Purity of Natural Products: Meta Analysis and Current Status─AnaPurNa 2.0

Building on the 2012 study "Analysis and Purification of Bioactive Natural Products", this work further explores the essential aspects that impact the purity and utility of contemporary natural product (NP) isolates. Recent advancements in FAIR data sharing enabled a secondary ("meta") analysis of the raw NMR spectra of 100 NPs selected randomly to assess their purity using quantitative NMR (qNMR). First, all 100 NPs were analyzed via rapid integration-based qNMR. Second, a detailed qNMR analysis of ten representative NPs involving impurity assignments and spreadsheet annotation was performed and coverage probabilities generated using the NIST uncertainty machine. The average purity of the isolates was ∼84% (±5%), equivalent to impurity levels of 16 (11-21)%. Outcomes show that 1H NMR spectra acquired primarily for structure determination are adequate for purity analysis. Consideration of all observed peak patterns made purity determinations cohesive and permitted an estimation of impurity identities. With proper instructions in place, the methodology became robust to the point that different participants generated congruent results. Guidelines for purity determination with relative (100%-based) qNMR methodology are presented. Further reflection on the results indicates the need for critical scrutiny of current practices of extraction, isolation, and purification involved in bioactive NP discovery.