Phenolic compounds may act as antioxidants by several different mechanisms, including free radical scavenging, chelation of metal ions and the inhibition of pro-oxidant enzymes (Amorati et al., 2006). In plants, phenolics are usually found in conjugated forms through the hydroxyl group. It is suggested that the increase in antioxidant activity and phenolic content in fermented rice bran can be attributed to hydrolytic enzymes, such as b-glucosidase, which are produced by fungi.
This was explained in a report by Bhanja et al. (2009) which stated that these enzymes act upon the substrate and increase the availability of free hydroxyl groups on the phenolic structure, thus increasing the content of free phenolics and subsequently the antioxidant activity of the substrate. As displayed in Table 2, only 2 types of phenolic acids were detected in mix-cultured rice bran, sinapic and ferulic acids, when compared to other extracts. Interestingly, as shown in Fig. 1, the antioxidant activity of all of the extracts tested was shown to be in the ascending order of nonfermented