Human cancer cell proliferation inhibition by a pentapeptide isolated and characterized from rice bran.

Food-derived bioactive peptides promote functional activity against diseases and present as nutraceutical agents. The purpose of our research was to isolate and fully characterize peptide(s) derived from rice bran having anti-cancer properties. Gastrointestinal juices resistant peptide fractions were initially generated from heat stabilized de-fatted rice bran from which <5 kDa fraction was shown to inhibit proliferation of cancer cells. Based on these published findings the <5 kDa peptide fraction was selected for further characterization to obtain single pure peptide(s) with enhanced anti-cancer properties. Purification and characterization from the fraction was done employing chromatography and mass spectrometric techniques. Cancer cell viability was measured using a cell titer assay that uses a tetrazolium dye [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt; (MTS)] and the electron coupling reagent, phenazine methosulfate. Ion-exchange chromatography elutes that showed anti-cancer properties were further purified to liberate pure peptide. The pure peptide at 600-700 microg/mL dose caused 84% inhibition to colon cancer cells (Caco-2, HCT-116) growth, 80% to breast cancer cells (MCF-7, MDA-MB-231) growth and 84% to liver cancer cells (HepG-2) growth. Mass spectrometry analysis and de novo sequencing revealed the sequence of Glu-Gln-Arg-Pro-Arg for the peptide with a molecular mass of 685.378 Da. A novel pentapeptide was isolated from rice bran to possess cancer growth inhibitory properties on colon, breast, lung and liver cancer cells. This peptide could serve as a nutraceutical agent against cancer.