Metal-Chelating, Tyrosinase-Inhibiting and Anti-Angiogenic Properties of Myo-Inositol Hexaphosphate Isolated from Stabilized Rice Bran

Myo-inositol hexaphosphate (IP6 or phytate) is a phosphorylated sugar alcohol that is found abundantly in cereals, oilseeds, nuts, grains and legumes; it has the highest amount in rice bran. In this study, IP6 was isolated from stabilized rice bran as its sodium salt (Na-IP6) in 9.63% yield. By total phosphorus determination, the isolated product was found to be 97.34% Na-IP6. Spectrophotometric measurements showed that Na-IP6 (EC50 = 59.52 +/- 0.12 ppm) is a more efficient Fe (II) chelator compared with ethylenediaminetetraacetic acid (EDTA) (EC50 = 278.19 +/- 4.04 ppm) at P<0.05. In vitro assessment of tyrosinase-inhibiting activity revealed that Na-IP6 (IC50 = 0.86 +/- 0.05 mM) is a more potent tyrosinase inhibitor (P<0.05) than hydroquinone (IC50 = 1.95 +/- 0.04 mM). A duck embryo chorioallantoic membrane (CAM) angiogenesis assay that employs digital imaging for quantification was used in this study and is described in this report for the first time. Image analysis revealed that at 48 h of treatment, the length, size and number of junctions of blood vessels were decreased in the CAMs treated with Na-IP6, indicating that Na-IP6 is an inhibitor of angiogenesis.