Isolation of 2,5-diketopiperazines from AZ78 with activity against .

Inhibitory activity of the biocontrol bacterial strain AZ78 is related to the production of cyclo(l-Pro-l-Tyr), a 2,5-diketopiperazine with and toxic activity against and Further investigation of culture filtrate organic extracts showed its ability to produce other 2,5-diketopiperazines. They were isolated and identified by spectroscopic (H NMR and ESIMS) and physic (specific optical rotation) methods as cyclo(l-Pro-l-Val), cyclo(d-Pro-d-Phe), cyclo(l-Pro-l-Leu), and cyclo(d-Pro-l-Tyr). When tested against the phytopathogenic Gram-positive bacterium LMG 3605, cyclo(l-Pro-l-Val) showed a toxic activity similar to chloramphenicol at a comparable concentration. Overall, these data suggest that 2,5-diketopiperazines represent a class of metabolites characterizing the metabolome of AZ78. Furthermore, the toxic activity showed by cyclo(l-Pro-l-Val) against LMG 3605 broaden the spectrum activity of 2,5-diketopiperazines against phytopathogenic microorganisms enforcing their potential development as biopesticides.[Figure: see text].