3.15. In Vitro Antifungal Bioassay

The antifungal activities were screened and evaluated by the poison plate technique [28]. All final compounds were dissolved in DMF (0.1 mL) before mixing with potato dextrose agar (PDA; 9.9 mL). The compounds were tested at a concentration of 50 μg mL⁻¹. All fungi were cultivated in PDA at 27 ± 1 °C for 4 days to make new mycelium for the identification of antifungal activity. Then, mycelia dishes of approximately 5 mm diameter were cut from the culture medium. A mycelium was obtained using a germ-free inoculation needle and inoculated in the middle of the PDA plate aseptically. The inoculated plates were incubated at 27 ± 1 °C for 5 days. DMF in sterile distilled water served as the negative control, whereas hymexazol served as the positive control. Each treatment condition consisted of three replicates. Radial growth of the fungal colonies was measured, and the data were statistically analyzed. Inhibitory effects of the test compounds in vitro on these fungi were calculated by the formula I (%) = [(C − T)/(C − 0.5)] × 100, where C represents the diameter of fungal growth on untreated PDA, T represents the diameter of fungi on treated PDA, and I represents the inhibition rate.