Displaying publications 1 - 20 of 44 in total

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  1. Interspecific variation in defense secretions of Malaysian termites from the genus Bulbitermes
    Chuah CH
    J Chem Ecol, 2005 Apr;31(4):819-27.
    PMID: 16124253
    The chemicals of the defense secretions of Malaysian Bulbitermes, B. singaporensis, B. germanus, B. sarawakensis, and Bulbitermes sp. B, show that B. singaporensis is distinct from the other species, which are themselves closely related; the genetic distance between B. singaporensis and B. germanus is 0.71. B. singaporensis contains tetracyclic kempane, and B. germanus and B. sarawakensis contain tricyclic trinervitene; Bulbitermes sp. B contains a mixture of kempane and trinervitene. The mono- and diterpenoid compositions are species-specific.
  2. Preparation of aerogel beads and microspheres based on chitosan and cellulose for drug delivery: A review
    Shi W, Ching YC, Chuah CH
    Int J Biol Macromol, 2021 Feb 15;170:751-767.
    PMID: 33412201 DOI: 10.1016/j.ijbiomac.2020.12.214
    Spherical aerogels are not easily broken during use and are easier to transport and store which can be used as templates for drug delivery. This review summarizes the possible approaches for the preparation of aerogel beads and microspheres based on chitosan and cellulose, an overview to the methods of manufacturing droplets is presented, afterwards, the transition mechanisms from sol to a spherical gel are reviewed in detail followed by different drying processes to obtain spherical aerogels with porous structures. Additionally, a specific focus is given to aerogel beads and microspheres to be regarded as drug delivery carriers. Furthermore, a core/shell architecture of aerogel beads and microspheres for controlled drug release is described and subjected to inspire readers to create novel drug release system. Finally, the conclusions and outlooks of aerogel beads and microspheres for drug delivery are summarized.
  3. A combined microwave pretreatment/solvent extraction process for the production of oil from palm fruit: optimisation, oil quality and effect of prolonged exposure
    Tan JC, Chuah CH, Cheng SF
    J Sci Food Agric, 2017 Apr;97(6):1784-1789.
    PMID: 27470073 DOI: 10.1002/jsfa.7975
    BACKGROUND: Conventional palm oil milling involves multiple stages after fruit collection; in particular, oil clarification introduces water into the pressed oil, which results in a large quantity of wastewater.

    RESULTS: A combined process of microwave pretreatment and solvent extraction to mill crude palm oil, without introducing water or steam, is described. An excellent yield (up to 30%) of oil was obtained with pretreatment in a 42 L, 1000 W and 2450 MHz microwave oven followed by hexane extraction. The optimum conditions (10 min microwave pretreatment and 12 h solvent extraction) yielded an oil with a low free fatty acid content (<1.0%) and an acceptable anisidine value (<3.0 meq kg(-1) ). The oil had a fatty acid composition not resembling those of conventional crude palm oil and crude palm kernel oil. In the pretreatment, the leached oil had 6.3% lauric acid whereas the solvent extracted oil had only 1.5% lauric acid. Among the factors affecting the oil quality, microwave pretreatment affected the oil quality significantly; however, an optimised duration that would ensure high efficiency in solvent extraction also resulted in ruptured fruitlets, although not to the extent of causing excessive oxidation. In fact, microwave pretreatment should exceed 12 min; after only 15 min, the oil had 1-methylcyclopentanol (12.96%), 1-tetradecanol (9.44%), 1-nonadecene (7.22%), nonanal (7.13%) and 1-tridecene (5.09%), which probably arose from the degradation of fibres.

    CONCLUSION: Microwave pretreatment represents an alternative milling process for crude palm oil compared with conventional processes in the omission of wet treatment with steam. © 2016 Society of Chemical Industry.

  4. Synthesis of chitosan aerogels as promising carriers for drug delivery: A review
    Wei S, Ching YC, Chuah CH
    Carbohydr Polym, 2020 Mar 01;231:115744.
    PMID: 31888854 DOI: 10.1016/j.carbpol.2019.115744
    Chitosan with abundant functional groups is regarded as important ingredients for preparing aerogel materials in life science. The biocompatibility and biodegradability of chitosan aerogels, coupled to the variety of chemical functionalities they include, result in them promising carriers for drug delivery. Moreover, chitosan aerogels as drug delivery vehicles can offer improved drug bioavailability and drug loading capacity due to their highly porous network, considerably large specific surface area and polycationic feature. The major focus of this review lies in preparation methods of chitosan aerogels from acidic aqueous solution and chitosan solution in Ionic Liquids (ILs). In addition, chitosan aerogels as drug delivery carriers are introduced in detail and expected to inspire readers to create new kind of drug delivery system based on chitosan aerogels. Finally, growing points and perspectives of chitosan aerogels in drug delivery system are given.
  5. Fulltext Applications of Lignocellulosic Fibers and Lignin in Bioplastics: A Review
    Yang J, Ching YC, Chuah CH
    Polymers (Basel), 2019 Apr 28;11(5).
    PMID: 31035331 DOI: 10.3390/polym11050751
    Lignocellulosic fibers and lignin are two of the most important natural bioresources in the world. They show tremendous potential to decrease energy utilization/pollution and improve biodegradability by replacing synthetic fibers in bioplastics. The compatibility between the fiber-matrix plays an important part in the properties of the bioplastics. The improvement of lignocellulosic fiber properties by most surface treatments generally removes lignin. Due to the environmental pollution and high cost of cellulose modification, focus has been directed toward the use of lignocellulosic fibers in bioplastics. In addition, lignin-reinforced bioplastics are fabricated with varying success. These applications confirm there is no need to remove lignin from lignocellulosic fibers when preparing the bioplastics from a technical point of view. In this review, characterizations of lignocellulosic fibers and lignin related to their applications in bioplastics are covered. Then, we generalize the developments and problems of lignin-reinforced bioplastics and modification of lignin to improve the interaction of lignin-matrix. As for lignocellulosic fiber-reinforced bioplastics, we place importance on the low compatibility of the lignocellulosic fiber-matrix. The applications of lignin-containing cellulose and lignocellulosic fibers without delignification in the bioplastics are reviewed. A comparison between lignocellulosic fibers and lignin in the bioplastics is given.
  6. Fulltext Enzymatic synthesis of structured lipids with behenic acid at the sn-1, 3 positions of triacylglycerols
    Kok WM, Chuah CH, Cheng SF
    Food Sci Biotechnol, 2018 Apr;27(2):353-366.
    PMID: 30263758 DOI: 10.1007/s10068-017-0271-3
    A long chain saturated fatty acid (SFA), behenic acid, is incorporated into the sn-1, 3 positions of triacylglycerols in palm olein (POo) and high-oleic sunflower oil (HOS) by solvent-free interesterification catalyzed by Lipozyme RM IM. The enzymatic interesterified HOS (EIE-HOS) yielded 76.5% of BOO and BOB as compared to 45.6% in POo (EIE-POo). The sn-2 position of EIE-HOS displayed 5.3 mol% of SFA which is significantly lower compared to 13.5 mol% in EIE-POo (P 
  7. Soldier defense secretions of the genus Hospitalitermes in Peninsular Malaysia
    Chuah CH, Goh SH, Tho YP
    J Chem Ecol, 1986 Mar;12(3):701-12.
    PMID: 24306909 DOI: 10.1007/BF01012103
    Soldier defense secretions of the genus Hospitalitermes (Isoptera, Termitidae, Nasutitermitinae) were chemically analyzed by GC-MS and were found to contain volatile monoterpenes and polyoxygenated diterpenes. Interspecific and intraspecific chemical variations for H. umbrinus, H. hospitalis, H. flaviventris, and H. bicolor are described. Interspecific variations in monoterpene and diterpene structures and compositions were evident. A remarkable example of large intraspecific variation from a single species was observed inH. umbrinus, indicating that colonies of this species can be separable into two chemically distinct groups. The diterpenes found in one of these groups have unusually high molecular weights.
  8. Interspecific variation in defense secretions of malaysian termites from the genusNasutitermes (Isoptera, nasutitermitinae)
    Chuah CH, Goh SH, Tho YP
    J Chem Ecol, 1989 Feb;15(2):549-63.
    PMID: 24271798 DOI: 10.1007/BF01014700
    The defense secretions of five species of MalaysianNasutitermes,N. longinasus, N. matangensis, N, havilandi, N. johoricus, andNasutitermes species 01, are compared.N. longinasus andN. species 01 provide trinervitene alcohols,N. havilandi mainly tricyclic trinervitene and tetracyclic kempane alcohols and acetates, whereasN. matangensis furnish acetyl/propionyl derivatives of trinervita-11(12),15(17)-dien-3α,9β,13α-triol (XXI and XXII). A new diterpene, assigned as trinervita-11(12),15(17)-dien-3α,13α-diol-3,13-O-diacetate (XVII), is isolated fromN. havilandi. The mono- and diterpenoid compositions, being species-specific, are useful for chemotaxonomic and phylogenetic studies.
  9. Chemical defense secretions of some species of Malaysian rhinotermitidae (Isoptera, Rhinotermitidae)
    Chuah CH, Goh SH, Tho YP
    J Chem Ecol, 1990 Mar;16(3):685-92.
    PMID: 24263584 DOI: 10.1007/BF01016479
    The defense secretions of the soldiers of the Malaysian rhinotermitid,Parrhinotermes aequalis (Havilandi) andP. pygmaeus (John),Termitogeton planus (Havilandi) andSchedorhinotermes malaccensis (Holmgren) consist mainly of vinyl ketones, whereas that ofProrhinotermes flavus (Bugnion & Popoff) gives (E)-1-nitropentadecene. The chemistry of the defense secretions ofParrhinotermes andTermitogeton is documented and based on their chemical relationships;Termitogeton shows a closer affinity to the Rhinotermitinae than Heterotermitinae.
  10. Stearic acids at sn-1, 3 positions of TAG are more efficient at limiting fat deposition than palmitic and oleic acids in C57BL/6 mice
    Gouk SW, Cheng SF, Ong AS, Chuah CH
    Br J Nutr, 2014 Apr 14;111(7):1174-80.
    PMID: 24286356 DOI: 10.1017/S0007114513003668
    In the present study, we investigated the effect of long-acyl chain SFA, namely palmitic acid (16:0) and stearic acid (18:0), at sn-1, 3 positions of TAG on obesity. Throughout the 15 weeks of the experimental period, C57BL/6 mice were fed diets fortified with cocoa butter, sal stearin (SAL), palm mid fraction (PMF) and high-oleic sunflower oil (HOS). The sn-1, 3 positions were varied by 16:0, 18:0 and 18:1, whilst the sn-2 position was preserved with 18:1. The HOS-enriched diet was found to lead to the highest fat deposition. This was in accordance with our previous postulation. Upon normalisation of total fat deposited with food intake to obtain the fat:feed ratio, interestingly, mice fed the SAL-enriched diet exhibited significantly lower visceral fat/feed and total fat/feed compared with those fed the PMF-enriched diet, despite their similarity in SFA-unsaturated fatty acid-SFA profile. That long-chain SFA at sn-1, 3 positions concomitantly with an unsaturated FA at the sn-2 position exert an obesity-reducing effect was further validated. The present study is the first of its kind to demonstrate that SFA of different chain lengths at sn-1, 3 positions exert profound effects on fat accretion.
  11. Biological properties of sodium alkyl methyl ester sulfonate/alkyltrimethylammonium bromide surfactant mixtures
    Wong SP, Lim WH, Cheng SF, Chuah CH
    Colloids Surf B Biointerfaces, 2012 Jan 1;89:48-52.
    PMID: 21937202 DOI: 10.1016/j.colsurfb.2011.08.021
    Quaternary ammonium compounds (QACs) are commonly used as disinfectant in medical care, food industry, detergents and glue industries. This is due to a small concentration of QACs is sufficient to inhibit the growth of various bacteria strains. In this work, the inhibitive power of cationic surfactants, alkyltrimethylammonium bromide (C(n)TAB) in the presence of anionic surfactants, sodium alkyl methyl ester α-sulfonate (C(n)MES) was studied. The growth inhibition test with gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria were used to determine the toxicity of single and mixed surfactants. Results from this work showed that certain mixed surfactants have lower minimum inhibition concentration (MIC) as compared to the single C(n)TAB surfactants. Besides that, it was also found that alkyl chain length and the mixing ratios of the surfactants play a significant role in determining the mixture inhibitive power.
  12. Very long chain fatty acid methyl esters in transesterified palm oil
    Puah CW, Choo YM, Ma AN, Chuah CH
    Lipids, 2006 Mar;41(3):305-8.
    PMID: 16711607
    Some unidentified minor compounds have been observed in the residue from short-path distillation of transesterified palm oil that are not detected in the original palm oil. A method combining short-path distillation to enrich the unknowns with fractionation using solid-phase extraction is described. The fractionated components were identified using GC coupled with MS. The transesterified palm oil was found to contain methyl esters of up to C32 carbon atoms. In the very long chain FAME with carbon numbers > or = 20, both even and odd carbon numbers accounted for 0.26 wt%, with C24 and C26 being the major ones present in the residue after short-path distillation of transesterified palm oil.
  13. Fulltext Preparation and Characterization of Starch/Empty Fruit Bunch-Based Bioplastic Composites Reinforced with Epoxidized Oils
    Yang J, Ching YC, Chuah CH, Liou NS
    Polymers (Basel), 2020 Dec 29;13(1).
    PMID: 33383626 DOI: 10.3390/polym13010094
    This study examined the development of starch/oil palm empty fruit bunch-based bioplastic composites reinforced with either epoxidized palm oil (EPO) or epoxidized soybean oil (ESO), at various concentrations, in order to improve the mechanical and water-resistance properties of the bio-composites. The SEM micrographs showed that low content (0.75 wt%) of epoxidized oils (EOs), especially ESO, improved the compatibility of the composites, while high content (3 wt%) of EO induced many voids. The melting temperature of the composites was increased by the incorporation of both EOs. Thermal stability of the bioplastics was increased by the introduction of ESO. Low contents of EO led to a huge enhancement of tensile strength, while higher contents of EO showed a negative effect, due to the phase separation. The tensile strength increased from 0.83 MPa of the control sample to 3.92 and 5.42 MPa for the composites with 1.5 wt% EPO and 0.75 wt% ESO, respectively. EOs reduced the composites' water uptake and solubility but increased the water vapor permeability. Overall, the reinforcing effect of ESO was better than EPO. These results suggested that both EOs can be utilized as modifiers to prepare starch/empty-fruit-bunch-based bioplastic composites with enhanced properties.
  14. Atypical peripheral ameloblastoma of the palate
    Siar CH, Ng KH, Ngui CH, Chuah CH
    J Laryngol Otol, 1990 Mar;104(3):252-4.
    PMID: 2341785
    Clinical, radiological and histological characteristics of the peripheral ameloblastoma are briefly outlined. A case found occurring in the palate and presenting with atypical histological features is reported. The differential diagnosis of this lesion, its treatment and histogenesis are discussed.
  15. Risk factors of carbapenem-resistant Enterobacteriaceae infection and colonisation: a Malaysian tertiary care hospital based case-control study
    Chuah CH, Gani Y, Sim B, Chidambaram SK
    J R Coll Physicians Edinb, 2021 03;51(1):24-30.
    PMID: 33877130 DOI: 10.4997/JRCPE.2021.107
    BACKGROUND: Carbapenem-resistant Enterobacteriaceae (CRE) infection has become a major challenge to clinicians. The aim of this study is to identify the risk factors of acquiring CRE to guide more targeted screening for hospital admissions.

    METHODS: This is a retrospective case-control study (ratio 1:1) where a patient with CRE infection or colonisation was matched with a control. The control was an individual who tested negative for CRE but was a close contact of a patient testing positive and was admitted at the same time and place. Univariate and multivariate statistical analyses were done.

    RESULTS: The study included 154 patients. The majority of the CRE was Klebsiella species (83%). From univariate analysis, the significant risk factors were having a history of indwelling devices (OR: 2.791; 95% CI: 1.384-5.629), concomitant other MDRO (OR: 2.556; 95% CI: 1.144-5.707) and hospitalisation for more than three weeks (OR: 2.331; 95% CI: 1.163-4.673). Multivariate analysis showed that being unable to ambulate on admission (adjusted OR: 2.345; 95% CI: 1.170-4.699) and antibiotic exposure (adjusted OR: 3.515; 95% CI: 1.377-8.972) were independent predictors. The in-hospital mortality rate of CRE infection was high (64.5%). CRE acquisition resulted in prolonged hospitalisation (median=35 days; P<0.001).

    CONCLUSION: CRE infection results in high morbidity and mortality. On top of the common risk factors, patients with mobility restriction, prior antibiotic exposures and hospitalisation for more than three weeks should be prioritised in the screening strategy to control the spread of CRE.

  16. Fulltext Nanotherapeutics for treating coronavirus diseases
    Gunathilake TMSU, Ching YC, Uyama H, Chuah CH
    J Drug Deliv Sci Technol, 2021 Aug;64:102634.
    PMID: 34127930 DOI: 10.1016/j.jddst.2021.102634
    Viral diseases have recently become a threat to human health and rapidly become a significant cause of mortality with a continually exacerbated unfavorable socio-economic impact. Coronaviruses, including severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome (MERS-CoV), and severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), have threatened human life, with immense accompanying morbidity rates; the COVID-19 (caused by SARS-CoV-2) epidemic has become a severe threat to global public health. In addition, the design process of antiviral medications usually takes years before the treatments can be made readily available. Hence, it is necessary to invest scientifically and financially in a technology platform that can then be quickly repurposed on demand to be adequately positioned for this kind of pandemic situation through lessons learned from the previous pandemics. Nanomaterials/nanoformulations provide such platform technologies, and a proper investigation into their basic science and biological interactions would be of great benefit for potential vaccine and therapeutic development. In this respect, intelligent and advanced nano-based technologies provide specific physico-chemical properties, which can help fix the key issues related to the treatments of viral infections. This review aims to provide an overview of the latest research on the effective use of nanomaterials in the treatment of coronaviruses. Also raised are the problems, perspectives of antiviral nanoformulations, and the possibility of using nanomaterials effectively against current pandemic situations.
  17. Soldier defense secretions of malaysian free-ranging termite of the genusLacessititermes (Isoptera, Nasutitermitinae)
    Goh SH, Chuah CH, Vadiveloo J, Tho YP
    J Chem Ecol, 1990 Feb;16(2):619-30.
    PMID: 24263517 DOI: 10.1007/BF01021792
    Soldiers of free-ranging termites of the genusLacessititermes (Isoptera, Nasutitermitinae) secrete from their frontal glands a mixture of monoterpenes, sesquiterpenes, and diterpenes.Lacessititermes ransoneti, L. laborator, andL. species A produce species-specific secretions, the composition being most complex forL. laborator. Apart from known mono- and dihydroxytrinervitadienes, the following new diterpenes were isolated and tentatively assigned as trinervita-1(15),8(19)-dien-2β,3α,9α,14α-tetraol 2,3,14-O-triacetate, trinervita-1(15),8(19)-dien-2β,3α,9β,14α-tetraol 2,3,14-O-triacetate, 2β,3α,9α, 14α-tetraacetoxy-1 (15), 8(19)-trinervitadiene, and 2β,3α,11α,13α-tetraacetoxy-1(15),8(19)-trinervitadiene. Data on intragenus chemical variations were subjected to canonical discriminant analysis and genetic distances among the species were calculated to depict intragenus identities and affinities.
  18. Extreme intraspecific chemical variability in soldier defense secretions of allopatric and sympatric colonies ofLongipeditermes longipes
    Goh SH, Chuah CH, Tho YP, Prestwich GD
    J Chem Ecol, 1984 Jun;10(6):929-44.
    PMID: 24318785 DOI: 10.1007/BF00987974
    The chemical defense secretions of major and minor soldiers of over 18 colonies of the primitive glue-squirting nasute termiteLongipeditermes longipes (Isoptera, Termitidae, Nasutitermitinae) were analyzed chormatographically. The colonies, collected from four rainforest sites in peninsular Malaysia, showed monoterpene patterns rich in pinenes and limonene but with few quantitative differences between colonies. In marked contrast, the diterpene chemistry is high variable, and includes tricyclic (trinervitane), tetracyclic (rippertane), bicyclic (secotrinervitane), and a new spirotetracyclic (longipane) skeleton. Three new natural products are included in this remarkable and unprecedented example of structural diversity among different colonies of a single species.
  19. Soldier defense secretions of the Malaysian termite,Hospitalioermes umbrinus (Isoptera, Nasutitermitinae)
    Chuah CH, Goh SH, Prestwich GD, Tho YP
    J Chem Ecol, 1983 Mar;9(3):347-56.
    PMID: 24407404 DOI: 10.1007/BF00988454
    Trinervita-1(15),8(19)-dien-2β,3α-diol and the new trinervita-1(15),8(19)-dien-2β, 3α-diol 2-O-acetate constitute the major diterpene constituents of the soldier defense secretions of the NasutitermiteHospitalitermes umbrinus of Malaysian region. Studies on the intraspecific variations on sympatric and allopatric populations indicate two distinct patterns of chemical composition.
  20. Long-chain SFA at the sn-1, 3 positions of TAG reduce body fat deposition in C57BL/6 mice
    Gouk SW, Cheng SF, Mok JS, Ong AS, Chuah CH
    Br J Nutr, 2013 Dec 14;110(11):1987-95.
    PMID: 23756564 DOI: 10.1017/S0007114513001475
    The present study aimed to determine the effect of positional distribution of long-chain SFA in TAG, especially at the sn-1, 3 positions, on fat deposition using the C57BL/6 mouse model. Throughout the 15 weeks of the study, mice were fed with diets fortified with palm olein (POo), chemically interesterified POo (IPOo) and soyabean oil (SOY). Mice receiving the SOY-enriched diet gained significantly higher amounts of subcutaneous fat (P= 0·011) and total fat (P= 0·013) compared with the POo group, despite similar body mass gain being recorded. During normalisation with food consumption to obtain the fat:feed ratio, mice fed with the POo-enriched diet exhibited significantly lower visceral (P= 0·044), subcutaneous (P= 0·006) and total (P= 0·003) fat:feed than those fed with the SOY-enriched diet. It is noteworthy that mice fed with the IPOo-enriched diet gained 14·3 % more fat per food consumed when compared with the POo group (P= 0·013), despite their identical total fatty acid compositions. This was mainly attributed to the higher content of long-chain SFA at the sn-1, 3 positions of TAG in POo, which results in delayed absorption after deacylation as evidenced by the higher amounts of long-chain SFA excreted in the faeces of mice fed with the POo-enriched diet. Negative correlations were found between the subcutaneous, visceral as well as total fat accretion per food consumption and the total SFA content at the sn-1, 3 positions, while no relationships were found for MUFA and PUFA. The present results show that the positional distribution of long-chain SFA exerts a more profound effect on body fat accretion than the total SFA content.
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