Phytate (myo-inositol-1,2,3,4,5,6-hexakisphosphate) (IP6) is the major organic phosphorus component in ceral grains, legumes and seeds high in oil. The high chelating ability of phytate decreases the nutritional availabilty of dietary metal ions (e.g., Ca2+, Fe3+ and Zn2+). Phytate could also decrease the affinity of hemoglobin for oxygen due to its very tight binding to deoxyhemoglobin. On the plus side, a novel anticancer function of phytate has been shown both in vivo and in vitro. Phytate exists in two conformations: a structure involving one axial and five equatorial phosphates (1a/5e) and a structure involving an inverted 5a/1e. As yet, no information is available on the conformational forms of different metal-phytate compounds. Consequently, we investigated the spectral features of nine representative metal-phytate compounds by solid state 1D 13C cross polarization magic angle spinning (CPMAS) and 2D 13C-1H heteronuclear correlation (HETCOR) NMR analysis. A broad resonance peak appeared in all 1D 13C NMR spectra of monovalent, divalent, and trivalent metal-phytate compounds, which could be deconvoluted to two separate peaks. 2D HETCOR clearly showed distinct proton peaks for hydrogens connected to carbons on the ring and in P-O-H bonds in K2H10IP6, KMgH9IP6, and K4Mg2H4IP6. Thus, based on the known structures of myo-inositol and Na phytate, we propose the presence of various deformed 1a/5e and 5e/1a conformations in these solid metal-phytate compounds. Structural information derived from this work contributed to a better understanding of the phytate-metal interaction mechanism.

Solid state 1D and 2D C-13 NMR spectroscopic investigations of conformational changes of metal phytate compounds

243rd National Meeting (2012)

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