Abstract: An optimal experimental procedure with the microplate-MTT colorimetric assay was developed, that was as follows: 90 μL of fungal spore suspension at concentration of 105 spores/mL was added in each well of the 96-well microplate first; 10 μL of the sample solution with its different concentration was then added, and cultivated for 48 h at 25 ºC in darkness; 10 μL of MTT solution at 8 mg/mL was added into each well, and incubated for another 10 h at 25 ºC and centrifuged; The supernatant was removed, and 150 μL of DMSO was added; After shaking for another 30 min at 15 rpm, light absorption values at 510 nm were obtained for the supernatant transferred in a new plate with a microplate spectrophotometer. With the optimal MTT assay mentioned above, the minimum inhibitory concentration (MIC) values of chelerythrine from Macleaya cordata on Fusarium oxysporum f. sp. niveum and Magnaporthe oryzae were 80 and 1.5 µg/mL respectively, and the median inhibitory concentration (IC50) values were 21.99 and 0.78 µg/mL, correspondingly. The MIC and IC50 values of diepoxin ζ from the endophytic fungus Dzf12 on Magnaporthe oryzae were 200 and 96.21 µg/mL. It indicated that the antifungal metabolites from plants and microbes could be evaluated fast and micro-quantitatively by using microplate-MTT colorimetric assay that is favorable for screening antifungal components with a high throughout.

Key words: microplate-MTT colorimetric assay, plant metabolites, microbial metabolites, antifungal activity