<p>ZnO nanopowders, used as UV filter in many sunscreen products, may cause adverse health effects to human tissue due to their ability to generate active free radicals through photocatalytic processes. In this study, we investigated the potential of modifying the surface of ZnO nanoparticles with varying volumes of red-flesh pitaya peel extract to reduce their photocatalytic activity. The modified materials were characterized using XRD, FESEM, FTIR, and UV–visible diffuse reflectance spectroscopy. Their color, antioxidant properties and photocatalytic activity were evaluated through the CIE L*a*b* colorimetric method, the ABTS radical scavenging assays, and the UV-light-induced degradation of methylene blue, respectively. The experimental results indicated that the surface modification of ZnO nanoparticles did not affect their UV absorption capacity but resulted in a dark yellow color and successfully suppressed their photocatalytic activity, which can be attributed to the presence of antioxidant phytochemicals and the formation of ZnC₂O₄ on ZnO surface. Owing to these alterations, the surface-modified ZnO nanoparticles can be promisingly applied as a safe and effective UV filter in sunscreen products designed for intermediate skin tones.</p> Graphical abstract <p></p>