Displaying publications 1 - 20 of 201 in total

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  1. Thayan R, Huat TL, See LL, Tan CP, Khairullah NS, Yusof R, et al.
    Trans R Soc Trop Med Hyg, 2009 Apr;103(4):413-9.
    PMID: 19203772 DOI: 10.1016/j.trstmh.2008.12.018
    Dengue infection is a major public health problem affecting millions of people living in tropical countries. With no suitable vaccines and specific antiviral drugs, treatment for dengue is usually symptomatic and supportive. Early diagnosis and recognition of severe disease is therefore crucial for better management of the patient. Two-dimension electrophoresis was used to identify disease-associated proteins that can be used for diagnosis and as drug targets for treatment. Two markers, identified by mass spectrometry analysis as alpha1-antitrypsin and NS1 proteins were found to be upregulated in dengue fever (DF; n=10) and dengue haemorrhagic fever (DHF; n=10) patients compared with healthy individuals (n=8). Both alpha1-antitrypsin and NS1 proteins were overexpressed two-fold in DHF patients compared with DF patients. Our study suggests that alpha1-antitrypsin and NS1 protein could be used as biomarkers as early indicators of DHF risk among patients with suspected dengue infection.
  2. Wong YH, Lau HW, Tan CP, Long K, Nyam KL
    ScientificWorldJournal, 2014;2014:789346.
    PMID: 24592184 DOI: 10.1155/2014/789346
    The aim of this study was to determine the best parameter for extracting phenolic-enriched kenaf (Hibiscus cannabinus L.) seeds by a pulsed ultrasonic-assisted extraction. The antioxidant activities of ultrasonic-assisted kenaf seed extracts (KSE) were determined by a 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity assay, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical scavenging assay, β -carotene bleaching inhibition assay, and ferric reducing antioxidant power (FRAP) assay. Total phenolic content (TPC) and total flavonoid content (TFC) evaluations were carried out to determine the phenolic and flavonoid contents in KSE. The KSE from the best extraction parameter was then subjected to high performance liquid chromatography (HPLC) to quantify the phenolic compounds. The optimised extraction condition employed 80% ethanol for 15 min, with the highest values determined for the DPPH, ABTS, and FRAP assay. KSE contained mainly tannic acid (2302.20 mg/100 g extract) and sinapic acid (1198.22 mg/100 g extract), which can be used as alternative antioxidants in the food industry.
  3. KoohiKamali S, Tan CP, Ling TC
    ScientificWorldJournal, 2012;2012:475027.
    PMID: 22593688 DOI: 10.1100/2012/475027
    In this study, the methanolysis process of sunflower oil was investigated to get high methyl esters (biodiesel) content using sodium methoxide. To reach to the best process conditions, central composite design (CCD) through response surface methodology (RSM) was employed. The optimal conditions predicted were the reaction time of 60 min, an excess stoichiometric amount of alcohol to oil ratio of 25%w/w and the catalyst content of 0.5%w/w, which lead to the highest methyl ester content (100%w/w). The methyl ester content of the mixture from gas chromatography analysis (GC) was compared to that of optimum point. Results, confirmed that there was no significant difference between the fatty acid methyl ester content of sunflower oil produced under the optimized condition and the experimental value (P ≥ 0.05). Furthermore, some fuel specifications of the resultant biodiesel were tested according to American standards for testing of materials (ASTM) methods. The outcome showed that the methyl ester mixture produced from the optimized condition met nearly most of the important biodiesel specifications recommended in ASTM D 6751 requirements. Thus, the sunflower oil methyl esters resulted from this study could be a suitable alternative for petrol diesels.
  4. Azila NM, Tan CP
    Med J Malaysia, 2005 Aug;60 Suppl D:35-40.
    PMID: 16315622
    Accreditation is a process by which official accrediting bodies evaluate institutions using a set of criteria and standards, following established procedures, to ensure a high quality of education needed to produce highly competent graduates. Additional objectives include (1) ensuring quality institutional functioning, (2) strengthening capabilities of educational institutions for service to the nation and (3) improving public confidence in medical schools. The accreditation process provides an opportunity for the institution to critically reflect upon all the aspects of its programme and the level of compliance or attainment of the requirements. The self-evaluation exercise, which identifies strengths and weaknesses, is perceived as formative. It is envisaged that eventually institutions will adopt a learning culture for curriculum development, implementation, monitoring and matching the outcomes. In conclusion, periodic accreditation activities can act as a "monitoring" system to ensure that the quality of medical education is maintained according to established standards.
  5. Tan CP, Rokiah P
    Med J Malaysia, 2005 Aug;60 Suppl D:48-53.
    PMID: 16315624
    Formative and summative student assessment has always been of concern to medical teachers, and this is especially important at the level of graduating doctors. The effectiveness and comprehensiveness of the clinical training provided is tested with the use of clinical cases, either with real patients who have genuine medical conditions, or with the use of standardised patients who are trained to simulate accurately actual patients. The Objective Structured Clinical Examination (OSCE) is one method of assessing the adequacy of clinical skills of medical students, and their level of competence. It can be used to test a variety of skills such as history taking (communication and interpersonal skills) and performing aspects of physical examination, undertaking emergency procedures, and interpreting investigational data. It can also be used to ensure an adequate depth and breadth of coverage of clinical skills expected of a graduating doctor.
  6. Lei J, He Y, Zhu S, Shi J, Tan CP, Liu Y, et al.
    Analyst, 2024 Jan 29;149(3):751-760.
    PMID: 38194259 DOI: 10.1039/d3an01536j
    Polyunsaturated fatty acids (PUFAs), such as arachidonic acid (ARA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), play an important role in the nutritional value of milk lipids. However, a comprehensive analysis of PUFAs and their esters in milk is still scarce. In this study, we developed a novel pseudotargeted lipidomics approach, named SpecLipIDA, for determining PUFA lipids in milk. Triglycerides (TGs) and phospholipids (PLs) were separated using NH2 cartridges, and mass spectrometry data in the information-dependent acquisition (IDA) mode were preprocessed by MS-DIAL, leading to improved identification in subsequent targeted analysis. The target matching algorithm, based on specific lipid cleavage patterns, demonstrated enhanced identification of PUFA lipids compared to the lipid annotations provided by MS-DIAL and GNPS. The approach was applied to identify PUFA lipids in various milk samples, resulting in the detection of a total of 115 PUFA lipids. The results revealed distinct differences in PUFA lipids among different samples, with 44 PUFA lipids significantly contributing to these differences. Our study indicated that SpecLipIDA is an efficient method for rapidly and specifically screening PUFA lipids.
  7. Goh KM, Maulidiani M, Rudiyanto R, Wong YH, Ang MY, Yew WM, et al.
    Talanta, 2019 Jun 01;198:215-223.
    PMID: 30876552 DOI: 10.1016/j.talanta.2019.01.111
    The technique of Fourier transform infrared spectroscopy is widely used to generate spectral data for use in the detection of food contaminants. Monochloropropanediol (MCPD) is a refining process-induced contaminant that is found in palm-based fats and oils. In this study, a chemometric approach was used to evaluate the relationship between the FTIR spectra and the total MCPD content of a palm-based cooking oil. A total of 156 samples were used to develop partial least squares regression (PLSR), artificial neural network (nnet), average artificial neural network (avNNET), random forest (RF) and cubist models. In addition, a consensus approach was used to generate fusion result consisted from all the model mentioned above. All the models were evaluated based on validation performed using training and testing datasets. In addition, the box plot of coefficient of determination (R2), root mean square error (RMSE), slopes and intercepts by 100 times randomization was also compared. Evaluation of performance based on the testing R2 and RMSE suggested that the cubist model predicted total MCPD content with the highest accuracy, followed by the RF, avNNET, nnet and PLSR models. The overfitting tendency was assessed based on differences in R2 and RMSE in the training and testing calibrations. The observations showed that the cubist and avNNET models possessed a certain degree of overfitting. However, the accuracy of these models in predicting the total MCPD content was high. Results of the consensus model showed that it slightly improved the accuracy of prediction as well as significantly reduced its uncertainty. The important variables derived from the cubist and RF models suggested that the wavenumbers corresponding to the MCPDs originated from the -CH=CH2 or CH=CH (990-900 cm-1) and C-Cl stretch (800-700 cm-1) regions of the FTIR spectrum data. In short, chemometrics in combination with FTIR analysis especially for the consensus model represent a potential and flexible technique for estimating the total MCPD content of refined vegetable oils.
  8. Sapai S, Loo JY, Ding ZY, Tan CP, Baskaran VM, Nurzaman SG
    Soft Robot, 2023 Dec;10(6):1224-1240.
    PMID: 37590485 DOI: 10.1089/soro.2022.0188
    Data-driven methods with deep neural networks demonstrate promising results for accurate modeling in soft robots. However, deep neural network models rely on voluminous data in discovering the complex and nonlinear representations inherent in soft robots. Consequently, while it is not always possible, a substantial amount of effort is required for data acquisition, labeling, and annotation. This article introduces a data-driven learning framework based on synthetic data to circumvent the exhaustive data collection process. More specifically, we propose a novel time series generative adversarial network with a self-attention mechanism, Transformer TimeGAN (TTGAN) to precisely learn the complex dynamics of a soft robot. On top of that, the TTGAN is incorporated with a conditioning network that enables it to produce synthetic data for specific soft robot behaviors. The proposed framework is verified on a widely used pneumatic-based soft gripper as an exemplary experimental setup. Experimental results demonstrate that the TTGAN generates synthetic time series data with realistic soft robot dynamics. Critically, a combination of the synthetic and only partially available original data produces a data-driven model with estimation accuracy comparable to models obtained from using complete original data.
  9. Bakibillah ASM, Kamal MAS, Tan CP, Susilawati S, Hayakawa T, Imura JI
    Sensors (Basel), 2021 Sep 30;21(19).
    PMID: 34640852 DOI: 10.3390/s21196533
    Traditional uncoordinated traffic flows in a roundabout can lead to severe traffic congestion, travel delay, and the increased fuel consumption of vehicles. An interesting way to mitigate this would be through cooperative control of connected and automated vehicles (CAVs). In this paper, we propose a novel solution, which is a roundabout control system (RCS), for CAVs to attain smooth and safe traffic flows. The RCS is essentially a bi-level framework, consisting of higher and lower levels of control, where in the higher level, vehicles in the entry lane approaching the roundabout will be made to form clusters based on traffic flow volume, and in the lower level, the vehicles' optimal sequences and roundabout merging times are calculated by solving a combinatorial optimization problem using a receding horizon control (RHC) approach. The proposed RCS aims to minimize the total time taken for all approaching vehicles to enter the roundabout, whilst minimally affecting the movement of circulating vehicles. Our developed strategy ensures fast optimization, and can be implemented in real-time. Using microscopic simulations, we demonstrate the effectiveness of the RCS, and compare it to the current traditional roundabout system (TRS) for various traffic flow scenarios. From the results, we can conclude that the proposed RCS produces significant improvement in traffic flow performance, in particular for the average velocity, average fuel consumption, and average travel time in the roundabout.
  10. Wong YH, Goh KM, Nyam KL, Cheong LZ, Wang Y, Nehdi IA, et al.
    Sci Rep, 2020 09 15;10(1):15110.
    PMID: 32934328 DOI: 10.1038/s41598-020-72118-z
    3-Monochloropropane-1,2-diol (3-MCPD) esters and glycidyl esters (GE) are heat-induced contaminants which form during oil refining process, particularly at the high temperature deodorization stage. It is worth to investigate the content of 3-MCPD and GE in fries which also involved high temperature. The content of 3-MCPD esters and GE were monitored in fries. The factors that been chosen were temperature and duration of frying, and different concentration of salt (NaCl). The results in our study showed that the effect was in the order of concentration of sodium chloride 
  11. Auwal SM, Zarei M, Tan CP, Basri M, Saari N
    Sci Rep, 2018 Jul 10;8(1):10411.
    PMID: 29991723 DOI: 10.1038/s41598-018-28659-5
    Bromelain-generated biopeptides from stone fish protein exhibit strong inhibitory effect against ACE and can potentially serve as designer food (DF) with blood pressure lowering effect. Contextually, the DF refer to the biopeptides specifically produced to act as ACE-inhibitors other than their primary role in nutrition and can be used in the management of hypertension. However, the biopeptides are unstable under gastrointestinal tract (GIT) digestion and need to be stabilized for effective oral administration. In the present study, the stone fish biopeptides (SBs) were stabilized by their encapsulation in sodium tripolyphosphate (TPP) cross-linked chitosan nanoparticles produced by ionotropic gelation method. The nanoparticles formulation was then optimized via Box-Behnken experimental design to achieve smaller particle size (162.70 nm) and high encapsulation efficiency (75.36%) under the optimum condition of SBs:Chitosan mass ratio (0.35), homogenization speed (8000 rpm) and homogenization time (30 min). The SBs-loaded nanoparticles were characterized for morphology by transmission electron microscopy (TEM), physicochemical stability and efficacy. The nanoparticles were then lyophilized and analyzed using Fourier transform infra-red spectroscopy (FTIR) and X-ray diffraction (XRD). The results obtained indicated a sustained in vitro release and enhanced physicochemical stability of the SBs-loaded nanoparticles with smaller particle size and high encapsulation efficiency following long period of storage. Moreover, the efficacy study revealed improved inhibitory effect of the encapsulated SBs against ACE following simulated GIT digestion.
  12. Nehdi IA, Sbihi HM, Blidi LE, Rashid U, Tan CP, Al-Resayes SI
    Protein Pept Lett, 2018;25(2):164-170.
    PMID: 28240158 DOI: 10.2174/0929866524666170223150839
    BACKGROUND: Biodiesel is a green fuel consisting of long chain fatty acid monoalkyl esters, which can be blended with diesel or used alone which is usually produced from vegetable oils/fats by either lipasecatalyzed transesterification. In this investigation, an enzyme (Novozym 435) catalyzed process was optimized to prepare methyl esters from crude Citrullus colocynthis oil (CCO) by transesterification of CCO with methanol. However, as per our knowledge, lipase-catalyzed transesterification have not been used for biodiesel production from Citrullus colocynthis.

    OBJECTIVE: The purpose of this work was to transesterify the CCO in the presence of Candida antarctica lipase as catalyst and methanol. Additionally, the physicochemical parameters/fuel properties of the Citrullus colocynthis methyl ester (CCME) were assessed and compared.

    METHODS: Lipase-catalyzed reactions were carried out in three necked flask (50 mL) attached with reflux condenser and thermometer, immersed in oil bath at constant stirring speed (400 rpm). The reaction mixture was consisted of CCO and varying the calculated amount of methanol, tert-butyl alcohol, and Novozym 435. The experimental parameters reaction time, methanol/oil molar ratio, reaction temperature, tert-butanol content, Novozym 435 content and water content were optimized for the transesterification reaction. The CCME yield was measured using gas chromatograph. The fuel properties of the produced CCME were determined as per American Society for Testing and Materials (ASTM) and European (EN) biodiesel standard methods.

    RESULTS: In this study, an enzymatic catalyst was employed to synthesize the CCME from CCO via transesterification. Several variables affecting the CCME yield were optimized as lipase quantity (4%), water content (0.5%), methanol/oil molar ratio (5:1), reaction temperature (43 °C), reaction medium composition (80% tertbutanol/ oil), and reaction time (3.7 h). A CCME yield of 97.8% was achieved using enzyme catalyzed transesterification of CCO under optimal conditions. The significant biodiesel fuel properties of CCME, i.e. cloud point (0.70 °C); cetane number (49.07); kinematic viscosity (2.27 mm2/s); flash point (143 °C); sulfur content (2 ppm) density (880 kg/m3) and acid value (0.076 mg KOH/g) were appraised. CCME also exhibited long-term storage stability (4.80 h) and all the biodiesel fuel properties were within the range of standards (ASTM D6751 and EN 14214).

    CONCLUSION: The lipase-catalyzed transesterification produced better conversion than the base-catalyzed reaction. The fuel properties of CCME were within the limits of the ASTM D6751 and EN14214 standards. Furthermore, CCME showed good oxidative stability and a long shelf life due its high natural antioxidant content. CCME showed better fuel properties and long-term storage stability due to which it can be used as a potential alternative fuel.

  13. Chong WT, Tan CP, Cheah YK, B Lajis AF, Habi Mat Dian NL, Kanagaratnam S, et al.
    PLoS One, 2018;13(8):e0202771.
    PMID: 30142164 DOI: 10.1371/journal.pone.0202771
    Red palm oil (RPO) is a natural source of Vitamin E (70-80% tocotrienol). It is a potent natural antioxidant that can be used in skin-care products. Its antioxidant property protects skin from inflammation and aging. In our work, a tocotrienol-rich RPO-based nanoemulsion formulation was optimized using response surface methodology (RSM) and formulated using high pressure homogenizer. Effect of the concentration of three independent variables [surfactant (5-15 wt%), co-solvent (10-30 wt%) and homogenization pressure (500-700 bar)] toward two response variables (droplet size, polydispersity index) was studied using central composite design (CCD) coupled to RSM. RSM analysis showed that the experimental data could be fitted into a second-order polynomial model and the coefficients of multiple determination (R2) is 0.9115. The optimized formulation of RPO-based nanoemulsion consisted of 6.09 wt% mixed surfactant [Tween 80/Span 80 (63:37, wt)], 20 wt% glycerol as a co-solvent via homogenization pressure (500 bar). The optimized tocotrienol-rich RPO-based nanoemulsion response values for droplet size and polydispersity index were 119.49nm and 0.286, respectively. The actual values of the formulated nanoemulsion were in good agreement with the predicted values obtained from RSM, thus the optimized compositions have the potential to be used as a nanoemulsion for cosmetic formulations.
  14. Auwal SM, Zainal Abidin N, Zarei M, Tan CP, Saari N
    PLoS One, 2019;14(5):e0197644.
    PMID: 31145747 DOI: 10.1371/journal.pone.0197644
    Stone fish is an under-utilized sea cucumber with many health benefits. Hydrolysates with strong ACE-inhibitory effects were generated from stone fish protein under the optimum conditions of hydrolysis using bromelain and fractionated based on hydrophobicity and isoelectric properties of the constituent peptides. Five novel peptide sequences with molecular weight (mw) < 1000 daltons (Da) were identified using LC-MS/MS. The peptides including Ala-Leu-Gly-Pro-Gln-Phe-Tyr (794.44 Da), Lys-Val-Pro-Pro-Lys-Ala (638.88 Da), Leu-Ala-Pro-Pro-Thr-Met (628.85 Da), Glu-Val-Leu-Ile-Gln (600.77 Da) and Glu-His-Pro-Val-Leu (593.74 Da) were evaluated for ACE-inhibitory activity and showed IC50 values of 0.012 mM, 0.980 mM, 1.310 mM, 1.440 mM and 1.680 mM, respectively. The ACE-inhibitory effects of the peptides were further verified using molecular docking study. The docking results demonstrated that the peptides exhibit their effect mainly via hydrogen and electrostatic bond interactions with ACE. These findings provide evidence about stone fish as a valuable source of raw materials for the manufacture of antihypertensive peptides that can be incorporated to enhance therapeutic relevance and commercial significance of formulated functional foods.
  15. Niaz A, Adnan A, Bashir R, Mumtaz MW, Raza SA, Rashid U, et al.
    Plants (Basel), 2021 Jun 02;10(6).
    PMID: 34199333 DOI: 10.3390/plants10061128
    The Tamarix dioica (T. dioica) is widely used medicinal plant to cure many chronic ailments. T. dioica is being used to manage diabetes mellitus in traditional medicinal system; however, very little scientific evidence is available on this plant in this context. The current study involves the fractionation of crude methanolic extract of T. dioica using n-hexane, ethyl acetate, chloroform, and n-butanol. The screening for antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay was carried out. The in vitro antidiabetic potential was assessed by measuring α-glucosidase inhibition. Total phenolic and flavonoid contents were also determined for each fraction. The metabolites were identified using highly sensitive and emerging 1H-NMR technique. The results revealed the ethyl acetate fraction as the most potent with DPPH scavenging activity of 84.44 ± 0.21% and α-glucosidase inhibition with IC50 value of 122.81 ± 2.05 µg/mL. The total phenolic and flavonoid content values of 205.45 ± 1.36 mg gallic acid equivalent per gram dried extract and 156.85 ± 1.33 mg quercetin equivalent per gram dried extract were obtained for ethyl acetate fraction. The bucketing of 1H-NMR spectra identified 22 metabolites including some pharmacologically important like tamarixetin, tamaridone, quercetin, rutin, apigenin, catechin, kaempferol, myricetin and isorhamnetin. Leucine, lysine, glutamic acid, aspartic acid, serine, and tyrosine were the major amino acids identified in ethyl acetate fraction. The molecular docking analysis provided significant information on the binding affinity among secondary metabolites and α-glucosidase. These metabolites were most probably responsible for the antioxidant activity and α-glucosidase inhibitory potential of ethyl acetate fraction. The study ascertained the ethnomedicinal use of T. dioica to manage diabetes mellitus and may be a helpful lead towards naturopathic mode for anti-hyperglycemia.
  16. Mediani A, Abas F, Khatib A, Tan CP, Ismail IS, Shaari K, et al.
    Plant Foods Hum Nutr, 2015 Jun;70(2):184-92.
    PMID: 25800644 DOI: 10.1007/s11130-015-0478-5
    The study investigated the changes in the metabolite, antioxidant and α-glucosidase inhibitory activities of Phyllanthus niruri after three drying treatments: air, freeze and oven dryings. Water extracts and extracts obtained using different solvent ratios of ethanol and methanol (50, 70, 80 and 100%) were compared. The relationships among the antioxidant, α-glucosidase inhibitory activity and metabolite levels of the extracts were evaluated using partial least-square analysis (PLS). The solvent selectivity was assessed based on the phytochemical constituents present in the extract and their concentrations quantitatively analyzed using high performance liquid chromatography. The freeze-dried P. niruri samples that were extracted with the mixture of ethanol or methanol with low ratio of water showed higher biological activity values compared with the other extracts. The PLS results for the ethanolic with different ratio and water extracts demonstrated that phenolic acids (chlorogenic acid and ellagic acid) and flavonoids were highly linked to strong α-glucosidase inhibitory and antioxidant activities.
  17. Mirhosseini H, Tan CP, Yusof S, Hamid NS
    Phytochem Anal, 2008 Sep-Oct;19(5):429-37.
    PMID: 18435528 DOI: 10.1002/pca.1068
    Solid-phase microextraction (SPME) coupled to gas chromatography has been applied for the headspace analysis (HS) of 12 target flavour compounds in a model orange beverage emulsion. The main volatile flavour compounds studied were: acetaldehyde, ethyl acetate, alpha-pinene, ethyl butyrate, beta-pinene, myrcene, limonene, gamma-terpinene, octanal, decanal, linalool and citral (neral plus geranial). After screening the fibre type, the effect of other HS-SPME variables such as adsorption temperature (25-55 degrees C), extraction time (10-40 min), sample concentration (1-100% w/w), sample amount (5-10 g) and salt amount (0-30% w/w) were determined using a two-level fractional factorial design (2(5-2)) that was expanded further to a central composite design. It was found that an extraction process using a carboxen-polydimethylsiloxane fibre coating at 15 masculineC for 50 min with 5 g of diluted emulsion 1% (w/w) and 30% (w/w) of sodium chloride under stirring mode resulted in the highest HS extraction efficiency. For all volatile flavour compounds, the linearity values were accurate in the concentration ranges studied (r(2) > 0.97). Average recoveries that ranged from 90.3 to 124.8% showed a good accuracy for the optimised method. The relative standard deviation for six replicates of all volatile flavour compounds was found to be less than 15%. For all volatile flavour compounds, the limit of detection ranged from 0.20 to 1.69 mg/L.
  18. Che Man YB, Tan CP
    Phytochem Anal, 2002 May-Jun;13(3):142-51.
    PMID: 12099104
    The effects of scanning rates (1, 5, 10 and 20 degrees C/min) on the DSC cooling profiles of 11 vegetable oils have been determined in order to monitor peak transition temperatures, onset temperatures and crystallisation enthalpies. Triacylglycerol (TAG) profiles and iodine value analyses were used to complement the DSC data. The melted samples exhibited complicated crystallising exotherms. As the cooling rate increased, the crystallisation temperature decreased and the breadth of the crystallisation exotherm on cooling from the melt increased. In addition, the intensity of the exothermic peak increased somewhat when the cooling rate was increased. At slow cooling rates, TAG had more time to interact. It is conceivable that, at a low cooling rate (1 degree C/min), a prominent exotherm would be observed on crystallisation of vegetable oils and fats. The occurrence of one exotherm upon cooling indicated the co-crystallisation of the TAG upon slow cooling. On the basis of the corollary results obtained, vegetable oils may be differentiated by their onset temperature (Ton) values in the DSC cooling curves. Generally, there was a shift of Ton toward lower values with increasing cooling rates.
  19. Tan CP, Man YC
    Phytochem Anal, 2002 May-Jun;13(3):129-41.
    PMID: 12099103
    The melting curves of 11 vegetable oils have been characterised. Vegetable oil samples that were cooled at a constant rate (5 degrees C/min) from the melt showed between one and seven melting endotherms upon heating at four different heating rates (1, 5, 10 and 20 degrees C/min) in a differential scanning calorimeter (DSC). Triacylglycerol (TAG) profiles and iodine value analyses were used to complement the DSC data. Generally, the melting transition temperature shifted to higher values with increased rates of heating. The breadth of the melting endotherm and the area under the melting peak also increased with increasing heating rate. Although the number of endothermic peaks was dependent on heating rate, the melting curves of the oil samples were not straightforward in that there was no correlation between the number of endothermic peaks and heating rates. Multiple melting behaviour in DSC experiments with different heating rates could be explained by: (1) the melting of TAG populations with different melting points; and (2) TAG crystal reorganisation effects. On the basis of the corollary results obtained, vegetable oils and fats may be distinguished from their offset-temperature (Toff) values in the DSC melting curves. The results showed that Toff values of all oil samples were significantly (p < 0.01) different in the melting curves scanned at four different scanning rates. These calorimetric results indicate that DSC is a valuable technique for studying vegetable oils.
  20. Wong PL, Ramli NS, Tan CP, Azlan A, Abas F
    Phytochem Anal, 2021 Sep;32(5):685-697.
    PMID: 33295100 DOI: 10.1002/pca.3015
    INTRODUCTION: Ardisia elliptica Thunb. (Primulaceae) is a medicinal herb that is traditionally used for the treatment of fever, diarrhoea, measles and herpes. However, there is limited information regarding the correlation of its phytoconstituents with the bioactivity. Optimisation of solvent extraction is vital for maximising retention of bioactive molecules.

    OBJECTIVE: This study investigated the metabolite variations in A. elliptica leaves and the correlation with antioxidant activities.

    METHODOLOGY: Total phenolic content (TPC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) and nitric oxide (NO) radicals scavenging assays were performed on A. elliptica leaves extracted with four different ethanol ratios (0%, 50%, 70% and absolute ethanol). The correlation of metabolites with antioxidant activities was evaluated using a nuclear magnetic resonance (NMR)-based metabolomics approach.

    RESULTS: The results showed that the 50% and 70% ethanolic extracts retained the highest TPC, and the 70% ethanolic extract was the most active, exhibiting half maximal inhibitory concentration (IC50 ) values of 10.18 ± 0.83 and 43.05 ± 1.69 μg/mL, respectively, in both radical scavenging assays. A total of 46 metabolites were tentatively identified, including flavonoids, benzoquinones, triterpenes and phenolic derivatives. The 50% and 70% ethanolic extracts showed similarities in metabolites content and were well discriminated from water and absolute ethanol extracts in a principal component analysis (PCA) model. Moreover, 31 metabolites were found to contribute significantly to the differentiation and antioxidant activity.

    CONCLUSION: This study provides information on bioactive compounds in A. elliptica leaves, which is promising as a functional ingredient for food production or for the development of phytomedicinal products.

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