In this study, the anti-diabetic, anti-inflammatory, anti-cytotoxic, and antibacterial effects of various substances were studied in vitro. Malachite green's photocatalytic effects were used to determine the optimised sample while it was exposed to visible light. The intended nanocomposites were created without any contaminants, according to XRD data. The overall characterisation results of the green synthesis of CS/SiO₂/TiO₂/CeO₂/Fe₃O₄ nanocomposites (CSTCF(G)) were superior to those of the chemical synthesis of CS/SiO₂/TiO₂/CeO₂/Fe₃O₄ nanocomposites (CSTCF(C)). At the five doses examined, the green synthesis of CS/SiO₂/TiO₂/CeO₂/Fe₃O₄ nanocomposites (CSTCF(G)) and chemical synthesis of CS/SiO₂/TiO₂/CeO₂/Fe₃O₄ nanocomposites (CSTCF(C)) resulted in higher α-glucosidase inhibition percentages in the antidiabetic assay. HaCaT cells and MCF-7 cells were less harmful when treated with chemically synthesized CS/SiO₂/TiO₂/CeO₂/Fe₃O₄ nanocomposites (CSTCF(C)), and green synthesized CS/SiO₂/TiO₂/CeO₂/Fe₃O₄ nanocomposites (CSTCF(G)). From the results of the cytotoxicity tests against MCF-7 cells and HaCaT cells using the nanocomposites, the IC₅₀ values of Salacia reticulata, green synthesized CS/SiO₂/TiO₂/CeO₂/Fe₃O₄ nanocomposites (CSTCF(G)), and chemically synthesized CS/SiO₂/TiO₂/CeO₂/Fe₃O₄ nanocomposites (CSTCF(C)) were calculated. This research work shows that the green synthesized CS/SiO₂/TiO₂/CeO₂/Fe₃O₄ nanocomposites (CSTCF(G)) have strong anti-inflammatory, antibacterial and anti-diabetic properties, as well as considerable suppression of high activation in in vivo zebrafish embryo toxicity. The novelty of this study focused on the revelation that green synthesized nanocomposites are more affordable, environmentally friendly and biocompatible than chemically synthesized ones.