BIOMEDICAL CHROMATOGRAPHY Biomed. Chromatogr. 18: 90–97 (2004) Published online in Wiley InterScience (www.interscience.wiley.com). ORIGINAL RESEARCH 90 DOI: 10.1002/bmc.297
D. I. Sánchez-Machado et al. ORIGINAL RESEARCH
Determination of the uronic acid composition of seaweed dietary ﬁbre by HPLC
D. I. Sánchez-Machado, J. López-Cervantes, J. López-Hernández*, P. Paseiro-Losada and J.Simal-Lozano
Departamento de Química Analítica, Nutrición y Bromatología, Facultad de Farmacia, Universidad de Santiago de Compostela, 15782 Santiago de Compostela, La Coruña, Spain Received 1 May 2003; accepted 20 May 2003
ABSTRACT: A high-performance liquid chromatographic (HPLC) method is described for determination of the ratio of β -d-mannuronic acid to α-l-guluronic acid (M/G ratio) indietary ﬁbre of edible seaweeds. Total dietary ﬁbre (TDF) content was determined gravimetrically. The TDF fraction was hydrolysed with 12 m and 1 m H2SO4, then neutralized with AG 4 × 4 resin. The uronic acids were separated in a Tracer Extrasil SAX 5 µm column (25 cm × 4 mm) at 35°C, with 2 mm KH2PO4 containing 5% methanol as mobile phase at a ﬂow rate of 1.5 mL/min. The detection wavelength was UV 210nm. The chromatographic identiﬁcations of β -d-mannuronic acid and α-l-guluronic acid were conﬁrmed by liquid chromatography–mass spectrometry (LCMS). The method precision was 1.4% for β -d-mannuronic acid and 3.5% for α-l-guluronic acid. The method was used to determine M/G ratio in canned seaweeds (Saccorhiza polyschides and Himanthalia elongata) and in dried seaweeds (H. elongata, Laminariaochroleuca, Undaria pinnatiﬁda, Palmaria sp. and Porphyra sp.). Copyright © 2003 John Wiley & Sons, Ltd. KEYWORDS: edible seaweeds; β -d-mannuronic acid and α-l-guluronic acid ratio; ion-exchange chromatography; LC-MS
Dietary ﬁbre is a complex plant material resistant to digestion by enzymes in the human digestive tract (Rojas, 1994). The principal sources of dietary ﬁbre arecell-wall components (cellulose, hemicellulose, lignin and pectic substances) and non-structural components (gums and mucilages), as well as industrial additives (modiﬁed cellulose, modiﬁed pectins, gums and algal polysaccharides); (Grigelmo-Miguel et al., 1999). Dietary ﬁbre can be classiﬁed into two groups, on the basis of hydrosolubility: the soluble fraction and the insoluble fraction, each withdifferent physiological effects (Lahaye, 1991). The importance of dietary ﬁbre for health (particularly with regard to diabetes, obesity, colonic cancer, constipation and hypercholesterolaemia) has been extensively documented (Grigelmo-Miguel et al., 1999). In parts of Asia, seaweed has constituted a highly valued food for thousands of years. In Europe and North America, the use of seaweed as food isless
*Correspondence to: J. López-Hernández, Departamento de Química Analítica, Nutrición y Bromatología, Facultad de Farmacia, Universidad de Santiago de Compostela, 15782 Santiago de Compostela, La Coruña, Spain. Email: email@example.com Abbreviations used: APcI(−), detector settings-negative atmospheric pressure chemical ionization mode; SIR, selected ion recording; TDF, total dietary ﬁbre.Contract/grant sponsor: Xunta de Galicia; contract/grand number: PGIDITO2RMA20301PR. Published online 25 November 2003 Copyright © 2003 John Wiley & Sons, Ltd.
widespread, and indeed in most regions seaweed consumption declined dramatically during the twentieth century as standards of living improved. More recently, however, seaweeds have been increasingly recognized as healthy and attractive foods(Pak and Araya, 1996). Seaweed dietary ﬁbre has a high proportion of soluble ﬁbre. In red seaweeds (Rhodophyta) the soluble fraction is principally composed of sulphated galactans such as agar or carrageenans, while in brown seaweeds (Phaeophyta) the soluble fraction is principally composed of alginates, fucans and laminarin; in both cases, the insoluble fraction is basically composed of...
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