Magnesium binding by gum arabic, locust bean gum, and arabinogalactan

The ability of gum arabic (GA), locust bean gum (LBG), and arabinogalactan (ABO) to complex with magnesium was investigated. Uronic acid presence, total endogenous magnesium, free endogenous magnesium over a pH range 6–8, ability to complex added magnesium, and ability to bind endogenous magnesium after partial digestion were determined. Only GA contained uronic acid, and also contained the most magnesium (2.08 ± 0.28 μg Mg mg−1 fiber). Using size exclusion chromatography to separate free endogenous magnesium from bound endogenous magnesium, all magnesium in the fibers was free. The addition of magnesium as magnesium sulfate to the fibers at pH 7 did not result in magnesium binding. Partial hydrolysis of the fibers with hemicellulase did not result in magnesium binding. From these results, magnesium does not form a stable complex with GA, LBG, or ABO at physiologically relevant pH levels, in the presence of excess amounts of magnesium, or after partial enzymatic hydrolysis.