
    Tetrahedron Letters 01/2014; 55(41):5635–5638. · 2.39 Impact Factor
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    ABSTRACT: The identification and application of (+)-(2R,3R)-1,1,4,4-tetraphenylbutane-1,2,3,4-tetrol (TETROL) as an efficient and selective host compound is described. Computational and single crystal X-ray diffraction analyses revealed that the butane backbone of TETROL adopts a relatively rigid anti-conformation, with the hydroxy groups oriented syn and connected through a cyclic, homodromic arrangement of their O-H bonds. This structure is stabilised through a pair of 1,3-hydrogen bonding interactions. TETROL forms inclusion complexes with pyridine and 3- and 4-methylpyridine, and does so selectively from mixtures of the pyridines. X-ray diffraction (single crystal and powder) and thermal analyses of the inclusion compounds are described.
    Tetrahedron 10/2013; 69(41):8713. DOI:10.1016/j.tet.2013.07.094 · 2.82 Impact Factor
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    ABSTRACT: Screening for new solid forms of the antihypertensive lisinopril was performed by recrystallization of the commercial form, lisinopril dihydrate, from various solvents and by exposing the product of its dehydration to a series of vapors under controlled conditions. Modifications other than the dihydrate encountered in the study included new anhydrous and amorphous forms, with intrinsic dissolution rates significantly greater than that of the dihydrate. Further physicochemical characterization included constant and programmed temperature powder X-ray diffraction, differential scanning calorimetry, thermogravimetry, and Fourier transform infrared spectroscopy. In the course of this study, the single-crystal X-ray structure of lisinopril dihydrate, [a = 14.550(2), b = 5.8917(8), c = 14.238(2) Å, β = 112.832(3)° at T = 173(2) K, space group P21 , Z = 2], was determined for the first time, revealing its double zwitterionic character in the solid state. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci.
    Journal of Pharmaceutical Sciences 10/2013; 102(10). DOI:10.1002/jps.23660 · 3.01 Impact Factor
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    ABSTRACT: The interaction in the solid state between ciprofloxacin (CIP) and norfloxacin (NOR) was investigated and a new multicomponent molecular complex (COP) was obtained and characterized. It is composed of equimolar quantities of both compounds, according to TLC and 1H NMR data. As single-crystal X-ray analysis showed, COP crystallizes in the triclinic system, space group P(1̅). The asymmetric unit comprises three independent zwitterions (A, B, and C) with contributions of both CIP and NOR, as well as 14.6 water molecules. At the zwitterion A site, the occurrence is about 37% (CIP), 63% (NOR); at the B site, there is predominantly CIP (70%); and at the C site the occurrence is about 43% (CIP) and 57% (NOR), yielding an overall 1:1 CIP-NOR ratio in the crystal. TG data evidenced a one-step loss of solvent (about 18% per COP zwitterion) below 110 °C, confirming the presence of water molecules. The propensity for heteroassociation between CIP and NOR, under the conditions described herein, originated a co-crystal reported for the first time between FQs, and became one of the most interesting aspects of this research.
    Crystal Growth & Design 03/2013; 13(3). DOI:10.1021/cg301299e · 4.56 Impact Factor
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    ABSTRACT: Tizoxanide [2-(hydroxy)-N-(5-nitro-2-thiazolyl)benzamide, TIZ] is a new potent anti-infective agent which may enhance current therapies for leishmaniasis, Chagas disease and viral hepatitis. The aim of this study was to identify the conformational preferences that may be related to the biological activity of TIZ by resolving its crystal structure and characterizing various physicochemical properties, including its experimental vibrational and 13C nuclear magnetic resonance properties, behavior on heating and solubility in several solvents at 25 °C. TIZ crystallizes from dimethylformamide as the carboxamide tautomer in the triclinic system, space group P(−1) (No. 2) with the following unit cell parameters at 173(2) K: a = 5.4110(3) Å, b = 7.3315(6) Å, c = 13.5293(9) Å, α = 97.528(3), β = 95.390(4), γ = 97.316(5), V = 524.41(6) Å3, Z = 2, Dc = 1.680 g/cm3, R1 = 0.0482 and wR2 = 0.0911 for 2374 reflections. This modification of TIZ has a ‘graphitic’ structure and is composed of tightly packed layers of extensively hydrogen-bonded molecules. The various spectroscopic data [Diffuse Fourier transform infrared (DRIFT) and FT-Raman, recorded in the range 3600–500 and 4000–200 cm−1 respectively, and solid-state 13C NMR] were consistent with the structure determined by X-ray crystallography. From DSC, TG and thermomicroscopy, it was concluded that TIZ is thermally stable as a solid and that melting is not an isolated event from the one-step thermal decomposition that it undergoes above 270 °C. This modification of TIZ is practically insoluble in water and slightly soluble in polar aprotic solvents such as dimethylsulfoxide, dimethylformamide and dioxane.
    Journal of Molecular Structure 03/2013; 1036:318–325. DOI:10.1016/j.molstruc.2012.12.004 · 1.60 Impact Factor
  • Mino R. Caira
    ChemInform 02/2013; 44(8). DOI:10.1002/chin.201308247
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    ABSTRACT: A series of oligomeric lactones, namely tetra- and hexasalicylides 1 and 2, was synthesized from various halogenated salicylic acids by a cyclocondensation reaction using POCl3. The clathrate inclusion properties of the macrocycles for some organic solvents were investigated. X-ray structures of several representative clathrates in this series were determined and the results were used to explain various features of their thermal desolvation. Halogen bonding (in particular C–I⋯OC) was found to play a significant role in the thermal stabilization of these crystalline clathrates.
    Tetrahedron 01/2013; 69(3):1120–1127. DOI:10.1016/j.tet.2012.11.057 · 2.82 Impact Factor
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    ABSTRACT: Naphthoquinones have been found to have a wide range of biological activities, including cytotoxicity to cancer cells. The secondary metabolites lapachol, α- and β-lapachone and a series of 25 related synthetic 1,4-naphthoquinones were screened against the oesophageal cancer cell line (WHCO1). Most of the compounds exhibited enhanced cytotoxicity (IC(50) 1.6-11.7 μM) compared to the current drug of choice cisplatin (IC(50) = 16.5 μM). This study also established that the two new synthetic halogenated compounds 12a and 16a (IC(50) = 3.0 and 7.3 μM) and the previously reported compound 11a (IC(50) = 3.9 μM), were non-toxic to NIH3T3 normal fibroblast cells. Cell death of oesophageal cancer cells by processes involving PARP cleavage caused by 11a was shown to be associated with elevated c-Jun levels, suggesting a role for this pathway in the mechanism of action of this cohort of naphthoquinone compounds.
    European Journal of Medicinal Chemistry 01/2013; 62C:98-110. DOI:10.1016/j.ejmech.2012.12.048 · 3.43 Impact Factor
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    ABSTRACT: The hydrolysis reaction of fenitrothion was studied in water containing 2% dioxane and in the presence of native cyclodextrins (α-, β- and γ-CD) and two commercially available modified derivatives, namely, permethylated β- and α-cyclodextrin (TRIMEB and TRIMEA, respectively). The kinetics of the reaction in the presence of TRIMEA could not be measured because the complex formed is insoluble and precipitated even at low concentration. On the other hand, the reaction is only weakly affected by the presence of α-CD. The hydrolysis reaction is inhibited by all the other cyclodextrins. From the kinetic data the association equilibrium constants for the formation of the 1:1 inclusion complexes were determined as 417, 511 and 99M−1 for β-CD, TRIMEB and γ-CD, respectively. Despite the differences in the association constants for β- and γ-CD, the observed inhibition effect is about the same and this is due to the fact that the rate of hydrolysis in the cavity of γ-CD is smaller than that in the cavity of β-CD. The strongest inhibitor is TRIMEB and this result is consistent with the known structure of the complex in the solid state.
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    ABSTRACT: An anhydrous 1:1 crystalline inclusion complex between the organophosphorus insecticide fenitrothion [O,O-dimethyl O-(3-methyl-4-nitrophenyl)phosphorothioate] and the host compound heptakis(2,6-di-O-methyl)-β-cyclodextrin (DIMEB) was prepared and its structure elucidated by single-crystal X-ray diffraction. This revealed two independent host molecules in the asymmetric unit. In one of these, the cavity is occupied by two disordered guest components (distinguishable as rotamers with respect to the P-OAr bond) while in the other, three distinct guest components with site-occupancies 0.44, 0.29 and 0.27 appear, the last having a reversed orientation relative to all the other components. Kinetic studies of the alkaline hydrolysis of fenitrothion in the presence of DIMEB showed a remarkable reduction of 84% in the rate of this reaction relative to that for the free substrate, a value exceeding those previously attained with the native hosts, β- and γ-cyclodextrin, and fully methylated β-cyclodextrin.
    Beilstein Journal of Organic Chemistry 01/2013; 9:106-17. DOI:10.3762/bjoc.9.14 · 2.80 Impact Factor
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    ABSTRACT: This book is a critical and lucid account of various synthetic methodologies and biological activities of different sized bioactive heterocyclic compounds. In effect, this book imparts a great deal of comprehensive reviews about the chemistry and biology of selected groups of heterocycles and natural products including important pharmaceuticals as well as agrochemical pesticides in one handy project. Besides, this compendious effort encompasses different methods of synthesis and biological evaluation of heterocyclic compounds. The main purpose of this book is to share the recent advances and scope of Bioactive Heterocycles for the future avenues in the field. It has specifically been designed by keeping in mind the wide interests of individuals engaged in the design and synthesis of biologically active heterocyclic compounds as well as research scientists in academia and industry. The authors expect this book to be a standard reference in Universities and industrial libraries.
    Bioactive Heterocycles: Synthesis and Biological Evaluation, Edited by K. L. Ameta, R. P. Pawar, A. J. Domb, 12/2012: chapter Chapter 2. Pyrrolo[1,2-a]quinolines: Synthesis and biological activity: pages 19-40; Nova Science Publishers., ISBN: 978-1-62257-636-4
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    ABSTRACT: Endosulfan is a highly toxic insecticide used in several countries and known to be relatively persistent in the environment. This recently banned agrochemical is capable of forming solid-state inclusion complexes with both native and derivatised cyclodextrins (CDs). Differential scanning calorimetry and powder X-ray diffraction (PXRD) techniques were used to confirm complexation of β-CD, γ-CD and randomly methylated β-CD (RAMEB) with the technical 7α:3β isomeric sample of endosulfan. The PXRD traces obtained for the inclusion complexes of the native CDs (β-CD and γ-CD) with endosulfan match those of other isostructural CD inclusion complexes. The single crystal X-ray structure of the complex formed between heptakis(2,6-di-O-methyl)-β-CD (DIMEB) and the β-endosulfan isomer is presented and shown to have a novel packing arrangement. The implications of the encapsulation of endosulfan in CDs are discussed with reference to the potential for sequestering the insecticide from contaminated areas.
    New Journal of Chemistry 09/2012; 36(10):2007-2013. DOI:10.1039/C2NJ40364A · 3.16 Impact Factor

Publication Stats

2k Citations
543.72 Total Impact Points

Institutions

  • 1972–2014
    • University of Cape Town
      • Department of Chemistry
      Kaapstad, Western Cape, South Africa
  • 2007–2011
    • Rhodes University
      • Department of Chemistry
      Grahamstad, Eastern Cape, South Africa
  • 2005
    • University of Louisiana at Monroe
      • Department of Basic Pharmaceutical Sciences
      Monroe, LA, United States
  • 1987–2005
    • Port Elizabeth Museum
      Port Elizabeth, Eastern Cape, South Africa
  • 2004
    • Academia Romana
      • Department of Organic Chemistry
      Bucureşti, Hunedoara, Romania
  • 2000
    • Okayama University
      • Faculty of Science
      Okayama, Okayama, Japan
  • 1999
    • University of Milan
      Milano, Lombardy, Italy