Displaying publications 1 - 20 of 24 in total

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  1. Fulltext Imidazolium-Linked Azido-Functionalized Guerbet Glycosides: Multifunctional Surfactants for Biofunctionalization of Vesicles
    Goh EW, Heidelberg T, Duali Hussen RS, Salman AA
    ACS Omega, 2019 Oct 15;4(16):17039-17047.
    PMID: 31646251 DOI: 10.1021/acsomega.9b02809
    Aiming for glycolipid-based vesicles for targeted drug delivery, cationic Guerbet glycosides with spacered click functionality were designed and synthesized. The cationic charge promoted the distribution of the glycolipids during the formulation, thereby leading to homogeneously small vesicles. The positive surface charge of the vesicles stabilizes them against unwanted fusion and promotes interactions of the drug carriers with typical negative charge-dominated target cells. High bioconjugation potential of the functionalized glycolipids based on the copper-catalyzed azide alkyne cycloaddition makes them highly valuable components for targeted drug delivery systems.
  2. Fulltext 4-Formyl-phenyl 2,3,4,6-tetra-O-acetyl-β-d-galactopyran-oside
    Hussen RS, Heidelberg T, Rodzi NZ, Ng SW, Tiekink ER
    Acta Crystallogr Sect E Struct Rep Online, 2011 Apr 1;67(Pt 4):o826.
    PMID: 21754110 DOI: 10.1107/S1600536811008257
    The galactose ring in the title compound, C(21)H(24)O(11), has a chair conformation with the substituted benzene ring occupying an equatorial position. The crystal packing features C-H⋯O inter-actions that lead to the formation of supra-molecular layers in the ab plane.
  3. Fulltext 4-Formyl-phenyl 2,3,4,6-tetra-O-acetyl-β-d-glucopyran-oside
    Heidelberg T, Hussen RS, Rodzi NZ, Ng SW, Tiekink ER
    Acta Crystallogr Sect E Struct Rep Online, 2011 Apr 1;67(Pt 4):o825.
    PMID: 21754109 DOI: 10.1107/S1600536811008099
    The pyran-oside ring in the title compound, C(21)H(24)O(11), has a chair conformation with the substituted benzene ring occupying an equatorial position. The crystal packing is dominated by C-H⋯O inter-actions that lead to the formation of supra-molecular layers in the ab plane.
  4. Thermo-kinetics of lipase-catalyzed synthesis of 6-O-glucosyldecanoate
    Gumel AM, Annuar MS, Heidelberg T, Chisti Y
    Bioresour Technol, 2011 Oct;102(19):8727-32.
    PMID: 21816608 DOI: 10.1016/j.biortech.2011.07.024
    Lipase-catalyzed synthesis of 6-O-glucosyldecanoate from d-glucose and decanoic acid was performed in dimethyl sulfoxide (DMSO), a mixture of DMSO and tert-butanol and tert-butanol alone with a decreasing order of polarity. The highest conversion yield (> 65%) of decanoic acid was obtained in the blended solvent of intermediate polarity mainly because it could dissolve relatively large amounts of both the reactants. The reaction obeyed Michaelis-Menten type of kinetics. The affinity of the enzyme towards the limiting substrate (decanoic acid) was not affected by the polarity of the solvent, but increased significantly with temperature. The esterification reaction was endothermic with activation energy in the range of 60-67 kJ mol⁻¹. Based on the Gibbs energy values, in the solvent blend of DMSO and tert-butanol the position of the equilibrium was shifted more towards the products compared to the position in pure solvents. Monoester of glucose was the main product of the reaction.
  5. Growth kinetics, effect of carbon substrate in biosynthesis of mcl-PHA by Pseudomonas putida Bet001
    Gumel AM, Annuar MS, Heidelberg T
    Braz J Microbiol, 2014;45(2):427-38.
    PMID: 25242925
    Growth associated biosynthesis of medium chain length poly-3-hydroxyalkanoates (mcl-PHA) in Pseudomonas putida Bet001 isolated from palm oil mill effluent was studied. Models with substrate inhibition terms described well the kinetics of its growth. Selected fatty acids (C8:0 to C18:1) and ammonium were used as carbon and nitrogen sources during growth and PHA biosynthesis, resulting in PHA accumulation of about 50 to 69% (w/w) and PHA yields ranging from 10.12 g L(-1) to 15.45 g L(-1), respectively. The monomer composition of the PHA ranges from C4 to C14, and was strongly influenced by the type of carbon substrate fed. Interestingly, an odd carbon chain length (C7) monomer was also detected when C18:1 was fed. Polymer showed melting temperature (T m) of 42.0 (± 0.2) °C, glass transition temperature (T g) of -1.0 (± 0.2) °C and endothermic melting enthalpy of fusion (ΔHf) of 110.3 (± 0.1) J g(-1). The molecular weight (M w) range of the polymer was relatively narrow between 55 to 77 kDa.
  6. Functional glycolipid-crown-ethers by click chemistry
    Salman AA, Tabandeh M, Heidelberg T, Duali Hussen RS
    Carbohydr Res, 2015 Apr 10;406:41-5.
    PMID: 25658065 DOI: 10.1016/j.carres.2014.12.015
    A series of glycolipid crown ether analogs was prepared by bis-propargylation of lauryl glycoside followed by subsequent click-coupling with ethylene glycol-based diazides. The triazole-linked macrocycles were obtained in remarkable high yields. While the surfactant assembly was affected by presence of sodium ions, suggesting the formation of complexes, no ion-selectivity was observed for the macrocylic ligands. Computational studies suggest a low but significant cation-binding activity of the macrocycle, involving coordination at both oxygen and nitrogen atoms.
  7. N-linked glycolipids by Staudinger coupling of glycosylated alkyl diazides with fatty acids
    Salman SM, Heidelberg T, Bin Tajuddin HA
    Carbohydr Res, 2013 Jun 28;375:55-62.
    PMID: 23685811 DOI: 10.1016/j.carres.2013.03.028
    Aiming for new glycolipids with enhanced chemical stability and close structural similarity to natural cell membrane lipids for the development of a drug delivery system, we have synthesized double amide analogs of glyco-glycerolipids. The synthesis applied a Staudinger reaction based coupling of a 1,3-diazide with fatty acid chlorides. While the concept furnished the desired glucosides in reasonable yields, the corresponding lactosides formed a tetrahydropyrimidine based 1:1 coupling product instead. This unexpected coupling result likely originates from steric hindrance at the iminophosphorane intermediate and provides an interesting core structure for potentially bioactive surfactants. The assembly behavior of both glycolipid types was investigated by optical polarizing microscopy, DSC and surface tension studies.
  8. A reevaluation of the epimeric and anomeric relationship of glucosides and galactosides in thermotropic liquid crystal self-assemblies
    Hashim R, Mirzadeh SM, Heidelberg T, Minamikawa H, Yoshiaki T, Sugimura A
    Carbohydr Res, 2011 Dec 27;346(18):2948-56.
    PMID: 22088885 DOI: 10.1016/j.carres.2011.10.032
    Anomers and epimers α- and β-gluco and -galactosides are expected to behave differently. However, recent results on a series of Guerbet glycosides have indicated similar liquid crystal clearing temperatures for pure β-glucosides and the corresponding α-galactosides. This observation has led to speculation on similarities in the self-assembly interactions between the two systems, attributed to the trans-configuration of the 4-OH group and the hydrophobic aglycon. Previous simulations on related bilayers systems support this hypothesis, by relating this clearing transition temperature to intralayer (sugar-sugar) hydrogen bonding. In order to confirm the hypothesis, the comparison was expanded to include the cis-configurated pair, that is, α-gluco/β-galactoside. A set of α-configurated Guerbet glucosides as well as octyl α-galactoside were prepared and their thermotropic phase behavior studied. The data obtained enabled a complete comparison of the isomers of interest. While the results in general are in line with a pairing of the stereo-isomers according to the indicated cis/trans-configuration, differences within the pairs can be explained based on the direction of hydrogen bonds from a simple modeling study.
  9. Alkyl-imidazolium glycosides: non-ionic-cationic hybrid surfactants from renewable resources
    Salman AA, Tabandeh M, Heidelberg T, Hussen RS, Ali HM
    Carbohydr Res, 2015 Aug 14;412:28-33.
    PMID: 26000863 DOI: 10.1016/j.carres.2015.04.022
    A series of surfactants combining carbohydrate and imidazolium head groups were prepared and investigated on their assembly behavior. The presence of the imidazolium group dominated the interactions of the surfactants, leading to high CMCs and large molecular surface areas, reflected in curved rather than lamellar surfactant assemblies. The carbohydrate, on the other hand, stabilized molecular assemblies slightly and reduced the surface tension of surfactant solutions considerably. A comparative emulsion study discourages the use of pure alkyl imidazolium glycosides owing to reduced assembly stabilities compared with APGs. However, the surfactants are believed to have potential as component in carbohydrate based surfactant mixtures.
  10. Functionalized glycolipids for potential bioconjugation of vesicles
    Tabandeh M, Goh EW, Salman AA, Heidelberg T, Duali Hussen RS
    Carbohydr Res, 2018 Nov;469:14-22.
    PMID: 30196011 DOI: 10.1016/j.carres.2018.08.016
    Two azide-terminated oligoethylene oxide spacered glycolipids have been synthesized, and their assembly behavior has been studied in comparison to the corresponding base surfactants. The results suggest potential of the Guerbet lactoside-based compound for targeted drug delivery, while a coiling of the ethylene oxide linker disfavors the application of the glucoside.
  11. Cation-stimulated drug delivery via lipid assembly comprising macrocyclized disaccharides - A DFT study
    Mazlee MTF, Heidelberg T, Ariffin A, Zain SM
    Carbohydr Res, 2023 Oct;532:108923.
    PMID: 37598565 DOI: 10.1016/j.carres.2023.108923
    In the attempt to create a delivery system for an alkali-cation stimulated drug release, a computational study was conducted, aiming for the evaluation of synthetic access towards glycolipid crown ethers analogs and their potential for coordination-induced changes of packing constraints for molecular assemblies. The results disfavor amide-linkages for the creation of macrocycles around the inter-glycosidic bond of a disaccharide. Conformational changes upon cation coordination of the macrocycle decrease the intersection area for easily accessible macrocycles based on lactose. This leads to shrinking intersection areas upon alkali complexation. Maltose-based analogs, on the other hand, exhibited the targeted increase of the glycolipid intersection area and, hence, may be considered as a promising resource.
  12. Renewable resources-based approach to biantennary glycolipids
    Tabandeh M, Salman AA, Goh EW, Heidelberg T, Hussen RSD
    Chem Phys Lipids, 2018 05;212:111-119.
    PMID: 29409839 DOI: 10.1016/j.chemphyslip.2018.01.011
    A new synthesis approach towards biantennary lipids of Guerbet glycoside type was developed based on oleic acid as sustainable resource. Functionalization of the double bond provided access to primary alcohols with α-branched C19-skeleton. Formulation studies with corresponding lactosides indicated formation of vesicles with high assembly stability. A relatively narrow bimodal size distribution of the latter, which turns into a narrow unimodal distribution of small vesicles upon addition of an ionic cosurfactant, suggests potential for a vesicular drug delivery system.
  13. New Y-shaped surfactants from renewable resources
    Ali TH, Hussen RS, Heidelberg T
    Colloids Surf B Biointerfaces, 2014 Nov 1;123:981-5.
    PMID: 25465761 DOI: 10.1016/j.colsurfb.2014.10.054
    A series of sugar-based surfactants, involving a single hydrophobic chain (C12) and two side-by-side arranged head groups, was prepared form simple glucose precursors. All surfactants were highly water soluble and exhibited exclusively micellar assemblies. This behavior makes them interesting candidates for oil in water emulsifiers.
  14. Alkyl triazole glycosides (ATGs)--a new class of bio-related surfactants
    Sani FA, Heidelberg T, Hashim R, Farhanullah
    Colloids Surf B Biointerfaces, 2012 Sep 1;97:196-200.
    PMID: 22609603 DOI: 10.1016/j.colsurfb.2012.03.030
    A series of glucose based surfactants varying in chain length and anomeric configuration were synthesized and investigated on their surfactant properties. The synthesis applied glycosylation of propargyl alcohol followed by cycloaddition with alkyl azides in CLICK chemistry fashion. This approach enables a homogeneous coupling of hydrophilic unprotected sugars and hydrophobic paraffin components in low molecular weight alcohols without solvent side reactions, as commonly found for APGs. The combination of alcohols as inert medium with practically quantitative coupling of the surfactant domains avoids particularly hydrophobic contaminations of the surfactant, thus providing access to pure surfactants. ATGs with chain lengths up to 12 carbons exhibit Krafft points below room temperature and no cloud points were detected. The values for the CMC of ATGs with 12 carbon alkyl chains and above were in good agreement with those of corresponding alkyl glucosides. However, lower homologues exhibited significantly smaller CMCs, and the trend of the CMC upon the chain length did not match common surfactant behavior. This deviation may be related to the triazole that links the two surfactant domains.
  15. Unexpected Reactions of Terminal Alkynes in Targeted "Click Chemistry'' Coppercatalyzed Azide-alkyne Cycloadditions
    Ali TH, Heidelberg T, Hussen RSD, Tajuddin HA
    Curr Org Synth, 2019;16(8):1143-1148.
    PMID: 31984920 DOI: 10.2174/1570179416666191105152714
    BACKGROUND: High efficiency in terms of reaction yield and purity has led to the extensive utilization of copper-catalyzed azide-alkyne cycloaddition (CuAAC) in various fields of chemistry. Its compatibility with low molecular weight alcohols promotes the application in surfactant synthesis to tackle the miscibility constraints of the reactants.

    OBJECTIVE: For the tuning of surfactant properties, double click coupling of the antipode precursors was attempted. Failure of the CuAAC to provide the targeted product in combination with unexpected reaction outputs led to an investigation of the side reaction.

    METHODS: The CuAAC-based coupling of sugar azide with propargyl building block in the presence of copper- (I) catalyst exclusively led to the mono-coupling product in a respectable yield of almost 80%. Besides the unexpected incomplete conversion, the loss of the remaining propargyl group, as indicated by both NMR and MS. On the other hand, application of substantial amounts of CuSO4 under reducing conditions in refluxing toluene/water furnished the alkyne dimer in a moderate yield of 43%, while no change of azide compound was noticed.

    RESULTS: The Cu(I)-catalyst applied for azide-alkyne cycloadditions enables the homo-coupling of certain terminal alkynes at a higher temperature. Moreover, aromatic propargyl ethers may be cleaved to furnish the corresponding phenol. The copper-catalyzed coupling appeared highly sensitive towards the alkyne compound. Only selected derivatives of propargyl alcohol were successfully dimerized.

    CONCLUSIONS: The observed failure of the Huisgen reaction for the synthesis of sugar-based surfactants may indicate non-recognized constrains of the reaction, which could affect its wide application in bioconjugation. The temperature requirement for the alternative dimerization of terminal alkynes renders this side reaction nonrelevant for typical click couplings, while narrow substrate diversity and moderate yield limit its synthetic application.

  16. Correlation of antioxidant activities with theoretical studies for new hydrazone compounds bearing a 3,4,5-trimethoxy benzyl moiety
    Kareem HS, Ariffin A, Nordin N, Heidelberg T, Abdul-Aziz A, Kong KW, et al.
    Eur J Med Chem, 2015 Oct 20;103:497-505.
    PMID: 26402727 DOI: 10.1016/j.ejmech.2015.09.016
    A new series of antioxidants, namely imines bearing the well-known free radical scavenger group 3,4,5-trimethoxybenzyloxy, was designed and synthesized. Theoretical calculations based on density functional theory (DFT) were performed to understand the antioxidant activities. Experimental studies evaluating the antioxidant activities of the compounds using DPPH and FRAP assays verified the predictions obtained by DMOL3 based on DFT.1. The DPPH radical scavenging activities depended on the substitution pattern of the aromatic aldehyde, with both the substitution type and position showing significant effects. Compounds 7b, 7c and 7d, which contain a phenolic hydroxyl group at the para position to the imine as well as, additional electron donating groups at the ortho-position to this hydroxyl group, exhibited IC₅₀ values of 62, 75 and 106 μg/mL, respectively, and potent antioxidant activities against DPPH, which were better than that of the reference compound BHT. With the exception of compounds 7a and 7h with a phenolic hydroxyl group at the ortho position, all of the investigated compounds exhibited ferric reducing activities above 1000 μM. Correlation analysis between the two antioxidant assays revealed moderate positive correlation (r = 0.59), indicating differing antioxidant activities based on the reaction mechanism. Therefore, imines bearing a 3,4,5-trimethoxybenzyloxy group can be proposed as potential antioxidants for tackling oxidative stress.
  17. Enzymatic synthesis of 6-O-glucosyl-poly(3-hydroxyalkanoate) in organic solvents and their binary mixture
    Gumel AM, Annuar MS, Heidelberg T
    Int J Biol Macromol, 2013 Apr;55:127-36.
    PMID: 23305702 DOI: 10.1016/j.ijbiomac.2012.12.028
    The effects of organic solvents and their binary mixture in the glucose functionalization of bacterial poly-3-hydroxyalkanoates catalyzed by Lecitase™ Ultra were studied. Equal volume binary mixture of DMSO and chloroform with moderate polarity was more effective for the enzyme catalyzed synthesis of the carbohydrate polymer at ≈38.2 (±0.8)% reactant conversion as compared to the mono-phasic and other binary solvents studied. The apparent reaction rate constant as a function of medium water activity (aw) was observed to increase with increasing solvent polarity, with optimum aw of 0.2, 0.4 and 0.7 (±0.1) observed in hydrophilic DMSO, binary mixture DMSO:isooctane and hydrophobic isooctane, respectively. Molecular sieve loading between 13 to 15gL(-1) (±0.2) and reaction temperature between 40 to 50°C were found optimal. Functionalized PHA polymer showed potential characteristics and biodegradability.
  18. Fluorescence probing of the temperature-induced phase transition in a glycolipid self-assembly: hexagonal ↔ micellar and cubic ↔ lamellar
    Zahid NI, Abou-Zied OK, Hashim R, Heidelberg T
    Langmuir, 2012 Mar 20;28(11):4989-95.
    PMID: 22364590 DOI: 10.1021/la3001976
    Water-driven self-assembly of lipids displays a variety of liquid crystalline phases that are crucial for membrane functions. Herein, we characterize the temperature-induced phase transitions in two compositions of an aqueous self-assembly system of the octyl β-D-glucoside (βGlcOC(8)) system, using steady-state and time-resolved fluorescence measurements. The phase transitions hexagonal ↔ micellar and cubic ↔ lamellar were investigated using tryptophan (Trp) and two of its ester derivatives (Trp-C(4) and Trp-C(8)) to probe the polar headgroup region and pyrene to probe the hydrophobic tail region. The polarity of the headgroup region was estimated to be close to that of simple alcohols (methanol and ethanol) for all phases. The pyrene fluorescence indicates that the pyrene molecules are dispersed among the tails of the hydrophobic region, yet remain in close proximity to the polar head groups. Comparing the present results with our previously reported one for βMaltoOC(12), increasing the tail length of the hexagonal phase from C(8) to C(12) leads to less interaction with pyrene, which is attributed to the more random and wobbling motion of the longer alkyl tail. We measured a reduction (more hydrophobic) in the ratio of the vibronic peak intensities of pyrene (I(1)/I(3)) for the lamellar phase compared to that of the cubic phase. The higher polarity in the cubic phase can be correlated to the nature of its interface, which curves toward the bulk water. This geometry also explains the slight reduction in polarity of the headgroup region compared to the other phases. Upon the addition of Trp-C(8), the fluorescence lifetime of pyrene is reduced by 28% in the lamellar and cubic phases, whereas the I(1)/I(3) value is only slightly reduced. The results reflect the dominant role of dynamic interaction mechanism between the C(8) chain of Trp-C(8) and pyrene. This mechanism may be important for these two phases since they participate in the process of membrane fusion. Both lipid compositions show completely reversible temperature-induced phase transitions, reflecting the thermodynamic equilibrium structures of their mesophases. Probing both regions of the different lipid phases reveals a large degree of heterogeneity and flexibility of the lipid self-assembly. These properties are crucial for carrying out different biological functions such as the ability to accommodate various molecular sizes.
  19. Fulltext Conjugated Oligo-Aromatic Compounds Bearing a 3,4,5-Trimethoxy Moiety: Investigation of Their Antioxidant Activity Correlated with a DFT Study
    Kareem HS, Nordin N, Heidelberg T, Abdul-Aziz A, Ariffin A
    Molecules, 2016 Feb 17;21(2).
    PMID: 26901175 DOI: 10.3390/molecules21020224
    A series of heterocyclic compounds bearing the well-known free radical scavenging 3,4,5-trimethoxybenzyloxy group, was synthesized. The key compound 4-(3,4,5-trimethoxybenzyl-oxy)benzohydrazide was converted into thiosemicarbazide derivatives, which were subsequently cyclized with NaOH to provide 1,2,4-triazole derivatives. Alternative treatment of the acid hydrazide with carbon disulfide in the presence of KOH led to the corresponding 1,3,4-oxadiazole and various alkylated derivatives. The newly synthesized compounds were purified and the structures of the products were elucidated and confirmed on the basis of their analytical and spectral data. Their antioxidant activities were evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH(•)) and Ferric Reducing Antioxidant Power (FRAP) assays. The thiosemicarbazide derivatives were highly active in both antioxidant assays with the lowest IC50 value for DPPH radical scavenging. Theoretical calculations based on density functional theory (DFT) were performed to understand the relative importance of NH, SH and CH hydrogens on the radical scavenging activities of these compounds.
  20. Fulltext Biosynthesis and characterization of polyhydroxyalkanoates copolymers produced by Pseudomonas putida Bet001 isolated from palm oil mill effluent
    Gumel AM, Annuar MS, Heidelberg T
    PLoS One, 2012;7(9):e45214.
    PMID: 23028854 DOI: 10.1371/journal.pone.0045214
    The biosynthesis and characterization of medium chain length poly-3-hydroxyalkanoates (mcl-PHA) produced by Pseudomonas putida Bet001 isolated from palm oil mill effluent was studied. The biosynthesis of mcl-PHA in this newly isolated microorganism follows a growth-associated trend. Mcl-PHA accumulation ranging from 49.7 to 68.9% on cell dry weight (CDW) basis were observed when fatty acids ranging from octanoic acid (C(8:0)) to oleic acid (C(18:1)) were used as sole carbon and energy source. Molecular weight of the polymer was found to be ranging from 55.7 to 77.7 kDa. Depending on the type of fatty acid used, the (1)H NMR and GCMSMS analyses of the chiral polymer showed a composition of even and odd carbon atom chain with monomer length of C4 to C14 with C8 and C10 as the principal monomers. No unsaturated monomer was detected. Thermo-chemical analyses showed the accumulated PHA to be semi-crystalline polymer with good thermal stability, having a thermal degradation temperature (T(d)) of 264.6 to 318.8 (± 0.2) (o)C, melting temperature (T(m)) of 43. (± 0.2) (o)C, glass transition temperature (T(g)) of -1.0 (± 0.2) (o)C and apparent melting enthalpy of fusion (ΔH(f)) of 100.9 (± 0.1) J g(-1).
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