Bioactive Bioxanthracene and Cyclodepsipeptides from the Entomopathogenic Fungus Blackwellomyces roseostromatus BCC56290

Abstract

In the course of our ongoing research targeting the identification of potential biocontrol agents from entomopathogenic fungi (EPF), we explored a solid-state rice fungal extract of <i>Blackwellomyces roseostromatus</i> BCC56290 derived from infected lepidopteran larvae. Chemical and biological prospections afforded four unprecedentedly reported natural products differentiated into a dimeric naphthopyran bioxanthracene ES-242 derivative (<b>1</b>) and three cyclodepsipeptides (<b>2</b>-<b>4</b>) in addition to two known cyclodepsipeptides, cardinalisamides B (<b>5</b>) and C (<b>6</b>). Chemical structures of the isolated compounds were elucidated through comprehensive 1D/2D NMR and HR-ESI-MS data together with comparisons to the reported literature. The absolute configuration of the isolated cyclodepsipeptides was determined using Marfey's method. All isolated compounds were assessed for their antimicrobial, cytotoxic, and nematicidal activities with some compounds revealing significant activities.