Dietary fibres are recognized for their health promoting properties; nevertheless, many of the physicochemical mechanisms behind these effects remain poorly understood. While it is understood that dietary fibres can associate with small molecules influencing, both positively or negatively their absorption, the molecular mechanism, by which these associations take place, needed further elucidatations. We proposed a study of the binding in soluble dietary fibres at a molecular level to establish binding constants for various fibres and nutritionally relevant ligands. The interactions between fibres and target compounds in general may be quite weak, but still have a major impact on the bioavailability. To gain insight to the binding mechanisms at a level of detail that has not earlier been achieved, we applied novel combinations of analytical techniques (MS, NMR, EPR) and both natural as well as synthetic probes to elucidate the associations in these complexes from macromolecular to atomic level. Glucans, xyloglucan, arabinoxylan and galactomannans served as model soluble fibres, representative of real food systems, allowing us to determine their binding constants with nutritionally relevant micronutrients, such as monosaccharides, bile acids, food dyes, and metals. Furthermore, we examined supramolecular interactions between fibre strands to evaluate contributions of several fibre strands to the micronutrient associations. At the atomic level, we applied complementary spectroscopies to identify the functional groups and atoms involved in the bonds between fibres and the ligands. The project executed a unique approach to quantify binding of small molecules by dietary fibres, which can further in the future be translated to polysaccharide interactions with ligands in a broad range of biological systems and disciplines. The findings originating from this study will further facilitate us to predictably utilize fibres in functional foods, which can have far-reaching consequences in human nutrition, and thereby also public health.
