Using UV–Vis Titration to Elucidate Novel Epigallocatechin Gallate (EGCG)-Induced Binding of the c-MYC G-Quadruplex

<b>Background/Objectives:</b> Aberrant expression of c-MYC drives aggressive cancers. A guanine-rich promoter sequence (Pu27) folds into a transcriptionally repressive G-quadruplex (G4). Epigallocatechin gallate (EGCG), the main green tea polyphenol, displays anticancer activity, but clear, easily replicated evidence for direct binding to the c-MYC G4 is lacking. We therefore obtained the first biophysical confirmation of an EGCG-c-MYC G4 interaction using routine UV-visible spectroscopy. <b>Methods</b>: A pre-annealed Pu27 G4 (5 µM) in potassium-rich buffer was titrated with freshly prepared EGCG (0-20 µM) at 25 °C. Full-range UV-Vis spectra (220-400 nm) were recorded after each addition, and absorbance variations at the DNA (260 nm) and ligand (275 nm) maxima were quantified across three independent replicates. <b>Results</b>: EGCG induced pronounced, concentration-dependent hyperchromicity at 260 nm, reaching ~8-10% above baseline at a 4:1 ligand/DNA ratio and exhibiting saturable binding behaviour. Concurrently, the 275 nm band displayed relative hypochromicity coupled with a subtle bathochromic shift. These reciprocal perturbations-absent in buffer-only controls-constitute definitive evidence of a specific EGCG•G4 complex most consistent with external π-stacking or groove engagement rather than intercalation. <b>Conclusions</b>: This study delivers the first rigorous, quantitative UV-Vis confirmation that a readily consumed dietary polyphenol directly targets the c-MYC promoter G4. By marrying conceptual elegance with methodological accessibility, it provides a compelling molecular rationale for EGCG's anti-oncogenic repertoire, inaugurates an expedient platform for screening G4-reactive nutraceuticals, and paves the way for structural and cellular investigations en route to next-generation c-MYC-directed therapies.