Displaying publications 21 - 40 of 681 in total

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  1. Yusof RM, Haque F, Ismail M, Hassan Z
    Asia Pac J Clin Nutr, 2000 Jun;9(2):130-5.
    PMID: 24394399
    Probiotic organism Bifidobacteria was isolated from the faeces of breast-fed infants at Universiti Putra Malaysia. Trypticase phytone peptone yeast extract agar (TPY) was used as a selective media for the isolation. Morphological examination of the isolates indicated that Bifidobacteria was Gram-positive rods in nature, curved with characteristics of V and Y shapes. The organisms were non-catalase producing, non-nitrate reducing, non-motile, had an absence of indole and were unable to liquify gelatin. The ratios of acetic and lactic acids were determined using high performance liquid chromatography (HPLC). Using carbohydrate fermentation profile test API-CH-50 kits, 20 Bifidobacteria strains had been identified: they were the species of Bifidobacteria infantis and two different sub-species, mainly infantis and lacentis. Based on a wide zone of inhibition, three suitable strains of B. infantis, Bifi-11, Bifi-19 and Bifi-20, were tested in weaning foods for antimicrobial activity towards two human pathogens: E. coli-0157 (World Health Organization) and Salmonella typhimurium S-285. The pH, titratable acidity of weaning foods and total colony count for Bifidobacteria, enteropathogenic Escherichia coli and S. typhimurium were recorded at 3-h intervals for 30 h. It was found that after 9 h of incubation of weaning foods, the pH declined to < 3.6 from pH 6.0, whereas titratable acidity increased from 0.026 to 0.08%. It was indicated that Bifidobacteria inhibited E. coli better than did S typhimurium due to low pH. After 24 h of incubation, approximately 98% of E. coli was inhibited by Bifidobacteria. It is suggested that the inhibitory effect of Bifidobacteria strains in weaning foods towards the growth of enteropathogenic E. coli and S. typhimurium was solely due to low pH and the production of volatile acid components by the organism.
    Matched MeSH terms: Chromatography, High Pressure Liquid
  2. Yuen KH, Choy WP, Tan HY, Wong JW, Yap SP
    J Pharm Biomed Anal, 2001 Feb;24(4):715-9.
    PMID: 11272330
    A simple high-performance liquid chromatographic method was developed for the determination of omeprazole in human plasma. Omeprazole and the internal standard, chloramphenicol, were extracted from alkalinized plasma samples using dichloromethane. The mobile phase was 0.05 M Na2HPO4-ACN (65:35, v/v) adjusted to pH 6.5. Analysis was run at a flow rate of 1.0 ml/min at a detection wavelength of 302 nm. The method was specific and sensitive with a detection limit of 2.5 ng/ml at a signal-to-noise ratio of 4:1. The limit of quantification was set at 5 ng/ml. The calibration curve was linear over a concentration range of 5-1280 ng/ml. Mean recovery value of the extraction procedure was about 96%, while the within and between day coefficient of variation and percent error values of the assay method were all less than 14%.
    Matched MeSH terms: Chromatography, High Pressure Liquid/methods*
  3. Yuen KH, Wong JW, Billa N, Julianto T, Toh WT
    Int J Clin Pharmacol Ther, 1999 Jul;37(7):319-22.
    PMID: 10442505
    The bioavailability of a generic preparation of metformin (Diabetmin from Hovid Sdn Bhd) was evaluated in comparison with a proprietary product (Glucophage from Lipha Pharma Ltd., UK).
    Matched MeSH terms: Chromatography, High Pressure Liquid
  4. Yuen KH, Peh KK
    J Chromatogr B Biomed Sci Appl, 1998 Sep 18;715(2):436-40.
    PMID: 9792531
    A simple high-performance liquid chromatographic method using fluorescence detection was developed for the determination of ketoconazole in human plasma. The method entailed direct injection of the plasma sample after deproteinization using acetonitrile. The mobile phase comprised 0.05 M disodium hydrogen orthophosphate and acetonitrile (50:50, v/v) adjusted to pH 6. Analysis was run at a flow-rate of 1.5 ml/min with the detector operating at an excitation wavelength of 260 nm and an emission wavelength of 375 nm. The method is specific and sensitive with a quantification limit of approximately 60 ng/ml and a detection limit of 40 ng/ml at a signal-to-noise ratio of 3:1. Mean absolute recovery value was about 105%, while the within-day and between-day coefficient of variation and percent error values of the assay method were all less than 14%. The calibration curve was linear over a concentration range of 62.5-8000 ng/ml.
    Matched MeSH terms: Chromatography, High Pressure Liquid/methods*
  5. Yuen KH, Desmukh AA, Newton JM
    Pharm Res, 1993 Apr;10(4):588-92.
    PMID: 8483843
    A novel multiparticulate sustained-release theophylline formulation, which consisted of spherical drug pellets coated with a rate-controlling membrane, was evaluated in vivo. Two preparations that differ solely in the coat thickness, and hence rate of in vitro drug release, were studied in comparison with a solution of the drug. Both preparations produced serum concentration profiles that are reflective of a slow and sustained rate of absorption. The in vivo release versus time profiles calculated using a deconvolution procedure showed that the two preparations differed in the rate but not the extent of drug release. Satisfactory correlation was also obtained between the in vivo and the in vitro results. When the two preparations were further compared using the parameters, time to reach peak concentration (Tp), peak concentration (Cp), and total area under the serum concentration versus time curves (AUC), a statistically significant difference was observed in the Tp and Cp values but not the AUC values, suggesting that the preparations differed in the rate but not the extent of absorption. In addition, the extent of absorption from both preparations was comparable to that obtained with the drug solution.
    Matched MeSH terms: Chromatography, High Pressure Liquid
  6. Yuen KH, Peh KK, Billa N, Chan KL, Toh WT
    Drug Dev Ind Pharm, 1998 Feb;24(2):193-6.
    PMID: 15605452
    The bioavailability of a generic preparation of acyclovir (Avorax) was compared with the innovator product, Zovirax. Twelve healthy volunteers participated in the study, conducted according to a randomized, two-way crossover design. The preparations were compared using the parameters area under the plasma concentration time curve (AUC(0-infinity), peak plasma concentration (Cmax), and time to reach peak plasma concentration (Tmax). No statistically significant difference was observed between the Tmax or the logarithmic transformed AUC(0-infinity) and C(max) values of the two preparations. In addition, the 90% confidence interval for the ratio of the logarithmic transformed AUC(0-infinity) values of Avorax over those of Zovirax was found to lie between 0.85 and 1.06, while that of the logarithmic transformed Cmax values was between 0.95 and 1.25, being within the bioequivalence limit of 0.80-1.25. Moreover, the elimination rate constant (k(e)), elimination half-life (t(1/2)), and apparent volume of distribution (Vd) values obtained with the two preparations were comparable and not significantly different statistically.
    Matched MeSH terms: Chromatography, High Pressure Liquid
  7. Yuen KH, Wong JW, Peh KK, Julianto T, Choy WP
    Drug Dev Ind Pharm, 2000 Jul;26(7):803-7.
    PMID: 10872103
    The bioavailability of a generic preparation of pentoxifylline sustained-release (SR) tablet was evaluated in comparison with a proprietary product (Trental 400). For the study, 12 healthy male volunteers participated; the study was conducted according to a randomized, two-way crossover design. The bioavailability was compared using the parameters total area under the plasma level-time curve AUC0-infinity, peak plasma concentration Cmax, and time to reach peak plasma concentration Tmax. No statistically significant difference was observed between the values of the two products in all three parameters. The 90% confidence interval for the ratio of the logarithmic transformed AUC0-infinity values of the generic pentoxifylline over those of Trental 400 was found to lie between 0.83 and 1.00, while that of the parameter Cmax was between 0.91 and 1.29. In addition, elimination half-life t1/2 and apparent volume of distribution Vd were calculated. There was no statistically significant difference between the t1/2 Vd values obtained from the data of the two preparations.
    Matched MeSH terms: Chromatography, High Pressure Liquid
  8. Yuen CW, Murugaiyah V, Najimudin N, Azzam G
    J Ethnopharmacol, 2021 Feb 10;266:113418.
    PMID: 32991971 DOI: 10.1016/j.jep.2020.113418
    ETHNOPHARMACOLOGICAL RELEVANCE: Danshen, is a traditional Chinese medicine obtained from the dried root and rhizome of Salvia miltiorrhiza Bunge. It is known to be used for neurological disorder including for Alzheimer's disease (AD). This study uncovers the effect of Danshen water extract on the Alzheimer's disease model of C.elegans.

    MATERIAL AND METHODS: The composition of Danshen water extract was determined using (High Performance Liquid Chromatography (HPLC). Then Thioflavin T assay was used to determined if Danshen water extract could prevent the aggregation of amyloid-β peptide (Aβ). Alzheimer's disease C.elegans model was used to determine the effect of Danshen water extract. Finally, the reactive oxygen species (ROS) was determined using the 2,7-dichlorofuorescein diacetate method.

    RESULTS: In this study, we found that standardized Danshen water extract that contains danshensu (1.26%), salvianolic acid A (0.35%) and salvianolic acid B (2.21%) are able to bind directly to Aβ and prevents it from aggregating. The IC50 for the inhibition of Aβ aggregation by Danshen water extract was 0.5 mg/ml. In the AD model of C.elegans, Danshen water extract managed to alleviates the paralysis phenotype. Furthermore, the administration of Danshen water extract displayed antioxidant properties toward the Aβ-induced oxidative stress.

    CONCLUSIONS: AD is a widespread neurodegenerative disease attributed to the accumulation of extracellular plaques comprising Aβ. Danshen water extract could significantly reduce the progress of paralysis in the AD model of C. elegans, showing promising results with its antioxidant properties. It can be concluded that Danshen water extract could potentially serve as a therapeutic for AD.

    Matched MeSH terms: Chromatography, High Pressure Liquid
  9. Yue, C.S., Ng, Q.N., Lim, A.K., Lam, M. H., Chee, K.N.
    MyJurnal
    In the present work, the biogenic amines tryptamine (TRP), putrescine (PUT), histamine (HIS), tyramine (TYR) and spermidine (SPD) were determined in 32 various types of tofu that were obtained from different states in Malaysia. Three main types of tofu; soft tofu, firm tofu and processed tofu, were analysed in the present work. The biogenic amine contents in the respective types of tofu were analysed by a reversed-phase HPLC with a DAD detector after the aqueous extraction and derivatisation with dansyl chloride. The LOD values ranged from 0.019 mg/L for PUT to 0.028 mg/L for TYR. While, the LOQ values ranged from 0.063 mg/L (PUT) to 0.096 mg/L (TYR). The recovery values for all the five amines ranged from 80.3% to 120.5% with RSD ≤ 3.1%. The total levels of biogenic amines found varied, ranging from 1.5 mg/kg to 687.9 mg/kg, with mean values (p < 0.05) in descending order of 44.6, 12.6, 9.1, 4.8 and 4.7 mg/kg for PUT, TYR, SPD, HIS and TRP, respectively. PUT and TRP were the most prevailing biogenic amines and they were found respectively in 90.62% of the tofu analysed. Significant positive correlations (r = 0.266 to 0.874, p < 0.05) were found between some individual biogenic amines and protein content in all the three types of tofu. However, negative correlations (r = -0.246 to -0.832, p < 0.05) were observed between biogenic amines and moisture content, and between biogenic amines and water activity in all the three types of tofu. Significant and strong correlations (r = 0.525 to 0.999, p < 0.05) were found between most of the individual biogenic amines and the total biogenic amines. Those tofu exceeding the legal limits may affect the health of sensitive individuals.
    Matched MeSH terms: Chromatography, High Pressure Liquid
  10. Yue CS, Lim AK, Chia ML, Wong PY, Chin JSR, Wong WH
    J Food Sci, 2023 Feb;88(2):650-665.
    PMID: 36624628 DOI: 10.1111/1750-3841.16404
    In this study, an improved dansyl-chloride derivatization technique using a microwave synthesizer was used for the qualitative and quantitative analyses of biogenic amine in the fresh meat samples. The derivatization technique was optimized in terms of temperature, reaction time, and spinning speed. The derivatization method together with a validated reversed-phase HPLC-DAD method was used for the determination of biogenic amines in chicken, beef, and mutton sold in the wet market. The results of the analyses showed that tryptamine, putrescine, and histamine were generally detected in all the three types of meat. Higher levels of histamine were found in chicken and beef. However, low levels of histamine were observed in mutton. Tyramine was either detected low or moderate in all the three types of meat. The biogenic amines of the fresh meat sold in the wet market is generally higher than the reported values. The mechanisms of biogenic amines-dansyl-chloride formation were investigated and proposed. PRACTICAL APPLICATION: The biogenic amine derivatization method was improved. The improved derivatization method can be potentially used for various food products beside meats for routine biogenic amine analyses due to its fast analysis time and simplicity. High levels of biogenic amines were generally found in the meat sold in the wet markets. However, proper handling of the raw meat can reduce the risk of infection.
    Matched MeSH terms: Chromatography, High Pressure Liquid/methods
  11. Yudthavorasit S, Wongravee K, Leepipatpiboon N
    Food Chem, 2014 Sep 01;158:101-11.
    PMID: 24731320 DOI: 10.1016/j.foodchem.2014.02.086
    Chromatographic fingerprints of gingers from five different ginger-producing countries (China, India, Malaysia, Thailand and Vietnam) were newly established to discriminate the origin of ginger. The pungent bioactive principles of ginger, gingerols and six other gingerol-related compounds were determined and identified. Their variations in HPLC profiles create the characteristic pattern of each origin by employing similarity analysis, hierarchical cluster analysis (HCA), principal component analysis (PCA) and linear discriminant analysis (LDA). As results, the ginger profiles tended to be grouped and separated on the basis of the geographical closeness of the countries of origin. An effective mathematical model with high predictive ability was obtained and chemical markers for each origin were also identified as the characteristic active compounds to differentiate the ginger origin. The proposed method is useful for quality control of ginger in case of origin labelling and to assess food authenticity issues.
    Matched MeSH terms: Chromatography, High Pressure Liquid/methods*
  12. 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.
    Matched MeSH terms: Chromatography, High Pressure Liquid
  13. Yodhnu S, Sirikatitham A, Wattanapiromsakul C
    J Chromatogr Sci, 2009 Mar;47(3):185-9.
    PMID: 19298703
    Mangosteen, Garcinia mangostana L., is known as the "Queen of fruits" and can be cultivated in the tropical rainforest such as Malaysia, Indonesia, and Thailand. Compounds isolated from the fruit peel of mangosteen contain abundant xanthones (especially alpha-mangostin). It has been used as traditional medicine such as anti-inflammatory and antibacterial and is popularly applied to cosmetic and pharmaceutical products. However, there is little information for quality and quantity determination of alpha-mangostin in mangosteen. Thus, the aim of this study was to set up a validated and stability-indicated isocratic reverse-phase high-performance liquid chromatographic (HPLC) method for quality control and quantity determination of a-mangostin from mangosteen peel extract. The assay was fully validated and shown to be linear (r(2) > 0.999), sensitive (LOD = 0.02 microg/mL and LOQ = 0.08 microg/mL), accurate (intra-day was between 98.1-100.8%, inter-day was between 90.0-101.3%), precise (intra-day variation < or = 1.8%, inter-day variation < or = 4.3%), specific, and with good recovery. Total analysis was approximately 8 min. The finalized method is also a stability-indicating assay. The present method should be useful for analytical research and for routine quality control analysis of alpha-mangostin in mangosteen peel extract and products of mangosteen.
    Matched MeSH terms: Chromatography, High Pressure Liquid/methods*
  14. Yip WK, Cheenpracha S, Chang LC, Ho CC, Seow HF
    Int J Oncol, 2010 Nov;37(5):1229-41.
    PMID: 20878070
    Secondary metabolites from actinomycetes especially the genus Streptomyces may be one of the most important sources for novel anticancer agents. A purified fraction from a novel actinomycete strain, Streptomyces sp. H7372, was elucidated in breast cancer cells. We have isolated three purified fractions from a novel strain, Streptomyces sp. H7372. One of the fractions, designated as 31-2, exhibited the strongest growth-inhibitory effect and thereby was selected for further studies. 31-2 exerted a growth-inhibitory effect on a panel of 15 human cancer and 2 non-malignant cell lines. In MCF-7 and MDA-MB-231 breast cancer cells, 31-2 induced a cytostatic (anti-proliferative) effect without causing cytotoxicity (cell death). Our data suggest that the cytostasis resulted from cell cycle arrest at the G1 phase in MCF-7 cells and at the S phase in MDA-MB-231 cells. Western blot analysis demonstrated a modulation of phosphorylation of the Rb and CDC2 proteins and of CDK4, cyclin D1 and cyclin D3 in the 31-2-treated breast cancer cell lines. The protein levels of CDK2, CDK6, and PCNA were not affected by 31-2 treatment. 31-2 also exhibited an anti-invasive effect in MDA-MB-231 cells. However, this effect is not attributed to the modulation of proteolytic activity in MDA-MB-231 cells as the enzymatic degradation of type IV collagen was not affected by 31-2. The 31-2 is a potent cytostatic and anti-invasive agent and modulates the cell cycle pathway. Together, these results will have important implications in searching for novel approaches to treat cancer.
    Matched MeSH terms: Chromatography, High Pressure Liquid
  15. Yim HS, Chye FY, Mah SY, Sia CM, Samuagam L, Ho CW
    Int J Med Mushrooms, 2013;15(1):9-19.
    PMID: 23510280
    Pleurotus porrigens is a well-known edible, wild mushroom enjoyed as a delicacy by aborigines in Sabah and as source of income for the aborigines who collect and sell them at tamu (local market). This study aimed to evaluate the antioxidant activity in vitro and identify potent antioxidative components of aqueous extracts of P. porrigens. The antioxidant activities were evaluated using DPPH radical scavenging ability, ABTS radical cation inhibition activity, ferric reducing/antioxidant power, and total phenolic content. Activity-guided purifications based on DPPH radical scavenging ability resulted in 5 subfractions (SF). The highest DPPH radical scavenging ability was found in SF-III and SF-IV, but all were lower than butylated hydroxyanisole (BHA) and α-tocopherol. Analysis with high-performance liquid chromatography-diode array detectors found presence of ascorbic acid and (+)-catechin in SFs of P. porrigens, as well as some unidentified components that may have contributed to the radical scavenging ability. In conclusion, aqueous extract of P. porrigens possesses promising antioxidant activities, although they are lesser in their partially purified SFs. Nonetheless, P. porrigens could be promoted as an antioxidant-rich food as part of a normal diet that provides antioxidative benefit.
    Matched MeSH terms: Chromatography, High Pressure Liquid/methods
  16. Yibadatihan S, Jinap S, Mahyudin NA
    PMID: 25396715 DOI: 10.1080/19440049.2014.978396
    Palm kernel cake (PKC) is a useful source of protein and energy for livestock. Recently, it has been used as an ingredient in poultry feed. Mycotoxin contamination of PKC due to inappropriate handling during production and storage has increased public concern about economic losses and health risks for poultry and humans. This concern has accentuated the need for the evaluation of mycotoxins in PKC. Furthermore, a method for quantifying mycotoxins in PKC has so far not been established. The aims of this study were therefore (1) to develop a method for the simultaneous determination of mycotoxins in PKC and (2) to validate and verify the method. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method using an electrospray ionisation interface (ESI) in both positive- and negative-ion modes was developed for the simultaneous determination of aflatoxins (AFB₁, AFB₂, AFG₁ and AFG₂), ochratoxin A (OTA), zearalenone (ZEA), deoxynivalenol (DON), fumonisins (FB₁ and FB₂), T-2 and HT-2 toxin in PKC. An optimum method using a 0.2 ml min⁻¹ flow rate, 0.2% formic acid in aqueous phase, 10% organic phase at the beginning and 90% organic phase at the end of the gradient was achieved. The extraction of mycotoxins was performed using a solvent mixture of acetonitrile-water-formic acid (79:20:1, v/v) without further clean-up. The mean recoveries of mycotoxins in spiked PKC samples ranged from 81% to 112%. Limits of detection (LODs) and limits of quantification (LOQs) for mycotoxin standards and PKC samples ranged from 0.02 to 17.5 μg kg⁻¹ and from 0.06 to 58.0 μg kg⁻¹, respectively. Finally, the newly developed method was successfully applied to PKC samples. The results illustrated the fact that the method is efficient and accurate for the simultaneous multi-mycotoxin determination in PKC, which can be ideal for routine analysis.
    Matched MeSH terms: Chromatography, High Pressure Liquid
  17. Yazid SNE, Thanggavelu H, Mahror N, Selamat J, Samsudin NIP
    Int J Food Microbiol, 2018 Oct 03;282:57-65.
    PMID: 29913332 DOI: 10.1016/j.ijfoodmicro.2018.06.007
    In studying the ecophysiology of fungal phytopathogens, several stages are involved (in vitro, greenhouse, in planta). Most in vitro studies extensively utilise the general growth media such as Potato Dextrose Agar and Malt Extract Agar. Although the crop components in these media serve as excellent carbon sources and yield luxuriant growth, they are not naturally contaminated with Aspergillus flavus and thus might result in under- or overestimation of its actual toxigenic potentials. Empirical data on the formulation of semi-synthetic growth medium mimicking the natural crop commonly contaminated by A. flavus for the ecophysiological studies in vitro are scarce. The present work was aimed at investigating the ecophysiology of A. flavus on commercial growth media (PDA, MEA); formulating maize- and peanut-based semi-synthetic growth media using two methods of raw material preparation (milling, hot water extraction) at different concentrations (1, 3, 5, 7, 9% w/v), and comparing the ecophysiological parameters between commercial and formulated growth media. Growth rates were obtained by computing the hyphal expansion data into y = mx + c equation. AFB1 was quantified using high performance liquid chromatography with fluorescence detector. Formulated media were found to yield significantly higher growth rates when compared to commercial media. However, commercial media yielded significantly higher AFB1 when compared to all formulated media. Between the two formulations, milling yielded significantly higher growth rates and AFB1 when compared to hot water extraction. Although in vitro data cannot directly extrapolate in planta performance, results obtained in the present work can be used to gauge the actual toxigenic potential of A. flavus in maize and peanut agro-ecosystems.
    Matched MeSH terms: Chromatography, High Pressure Liquid
  18. Yassin AA, Mohamed IO, Ibrahim MN, Yusoff MS
    Appl Biochem Biotechnol, 2003 Jul;110(1):45-52.
    PMID: 12909731
    Immobilized PS-C 'Amano' II lipase was used to catalyze the interesterification of palm olein (POo) with 30, 50, and 70% stearic acid in n-hexane at 60 degrees C. The catalytic performance of the immobilized lipase was evaluated by determining the composition change of fatty acyl groups and triacylglycerol (TAG) by gas liquid chromatography and high-performance liquid chromatography, respectively. The interesterification process resulted in the formation of new TAGs, mainly tripalmitin and dipalmitostearin, both of which were absent in the original oil. These changes in TAG composition resulted in an increase in slip melting point, from the original 25.5 degrees C to 36.3, 37.0, and 40.0 degrees C in the modified POo with 30, 50, and 70% stearic acid, respectively. All the reactions attained steady state in about 6 h. This type of work will find great applications in food industries, such as confectionery.
    Matched MeSH terms: Chromatography, High Pressure Liquid
  19. Yap SP, Julianto T, Wong JW, Yuen KH
    J Chromatogr B Biomed Sci Appl, 1999 Dec 10;735(2):279-83.
    PMID: 10670741
    A simple high-performance liquid chromatographic method using fluorescence detection was developed for the determination of vitamin E especially delta-, gamma- and alpha-tocotrienols in human plasma. The method entailed direct injection of plasma sample after deproteinization using a 3:2 mixture of acetonitrile-tetrahydrofuran. The mobile phase comprised 0.5% (v/v) of distilled water in methanol. Analyses were run at a flow-rate of 1.5 ml/min with the detector operating at an excitation wavelength of 296 nm and emission wavelength of 330 nm. This method is specific and sensitive, with a quantification limit of approximately 40, 34 and 16 ng/ml for alpha-, gamma- and delta-tocotrienol, respectively. The mean absolute recovery values were about 98% while the within-day and between-day relative standard deviation and percent error values of the assay method were all less than 12.0% for alpha-, gamma- and delta-tocotrienol. The calibration curve was linear over a concentration range of 40-2500, 30-4000 and 16-1000 ng/ml for alpha-, gamma- and delta-tocotrienol, respectively. Application of the method in a bioavailability study for determination of the above compounds was also demonstrated.
    Matched MeSH terms: Chromatography, High Pressure Liquid/methods*
  20. Yap SP, Yuen KH
    Int J Pharm, 2004 Aug 20;281(1-2):67-78.
    PMID: 15288344
    A single dose comparative bioavailability study was conducted to evaluate the bioavailability of tocotrienols from two self-emulsifying formulations, one of which produced an emulsion that readily lipolysed under in vitro condition (SES-A), while the other produced a finer dispersion with negligible lipolysis (SES-B) in comparison with that of a non-self-emulsifying formulation in soya oil. The study was conducted according to a three-way crossover design using six healthy human volunteers. Statistically significant differences were observed between the logarithmic transformed peak plasma concentration (Cmax) and total area under the plasma concentration-time curve (AUC(0-infinity)) values of both SES-A and -B compared to NSES-C indicating that SES-A and -B achieved a higher extent of absorption compared to NSES-C. Moreover, the 90% confidence interval of the AUC(0-infinity) values of both SES-A and -B over those of NSES-C were between 2-3 suggesting an increase in bioavailability of about two-three times compared to NSES-C. Both SES-A and -B also achieved a faster onset of absorption. However, both SES-A and -B had comparable bioavailability, despite the fact that SES-B was able to form emulsions with smaller droplet size. Thus, it appeared that both droplet sizes as well as the rate and extent of lipolysis of the emulsion products formed were important for enhancing the bioavailability of the tocotrienols from the self-emulsifying systems.
    Matched MeSH terms: Chromatography, High Pressure Liquid
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