Anticancer activities of bioactive peptides derived from rice husk both in free and encapsulated form in chitosan

Abstract

Cereal grain-derived protein hydrolysates exert beneficial effects for human health, thus utilization of by-products with high protein content has drawn attention. In this study, hot water extraction of rice husk has been optimized to obtain protein hydrolysate with the highest anticancer activity. The optimum protein value was obtained as 2.40 g/L corresponding to 43.2 g protein/kg dried rice husk under the conditions of 60 °C, 2.0 mL/min flow rate and pH 10.0. The protein hydrolysate was encapsulated with chitosan, where the mean particle size of protein hydrolysate (0.3%) loaded chitosan nanoparticles was 256.4 ± 33.4 nm with 89% encapsulation efficiency and a 65% release at the end of 6 days. Cytotoxicity assays showed that the lowest cell viabilities have been achieved with A549 and MCF7 cells with IC50 values of 1.98 and 3.58 µg/mL, respectively, whereas nuclear fragmentation and apoptotic bodies were observed through Hoechst 33342 staining. The cytotoxic effect might be associated with the wide variety of peptide/protein subunits ranging from 10 kDa to more than 180 kDa in the protein hydrolysate of rice husk.