Sulfonated graft copolymer obtained by radical graft copolymerization of one or more synthetic monomers in the presence of hydroxyl-containing naturally derived materials. The graft copolymer includes 0.1 to 100 wt %, based on weight of the total synthetic monomers, of at least one monoethylenically unsaturated monomer having a sulfonic acid group, monoethylenically unsaturated sulfuric acid ester or salt thereof, with the monomer and hydroxyl-containing naturally derived materials present in a weight ratio of 5:95 to 95:5.