for 30 min before being measured for light absorption values at a wavelength of 517 nm. The control group consisted of the following: (1) standard BHA antioxidant (butylated hydroxyanisole) and (2) methanol. The measured values were used to calculate DPPH• radical scavenging percentage from the equation [1 - (A517 of sample/ A517 of control)] × 100. IC50 (mg/ml) (concentration value of extracts capable of scavenging DPPH• at 50%) was then calculated from the graph of relationships between percentage scavenging and extract amount.
2.2.3.1.2. Ferric Reducing Ability of Plasma (FRAP) Assay
FRAP is the method for testing ability to change Fe3+ to Fe2+ in which the reaction creates a dark blue color.
This analysis can be performed by preparing a FRAP stock solution containing the following: (1) 300 mM concentrated acetate buffer at pH 3.6, (2) 10 mM concentrated TPTZ solution in 40 mM concentrated HCl and (3) 20 mM concentrated FeCl3•6H2O solution. The aforementioned stock solution was then fermented at 37°C before being used for analysis of antioxidant amounts. The experimentation method modified from [24] and [28] mixed 300 μl of rough extracts from rice with FRAP solution at a volume of 1.7 ml. The mixture obtained was then left to react at room temperature for 1 hr. Next, the mixture was measured for light absorption values at a wavelength of 593 nm. The standard antioxidant used to compare with the findings was FeSO4 with a known concentration value. The analysis results were displayed in μmol FeSO4/g fresh weight.