CHARACTERIZATION OF BIOAVAILABLE COMPOUNDS IN BLACK AND RED PIGMENTED RICE CULTIVARS IN THAILAND

Pigmented rice (Oryza sativa L.) cultivars become increasingly important in the agro-industry due to their bioavailable compounds that have the ability to inhibit the formation and/or to reduce the concentration of reactive cell-damaging free radicals. Moreover, the pigments of pigmented rice are also used as food colorants in food industries. Antioxidant activity, total phenolic content, monomeric anthocyanin content and total carotenoids in two black rice (‘Homnil’ and black sticky rice) and red rice (‘Hommali’) grown during 2006 and 2007 in Thailand were investigated. The antioxidant activity (DPPH radical scavenging activity) of red rice was significantly higher than that of black rice and black sticky rice (88.95%, 83.91 and 81.15%, respectively). However, the highest monomeric anthocyanin content and total carotenoids content were found in black sticky rice followed by black rice and red rice. Black rice exhibited the highest total phenolic content, but no significant difference was found between red rice and black sticky rice. Significant differences of antioxidant activity, total phenolic and total carotenoids content were observed between two black rice cultivars, whereas monomeric anthocyanin content was not significantly different between these two cultivars.