Displaying publications 1 - 20 of 69 in total

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  1. Fulltext Caffeoylquinic acids in leaves of selected Apocynaceae species: Their isolation and content
    Wong SK, Lim YY, Ling SK, Chan EW
    Pharmacognosy Res, 2014 Jan;6(1):67-72.
    PMID: 24497746 DOI: 10.4103/0974-8490.122921
    Three compounds isolated from the methanol (MeOH) leaf extract of Vallaris glabra (Apocynaceae) were those of caffeoylquinic acids (CQAs). This prompted a quantitative analysis of their contents in leaves of V. glabra in comparison with those of five other Apocynaceae species (Alstonia angustiloba, Dyera costulata, Kopsia fruticosa, Nerium oleander, and Plumeria obtusa), including flowers of Lonicera japonica (Japanese honeysuckle), the commercial source of chlorogenic acid (CGA).
  2. Fulltext Antiproliferative activity of Vallaris glabra Kuntze (Apocynaceae)
    Wong SK, Lim YY, Ling SK, Chiang Chan EW
    Pharmacogn Mag, 2014 Apr;10(Suppl 2):S232-9.
    PMID: 24991097 DOI: 10.4103/0973-1296.133238
    Our earlier study on the antiproliferative (APF) activity of leaf extracts of ten Apocynaceae species showed that leaves of Vallaris glabra possessed strong and broad-spectrum properties.
  3. Extraction methods of butterfly pea (Clitoria ternatea) flower and biological activities of its phytochemicals
    Jeyaraj EJ, Lim YY, Choo WS
    J Food Sci Technol, 2021 Jun;58(6):2054-2067.
    PMID: 33967304 DOI: 10.1007/s13197-020-04745-3
    Clitoria ternatea or commonly known as 'Butterfly pea' has been used traditionally in Ayurvedic medicine in which various parts of the plants are used to treat health issues such as indigestion, constipation, arthritis, skin diseases, liver and intestinal problems. The flowers of C. ternatea are used worldwide as ornamental flowers and traditionally used as a food colorant. This paper reviews the recent advances in the extraction and biological activities of phytochemicals from C. ternatea flowers. The application of maceration or ultrasound assisted extraction greatly increased the yield (16-247% of increase) of phytochemicals from C. ternatea flowers. Various phytochemicals such as kaempferol, quercetin and myricetin glycosides as well as anthocyanins have been isolated from C. ternatea flowers. Clitoria ternatea flower extracts were found to possess antimicrobial, antioxidant, anti-inflammatory, cytotoxic and antidiabetic activities which are beneficial to human health. Clitoria ternatea flower is a promising candidate for functional food applications owing to its wide range of pharmacotherapeutic properties as well as its safety and effectiveness.
  4. Enzymatic synthesis of quercetin oleate esters using Candida antarctica lipase B
    Saik AY, Lim YY, Stanslas J, Choo WS
    Biotechnol Lett, 2017 Feb;39(2):297-304.
    PMID: 27812823 DOI: 10.1007/s10529-016-2246-5
    OBJECTIVES: To investigate the lipase-catalyzed acylation of quercetin with oleic acid using Candida antarctica lipase B.

    RESULTS: Three acylated analogues were produced: quercetin 4'-oleate (C33H42O8), quercetin 3',4'-dioleate (C51H74O9) and quercetin 7,3',4'-trioleate (C69H106O10). Their identities were confirmed with UPLC-ESI-MS and (1)H NMR analyses. The effects of temperature, duration and molar ratio of substrates on the bioconversion yields varied across conditions. The regioselectivity of the acylated quercetin analogues was affected by the molar ratio of substrates. TLC showed the acylated analogues had higher lipophilicity (152% increase) compared to quercetin. Partition coefficient (log P) of quercetin 4'-oleate was higher than those of quercetin and oleic acid. Quercetin 4'-oleate was also stable over 28 days of storage.

    CONCLUSIONS: Quercetin oleate esters with enhanced lipophilicity can be produced via lipase-catalyzed reaction using C. antarctica lipase B to be used in topical applications.

  5. Fulltext Antioxidant, cytotoxic, and antibacterial activities of Clitoria ternatea flower extracts and anthocyanin-rich fraction
    Jeyaraj EJ, Lim YY, Choo WS
    Sci Rep, 2022 09 01;12(1):14890.
    PMID: 36050436 DOI: 10.1038/s41598-022-19146-z
    Clitoria ternatea flower is a traditional medicinal herb that has been used as a natural food colourant. As there are limited studies on investigating the bioactivities of the anthocyanin-rich fraction of Clitoria ternatea flower, this study aimed to determine an efficient column chromatography method to obtain the anthocyanin-rich fraction from this flower and characterise its composition, antioxidant, antibacterial, and cytotoxic activities. Amberlite XAD-16 column chromatography was more efficient in enriching the total anthocyanin content (TAC) of the fraction with the highest TAC to total phenolic content (TPC) ratio of 1:6 than that using C18-OPN. A total of 11 ternatin anthocyanins were characterised in the anthocyanin-rich fraction by LC-MS analysis. The antioxidant activity of the anthocyanin-rich fraction was more potent in the chemical-based assay with an IC50 value of 0.86 ± 0.07 mg/mL using 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay than cellular antioxidant assay using RAW 264.7 macrophages. In vitro cytotoxicity assay using human embryonic kidney HEK-293 cell line showed the anthocyanin-rich fraction to be more toxic than the crude extracts. The anthocyanin-rich fraction had more potent antibacterial activity than the crude extracts against Bacillus cereus, Bacillus subtilis, and Escherichia coli. The anthocyanin-rich fraction of C. ternatea has the potential to be used and developed as a functional food ingredient or nutraceutical agent.
  6. Fulltext Sources and relative stabilities of acylated and nonacylated anthocyanins in beverage systems
    Vidana Gamage GC, Lim YY, Choo WS
    J Food Sci Technol, 2022 Mar;59(3):831-845.
    PMID: 35185195 DOI: 10.1007/s13197-021-05054-z
    Anthocyanins are considered as the largest group of water-soluble pigments found in the vacuole of plant cells, displaying range of colors from pink, orange, red, purple and blue. They belong to flavonoids, a polyphenolic subgroup. Application of anthocyanins in food systems as natural food colourants is limited due to the lack of stability under different environmental conditions such as light, pH, heat etc. Anthocyanins esterified with one or more acid groups are referred as acylated anthocyanins. Based on the presence or absence of acyl group, anthocyanins are categorized as acylated and nonacylated anthocyanins. Acylated anthocyanins are further classified as mono, di, tri, tetra acylated anthocyanins according to the number of acyl groups present in the anthocyanin. This review classifies common anthocyanin sources into non-acylated, mono-, di-, tri- and tetra-acylated anthocyanins based on the major anthocyanins present in these sources. The relative stabilities of these anthocyanins with respect to thermal, pH and photo stress in beverage systems are specifically discussed. Common anthocyanin sources such as elderberry, blackberry, and blackcurrant mainly contain nonacylated anthocyanins. Red radish, purple corn, black carrot also mainly contain mono acylated anthocyanins. Red cabbage and purple sweet potato have both mono and diacylated anthocyanins. Poly acylated anthocyanins show relatively higher stability compared with nonacylated and monoacylated anthocyanins. Several techniques such as addition of sweeteners, co-pigmentation and acylation techniques could enhance the stability of nonacylated anthocyanins. Flowers are main sources of polyacylated anthocyanins having higher stability, yet they have not been commercially exploited for their anthocyanins.
  7. Fulltext Anthocyanins From Clitoria ternatea Flower: Biosynthesis, Extraction, Stability, Antioxidant Activity, and Applications
    Vidana Gamage GC, Lim YY, Choo WS
    Front Plant Sci, 2021;12:792303.
    PMID: 34975979 DOI: 10.3389/fpls.2021.792303
    Clitoria ternatea plant is commonly grown as an ornamental plant and possesses great medicinal value. Its flower is edible and also known as blue pea or butterfly pea flower. The unique feature of anthocyanins present in blue pea flowers is the high abundance of polyacylated anthocyanins known as ternatins. Ternatins are polyacylated derivatives of delphinidin 3,3',5'-triglucoside. This review covers the biosynthesis, extraction, stability, antioxidant activity, and applications of anthocyanins from Clitoria ternatea flower. Hot water extraction of dried or fresh petals of blue pea flower could be employed successfully to extract anthocyanins from blue pea flower for food application. Blue pea flower anthocyanins showed good thermal and storage stability, but less photostability. Blue pea flower anthocyanins also showed an intense blue colour in acidic pH between pH 3.2 to pH 5.2. Blue pea flower anthocyanin extracts demonstrate significant in vitro and cellular antioxidant activities. Blue pea flower anthocyanins could be used as a blue food colourant in acidic and neutral foods. The incorporation of blue pea flower anthocyanins in food increased the functional properties of food such as antioxidant and antimicrobial properties. Blue pea flower anthocyanins have also been used in intelligent packaging. A comparison of blue pea flower anthocyanins with two other natural blue colouring agents used in the food industry, spirulina or phycocyanin and genipin-derived pigments is also covered. Anthocyanins from blue pea flowers are promising natural blue food colouring agent.
  8. Structural approaches for the DNA binding motifs prediction in Bacillus thuringiensis sigma-E transcription factor (σETF)
    Lim YY, Lim TS, Choong YS
    J Mol Model, 2019 Sep 05;25(10):301.
    PMID: 31486892 DOI: 10.1007/s00894-019-4192-3
    The sigma-E transcription factor (σETF) can be found in most of the bacteria cells including Bacillus thuringiensis. However, the cellular regulatory mechanisms of these transcription factors in the mass production of δ-endotoxins during sporulation stage are yet to be revealed. In addition, the recognition of DNA towards σETF DNA binding motifs that led to the transcription activities is also being poorly studied. Therefore, this work studied the possible DNA binding motifs of σETF by utilising in silico approaches. The structure of σETF was first built via three different computational methods. A cognate DNA sequence was then docked to the predicted σETF DNA-binding motifs. The binding free energy calculated using molecular mechanics/Poisson-Boltzmann surface area (MM-PBSA) for triplicate 50 ns simulation of σETF-DNA complex revealed favourable binding energy of DNA to σETF (average ∆Gbind = -34.57 kcal/mol) mainly driven by non-polar interactions. This study revealed that σETF LYS131, ARG133, PHE138, TRP146, ARG222, LYS225 and ARG226 are most likely the key residues upon the binding and recognition of DNA prior to transcription actives. Since determination of genome-regulating protein which recognises specific DNA sequence is important to discriminate between the proteins preferences for different genes, this study might provide some understanding on the possible σETF-DNA recognition prior to transcription initiated for the δ-endotoxins production.
  9. Fulltext Inhibition of euchromatic histone methyltransferase 1 and 2 sensitizes chronic myeloid leukemia cells to interferon treatment
    Loh SW, Ng WL, Yeo KS, Lim YY, Ea CK
    PLoS One, 2014;9(7):e103915.
    PMID: 25079219 DOI: 10.1371/journal.pone.0103915
    H3K9 methylation is one of the essential histone post-translational modifications for heterochromatin formation and transcriptional repression. Recently, several studies have demonstrated that H3K9 methylation negatively regulates the type I interferon response.
  10. Fulltext Inducible RasGEF1B circular RNA is a positive regulator of ICAM-1 in the TLR4/LPS pathway
    Ng WL, Marinov GK, Liau ES, Lam YL, Lim YY, Ea CK
    RNA Biol, 2016 09;13(9):861-71.
    PMID: 27362560 DOI: 10.1080/15476286.2016.1207036
    Circular RNAs (circRNAs) constitute a large class of RNA species formed by the back-splicing of co-linear exons, often within protein-coding transcripts. Despite much progress in the field, it remains elusive whether the majority of circRNAs are merely aberrant splicing by-products with unknown functions, or their production is spatially and temporally regulated to carry out specific biological functions. To date, the majority of circRNAs have been cataloged in resting cells. Here, we identify an LPS-inducible circRNA: mcircRasGEF1B, which is predominantly localized in cytoplasm, shows cell-type specific expression, and has a human homolog with similar properties, hcircRasGEF1B. We show that knockdown of the expression of mcircRasGEF1B reduces LPS-induced ICAM-1 expression. Additionally, we demonstrate that mcircRasGEF1B regulates the stability of mature ICAM-1 mRNAs. These findings expand the inventory of functionally characterized circRNAs with a novel RNA species that may play a critical role in fine-tuning immune responses and protecting cells against microbial infection.
  11. Fulltext JMJD8 is a positive regulator of TNF-induced NF-κB signaling
    Yeo KS, Tan MC, Wong WY, Loh SW, Lam YL, Tan CL, et al.
    Sci Rep, 2016 Sep 27;6:34125.
    PMID: 27671354 DOI: 10.1038/srep34125
    TNF-induced signaling mediates pleiotropic biological consequences including inflammation, immunity, cell proliferation and apoptosis. Misregulation of TNF signaling has been attributed as a major cause of chronic inflammatory diseases and cancer. Jumonji domain-containing protein 8 (JMJD8) belongs to the JmjC family. However, only part of the family members has been described as hydroxylase enzymes that function as histone demethylases. Here, we report that JMJD8 positively regulates TNF-induced NF-κB signaling. Silencing the expression of JMJD8 using RNA interference (RNAi) greatly suppresses TNF-induced expression of several NF-κB-dependent genes. Furthermore, knockdown of JMJD8 expression reduces RIP ubiquitination, IKK kinase activity, delays IκBα degradation and subsequently blocks nuclear translocation of p65. In addition, JMJD8 deficiency enhances TNF-induced apoptosis. Taken together, these findings indicate that JMJD8 functions as a positive regulator of TNF-induced NF-κB signaling.
  12. Fulltext Transcriptomic analysis of the role of RasGEF1B circular RNA in the TLR4/LPS pathway
    Ng WL, Marinov GK, Chin YM, Lim YY, Ea CK
    Sci Rep, 2017 09 25;7(1):12227.
    PMID: 28947785 DOI: 10.1038/s41598-017-12550-w
    Circular RNAs (circRNAs) have recently emerged as a large class of novel non-coding RNA species. However, the detailed functional significance of the vast majority of them remains to be elucidated. Most functional characterization studies targeting circRNAs have been limited to resting cells, leaving their role in dynamic cellular responses to stimuli largely unexplored. In this study, we focus on the LPS-induced cytoplasmic circRNA, mcircRasGEF1B, and combine targeted mcircRasGEF1B depletion with high-throughput transcriptomic analysis to gain insight into its function during the cellular response to LPS stimulation. We show that knockdown of mcircRasGEF1B results in altered expression of a wide array of genes. Pathway analysis revealed an overall enrichment of genes involved in cell cycle progression, mitotic division, active metabolism, and of particular interest, NF-κB, LPS signaling pathways, and macrophage activation. These findings expand the set of functionally characterized circRNAs and support the regulatory role of mcircRasGEF1B in immune response during macrophage activation and protection against microbial infections.
  13. Fulltext JMJD8 is a novel endoplasmic reticulum protein with a JmjC domain
    Yeo KS, Tan MC, Lim YY, Ea CK
    Sci Rep, 2017 11 13;7(1):15407.
    PMID: 29133832 DOI: 10.1038/s41598-017-15676-z
    Jumonji C (JmjC) domain-containing proteins have been shown to regulate cellular processes by hydroxylating or demethylating histone and non-histone targets. JMJD8 belongs to the JmjC domain-only family that was recently shown to be involved in angiogenesis and TNF-induced NF-κB signaling. Here, we employed bioinformatic analysis and immunofluorescence microscopy to examine the physiological properties of JMJD8. We demonstrated that JMJD8 localizes to the lumen of endoplasmic reticulum and that JMJD8 forms dimers or oligomers in vivo. Furthermore, we identified potential JMJD8-interacting proteins that are known to regulate protein complex assembly and protein folding. Taken together, this work demonstrates that JMJD8 is the first JmjC domain-containing protein found in the lumen of the endoplasmic reticulum that may function in protein complex assembly and protein folding.
  14. Fulltext Identification of 5-Methoxy-2-(Diformylmethylidene)-3,3-Dimethylindole as an Anti-Influenza A Virus Agent
    Tan MC, Wong WY, Ng WL, Yeo KS, Mohidin TB, Lim YY, et al.
    PLoS One, 2017;12(1):e0170352.
    PMID: 28114392 DOI: 10.1371/journal.pone.0170352
    Influenza virus is estimated to cause 3-5 million severe complications and about 250-500 thousand deaths per year. Different kinds of anti-influenza virus drugs have been developed. However, the emergence of drug resistant strains has presented a big challenge for efficient antiviral therapy. Indole derivatives have been shown to exhibit both antiviral and anti-inflammatory activities. In this study, we adopted a cell-based system to screen for potential anti-IAV agents. Four indole derivatives (named 525A, 526A, 527A and 528A) were subjected to the antiviral screening, of which 526A was selected for further investigation. We reported that pre-treating cells with 526A protects cells from IAV infection. Furthermore, 526A inhibits IAV replication by inhibiting the expression of IAV genes. Interestingly, 526A suppresses the activation of IRF3 and STAT1 in host cells and thus represses the production of type I interferon response and cytokines in IAV-infected cells. Importantly, 526A also partially blocks the activation of RIG-I pathway. Taken together, these results suggest that 526A may be a potential anti-influenza A virus agent.
  15. Bioactivity-guided isolation of anticancer agents from Bauhinia kockiana Korth
    Chew YL, Lim YY, Stanslas J, Ee GC, Goh JK
    Afr J Tradit Complement Altern Med, 2014;11(3):291-9.
    PMID: 25371595
    BACKGROUND: Flowers of Bauhinia kockiana were investigated for their anticancer properties.

    METHODS: Gallic acid (1), and methyl gallate (2), were isolated via bioassay-directed isolation, and they exhibited anticancer properties towards several cancer cell lines, examined using MTT cell viability assay. Pyrogallol (3) was examined against the same cancer cell lines to deduce the bioactive functional group of the phenolic compounds.

    RESULTS: The results showed that the phenolic compounds could exhibit moderate to weak cytotoxicity towards certain cell lines (GI50 30 - 86 µM), but were inactive towards DU145 prostate cancer cell (GI50 > 100 µM).

    CONCLUSION: It was observed that pyrogallol moiety was one of the essential functional structures of the phenolic compounds in exhibiting anticancer activity. Also, the carboxyl group of compound 1 was also important in anticancer activity. Examination of the PC-3 cells treated with compound 1 using fluorescence microscopy showed that PC-3 cells were killed by apoptosis.

  16. Fulltext Assessment of phytochemical content, polyphenolic composition, antioxidant and antibacterial activities of Leguminosae medicinal plants in Peninsular Malaysia
    Chew YL, Chan EW, Tan PL, Lim YY, Stanslas J, Goh JK
    BMC Complement Altern Med, 2011;11:12.
    PMID: 21306653 DOI: 10.1186/1472-6882-11-12
    Many medicinal plants from Leguminosae family can be found easily in Malaysia. These plants have been used as traditional medicines by local ethnic groups, where they are prepared as decoction, pastes for wound infections, and some have been eaten as salad. This paper focused on the assessment of antioxidant potential, antibacterial activity and classes of phytochemicals of nine plants from the Leguminosae family.
  17. Time trends in upper gastrointestinal diseases and Helicobacter pylori infection in a multiracial Asian population--a 20-year experience over three time periods
    Leow AH, Lim YY, Liew WC, Goh KL
    Aliment Pharmacol Ther, 2016 Apr;43(7):831-7.
    PMID: 26847417 DOI: 10.1111/apt.13550
    Marked epidemiological changes in upper gastrointestinal diseases and Helicobacter pylori infection have taken place in the Asian Pacific region. In particular, differences with respect to race in the multiracial Asian population in Malaysia have been important and interesting.
  18. Corrigendum to "Biosynthesis of agar in red seaweeds: A review" [Carbohydr. Polym. 164 (2017) 23-30]
    Lee WK, Lim YY, Leow AT, Namasivayam P, Ong Abdullah J, Ho CL
    Carbohydr Polym, 2017 08 01;169:533.
    PMID: 28504177 DOI: 10.1016/j.carbpol.2017.03.085
  19. Biosynthesis of agar in red seaweeds: A review
    Lee WK, Lim YY, Leow AT, Namasivayam P, Ong Abdullah J, Ho CL
    Carbohydr Polym, 2017 May 15;164:23-30.
    PMID: 28325321 DOI: 10.1016/j.carbpol.2017.01.078
    Agar is a jelly-like biopolymer synthesized by many red seaweeds as their major cell wall component. Due to its excellent rheological properties, it has been exploited commercially for applications in food, cosmetic, pharmaceutical, biomedical and biotechnology industries. Despite its multiple uses, the biosynthesis of this phycocolloid is not fully understood. The current knowledge on agar biosynthesis is inferred from plant biochemistry and putative pathways for ulvan and alginate biosynthesis in green and brown seaweeds, respectively. In this review, the gaps in our current knowledge on agar biosynthetic pathway are discussed, focusing on the biosynthesis of agar precursors, elongation of agar polysaccharide chain and side chain modification. The development of molecular markers for the screening of desired seaweeds for industrial exploitation is also discussed.
  20. Fulltext Typologies and Psychological Profiles of Child Sexual Abusers: An Extensive Review
    Lim YY, Wahab S, Kumar J, Ibrahim F, Kamaluddin MR
    Children (Basel), 2021 Apr 25;8(5).
    PMID: 33922985 DOI: 10.3390/children8050333
    Child sexual abuse is a public health issue that has been associated with a variety of negative health outcomes. Child sexual abusers constitute a heterogeneous population of individuals. This review lays out an overview of the current understanding of typologies and psychological profiles of child sexual abusers. Typologies of child sexual abusers in general and online child sexual abusers are reviewed to summarise the existing knowledge. Psychological traits including personality traits, cognitive distortion, empathy, and impulsivity are examined to provide a wider perspective of the psycho-criminogenic factors of child sexual abuse. Although past research on child sexual abusers has provided insights into the organisation and classification of different types of child sexual abusers, the classification of these typologies has drawn widespread criticisms. In this review, we discuss the challenges and limitations pertaining to the existing typologies and studies related to the psychological profile of child sexual abusers.
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