Flavonoid Composition and Molecular Basis of the Potential Sexual-Enhancing Properties of a Turnera diffusa Extract (Liboost®)

Background/Objectives: Sexual dysfunction is a prevalent and multifactorial condition affecting a large proportion of the global population, with limited therapeutic options beyond pharmacological approaches primarily targeting erectile dysfunction. This has increased interest in botanical supplements for sexual health, although mechanistic evidence and clear links between phytochemical composition and biological activity remain scarce. The present study provides an integrative evaluation of a commercial Turnera diffusa extract (Liboost®) formulated to support sexual health by combining detailed phytochemical characterization with targeted in vitro mechanistic assays. Methods: The extract was characterized by HPLC-DAD-HRMS, enabling the identification and semi-quantification of its major constituents. A total of 49 compounds were detected, predominantly flavonoids, including luteolin- and apigenin-derived glycosides, flavonols, methoxyflavones, flavanones, and coumaroyl derivatives, with a total quantified flavonoid content of 15.9 mg·g−1. Biological activity was evaluated in human cell models without cytotoxic effects at the tested concentrations. Results: Liboost® significantly reduced PDE5 expression, inhibited aromatase activity, and moderately increased nitric oxide production. These complementary effects suggest a multi-target modulation of pathways involved in sexual function, integrating vascular, endocrine, and nitrergic mechanisms. Conclusions: Although limited to in vitro models, the findings provide mechanistic support for the biological activity of T. diffusa extracts and highlight the importance of linking phytochemical composition with functional evidence when evaluating botanical supplements.