Applying LC-MS de-replication strategies for the discovery of new natural products

De-replication is a key process in the discovery of new bioactive molecules from natural sources. Fundación MEDINA extensively applies de-replication techniques on bioactive samples to focus its fermentation and isolation resources only on potentially new molecules. With the aim of discovering novel molecules with unknown activities, LC-MS de-replication was applied to a subset of non bioactive samples generated from fungi fermented in 8-medium nutritional arrays. Selected samples were analyzed by LC-LRMS, and the chromatographic components were compared against an in-house database to identify those containing potentially novel molecules in a semi-automated process that allows us to process daily a hundred samples per instrument. LC-HRMS was used to determine the molecular formula of relatively intense and unidentified peaks. When the molecular formula is not found in natural product databases, the molecule is isolated, characterized and added to our compound collection.

The method's success will be illustrated by the identification and isolation of three new cyclic tetra-peptides from Onychochola sclerotica (Ascomycota, Arachnomycetales) that subsequently demonstrated activity as cardiac calcium channel blockers.