Figure 3

(a) Quantification of cellular ROS levels via the fluorescent DCFH-DA assay in the S. cerevisiae WT and yeast mutants ∆sch9, the ∆rim15, the ∆msn2, the ∆msn4 and the ∆asg1 strains. Strains were treated with antioxidants 0.008 mg/mL of quercetin (Q), 0.002 mg/mL of protocatechuic acid (PCA) or 0.1 mg/mL Hom Dang rice bran extract (HD). After, cells were exposed to 5 mM of hydrogen peroxide (H₂O₂) for 10 mins (upper panel) or 1 hr (lower panel) to induce generation of ROS. Endogenous ROS levels of cells were measured. Error bars represent standard error of the mean (SEM) (*p, ^#p < 0.01, two-tailed Student’s t test compared to untreated condition and wild-type, respectively). (b) The oxidative stress resistance of the WT, the ∆sir2 and the ∆tor1 strains were examined via spot assays. Cells were first treated or untreated with antioxidants quercetin (Q), protocatechuic acid (PCA) or Hom Dang rice bran extract (HD), and then exposed to 5 mM hydrogen peroxide (H₂O₂) for 10 mins (upper panel) or 1 hr (lower panel) prior to be spotted on YPD plates. Growth was examined after incubation in a dark room at 30 °C for 48 hr. Three independent experiments were done. (c) The life-spans of yeast deletion mutants lacking longevity factors Sch9, Rim15, Msn2, Msn4 or Asg1 in the presence and absence of antioxidants quercetin (Q), protocatechuic acid (PCA) or Hom Dang rice bran extract (HD). Survival curves of chronologically aging yeast cells from day 0 to day 30 were shown. Lack of Sch9 significantly increased the longevity while, in contrast, lack of Rim15, Msn2, Msn4 or Asg1 significantly decreased the longevity of S. cerevisiae. Pretreatment with antioxidants quercetin (Q) or protocatechuic acid (PCA) or Hom Dang rice bran extract (HD) showed increasing life-span extension in the WT, the ∆rim15, the ∆msn2, the ∆msn4 and the ∆asg1 strains. (*p, ^#p < 0.01, two-tailed Student’s t test compared to untreated condition and wild-type, respectively). Data were presented as means ± SEM (n = 9).