Effect of extraction conditions on phenolic content, anthocyanin content and antioxidant activity of bran extracts from Thai rice cultivars

摘要

The bran of two cultivars of Thai non-glutinous rice, namely Khao dawk mali 105 (white rice) and Horn nil (purple rice); and two varieties of Thai glutinous rice, namely Kiaw Ngu (white rice) and Leum Pua (dark purple rice) were assessed regarding their compositions, total phenolic content and antioxidant activity. The aims of this research were to (1) identify the major components of the various kinds of Thai rice bran and their properties, (2) evaluate the effect of extracting solvent on the chemical compositions and antioxidant activity of extracts, and (3) optimize the appropriate extraction temperature and extraction time for obtaining high-efficiency extracts. The amounts of 3 major groups of bioactive compounds, including phenolic acids, flavonoids and anthocyanins, were investigated using high-performance liquid chromatography. The highest values of phenolic acids, flavonoids, anthocyanins, total phenolic content, and antioxidant activity based on 2,2-diphenyl-1-picryihydrazyl (DPPH) radical scavenging activity and ferric reducing antioxidant power (FRAP) assays were detected in extracts obtained using 65% (v/v) ethanol. The extraction process conducted at 60 degrees C for 60 min provided the highest values of bioactive compounds, total phenolic content, DPPH radical scavenging activity and FRAP.