The present invention easily and efficiently provides a peroxisome proliferator-activated receptor ligand, and a composition for amelioration of insulin resistance or for prevention and/or amelioration of the insulin resistance syndrome containing the same, as an active ingredient. The present invention relates to a peroxisome proliferator-activated receptor ligand which comprises a prenylflavonoid, a chalcone derivative exclusive of prenylflavonoids, a flavonol derivative exclusive of prenylflavonoids, and a salt, a glycoside and/or an esterified substance thereof acceptable as a pharmaceutical preparation or a food or a beverage; a composition containing the above ligand; a plant-derived extract containing the above ligand; and a process for producing the above extract.