The role and importance of the identification of natural products are discussed in the perspective of the study of secondary metabolites. The rapid identification of already reported compounds, or structural dereplication, is recognized as a key element in natural product chemistry. The biological taxonomy of metabolite producing organisms, the knowledge of metabolite molecular structures, and the availability of metabolite spectroscopic signatures are considered as the three pillars of structural dereplication. The role and the construction of databases is illustrated by references to the KNApSAcK, UNPD, CSEARCH, and COCONUT databases, and by the importance of calculated taxonomic and spectroscopic data as substitutes for missing or lost original ones. Two NMR-based tools, the PNMRNP database that derives from UNPD, and KnapsackSearch, a database generator that provides taxonomically focused libraries of compounds, are proposed to the community of natural product chemists. The study of the alkaloids from Urceolina peruviana, a plant from the Andes used in traditional medicine for antibacterial and anticancer actions, has given the opportunity to test different approaches to dereplication, favoring the use of publicly available data sources.

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Streptomyces coelicolor A3(2) is considered as the model strain among the Streptomyces and has the capacity to produce several natural molecules. Our hypothesis was that cultivation of the strain onto a complex carbon source such as wheat bran would induce the production of various secondary metabolites due to the presence of complex polysaccharides. A multi-approach has been performed in order to investigate: 1) whether that strain could degrade lignocellulose; 2) which enzymatic and metabolic pathways secondary were over-expressed when grown on wheat bran. The transcriptomic approach showed the expression of several CAZymes significantly expressed when grown on wheat bran such as endoglucanases (encoding for GH74, GH5_8 and GH12) and xylanases (GH11 and CE4 encoding for respectively endo-1,4-beta-xylanase and an acetyl-xylan esterase). Enzymatic activities showed an expression of xylanase (115.3 ± 32.2 mUI/mL) and laccase-peroxidase (101.5 ± 10.9 mUI/mL) during wheat bran degradation by Streptomyces coelicolor A3(2). Metabolomics showed that the production of secondary metabolites differed between growth on either glucose or wheat bran as carbon source which may be correlated to the complexity of carbon compounds within wheat bran which are similar to the ones encountered in soils and should represent more the in situ carbon conditions which Streptomyces might face off. This opens opportunities for the bioproduction of molecules of interest from wheat bran.

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