Prealamethicin F50 and related peptaibols from : Validation of their authenticity via chemical analysis.

In the field of natural products chemistry, a common question pertains to the authenticity of an isolated compound, i.e. are the interesting side chains biosynthesized naturally or an artefact of the isolation/purification processes? The droplet-liquid microjunction-surface sampling probe (droplet-LMJ-SSP) coupled to a hyphenated system (UPLC-UV-HRESIMS) empowers the analysis of natural product sources , providing data on the biosynthetic timing and spatial distribution of secondary metabolites. In this study the droplet-LMJ-SSP was utilized to validate the authenticity of two new peptaibols ( and ) as biosynthesized secondary metabolites, even though both them had structural features that could be perceived as artefacts. Compounds and were isolated from the scaled up fermentation of (strain MSX70741), along with a new member of the trichobrevin BIII complex (), and four known compounds (-). The structures of the isolates were established using a set of spectroscopic and spectrometric methods, and their absolute configurations were determined by Marfey's analysis. The cytotoxic activity of compounds , , and was evaluated against a panel of cancer cell lines, where cytotoxic activity in the single digit μM range was observed.