Quantification of brown rice compounds with antioxidant properties compared with rice bran

Rice is an important staple food for more than half of the world population and is mainly consumed as cooked white rice. White rice is known to contain the highest carbohydrate content [1] thus being considered a highly glycemic food. To improve the nutritional value of rice different strategies have been suggested, namely the selection of rice varieties with higher nutritional value [2], and the consumption of brown rice, which is receiving increasing attention due to its beneficial health effects [3]. The bran of brown rice is also an important source of fiber, minerals, proteins, vitamins, and health promoting compounds with antioxidant activity, including γ-oryzanol, γ-aminobutyric acid (GABA), phytic acid, ferulic acid and p-coumaric acid [4,5]. 

In this study, the content of these antioxidant compounds in brown rice and in the bran of the rice variety Ariete was determined. The extraction protocol was optimized for each compound, including quantification by high performance liquid chromatography (HPLC) coupled to a diode array (DAD) or refractive index (RI) detector. 

All compounds were present in higher amounts in the bran with phytic acid being the major compound with 7.59 and 0.85 g/100 g in the bran and brown rice. The minor compound was p-coumaric acid with 74.04 mg/100 g in the bran and 3.18 mg/100 g in the brown rice.

The quantification of these antioxidant compounds is of great importance for the selection the appropriate rice processing method and for development of a database of antioxidant composition of rice varieties.