3.2. Total phenolic content (TPC)
Phenolic compounds may directly contribute to antioxidant
activities; therefore, total phenolic content (TPC) in cereal grains
was measured. The TPC was expressed as milligrams of ferulic acid
equivalents (FAE) per gram of rice (Table 2). TPC ranged from 3.58
to 16.74 mg FAE/ g rice in soluble fractions. Black rice had the highest
TPC in the soluble fractions among all the rice samples. Insoluble
bound fractions had TPC ranging from 0.75 to 4.79 mg FAE/
g rice, with light-purple rice exhibiting the highest contents compared
to the black and white samples.
TPC in soluble fractions were higher than insoluble bound fractions.
Thus phenolic compounds of breeding lines mainly occurred
in soluble free fractions except for YF45 (white rice) and YF67
(light-purple) which had higher insoluble bound TPC (4.45 and
4.79 mg/g, respectively) than those of soluble fractions (Table 2).
It could be due to some important genes that control the linkage
between phenolics and lignins which segregated and assorted
resulting in different offsprings of rice hybrid. Furthermore, the
TPC of soluble fractions of black rice was significantly higher than
that in light-purple and white rice. The TPC of soluble fractions of
black rice YF53 was the highest among all fractions in the 17 samples,
which showed that hybridisation could enhance the total soluble
phenolic content (Table 2).