3.5.2. Antifungal Activity

The methanol extract and isolated compounds were tested in 96-well microtiter plate assays against the phytopathogenic ascomycetes Botrytis cinerea Pers. and Septoria tritici Desm. and the oomycete Phytophthora infestans (Mont.) de Bary according to the monitoring methods approved by the fungicide resistance action committee (FRAC) with minor modifications as described before [22]. Crude extracts and fractions were examined at a final concentration of 125 μg/mL, while pure compounds were tested in a serial dilution, ranging from 100 to 0.1 μM. The solvent DMSO was used as negative control (max. concentration 2.5%), and the commercially used fungicides epoxiconazole and terbinafine (Sigma-Aldrich, Darmstadt, Germany) served as positive controls. Five to seven days after inoculation, pathogen growth was evaluated by measurement of the optical density (OD) at λ 405 nm with a TecanGENios Pro microplate reader (5 measurements per well using multiple reads in a 3 × 3 square). Each experiment was carried out in triplicates.