Isolation and antifungal properties of cyclo(d-Tyr-l-Leu) diketopiperazine isolated from Bacillus sp. associated with rhabditid entomopathogenic nematode

Abstract

Bacillus sp. associated with an entomopathogenic nematode is shown to produce diketopiperazine (DKP) that showed stronger antifungal activity against Colletotrichum gloeosporioides [minimum inhibitory concentration (MIC): 8 μg mL^− 1] than commercial fungicide oligochitosan (MIC: 125 μg mL^− 1). DKP identified as cyclo(d-Tyr-l-Leu) was isolated for the first time from a natural source with a d-tyrosine residue. This report also demonstrates for the first time an antifungal property exploration of cyclo(Tyr-Leu) class of dipeptides. The structural elucidation was carried out using 1D, 2D NMR methods and HPLC.

Keywords::

• diketopiperazine
• antifungal activity
• minimum inhibitory concentration
• disc diffusion method

Acknowledgements

We are grateful to Mr Manoj M. Kushwaha of Thermo Fisher Scientific India Pvt. Ltd, Mumbai for providing HR-ESI-MS analysis. This work was funded by the Indian Council of Medical Research (ICMR) and CSIR under 12^th Five-Year Plan (FYP) project CroPP.