Displaying publications 1 - 20 of 50 in total

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  1. Al-Mehana WN, Yahya R, Sonsudin F, Al-Mehana IN, Lo KM
    Acta Crystallogr Sect E Struct Rep Online, 2012 Oct 1;68(Pt 10):o2990.
    PMID: 23125764 DOI: 10.1107/S1600536812038354
    The complete molecule of the title compound, C(18)H(20)N(2)O(4), is generated by inversion symmetry. The conformation around the C=N bond is E. With the exception of the eth-oxy substituent, the mol-ecule is essentially planar with an r.m.s. deviation of 0.0455 Å. In the crystal, mol-ecules are linked by O-H⋯N hydrogen bonds into a two-dimensional supra-molecular network parallel to the bc plane.
  2. Al-Mehana WN, Shakir RM, Yahya R, Abd Halim SN, Tiekink ER
    Acta Crystallogr Sect E Struct Rep Online, 2011 Jul 1;67(Pt 7):o1659.
    PMID: 21837059 DOI: 10.1107/S1600536811022410
    The complete mol-ecule in the title compound, C(22)H(20)N(2)O(4), is generated by the application of an inversion centre. With the exception of the terminal acetyl-ene groups [C-O-C-C = -78.02 (17)°], the remaining atoms constituting the mol-ecule are essentially coplanar. The configuration around the C=N bond [1.282 (2) Å] is E. The formation of supra-molecular chains mediated by C-H⋯O inter-actions, occurring between methyl-ene H and meth-oxy O atoms, is the most notable feature of the crystal packing.
  3. Al-Mehana WN, Yahya R, Lo KM
    PMID: 22219934 DOI: 10.1107/S160053681104102X
    The mol-ecule of the title compound, C(20)H(16)N(2)O(2), is centrosymmetric with the mid-point of the central N-N bond located on an inversion center. The configuration around the C=N bond is E. The whole mol-ecule (except for the H atoms) is approximately planar, with an r.m.s. deviation of 0.07 Å. In the crystal, the presence of weak inter-molecular C-H⋯O hydrogen bonding involving each acetyl-ene H atom and the adjacent phen-oxy O atom results in the formation of supra-molecular chains.
  4. Soume BB, Yahya R, Gan SN, Ng SW
    PMID: 21201619 DOI: 10.1107/S1600536808025798
    In the crystal structure of the title compound, [Cr(3)(C(2)Cl(3)O(2))(7)O(H(2)O)(2)]·3CH(3)CN, the trinuclear [Cr(3)O(H(2)O)(2)(Cl(3)CCO(2))(7)] mol-ecule has an oxide O atom that is connected to one monodentate trichloro-acetate-coordinated and two water-coordinated Cr(III) atoms, the three metal atoms forming the points of an equilateral triangle. Each of the six remaining carboxyl-ate groups bridges a Cr-O-Cr fragment. The cluster inter-acts with the three solvent mol-ecules through water-acetonitrile O-H⋯N hydrogen bonds. Adjacent clusters are linked by a water-carboxylate O-H⋯O hydrogen bond to give a helical chain. One of the CCl(3) groups was found to be disordered over two positions, with the major component having a site-occupancy factor of 0.64 (1).
  5. Loke SC, Kanesvaran R, Yahya R, Fisal L, Wong TW, Loong YY
    Ann Acad Med Singap, 2009 Dec;38(12):1074-80.
    PMID: 20052443
    INTRODUCTION: Intravenous calcium gluconate has been used to prevent postoperative hypocalcaemia (POH) following parathyroidectomy for secondary hyperparathyroidism in chronic kidney disease (CKD).

    MATERIALS AND METHODS: Retrospective data were obtained for 36 patients with CKD stage 4 and 5 after parathyroid surgery, correlating albumin-corrected serum calcium with the infusion rate of calcium gluconate. Calcium flux was characterised along with excursions out of the target calcium range of 2 to 3 mmol/L. With this data, an improved titration regimen was constructed.

    RESULTS: Mean peak efflux rate (PER) from the extracellular calcium pool was 2.97 mmol/h occurring 26.6 hours postoperatively. Peak calcium efflux tended to occur later in cases of severe POH. Eighty-one per cent of patients had excursions outside of the target calcium range of 2 to 3 mmol/L. Mean time of onset for hypocalcaemia was 2 days postoperatively. Hypocalcaemia was transient in 25% and persistent in 11% of patients.

    CONCLUSION: A simple titration regimen was constructed in which a 10% calcium gluconate infusion was started at 4.5 mL/h when serum calcium was <2 mmol/L, then increased to 6.5 mL/h and finally to 9.0 mL/h if calcium continued falling. Preoperative oral calcium and calcitriol doses were maintained. Blood testing was done 6-hourly, but when a higher infusion rate was needed, 4-hourly blood testing was preferred. Monitoring was discontinued if no hypocalcaemia developed in the fi rst 4 days after surgery. If hypocalcaemia persisted 6 days after surgery, then the infusion was stopped with further monitoring for 24 hours.

  6. Khor BH, Chinna K, Abdul Gafor AH, Morad Z, Ahmad G, Bavanandam S, et al.
    BMC Health Serv Res, 2018 Dec 04;18(1):939.
    PMID: 30514284 DOI: 10.1186/s12913-018-3702-9
    BACKGROUND: This study aimed to assess the situational capacity for nutrition care delivery in the outpatient hemodialysis (HD) setting in Malaysia by evaluating dietitian accessibility, nutrition practices and patients' outcomes.

    METHODS: A 17-item questionnaire was developed to assess nutrition practices and administered to dialysis managers of 150 HD centers, identified through the National Renal Registry. Nutritional outcomes of 4362 patients enabled crosscutting comparisons as per dietitian accessibility and center sector.

    RESULTS: Dedicated dietitian (18%) and visiting/shared dietitian (14.7%) service availability was limited, with greatest accessibility at government centers (82.4%) > non-governmental organization (NGO) centers (26.7%) > private centers (15.1%). Nutritional monitoring varied across HD centers as per albumin (100%) > normalized protein catabolic rate (32.7%) > body mass index (BMI, 30.7%) > dietary intake (6.0%). Both sector and dietitian accessibility was not associated with achieving albumin ≥40 g/L. However, NGO centers were 36% more likely (p = 0.030) to achieve pre-dialysis serum creatinine ≥884 μmol/L compared to government centers, whilst centers with dedicated dietitian service were 29% less likely (p = 0.017) to achieve pre-dialysis serum creatinine ≥884 μmol/L. In terms of BMI, private centers were 32% more likely (p = 0.022) to achieve BMI ≥ 25.0 kg/m2 compared to government centers. Private centers were 62% less likely (p 

  7. Wong XZ, Gan CC, Mohamed R, Yahya R, Ganapathy S, Tan SS, et al.
    BMC Nephrol, 2020 11 13;21(1):480.
    PMID: 33187498 DOI: 10.1186/s12882-020-02154-4
    BACKGROUND: Hepatitis C virus (HCV) infects more than 71 million people worldwide and chronic HCV infection increases the risk of liver cirrhosis and failure. Haemodialysis (HD) is one of the renal replacement therapies with risk of HCV transmission. Anti-HCV antibodies are the serological screening test for HCV infection that does not detect active phase of infection. Majority HCV infected HD patients in Malaysia do not have further HCV RNA performed due to high cost and thus HCV treatment is less frequently offered. HCV Core Antigen (HCV Ag) can potentially be used to diagnose active HCV infection in HD population in comparison to HCV RNA, at lower cost.

    METHODS: We conducted a cross-sectional study to assess the correlation between HCV Ag and HCV RNA and to identify the prevalence of active HCV infection among HCV seropositive HD patients from dialysis centres across West Malaysia from July 2019 to May 2020. Pre-dialysis blood was taken and tested for both HCV Ag and HCV RNA tests. HCV Ag was tested with Abbott ARCHITECT HCV Ag test.

    RESULTS: We recruited 112 seropositive HD patients from 17 centres with mean age of 54.04 ± 11.62 years, HD vintage of 14.1 ± 9.7 years, and male constitute 59.8% (67) of the study population. HCV Ag correlates well with HCV RNA (Spearman test coefficient 0.833, p  3000 IU/mL, HCV Ag had a higher sensitivity of 95.1% and greater correlation (Spearman test coefficient 0.897, p 

  8. Dendooven A, Peetermans H, Helbert M, Nguyen TQ, Marcussen N, Nagata M, et al.
    BMC Nephrol, 2021 05 24;22(1):193.
    PMID: 34030637 DOI: 10.1186/s12882-021-02365-3
    BACKGROUND: Kidney biopsy registries all over the world benefit research, teaching and health policy. Comparison, aggregation and exchange of data is however greatly dependent on how registration and coding of kidney biopsy diagnoses are performed. This paper gives an overview over kidney biopsy registries, explores how these registries code kidney disease and identifies needs for improvement of coding practice.

    METHODS: A literature search was undertaken to identify biopsy registries for medical kidney diseases. These data were supplemented with information from personal contacts and from registry websites. A questionnaire was sent to all identified registries, investigating age of registries, scope, method of coding, possible mapping to international terminologies as well as self-reported problems and suggestions for improvement.

    RESULTS: Sixteen regional or national kidney biopsy registries were identified, of which 11 were older than 10 years. Most registries were located either in Europe (10/16) or in Asia (4/16). Registries most often use a proprietary coding system (12/16). Only a few of these coding systems were mapped to SNOMED CT (1), older SNOMED versions (2) or ERA-EDTA PRD (3). Lack of maintenance and updates of the coding system was the most commonly reported problem.

    CONCLUSIONS: There were large gaps in the global coverage of kidney biopsy registries. Limited use of international coding systems among existing registries hampers interoperability and exchange of data. The study underlines that the use of a common and uniform coding system is necessary to fully realize the potential of kidney biopsy registries.

  9. Farhan N, Al-Maleki AR, Sarih NM, Yahya R
    Bioorg Chem, 2023 Nov;140:106786.
    PMID: 37586131 DOI: 10.1016/j.bioorg.2023.106786
    Recent studies show that some metal ions, injure microbial cells in various ways due to membrane breakdown, protein malfunction, and oxidative stress. Metal complexes are suited for creating novel antibacterial medications due to their distinct mechanisms of action and the variety of three-dimensional geometries they can acquire. In this Perspective, the present study focused on new antibacterial strategies based on metal oleoyl amide complexes. Thus, oleoyl amides ligand (fatty hydroxamic acid and fatty hydrazide hydrate) with the transition metal ions named Ag (I), Co (II), Cu (II), Ni (II) and Sn (II) complexes were successfully synthesized in this study. The metals- oleoyl amide were characterized using elemental analysis, and fourier transforms infrared (FTIR) spectroscopy. The antibacterial effect of metals- oleoyl amide complexes was investigated for Gram-negative bacteria (Escherichia coli) and Gram-positive bacteria (Staphylococcus aureus) by analysing minimum inhibitory concentration (MIC), minimal bactericidal concentration (MBC), and scanning electron microscopy (SEM). The results showed that metal-oleoyl amide complexes have high antibacterial activity at low concentrations. This study inferred that metal oleoyl amide complexes could be utilised as a promising therapeutic antibacterial agent.
  10. Farhan N, Rageh Al-Maleki A, Ataei S, Muhamad Sarih N, Yahya R
    Bioorg Chem, 2023 Jun;135:106511.
    PMID: 37027951 DOI: 10.1016/j.bioorg.2023.106511
    Medication products from natural materials are preferred due to their minimal side effects. Extra-virgin olive oil (EVOO) is a highly acclaimed Mediterranean diet and a common source of lipids that lowers morbidity and disease severity. This study synthesised two fatty amides from EVOO: hydroxamic fatty acids (FHA) and fatty hydrazide hydrate (FHH). The Density Functional Theory (DFT) was applied to quantum mechanics computation. Nuclear magnetic resonance (NMR), Fourier transforms infrared (FTIR), and element analysis were used to characterise fatty amides. Likewise, the minimum inhibitory concentration (MIC) and timing kill assay were determined. The results revealed that 82 % for FHA and 80 % for FHH conversion were achieved. The amidation reagent/EVOO ratio (mmol: mmol) was 7:1, using the reaction time of 12 h and hexane as an organic solvent. The results further revealed that fatty amides have high antibacterial activity with low concentration at 0.04 μg/mL during eight h of FHA and 0.3 μg/mL during ten h of FHH. This research inferred that FHA and FHH could provide an alternative and effective therapeutic strategy for bacterial diseases. Current findings could provide the basis for the modernisation/introduction of novel and more effective antibacterial drugs derived from natural products.
  11. Leong ST, Liew SY, Khaw KY, Ahmad Hassali H, Richomme P, Derbré S, et al.
    Bioorg Chem, 2023 Dec;141:106859.
    PMID: 37742494 DOI: 10.1016/j.bioorg.2023.106859
    A bio-assay guided fractionation strategy based on cholinesterase assay combined with 13C NMR-based dereplication was used to identify active metabolites from the bark of Mesua lepidota. Eight compounds were identified with the aid of the 13C NMR-based dereplication software, MixONat, i.e., sitosterol (1), stigmasterol (2), α-amyrin (3), friedelin (6), 3β-friedelinol (7), betulinic acid (9), lepidotol A (10) and lepidotol B (11). Further bio-assay guided isolation of active compounds afforded one xanthone, pyranojacareubin (12) and six coumarins; lepidotol A (10), lepidotol B (11), lepidotol E (13), lepidotin A (14), and lepidotin B (15), including a new Mammea coumarin, lepidotin C (16). All the metabolites showed strong to moderate butyrylcholinesterase (BChE) inhibition. Lepidotin B (15) exhibited the most potent inhibition towards BChE with a mix-mode inhibition profile and a Ki value of 1.03 µM. Molecular docking and molecular dynamics simulations have revealed that lepidotin B (15) forms stable interactions with key residues within five critical regions of BChE. These regions encompass residues Asp70 and Tyr332, the acyl hydrophobic pocket marked by Leu286, the catalytic triad represented by Ser198 and His438, the oxyanion hole (OH) constituted by Gly116 and Gly117, and the choline binding site featuring Trp82. To gauge the binding strength of lepidotin B (15) and to pinpoint pivotal residues at the binding interface, free energy calculations were conducted using the Molecular Mechanics Generalized Born Surface Area (MM-GBSA) approach. This analysis not only predicted a favourable binding affinity for lepidotin B (15) but also facilitated the identification of significant residues crucial for the binding interaction.
  12. Selvanathan V, Azzahari AD, Abd Halim AA, Yahya R
    Carbohydr Polym, 2017 Jul 01;167:210-218.
    PMID: 28433156 DOI: 10.1016/j.carbpol.2017.03.023
    A first-of-its-kind, eco-friendly quasi-solid bioelectrolyte derived from potato starch was prepared. Starch was chemically modified via phthaloylation to synthesize amorphous, hydrophobic starch derivative and the attachment of the phthaloyl group was confirmed via FTIR which showed phthalate ester peak at 1715cm-1; and 1H NMR peaks between 7.30-7.90ppm attributed to the aromatic protons of the phthaloyl group. The resulting starch derivative was then infused with ternary natural deep eutectic solvent (NADES) made from different molar ratios of choline chloride, urea and glycerol. Electrochemical Impedance Spectroscopy (EIS) revealed that the highest ionic conductivity was obtained by the system consisting of NADES with choline chloride:urea:glycerol in molar ratios of 4:6:2, with a magnitude of 2.86mScm-1, hence validating the prospects of the materials to be further experimented as an alternative electrolyte in various electrochemical devices.
  13. Yusuf SNF, Azzahari AD, Selvanathan V, Yahya R, Careem MA, Arof AK
    Carbohydr Polym, 2017 Feb 10;157:938-944.
    PMID: 27988011 DOI: 10.1016/j.carbpol.2016.10.032
    A binary salt system utilizing lithium iodide (LiI) as the auxiliary component has been introduced to the N-phthaloylchitosan (PhCh) based gel polymer electrolyte consisting of ethylene carbonate (EC), dimethylformamide (DMF), tetrapropylammonium iodide (TPAI), and iodine (I2) in order to improve the performance of dye-sensitized solar cell (DSSC) with efficiency of 6.36%, photocurrent density, JSC of 17.29mAcm-2, open circuit voltage, VOC of 0.59V and fill factor, FF of 0.62. This efficiency value is an improvement from the 5.00% performance obtained by the DSSC consisting of only TPAI single salt system. The presence of the LiI in addition to the TPAI improves the charge injection rates and increases the iodide contribution to the total conductivity and both factors contribute to the increase in efficiency of the DSSC. The interaction behavior between polymer-plasticizer-salt was thoroughly investigated using EIS, FTIR spectroscopy and XRD.
  14. Asghar M, Yahya R, Yap AUJ, Azzahari AD, Omar RA
    Caries Res, 2022;56(3):149-160.
    PMID: 35871511 DOI: 10.1159/000525505
    Silver diammine fluoride (SDF) is known as a noninvasive, cost-effective, safe, and simple method of dental caries treatment. However, staining and discoloration seem inseparable with SDF and continue as a cosmetic concern. Research is ongoing to overcome these issues, for example, by using glutathione (G) or potassium iodide among others. Therefore, the study aimed to investigate the effects of incorporating different concentrations of capping agents on SDF chemistry and SDF-mediated tooth staining at different time points. Tannic acid (TA), gallic acid (GA), carboxymethyl chitosan (CM), and G at different concentrations (5, 10, and 15% w/v) were incorporated in 30% SDF. FTIR and UV-Vis spectroscopies of the prepared solutions was performed to evaluate chemical changes. Time-dependent color changes (ΔE) in bovine dentine specimens (6 × 6 × 1 ± 0.25 mm3) were measured spectrophotometrically at application/washup, 1 and 3 h, after 1, 2, 4, 7, and 14 days. Results showed suppression of FTIR peaks at 3,358 cm-1 and 1,215 cm-1 in capping agent-modified SDF indicative of a successful capping effect of the silver ions, which was corroborated by UV-Vis blueshift of ∼∆32 nm. The capping effect on SDF increased proportionally with the concentrations of TA, GA, CM, and G used. A more pronounced tooth staining reduction however was shown more in TA- and G- rather than in GA- and CM-modified SDF. At day 14, SDF showed the highest mean ΔE(50.14 ± 2.14), while 15% TA showed the lowest ΔE(30.14 ± 0.81). In conclusion, capping agent incorporation significantly reduced SDF-mediated tooth staining. This reduction in staining is more dependent on the respective capping agent functional groups than concentrations per se. The potential of capping agents to minimize tooth staining of SDF was TA>G>CM>GA.
  15. M Zawawi SM, Yahya R, Hassan A, Mahmud HN, Daud MN
    Chem Cent J, 2013;7(1):80.
    PMID: 23634962 DOI: 10.1186/1752-153X-7-80
    Metal tungstates have attracted much attention due to their interesting structural and photoluminescence properties. Depending on the size of the bivalent cation present, the metal tungstates will adopt structures with different phases. In this work, three different phases of metal tungstates MWO4 (M= Ba, Ni and Bi) were synthesized via the sucrose templated method.
  16. Tan MH, Yee SY, Yahya R
    Clin Med (Lond), 2022 Mar;22(2):169-171.
    PMID: 38589183 DOI: 10.7861/clinmed.2021-0789
    Carbamazepine remains a first-line antiepileptic medication for the treatment of partial seizures. Despite its widespread use, carbamazepine has significant neurotoxicity and hypersensitivity reactions. We report a case of a patient post-kidney transplant who was on regular carbamazepine for childhood epilepsy and developed nystagmus, diplopia and a broad-base gait after receiving diltiazem. Understanding of the interaction between diltiazem and carbamazepine is necessary to prevent the neurotoxic effects.
  17. Naeem R, Ali Ehsan M, Yahya R, Sohail M, Khaledi H, Mazhar M
    Dalton Trans, 2016 Oct 14;45(38):14928-39.
    PMID: 27549401 DOI: 10.1039/c6dt02656g
    Pristine Mn2O3 and Ag-Mn2O3 composite thin films have been developed on fluorine doped tin oxide (FTO) coated glass substrates at 450 °C by aerosol assisted chemical vapor deposition (AACVD) using a methanol solution of a 1 : 2 mixture of acetatoargentate(i), Ag(CH3COO), and a newly synthesized manganese complex, [Mn(dmae)2(TFA)4] (1) (dmae = N,N-dimethylaminoethanolate, TFA = trifluoroacetate). The phase purity and stoichiometric composition of the films were investigated by X-ray diffraction (XRD) and Raman spectroscopy techniques. Energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) analyses revealed a Ag to Mn ratio of 1 : 2 and further confirmed the uniform dispersion of Ag nanoparticles into the Mn2O3 structure. Optical studies showed a direct band gap of 2.0 eV for the pristine Mn2O3 film that was lowered to 1.8 eV for Ag-Mn2O3 due to the plasmonic interaction of Ag with Mn2O3. The Ag-Mn2O3 composite film displayed enhanced photocatalytic activity in photoelectrochemical (PEC) water splitting and yielded a photocurrent of 3 mA cm(-2) at 0.7 V versus Ag/AgCl which was 1.6 times higher than a pristine Mn2O3 film alone, under AM 1.5 G illumination (100 mW cm(-2)). The high PEC efficiency is mainly due to the plasmonic effect of Ag nanoparticles, which enhances the visible light absorption, efficient electron-hole separation and high carrier mobility of the Ag-Mn2O3 photoelectrode. The charge carrier density of Ag-Mn2O3 is two times higher than the pristine Mn2O3 as calculated by the Mott-Schottky plot. Based on the PEC studies a mechanism is proposed to elucidate the high activity of Ag-Mn2O3 in PEC water splitting.
  18. Hammed WA, Rahman MS, Mahmud HNME, Yahya R, Sulaiman K
    Des Monomers Polym, 2017;20(1):368-377.
    PMID: 29491808 DOI: 10.1080/15685551.2016.1271086
    A soluble poly (n-vinyl carbazole)-polypyrrole (PNVC-Ppy) copolymer was prepared through oxidative chemical polymerization wherein dodecyl benzene sulfonic acid (DBSA) was used as a dopant to facilitate polymer-organic solvent interaction and ammonium persulfate (APS) was used as an oxidant. Compared with undoped PNVC-Ppy, the DBSA-doped PNVC-Ppy copolymer showed higher solubility in some selected organic solvents. The composition and structural characteristics of the DBSA-doped PNVC-Ppy were determined by Fourier transform infrared, ultraviolet-visible, and X-ray diffraction spectroscopic methods. Field emission scanning electron microscopic method was employed to observe the morphology of the DBSA-doped PNVC-Ppy copolymer. The electrical conductivity of the DBSA-doped PNVC-Ppy copolymer was measured at room temperature. The conductivity increased with increasing concentration of APS oxidant, and the highest conductivity was recorded at 0.004 mol/dm3APS at a polymerization temperature of -5 °C. The increased conductivity can be explained by the extended half-life of pyrrole free radical at a lower temperature and a gradual increase in chain length over a prolonged time due to the slow addition of APS. Furthermore, the obtained soluble copolymer exhibits unique optical and thermal properties different from those of PNVC and Ppy.
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