Review of possible boron speciation relating to its essentiality

Abstract

Boron is one of the very few elements known to be essential in plants and is yet to be unequivocally proven as essential in animals and humans. Animal and human research on essentiality would benefit if the speciation of boron in biological fluids and tissues could be determined. This is complicated by the myriad of functional biomolecules with which inorganic borates can react and by the exceedingly low concentrations of boron present under physiological conditions. This review brings together published literature on the interaction of boron with biochemical systems which bear on the question of its essentiality. Some fundamentals of boron chemistry that are germane to the issue of speciation in living organisms are reviewed. Potential mechanisms of boron action in plants are discussed, with a view toward predicting effects in other organisms. Complexation with polyhydroxyl compounds, a well-known feature of boron chemistry, and interactions with enzymes, cofactors (NAD/NADP), and membranes are proposed as the most likely sites of boron involvement. Non-destructive techniques that might be utilized to directly study boron speciation in biological systems are discussed. © 1997 Wiley-Liss, Inc.