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  • 1.
    Hefni, Mohammed E.
    et al.
    Linnéuniversitetet, Fakulteten för Hälso- och livsvetenskap (FHL), Institutionen för kemi och biomedicin (KOB). Mansoura Univ, Egypt.
    Amann, Laura S.
    Tech Univ Munich, Germany.
    Witthöft, Cornelia M.
    Linnéuniversitetet, Fakulteten för Hälso- och livsvetenskap (FHL), Institutionen för kemi och biomedicin (KOB).
    A HPLC-UV Method for the Quantification of Phenolic Acids in Cereals2019Ingår i: Food Analytical Methods, ISSN 1936-9751, E-ISSN 1936-976X, Vol. 12, nr 12, s. 2802-2812Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cereals are a good source of phenolic acids, most of which are present in bound form. The aim of this study was to develop a method for quantifying total phenolic acids in cereals that includes a robust step for hydrolysis of bound forms. Different hydrolysis procedures were evaluated. Acid hydrolysis, even with subsequent use of enzymes, proved unsuitable for releasing bound phenolic acids from the cereal matrix. Base hydrolysis (3 M, 90 min) resulted in the highest extractability, with average recoveries of 88-108% for cereal phenolic acids. The phenolic acid content in cereals (two cultivars each of rye, barley, and oats, and eight cultivars of wheat) varied up to 2-fold between cereal genotypes and 1.5-fold within genotypes. The highest content was found in rye, followed by wheat, barley, and oats. Ferulic acid dominated in all cereals, amounting to 48-72% of total phenolic acid content.

  • 2.
    Hefni, Mohammed E.
    et al.
    Mansoura University, Egypt ; Canterbury Health Laboratories, New Zealand.
    McEntyre, Christopher
    Canterbury Health Laboratories, New Zealand ; University of Canterbury, New Zealand.
    Lever, Michael
    Canterbury Health Laboratories, New Zealand ; University of Canterbury, New Zealand ; University of Otago Christchurch, New Zealand.
    Slow, Sandy
    Canterbury Health Laboratories, New Zealand ; University of Otago Christchurch, New Zealand.
    A Simple HPLC Method with Fluorescence Detection for Choline Quantification in Foods2015Ingår i: Food Analytical Methods, ISSN 1936-9751, E-ISSN 1936-976X, Vol. 8, nr 9, s. 2401-2408Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A high-performance liquid chromatography–fluorescence detection (HPLC-FLD) method was developed and validated for choline quantification in foods. Samples were extracted by homogenizing in chloroform/methanol/water and hydrolyzing in HCl-acetonitrile. Choline was derivatized using 1-naphthyl isocyanate and quantified by HPLC-fluorescence detection. Average recovery using choline iodide as the standard (n = 6) ranged from 84 ± 6 % for whole-wheat flour to 106 ± 5 % for milk. Recovery after addition of dietary lecithin to two different food matrices faba beans and for whole-wheat flour (n = 6) was 83 ± 5 %. The precision of the analysis (coefficient of variation) ranged from 2 to 13 %. Accuracy was evaluated by analyzing dietary lecithin using HPLC-FLD, liquid chromatography–mass spectrometry, and nuclear magnetic resonance, which across the different methods agreed within 15 %. This method was applied to quantify the choline content in different food matrices, and provides a simple, inexpensive method that could be widely used.

  • 3.
    Hefni, Mohammed E.
    et al.
    Mansoura University, Egypt ; Canterbury Health Laboratories, New Zealand.
    McEntyre, Christopher
    Canterbury Health Laboratories, New Zealand ; University of Canterbury, New Zealand.
    Lever, Michael
    Canterbury Health Laboratories, New Zealand ; University of Canterbury, New Zealand ; University of Otago Christchurch, New Zealand.
    Slow, Sandy
    Canterbury Health Laboratories, New Zealand ; University of Otago Christchurch, New Zealand.
    Validation of HPLC-UV Methods for the Quantification of Betaine in Foods by Comparison with LC-MS2016Ingår i: Food Analytical Methods, ISSN 1936-9751, E-ISSN 1936-976X, Vol. 9, nr 2, s. 292-299Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The importance of dietary betaine is increasingly recognized. The aim of this study was to develop a simple high-performance liquid chromatography with standard ultraviolet spectrometric detection (HPLC-UV) method for betaine (N,N,N-trimethylglycine) determination in foods after derivatization. Two methods were used for betaine derivatization. Thereafter, derivatized betaine was quantified using HPLC-UV, and the results were compared with liquid chromatography mass spectrometry (LC-MS). The established derivatizing agent 2′-naphthacyl triflate and a novel derivatizing agent 2-bromo-2′-acetonaphthone produced the same cationic derivative when they react with betaine. The calibration curves were linear up to 1000 μmol/L (R 2 = 0.9974 for 2′-naphthacyl triflate and 0.9995 for 2-bromo-2′-acetonaphthone). The limit of detection was 1 μmol/L for both methods (2′-naphthacyl triflate and 2-bromo-2′-acetonaphthone), confirming sufficient sensitivity for betaine quantification in foods. The average recovery from different food matrices (wheat flour and spinach) (n = 12) was 99 ± 9 %, 95 ± 10 %, and 101 ± 8 % for LC-MS, 2′-naphthacyl triflate, and 2-bromo-2′-acetonaphthone, respectively. Inter- and intra-assay coefficients of variation (CVs) in the control samples (whole wheat flour) were below 10 %. Quantitative results for foods analyzed using 2′-naphthacyl triflate and 2-bromo-2′-acetonaphthone were comparable to LC-MS (R 2 = 0.992 and 0.990), respectively. The highest betaine content (~160 mg/100 g) was found in spinach followed by faba bean, wheat flour, and beetroot. These methods can be widely used for betaine quantification because of the simplicity of the derivatization procedures, and the commercial availability of the derivatizing reagent (2-bromo-2′-acetonaphthone) or through the relatively easy synthesis of 2-naphthacyl triflate.

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