Competitive ultrafiltration: A ligand-displacement strategy for rapid discovery of high-quality neuraminidase inhibitors from natural product mixtures.

The rapid discovery of high-quality natural products (NPs) that combine potent biological activity with structural diversity remains a major challenge. Traditional bioactivity-guided isolation is time-consuming and labor-intensive, and although the development of multi-omics technologies has accelerated NP digging, these approaches primarily emphasize structural novelty rather than biological activity. To overcome this limitation, we developed a novel model - competitive ultrafiltration (CUF), based on the principle of target-site occupancy competition. By exploiting the displacement effect of high-affinity inhibitors on low-affinity ligands, CUF enables the selective enrichment of potent active compounds with diverse scaffolds from complex mixtures. Using the screening of neuraminidase (NA) inhibitors as a study, we validated the feasibility of CUF through model construction, limit of detection analysis, and mixed-library verification. Subsequently, CUF was applied to Lonicera japonica extract, resulting in the identification of two NA inhibitors. Both of the chlorogenic acid and luteoloside exhibited significant inhibitory activity, confirming the practical applicability of this method. This study demonstrates that CUF provides a promising tool for lead compound discovery in drug development.