In addition, as shown in Fig. 4 and Fig. 5, FSW extract exhibited greater protection for supercoiled DNA than USW; the
extract of USW showed supercoiled DNA of 45.00 ± 2.19%, while a significantly higher (p < 0.05) supercoiled DNA of 57.91 ± 1.62% was noted for the extract of FSW. It was also reported by Singh et al. (2010) and Xiao et al. (2014) that fermented legume extracts showed higher DNA damage protection than unfermented legume extracts due to higher phenolic and isoflavone aglycone contents in the fermented samples. Marazza et al. (2012) reported that the oxidation of DNA was inhibited mainly due to a higher concentration of isoflavone aglycones which contained free phenolic groups in their structures cable of scavenging hydroxyl radicals generated by Fenton’s reaction. Therefore, higher accumulation of phenolic and isoflavone aglycones is thus an indicative of enhanced protection of supercoiled DNA during L. plantarum fermentation. These findings are of great interest because this is the first time that the ability of fermented soy whey using L. plantarum to inhibit the plasmid DNA oxidation has been reported.