Structure-activity relationships of the benzaldehydes in targeting the oxidative-stress response system of fungi. (A) Benzaldehyde and its structural analogs used in this study. (1) Benzaldehyde (parent compound), (2) trans-Cinnamaldehyde, (3) 2-Hydroxy-5-methoxybenzaldehyde, (4) 2-Hydroxy-3-methoxybenzaldehyde (o-Vanillin), (5) 3,5-Dimethoxybenzaldehyde, (6) 2,5-Dimethoxybenzaldehyde, (7) 2-Methoxybenzaldehyde, (8) 2,3-Dimethoxybenzaldehyde. (B) Responses of Saccharomyces cerevisiae wild type and antioxidation mutant strains to the treatment of benzaldehyde analogs. Sensitive mutants in each treatment were designated under the yeast dilution bioassay (100 to 105 indicates the dilution rate for spotting onto agar plate). (C) Recovery of the growth of yeast cells treated with 3,5-dimethoxybenzaldehyde (3,5-D) by reduced form of glutathione (GSH; 0.1 mM), but not by oxidized form of glutathione (GSSG; 0.1 mM). (D) Sensitive responses of A. fumigatus MAPK mutants (sakA Δ and mpkC Δ) to 3,5-dimethoxybenzaldehyde (3,5-D)(%: Growth inhibition rate, SD < 5%).