The inhibition occurred before the production of norsolorinic acid (NOR), the first stable intermediate
in the AF biosynthetic pathway. Metabolomics studies suggested that the glycolysis pathway was inhibited in mycelia grown in the presence of D-glucal. Using quantitative reverse transcription-PCR (qRT-PCR), we showed that exogenous D-glucal suppressed expression of AF biosynthetic genes tested but enhanced expression of kojic acid biosynthetic genes. Results Use of D-glucal and D-galactal as the sole carbohydrate source did not support mycelial BTSA1 growth The usual GMS medium used for culturing A. flavus contains 50 mg/mL glucose [17]. To examine if D-glucal and D-galactal could be used as the sole carbohydrate for mycelial growth, we replaced the glucose in the medium with 20 or 40 mg/mL D-glucal buy Cilengitide or D-galactal. Media containing either 20 or 40 mg/mL D-glucose were used as the control. After incubation of A. flavus A 3.2890 spores in these media for 3 d, we observed no mycelial growth in media with D-glucal or D-galactal, while abundant mycelial growth was observed in those two controls (Figure 1). No selleck products further growth was observed in media with D-glucal or D-galactal even when the incubation period was extended
to 10 d, suggesting neither these two sugar analogs support mycelial growth when used as the sole carbohydrate. Figure 1 D-glucal or D-galactal as the sole carbohydrate source did not support mycelial
growth. A. flavus cultured for 3 d in GMS media in which glucose was replaced by 20 or 40 mg/mL D-glucal or D-galactal. GMS media containing 20 or 40 mg/mL D-glucose were used as controls. No visible mycelial growth Acetophenone was observed in D-glucal- or D-galactal-containing media. D-glucal inhibited AF biosynthesis and sporulation without affecting mycelial growth in GMS media To test whether D-glucal or D-galactal inhibit AF biosynthesis, spores of A. flavus A 3.2890 were inoculated in GMS liquid media (containing 50 mg/mL glucose) supplied with 2.5, 5, 10, 20, or 40 mg/mL of D-glucal or D-galactal and cultured at 28°C for 5 d. GMS media with the same amounts of additional D-glucose were used as controls. AFs were extracted from each sample, and the AFB1 contents were quantified using high pressure liquid chromatography (HPLC). As shown in Figure 2A, the AFB1 content was reduced significantly in samples with 2.5 to 40 mg/mL D-glucal. An almost complete inhibition was observed when 40 mg/mL D-glucal was used. In contrast, GMS media supplied with 2.5,5 or 10 mg/mL D-glucose promoted AFB1 production (Figure 2A). In samples supplied with D-galactal only a slight inhibition on AFB1 production was detected at the concentration of 40 mg/mL (Figure 2A). Using thin layer chromatography (TLC) analyses, we showed further that production of other AFs such as AFB1 and AFG1 were also inhibited by D-glucal (Figure 2B).