Boron NMR as a Method to Screen Natural Product Libraries for B-Containing Compounds.

Natural products are biologically relevant metabolites exploited for biomedicine and biotechnology. The frequent reisolation of known natural products questions whether existing discovery models are still capable of identifying novel compounds. As innovative NMR-based screening techniques can help overcome these challenges, we applied a phase cycling composite pulse sequence to 11B NMR experiments to enhance their sensitivity to screen libraries for novel boron-containing molecules. Aplasmomycin and autoinducer-2 were detected in crude and enhanced microbial fractions, via their boron signals, as proof of concept. Subsequently, a screen of 21 crude plant and 50 crude marine microbial extracts were chosen at random and analyzed with the optimized 11B experiment for feasibility as a high throughput discovery method. Eight of the plant samples and 13 of the microbial samples were identified as boron-containing, suggesting that there is a higher presence of boron metabolites available from natural sources than previously known due to a lack of appropriate discovery methods. As a result, we believe that this optimized 11B NMR experiment can serve as a robust method for quick and facile discovery of novel boron-containing metabolites from a variety of natural sources.