Comprehensive profiling of potential sources of cosmeceutical agents: Streptomyces griseus, Pseudonocardia alni and Flammulina velutipes

The FP-7 European project MICROSMETICS aims to discover and develop novel cosmeceutical agents from the microbial diversity. Within this context, more than 110 potential candidate strains including fungi and actinomycetes were selected from a Rational Drug Design Tool based on a functional prediction model, virtual screening and similarity search. Several extracts were generated and biologically evaluated for their skin-protecting, skin-lightening, and antioxidant properties.

The in-depth studies of three potential cosmeceutical strains Streptomyces griseus, Pseudonocardia alni and Flammulina velutipes are presented in this work. At first, the methanol and ethyl acetate extracts of each species were thoroughly investigated by applying a dereplication strategy combining ¹³C NMR and LC-HRMS analysis without any isolation procedure. Specifically, a single ¹³C NMR spectrum was recorded and a recently developed computer-aided identification method was applied to identify the major compounds and the main classes of metabolites in the crude extracts [1]. The principle of this method is based on the calculation of a score resulting from a database searching method where predicted ¹³C NMR chemical shift values of known natural metabolites are compared to experimental ¹³C NMR signals of the crude mixture. In parallel, a fast LC-ESI-QTOF-MS methodology was applied in both positive and negative modes. Several minor components were identified on the basis of chromatographic and spectrometric features (Rt, UV, accurate m/z, proposed EC, DBE). In order to provide a detailed chemical profile of the active substances of the mixtures, all extracts were fractionated by Centrifugal Partition Chromatography. Overall, the global metabolite profiles of all six extracts revealed highly diverse molecular structures belonging to low molecular weight metabolites involved in primary metabolism (amino acids, nucleosides, fatty acids) as well as a diversity of secondary metabolites specific of each species and related to their biological activity.

[1] Bakiri et al., J Nat Prod. Apr 17