MyMedR

Fulltext 2-{1-[2-(Bis{2-[1-(5-chloro-2-hydroxy-phen-yl)ethyl-ideneamino]eth-yl}amino)-ethyl-iminio]eth-yl}-4-chloro-phenolate toluene hemisolvate

Lee SM, Ali HM, Lo KM, Ng SW

Acta Crystallogr Sect E Struct Rep Online, 2009;65(Pt 2):o409.

PMID: 21582001 DOI: 10.1107/S1600536809002906

In the toluene hemisolvated tripodal tris-(2-amino-ethyl)amine Schiff base, C(30)H(33)Cl(3)N(4)O(3)·0.5C(7)H(8), one of the three imino N atoms is protonated, forming a hydrogen bond with the O atom at an adjacent benzene ring. The other two imino N atoms act as hydrogen-bond acceptors from phenolate OH groups. The toluene solvent mol-ecule is disordered about a centre of inversion.

Fulltext 3-Hydr-oxy-N'-isopropyl-idene-2-naphthohydrazide

Lee SM, Lo KM, Ali HM, Ng SW

Acta Crystallogr Sect E Struct Rep Online, 2009;65(Pt 12):o3282.

PMID: 21578975 DOI: 10.1107/S1600536809050661

The title Schiff base, C(14)H(14)N(2)O(2), is close to being planar (r.m.s. deviation for the non-hydrogen atoms = 0.052 Å) and an intra-molecular N-H⋯O hydrogen bond generates an S(6) ring. In the crystal, the moleucles are linked by O-H⋯O hydrogen bonds, giving rise to helical chains propagating along the c axis of the tetra-gonal unit cell.

Fulltext catena-Poly[[triphenyl-tin(IV)]-μ-2-[(3,5-di-tert-butyl-4-hydroxy-benz-yl)sulfan-yl]acetato-κO:O']

Lee SM, Lo KM, Mohd Ali H, Robinson WT

Acta Crystallogr Sect E Struct Rep Online, 2009;65(Pt 7):m808.

PMID: 21582732 DOI: 10.1107/S1600536809023150

The title compound, [Sn(C(6)H(5))(3)(C(17)H(25)O(3)S)](n), comprises two symmetry-independent five-coordinated triphenyl-tin mol-ecules which are linked by carboxyl-ate bridges into a polymeric chain. The Sn(IV) atom is in a distorted trans-C(3)SnO(2) trigonal-bipyramidal geometry. The presence of two bulky tert-butyl groups on the benzene ring prevents any hydrogen-bonding inter-actions involving the hydroxyl substituents.

Fulltext [N'-(5-Chloro-2-oxidobenzyl-idene-κO)-3-hydr-oxy-2-naphthohydrazidato-κN',O]dimethyl-tin(IV)

Lee SM, Lo KM, Mohd Ali H, Ng SW

Acta Crystallogr Sect E Struct Rep Online, 2009;65(Pt 7):m816.

PMID: 21582739 DOI: 10.1107/S1600536809022259

The Sn(IV) atom in the title compound, [Sn(CH(3))(2)(C(18)H(11)ClN(2)O(3))], shows a trans-C(2)NO(2)Sn trigonal-bipyramidal coordin-ation; the axial O-Sn-O angle is 155.22 (5)°. The tridentate N'-(5-chloro-2-oxidobenzyl-idene)-3-hydr-oxy-2-naphthohydrazidate dianion is stabilized by an intra-molecular O-H⋯N hydrogen bond.

Fulltext {N'-[1-(5-Bromo-2-oxidophenyl-κO)ethyl-idene]-3-hydroxy-2-naphtho-hydrazidato-κN',O}dibutyl-tin(IV)

Lee SM, Lo KM, Ali HM, Ng SW

Acta Crystallogr Sect E Struct Rep Online, 2009;65(Pt 8):m863.

PMID: 21583331 DOI: 10.1107/S160053680902457X

The Sn(IV) atom in the title compound, [Sn(C(4)H(9))(2)(C(19)H(13)BrN(2)O(3))], shows a distorted cis-C(2)NO(2)Sn trigonal-bipyramidal coordination. Both butyl chains and the naphth-yl-oxy portion are disordered over two sets of sites of equal occupancy.

Fulltext [N'-(5-Bromo-2-oxidobenzyl-idene-κO)-3-hydr-oxy-2-naphthohydrazidato-κN',O]dibutyl-tin(IV)

Lee SM, Lo KM, Ali HM, Ng SW

Acta Crystallogr Sect E Struct Rep Online, 2009;65(Pt 8):m862.

PMID: 21583330 DOI: 10.1107/S1600536809024477

The Sn(IV) atom in the title compound, [Sn(C(4)H(9))(2)(C(18)H(11)BrN(2)O(3))], shows a distorted cis-C(2)NO(2)Sn trigonal-bipyramidal coordination. One of the butyl chains is disordered over two sites in a 0.60 (1):0.40 (1) ratio.

Fulltext [N'-(5-Chloro-2-oxidobenzyl-idene-κO)-3-hydr-oxy-2-naphthohydrazidato-κN',O]diphenyl-tin(IV)

Lee SM, Lo KM, Ali HM, Ng SW

Acta Crystallogr Sect E Struct Rep Online, 2009;65(Pt 12):m1689.

PMID: 21578694 DOI: 10.1107/S1600536809050107

The Sn(IV) atom in the title compound, [Sn(C(6)H(5))(2)(C(18)H(11)ClN(2)O(3))], is O,N,O'-chelated by the deprotonated Schiff base ligand and further bonded by two phenyl rings in a distorted cis-C(2)SnNO(2) trigonal-bipyramidal geometry [C-Sn-C = 125.7 (2)°]. The two phenyl rings are oriented at a dihedral angle of 55.2 (3)°. Intra-molecular O-H⋯N hydrogen bonding is present in the crystal structure.

Fulltext Bis[4-(dimethyl-amino)pyridinium] tetra-bromidobis(4-methyl-phen-yl)stannate(IV)

Lee SM, Lo KM, Mohd Ali H, Robinson WT

Acta Crystallogr Sect E Struct Rep Online, 2009;65(Pt 9):m1040.

PMID: 21577403 DOI: 10.1107/S1600536809030323

In the title compound, (C(7)H(11)N(2))(2)[SnBr(4)(C(7)H(7))(2)], the tetra-bromidobis(4-methyl-phen-yl)stannate(IV) anion possesses a centre of inversion located at the Sn(IV) atom. In the crystal structure, two inversion-related cations are linked to the anion via weak N-H⋯Br hydrogen bonds.

Fulltext Bis[4-(dimethyl-amino)pyridinium] tetra-bromidobis(4-chloro-phen-yl)stannate(IV)-4-bromo-chloro-benzene (1/1)

Lee SM, Lo KM, Mohd Ali H, Robinson WT

Acta Crystallogr Sect E Struct Rep Online, 2009;65(Pt 9):m1039.

PMID: 21577402 DOI: 10.1107/S1600536809030232

In the title compound, (C(7)H(11)N(2))(2)[SnBr(4)(C(6)H(4)Cl)(2)]·C(6)H(4)BrCl, the Sn(IV) atom in the tetra-bromidobis(4-chloro-phen-yl)stannate(IV) anion lies on a centre of inversion. The distances between the 4-(dimethyl-amino)pyridinium N atom and the Br atoms of the anion are 3.450 (2) and 3.452 (2) Å, suggesting weak hydrogen bonding. The 4-bromo-chloro-benzene solvent mol-ecule, which is a bromination by-product from the reaction, is disordered about a twofold rotation axis with approximately equal occupancy.

Fulltext Draft Genome Sequences of Three Multiantibiotic-Resistant Campylobacter jejuni Strains (2865, 2868, and 2871) Isolated from Poultry at Retail Outlets in Malaysia

Teh AH, Lee SM, Dykes GA

Genome Announc, 2016;4(3).

PMID: 27151799 DOI: 10.1128/genomeA.00331-16

Campylobacter jejuni is a frequent cause of human bacterial gastrointestinal foodborne disease worldwide. Antibiotic resistance in this species is of public health concern. The draft genome sequences of three multiantibiotic-resistant C. jejuni strains (2865, 2868, and 2871) isolated from poultry at retail outlets in Malaysia are presented here.

Fulltext Antioxidant and antibacterial activity of Rhoeo spathacea (Swartz) Stearn leaves

Tan JB, Lim YY, Lee SM

J Food Sci Technol, 2015 Apr;52(4):2394-400.

PMID: 25829624 DOI: 10.1007/s13197-013-1236-z

The decoction and infusion of Rhoeo spathacea (Swartz) Stearn leaves have been recognized as a functional food particularly in South America, but has not yet gained international popularity as a beverage. The primary aim of this study was to establish the viability of R. spathacea aqueous leaf extracts as a beverage, in terms of its antioxidant activity and antibacterial activity. The antioxidant contents of aqueous and methanol leaf extracts were evaluated by the total phenolic content (TPC) and total flavonoid content (TFC) assays. The antioxidant activities measured were DPPH radical scavenging activity (FRS), ferric reducing power (FRP) and ferrous ion chelating (FIC) activity. The aqueous leaf extracts in the forms of decoction and infusion, were found to have comparable TPC and antioxidant activity with other herbal teas previously reported by our research group. Both decoction and infusion also exhibited antibacterial activity against six species of Gram positive and four species of Gram negative bacteria, notably methicillin-resistant Staphylococcus aureus and Neisseria gonorrhoeae. A total of four different known phenolic compounds were identified by HPLC and MS, three of which have not been previously reported to be found in this plant. Both the decoction and infusion of the leaves R. spathacea have potential to be popularized into a common beverage.

Growth in the presence of specific antibiotics induces biofilm formation by a Campylobacter jejuni strain sensitive to them but not in resistant strains

Teh AHT, Lee SM, Dykes GA

J Glob Antimicrob Resist, 2019 09;18:55-58.

PMID: 31163253 DOI: 10.1016/j.jgar.2019.05.020

OBJECTIVE: Campylobacter jejuni (C. jejuni) are among the most frequently identified bacteria associated with human gastroenteritis worldwide. Exposure to antibiotics may induce or inhibit biofilm formation in some bacterial species. Little work has been reported on the influence of antibiotics on biofilm formation by C. jejuni.

METHODS: This study investigated the effect of six different classes of antibiotics with different modes of action (ampicillin, ciprofloxacin, erythromycin, nalidixic acid, rifampicin and tetracycline) on biofilm formation in vitro by seven C. jejuni from poultry with different antibiotic resistance profiles.

RESULTS: The results indicated that in the presence of most of the tested antibiotics, biofilm formation by C. jejuni strains, which are resistant to them, was reduced but biofilm formation in sensitive strains was increased.

CONCLUSION: The ability of certain antibiotics to induce biofilm formation by a tested C. jejuni strain is of concern, with respect to the effective control of disease caused by this pathogen; however, further work is required to confirm how widespread this feature is.

A statistical approach for modelling the physical process of bacterial attachment to abiotic surfaces

Wang Y, Lee SM, Gentle IR, Dykes GA

Biofouling, 2020 11;36(10):1227-1242.

PMID: 33412938 DOI: 10.1080/08927014.2020.1865934

A statistical approach using a polynomial linear model in combination with a probability distribution model was developed to mathematically represent the process of bacterial attachment and study its mechanism. The linear deterministic model was built based on data from experiments investigating bacterial and substratum surface physico-chemical factors as predictors of attachment. The prediction results were applied to a normal-approximated binomial distribution model to probabilistically predict attachment. The experimental protocol used mixtures of Streptococcus salivarius and Escherichia coli, and mixtures of porous poly(butyl methacrylate-co-ethyl dimethacrylate) and aluminum sec-butoxide coatings, at varying ratios, to allow bacterial attachment to substratum surfaces across a range of physico-chemical properties (including the surface hydrophobicity of bacterial cells and the substratum, the surface charge of the cells and the substratum, the substratum surface roughness and cell size). The model was tested using data from independent experiments. The model indicated that hydrophobic interaction was the most important predictor while reciprocal interactions existed between some of the factors. More importantly, the model established a range for each factor within which the resultant attachment is unpredictable. This model, however, considers bacterial cells as colloidal particles and accounts only for the essential physico-chemical attributes of the bacterial cells and substratum surfaces. It is therefore limited by a lack of consideration of biological and environmental factors. This makes the model applicable only to specific environments and potentially provides a direction to future modelling for different environments.

Fulltext N'-[1-(5-Bromo-2-hy-droxy-phen-yl)ethyl-idene]isonicotinohydrazide monohydrate: crystal structure and Hirshfeld surface analysis

Lee SM, Halcovitch NR, Jotani MM, Tiekink ERT

Acta Crystallogr E Crystallogr Commun, 2017 Apr 01;73(Pt 4):630-636.

PMID: 28435737 DOI: 10.1107/S2056989017004790

In the title isonicotinohydrazide hydrate, C14H12BrN3O2·H2O {systematic name: N'-[(1E)-1-(5-bromo-2-hy-droxy-phen-yl)ethyl-idene]pyridine-4-carbohydrazide monohydrate}, the central CN2O region of the organic mol-ecule is planar and the conformation about the imine-C=N bond is E. While an intra-molecular hy-droxy-O-H⋯N(imine) hydrogen bond is evident, the dihedral angle between the central residue and the benzene rings is 48.99 (9)°. Overall, the mol-ecule is twisted, as seen in the dihedral angle of 71.79 (6)° between the outer rings. In the crystal, hydrogen-bonding inter-actions, i.e. hydrazide-N-H⋯O(water), water-O-H⋯O(carbon-yl) and water-O-H⋯N(pyrid-yl), lead to supra-molecular ribbons along the a-axis direction. Connections between these, leading to a three-dimensional architecture, are mediated by Br⋯Br halogen bonding [3.5366 (3) Å], pyridyl-C-H⋯O(carbon-yl) as well as weak π-π inter-actions [inter-centroid separation between benzene rings = 3.9315 (12) Å]. The Hirshfeld surface analysis reveals the importance of hydrogen atoms in the supra-molecular connectivity as well as the influence of the Br⋯Br halogen bonding.

(Tris{2-[(5-chloro-2-oxido-benzyl-idene-κO)amino-κN]eth-yl}amine-κN)-ytterbium(III): crystal structure and Hirshfeld surface analysis

Lee SM, Lo KM, Tan SL, Tiekink ER

Acta Crystallogr E Crystallogr Commun, 2016 Oct 1;72(Pt 10):1390-1395.

PMID: 27746926

The Yb(III) atom in the title complex, [Yb(C27H24Cl3N4O3)] [systematic name: (2,2',2''-{(nitrilo)-tris-[ethane-2,1-di-yl(nitrilo)-methylyl-idene]}tris-(4-chloro-phenolato)ytterbium(III)], is coordinated by a trinegative, hepta-dentate ligand and exists within an N4O3 donor set, which defines a capped octa-hedral geometry whereby the amine N atom caps the triangular face defined by the three imine N atoms. The packing features supra-molecular layers that stack along the a axis, sustained by a combination of aryl-C-H⋯O, imine-C-H⋯O, methyl-ene-C-H⋯π(ar-yl) and end-on C-Cl⋯π(ar-yl) inter-actions. A Hirshfeld surface analysis points to the major contributions of C⋯H/ H⋯C and Cl⋯H/H⋯Cl inter-actions (along with H⋯H) to the overall surface but the Cl⋯H contacts are at distances greater than the sum of their van der Waals radii.

Zwitterionic 4-bromo-6-meth-oxy-2-{[tris-(hy-droxy-meth-yl)methyl]-iminiumyl-meth-yl}phenolate: crystal structure and Hirshfeld surface analysis

Lee SM, Lo KM, Tan SL, Tiekink ER

Acta Crystallogr E Crystallogr Commun, 2016 Aug 1;72(Pt 8):1223-7.

PMID: 27536419 DOI: 10.1107/S2056989016012159

In the solid state, the title compound, C12H16BrNO5 [systematic name: 4-bromo-2-((1E)-{[1,3-dihy-droxy-2-(hy-droxy-meth-yl)propan-2-yl]iminium-yl}meth-yl)-6-meth-oxy-benzen-1-olate], C12H16BrNO5, is found in the keto-amine tautomeric form, with an intra-molecular iminium-N-H⋯O(phenolate) hydrogen bond and an E conformation about the C=N bond. Both gauche (two) and anti relationships are found for the methyl-hydroxy groups. In the crystal, a supra-molecular layer in the bc plane is formed via hy-droxy-O-H⋯O(hy-droxy) and charge-assisted hy-droxy-O-H⋯O(phenolate) hydrogen-bonding inter-actions; various C-H⋯O inter-actions provide additional cohesion to the layers, which stack along the a axis with no directional inter-actions between them. A Hirshfeld surface analysis confirms the lack of specific inter-actions in the inter-layer region.

Fulltext Electrochemical Preparation and Characterization of a Gold Nanoparticles Graphite Electrode: Application to Myricetin Antioxidant Analysis

Ng KL, Lee SM, Khor SM, Tan GH

Anal Sci, 2015;31(10):1075-81.

PMID: 26460374 DOI: 10.2116/analsci.31.1075

Graphite material is abundantly available from recyclable sources. It possesses a good electrical conductance property, which makes it an attractive material as a working electrode. However, due to a high activation overpotential it has limited applications as compared to other solid metal electrodes. In this present work, we obtained a graphite rod from a used battery, and carried out electrochemical improvements by electro-deposition with gold nanoparticles (AuNPs). The heterogeneous electron transfer rate and electron transfer resistance of the fabricated electrode were improved. The electrode overpotential has shown improvement by 50 mV, and the effective surface area has increased by 2 fold. To determine the practicability of the AuNPs/graphite electrode, we used the electrode in the analysis of myricetin. A square-wave voltammetry was used in the analysis, and the detection response increased by 2.5 fold, which suggested an improvement in the electrode sensitivity.

The Influence of Prior Modes of Growth, Temperature, Medium, and Substrate Surface on Biofilm Formation by Antibiotic-Resistant Campylobacter jejuni

Teh AH, Lee SM, Dykes GA

Curr Microbiol, 2016 Dec;73(6):859-866.

PMID: 27623781

Campylobacter jejuni is one of the most common causes of bacterial gastrointestinal food-borne infection worldwide. It has been suggested that biofilm formation may play a role in survival of these bacteria in the environment. In this study, the influence of prior modes of growth (planktonic or sessile), temperatures (37 and 42 °C), and nutrient conditions (nutrient broth and Mueller-Hinton broth) on biofilm formation by eight C. jejuni strains with different antibiotic resistance profiles was examined. The ability of these strains to form biofilm on different abiotic surfaces (stainless steel, glass, and polystyrene) as well as factors potentially associated with biofilm formation (bacterial surface hydrophobicity, auto-aggregation, and initial attachment) was also determined. The results showed that cells grown as sessile culture generally have a greater ability to form biofilm (P

Comparative Study of Betacyanin Profile and Antimicrobial Activity of Red Pitahaya (Hylocereus polyrhizus) and Red Spinach (Amaranthus dubius)

Yong YY, Dykes G, Lee SM, Choo WS

Plant Foods Hum Nutr, 2017 Mar;72(1):41-47.

PMID: 27917454 DOI: 10.1007/s11130-016-0586-x

Betacyanins are reddish to violet pigments that can be found in red pitahaya (Hylocereus polyrhizus) and red spinach (Amaranthus dubius). This study investigated the impact of sub-fractionation (solvent partitioning) on betacyanin content in both plants. Characterization of betacyanins and evaluation of their antimicrobial activities were also carried out. Betanin was found in both plants. In addition, isobetanin, phyllocactin and hylocerenin were found in red pitahaya whereas amaranthine and decarboxy-amaranthine were found in red spinach. Sub-fractionated red pitahaya and red spinach had 23.5 and 121.5 % more betacyanin content, respectively, than those without sub-fractionation. Sub-fractionation increased the betanin and decarboxy-amaranthine content in red pitahaya and red spinach, respectively. The betacyanin fraction from red spinach (minimum inhibitory concentration [MIC] values: 0.78-3.13 mg/mL) demonstrated a better antimicrobial activity profile than that of red pitahaya (MIC values: 3.13-6.25 mg/mL) against nine Gram-positive bacterial strains. Similarly, the red spinach fraction (MIC values: 1.56-3.13 mg/mL) was more active than the red pitahaya fraction (MIC values: 3.13-6.25 mg/mL) against five Gram-negative bacterial strains. This could be because of a higher amount of betacyanin, particularly amaranthine in the red spinach.

Biofilm inhibiting activity of betacyanins from red pitahaya (Hylocereus polyrhizus) and red spinach (Amaranthus dubius) against Staphylococcus aureus and Pseudomonas aeruginosa biofilms

Yong YY, Dykes G, Lee SM, Choo WS

J Appl Microbiol, 2019 Jan;126(1):68-78.

PMID: 30153380 DOI: 10.1111/jam.14091

AIMS: To investigate the biofilm inhibitory activity of betacyanins from red pitahaya (Hylocereus polyrhizus) and red spinach (Amaranthus dubius) against Staphylococcus aureus and Pseudomonas aeruginosa biofilms.

METHODS AND RESULTS: The pulp of red pitahaya and the leaves of red spinach were extracted using methanol followed by subfractionation to obtain betacyanin fraction. The anti-biofilm activity was examined using broth microdilution assay on polystyrene surfaces and expressed as minimum biofilm inhibitory concentration (MBIC). The betacyanin fraction from red spinach showed better anti-biofilm activity (MBIC: 0·313-1·25 mg ml-1 ) against five Staph. aureus strains while the betacyanin fraction from red pitahaya showed better anti-biofilm activity (MBIC: 0·313-0·625 mg ml-1 ) against four P. aeruginosa strains. Both betacyanin fraction significantly reduced hydrophobicity of Staph. aureus and P. aeruginosa strains. Numbers of Staph. aureus and P. aeruginosa attached to polystyrene were also reduced without affecting their cell viability.

CONCLUSION: Betacyanins can act as anti-biofilm agents against the initial step of biofilm formation, particularly on a hydrophobic surface like polystyrene.

SIGNIFICANCE AND IMPACT OF THE STUDY: This study is the first to investigate the use of betacyanin as a biofilm inhibitory agent. Betacyanin could potentially be used to reduce the risk of biofilm-associated infections.

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