Displaying all 5 publications

  1. Lee, S.Y.
    Tapioca starch, poly(lactic acid) and Cloisite 10A nanocomposite foams were prepared by twin screw extrusion. Residence time distribution (RTD) in an extruder is a useful means of determining optimal processing conditions for mixing, cooking and shearing reactions during the process. RTD was obtained by inputting a pulse-like stimulus and measuring its profile at the exit or other point in the extruder. During processing, after the steady state had been reached, a fixed amount of tracer was instantaneously fed into the extruder and its concentration was measured from the samples collected at fixed time intervals in the extruder exit. The tracer concentration was the value of the redness, a* was used as a measure of red colour intensity of the concentration of tracer in the extrudate. Meanwhile, the effects of two screw configurations (compression and mixing screws) and two barrel temperatures (150 and 160ºC) on RTD of nanocomposite foams were also studied. The influences of screw configurations and barrel temperatures on RTD were analyzed using the mean residence time (MRT) and variance. Screw configurations and temperatures had significant effects (P
  2. Lee, S.Y., Ismail, I.S., Ang, E.L., Abas, F.
    Neptunia oleracea Lour. is a tropical plant cultivated in Southeast Asia. It is consumed as vegetable and traditional herb for the treatment of several disorders. The objective of the present work was to isolate the phenolic compounds from N. oleracea, followed by their bioactivity evaluation and quantitative analysis. The ethyl acetate (EtOAc) and methanol (MeOH) fractions of N. oleracea were subjected to various chromatographic techniques to isolate the phenolic compounds. The isolated phenolic compounds were characterised by several spectroscopic methods, including mass spectrometry (MS) and nuclear magnetic resonance (NMR). Then, these compounds were subjected to DPPH free radical scavenging as α-glucosidase inhibitory assays for the evaluation of their activities. Their contents in the fractions were analysed via high performance liquid chromatography (HPLC) quantitative analysis. Five phenolic compounds including quercetin-3-O-β-D-xylopyranoside (1), quercetin-3-O-α-Larabinopyranoside (2), quercetin-3-O-α-L-rhamnoside (3), methylgallate (4) and rutin (5) were isolated from N. oleracea for the first time. Evaluation on the DPPH free radical scavenging and α-glucosidase inhibitory activities of these compounds showed that methylgallate (4) was the most potent antioxidant and α-glucosidase inhibitors among them, with IC50 values of 17.25 and 50.76 μM, respectively. The HPLC quantitative analysis revealed the high content of the quercetin derivatives (compounds 1, 2 and 3) in the EtOAc fraction (ranging from 125.68 to 157.55 μg/mg) and methylgallate (4) in the MeOH fraction (75.25 μg/mg). Comparison of the bioactivities of the isolated phenolic compounds with the fractions indicated their significant contribution for the DPPH free radical scavenging of N. oleracea; while they might be working synergistically for the α-glucosidase inhibitory activity. The results of the present work could help to validate the contribution of phenolic compounds for the studied bioactivities of N. oleracea.
  3. Lee, S.Y., Cheah, S.K., Muhammad, M., Aniza, I.
    Medicine & Health, 2020;15(1):156-165.
    Penilaian anestetik pra-operasi adalah penting semasa penjagaan perioperatif. Matlamat utama kajian ini adalah untuk menilai tahap kepuasaan pesakit dan faktor-faktor yang mempengaruhi kepuasaan pesakit terhadap klinik pra-anestetik. Sejumlah 304 orang pesakit yang menghadiri klinik pra-anestetik telah terlibat dalam kajian ini. Kajian kepuasaan selidik dwibahasa (Bahasa Inggeris dan Bahasa Melayu) dengan berjumlah 18 soalan menguji faktor-faktor bukan penyedia (kemudahan klinik, kesesuaian masa menunggu) dan faktor-faktor penyedia (perkhidmatan doktor, pegawai kaunter, jururawat dan kakitangan sokongan) telah dikaji. Kajian kepuasaan selidik menggunakan format skala Likert lima mata skor sangat setuju/tidak setuju telah digunakan untuk menilai tahap kepuasaan pesakit. Secara keseluruhan, peratusan kepuasaan pesakit terhadap penilaian pra-anestetik dilaporkan sebagai 98.7% dengan skor purata untuk perkhidmatan doktor (4.49 + 0.60), pegawai kaunter (4.48 + 0.61), kakitangan sokongan (4.47 + 0.62), kemudahan klinik dan kesesuaian masa menunggu (4.40 + 0.62). Semua faktor-faktor yang dikaji menunjukkan hubungan yang signifikan (p
  4. Lee, S.Y., Mediani, A., Nur Ashikin, A.H., Abas, F., Azliana, A.B.S.
    The study was aimed to determine the antioxidant and α-glucosidase inhibition activities of
    the stem and leaf of five different traditional medicinal plants. The studied plants exhibited
    varied antioxidant and α-glucosidase inhibition activities. The antioxidant activities of the
    plants were determined through their free radical scavenging capabilities using DPPH assay.
    The most potent antioxidant activity was demonstrated by Neptunia oleracea with an IC50 of
    35.45 and 29.72 μg/mL for leaf and stem, respectively. For α-glucosidase inhibition activity,
    Neptunia oleracea exhibited potential α-glucosidase inhibition activity with IC50 value of
    19.09 and 19.74 μg/mL for leaf and stem, respectively. The highest total phenolic content
    (TPC) was also marked in Neptunia oleracea leaf and stem with value of 40.88 and 21.21 mg
    GAE/g dry weight, respectively. The results also showed that Strobilanthes crispus collected
    from two different locations possessed different levels of phenolic content, antioxidant and
    α-glucosidase inhibition activities. The study revealed that phenolic compounds could be the
    main contributors to the antioxidant and α-glucosidase inhibition activities with R values of 78.9
    and 67.4%, respectively. In addition, antioxidant and α-glucosidase were positively correlated
    (R = 81.9%). Neptunia oleracea could be suggested as a potential natural source of antioxidant
    and antidiabetic compounds that can be used for the prevention or treatment of diabetes.
  5. Siti Zulaikha, A.G., Mediani, A., Khoo, L.W., Lee, S.Y., Leong, S.W., Abas, F.
    The main purpose of this study was to evaluate the antioxidant and α-glucosidase inhibitory
    activities of Phyllanthus acidus. The P. acidus fruits were dried using three different methods,
    namely oven (OD), air (AD) and freeze (FD) dryings and extracted with ethanol at different
    ratios (50 and 100%). The proximate analysis and total phenolic content (TPC) as well as
    free radical scavenging and α-glucosidase inhibitory activities were determined. The proximate
    analysis of P. acidus fruit indicated that all the dried samples contained potential nutrient
    contents. The highest TPC value, α-glucosidase inhibitory and antioxidant activities were
    observed for 50% ethanolic extract from OD method with TPC value of 28.39 mg GAE/g dried
    extract, IC50 value of 12.394 μg/mL and 64.17% inhibition, respectively. The study revealed
    that phenolic compounds could be the main contributors to the antioxidant and α-glucosidase
    inhibitory activities based on the Pearson correlation coefficients with R values of 95.0 and
    73.8%, respectively. The study could provide scientific evidence for some folk uses in the
    treatment of diseases related to the production of reactive oxygen species and oxidative stress.
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