The changes produced in natural-product compounds by nanocatalysts can be important in the search for new uses of these compounds as medicinal drugs and in food processing. In this research a nanocatalyst was used to convert a natural plant compound to a compound with strong antioxidant properties. In this study lilial was reduced to hydroxyl lilial (Hl) using a magnetic Fe3O4@SiO2-Ag nanocomposite. The iron oxide was synthesized using a sol-gel method to attain a nanoparticle size of 14 nm. Silica oxide nanoparticles were then used to coat the iron oxide, using tetraethyl orthosilicate (TEOS) as the silica source. Finally, core-shell Fe3O4@SiO2-Ag microspheres were created to form a nanocatalyst; the size was calculated with x-ray diffraction (XRD) to be 24 nm. Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscope (SEM), ultraviolet-visible spectrophotometry (UV-Vis), gas chromatography-mass spectroscopy (GC-MS), and XRD were used for identification of the Hl compound and preparation of the Fe3O4@SiO2-Ag nanocatalyst. Measurement of antioxidant and antibacterial activity showed that the Hl compound was effective both as an antioxidant and a bactericide.