In this assay, extracts and fractions were used in a redox-linked reaction whereby the antioxidants
present in the sample act as the oxidants. Reduction of the ferric-tripyridyltriazine complex to the
ferrous complex forms an intense blue colour which can be measured at 593 nm. The intensity of the
colour is related to the amount of antioxidant reductants in the extracts. The trend for ferric
ion-reducing activities of different fractions is shown in Table 2. The antioxidant activity of the ethyl
acetate fraction was significantly stronger than that of the others. There was insignificant difference in
the antioxidant activities among the ethanol extract fraction, n-butanol fraction and water fraction,
while the antioxidant activity of the petroleum ether fraction was the poorest. Like the results obtained
from the DPPH and ABTS assay, the ethyl acetate fraction showed relatively strong ferric ion-reducing
activity while all the other fractions showed lower ferric ion-reducing activities.