Muscotoxins are cyanobacterial cyclic lipopeptides with potential applications in biomedicine and biotechnology. In this study, Desmonostoc muscorum CCALA125 strain extracts were enriched by polymeric resin treatment, and subjected to HPCCC affording three cyclic lipopeptides (1⁻3), which were further repurified by semi-preparative HPLC, affording 1, 2, and 3, with a purity of 86%, 92%, and 90%, respectively. The chemical identities of 2⁻3 were determined as muscotoxins A and B, respectively, by comparison with previously reported ESI-HRMS/MS data, whereas 1 was determined as a novel muscotoxin variant (muscotoxin C) using NMR and ESI-HRMS/MS data. Owing to the high yield (50 mg), compound 2 was broadly screened for its antimicrobial potential exhibiting a strong antifungal activity against Alternaria alternata, Monographella cucumerina, and Aspergillus fumigatus, with minimum inhibitory concentration (MIC) values of 0.58, 2.34, and 2.34 µg/mL; respectively, and weak antibacterial activity against Bacillus subtilis with a MIC value of 37.5 µg/mL. Compounds 1 and 3 were tested only against the plant pathogenic fungus Sclerotinia sclerotiorum due to their low yield, displaying a moderate antifungal activity. The developed chromatographic method proved to be an efficient tool for obtaining muscotoxins with potent antifungal properties.

Institut des Sciences Analytiques University of Lyon CNRS Université Claude Bernard Lyon 1 Ens de Lyon UMR 5280 5 rue de la Doua 69100 Villeurbanne France

Laboratory of Algal Biotechnology Centre ALGATECH Institute of Microbiology of the Czech Academy of Sciences Opatovický mlýn Novohradská 237 379 81 Třeboň Czech Republic

Laboratory of Molecular Structure Characterization Institute of Microbiology of the Czech Academy of Sciences Vídeňská 1083 142 20 Prague Czech Republic

Plant Biotechnology Department AGRITEC Plant Research Ltd Zemědělská 2520 16 787 01 Šumperk Czech Republic

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