A Hybrid In Silico/In Vitro Target Fishing Study to Mine Novel Targets of Urolithin A and B: A Step Towards a Better Comprehension of Their Estrogenicity

Scope Urolithin A and B are gut metabolites of ellagic acid and ellagitannins associated with many beneficial effects. Evidence in vitro pointed to their potential as estrogenic modulators. However, both molecular mechanisms and biological targets involved in such activity are still poorly characterized, preventing a comprehensive understanding of their bioactivity in living organisms. This study aimed at rationally identifying novel biological targets underlying the estrogenic-modulatory activity of urolithins. Methods and results The work relies on an in silico/in vitro target fishing study coupling molecular modeling with biochemical and cell-based assays. Estrogen sulfotransferase and 17β-hydroxysteroid dehydrogenase are identified as potentially subject to inhibition by the investigated urolithins. The inhibition of the latter undergoes experimental confirmation either in a cell-free or cell-based assay, validating computational outcomes. Conclusions The work describes target fishing as an effective tool to identify unexpected targets of food bioactives detailing the interaction at a molecular level. Specifically, it described, for the first time, 17β-hydroxysteroid dehydrogenase as a target of urolithins and highlighted the need of further investigations to widen the understanding of urolithins as estrogen modulators in living organisms.