Antifungal Halogenated Cyclopentenones from the Endophytic Fungus Saccharicola bicolor of Bergenia purpurascens by One Strain-Many Compounds Strategy.

Phytopathogenic fungi have been acknowledged 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 one strain-many compounds strategy. Their structures and absolute configurations were elucidated based on extensive spectroscopic analysis, X-ray crystallographic analysis, and TD-DFT-ECD 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 proved to be potently antifungal against S. sclerotiorum in vitro and in vivo. This work provides an effective strategy for searching antifungal candidate agents.