Fig. 3

Analysis of the antioxidant potential of the tested compounds. a Growth spot assay showing wild type (H99) cells incubated on either YPD alone, YPD containing 3 mM of hydrogen peroxide (H₂O₂), or YPD containing 3 mM H₂O₂ and an antioxidant (10 μM PDTC, 1 mM RA, 10 mM AA, or 10 mM GSH). b Disc diffusion assay represents resistance of wild type strain (H99) to increasing concentrations of H₂O₂ (25, 50, 100 mM). ~ 2 × 10⁶ of cells were spread over YPD plates containing no antioxidant, or 10 μM PDTC, 1 mM RA, 10 mM AA, or 10 mM GSH. All antioxidants rescued growth in the presence of 3 mM H₂O₂ with AA and GSH having more visible effect as compared to PDTC and RA. c A fluorescence assay to measure ROS in wild type strain (H99) was performed, wherein greater fluorescence indicates higher levels of ROS. There is an increase of ROS in the presence of FLC (p < 0.01), and ROS is reduced in the presence of FLC and an antioxidant (p < 0.01, either 10 μM PDTC, 1 mM, RA, 10 mM AA, or 10 mM GSH) as indicated by a star. d Fluorescence assay to measure ROS in wild type (H99) and in metallothionein mutant strains (cmt1Δ, cmt2Δ, cmt1/2Δ) was performed where the cells were treated with 32 μg/mL FLC. A significance of the increase in ROS in the mutant as compared to the wild type control is indicated by a star, based on three replicates (p < 0.05)