Phytopathogenic fungi have been considered as being an enormous threat in the agricultural system. In our search of new antifungal natural products, nine new halogenated cyclopentenones, bicolorins A-I (1-3, and 5-10), along with three known cyclopentenones (4, 11, and 12) were isolated from the endophytic fungus Saccharicola bicolor of Bergenia purpurascens by the one strain-many compounds strategy. Their structures and absolute configurations were elucidated based on extensive spectroscopic analysis, X-ray crystallographic analysis, and time-dependent density functional theory-equivalent circulating density calculations. Compounds 1-12 showed antifungal activities against five phytopathogenic fungi (Uromyces viciae-fabae, Pythium dissimile, Gibberella zeae, Aspergillus niger, and Sclerotinia sclerotiorum). Especially, bicolorins B and D (2 and 5) exhibited strong antifungal activities against P. dissimile with the MIC values of 6.2 and 8.5 μg/mL, respectively, compared with the positive control cycloheximide (MIC of 8.6 μg/mL). Additionally, bicolorin D was proven to be potently antifungal against S. sclerotiorum in vitro and in vivo. This work provides an effective strategy for searching antifungal candidate agents.
Keywords: Bergenia purpurascens; Saccharicola bicolor; antifungal activities; cyclopentenone; one strain-many compounds strategy; phytopathogenic fungi.