Flavonoids as Inhibitors of VEGFR2 Signaling: Structural Insights for the Development of Safer Anti-Angiogenic Therapies.

Vascular endothelial growth factor (VEGF) is a key regulator of angiogenesis and an established therapeutic target in diseases such as cancer and ocular disorders. However, long-term use of most current anti-VEGF agents is often limited by their associated side effects, including hypertension, bleeding, and gastrointestinal complications. These limitations have stimulated interest in naturally occurring VEGF inhibitors derived from dietary sources, which may offer safer alternatives due to their favorable safety profiles. In this study, we investigated shared structural features of potent VEGFR2 inhibitors, focusing on naturally derived polyphenols. Polyphenols representing multiple structural subclasses were evaluated for their ability to inhibit VEGFR2 kinase activity using an in vitro kinase assay, to suppress VEGF-induced phosphorylation of VEGFR2 and downstream MAPK signaling in endothelial cells by Western blot, and to reduce VEGF-stimulated endothelial cell proliferation. Across all assays, flavonoids with strong VEGFR2 inhibitory activity displayed consistent structural characteristics, including the number and specific positioning of hydroxyl groups on the A- and B-rings, as well as specific structural elements of the C-ring. Our findings provide a strong foundation for further structure-activity relationship (SAR) studies and facilitate identification of key molecular determinants required for VEGFR2 inhibition. Elucidation of these structural patterns may contribute to the development of more effective and safer angiogenesis inhibitors with reduced adverse effects.