Antibiotic Activity of a <i>Paraphaeosphaeria sporulosa</i>-Produced Diketopiperazine against <i>Salmonella enterica</i>
2020
Raffaele Carrieri | Giorgia Borriello | Giulio Piccirillo | Ernesto Lahoz | Roberto Sorrentino | Michele Cermola | Sergio Bolletti Censi | Laura Grauso | Alfonso Mangoni | Francesco Vinale
A diketopiperazine has been purified from a culture filtrate of the endophytic fungus <i>Paraphaeosphaeria sporulosa</i>, isolated from healthy tissues of strawberry plants in a survey of microbes as sources of anti-bacterial metabolites. Its structure has been determined by nuclear magnetic resonance (NMR) and liquid chromatography–mass spectrometry (LC–MS) analyses and was found to be identical to <i>cyclo</i>(L-Pro-L-Phe) purified from species of other fungal genera. This secondary metabolite has been selected following bioguided-assay fractionation against two strains of <i>Salmonella enterica</i>, the causal agent of bovine gastroenteritis. The diketopiperazine <i>cyclo</i>(L-Pro-L-Phe), isolated for the first time from <i>Paraphaeosphaeria</i> species, showed minimum inhibitory concentration (MIC) values of 71.3 and 78.6 μg/mL against the two <i>S.</i> <i>enterica</i> strains. This finding may be significant in limiting the use of synthetic antibiotics in animal husbandry and reducing the emergence of bacterial multidrug resistance. Further in vivo experiments of <i>P. sporulosa</i> diketopiperazines are important for the future application of these metabolites.
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