2, 5‐Diketopiperazine Derivatives From Coculture of Escherichia coli and Mogroside V

Escherichia coli ( E. coli ), a versatile bacterium, is also recognized for its ability to produce a range of secondary metabolites with significant biological activities. Especially in so‐called biotransformation processes, E . coli is frequently utilized to catalyze the conversion of substrate molecules into diverse compounds through biosynthesis and metabolic pathways. However, studies focusing on the use of small molecules to stimulate microbial expression remain limited. In this study, mogroside V was cocultured with E. coli , resulting in the isolation of five secondary metabolites ( 1 – 5 ) from the culture medium, including four types of 2,5‐diketopiperazines. The structures of these compounds were confirmed by NMR and MS spectra. Preliminary antibacterial results indicated that Compounds 1 – 4 had good inhibitory activity against MRSA and Bacillus subtilis , using the disk diffusion method. All of the isolates had no obvious antibacterial activity against Staphylococcus aureus and Bacillus megaterium .