Green tea extract bio-templated synthesis of Ag NPs immobilized magnetic nanocomposite: Evaluation of its catalytic activity and its performance for the treatment of gastrointestinal system cancers

•Green supported of silver nanoparticles silver nanoparticles over calcium lignosulfonate functionalized Fe3O4 nanocomposite mediated by green tea extract.•Green tea extract act as a reducing and stabilizing agent without any toxic regents.•Fe3O4@CLS/Ag nanocomposite was prepare and characterized.•Fe3O4@CLS/Ag nanocomposite shown good antioxidant and anti-gastrointestinal system cancers.