PROBLEM TO BE SOLVED: To provide a dipeptidyl peptidase-IV inhibitor, a blood glucose level increase inhibitor, and an antidiabetic agent, which are derived from natural products and highly safe.SOLUTION: The present invention provides a tea leaf proteolysate that is obtained by extracting tea leaves or tea leaves with an alkaline solution and treating the extract with an enzyme having protease activity. The tea leaf proteolysate has high inhibitory activity against dipeptidyl peptidase-IV and suppresses an increase in blood glucose level.SELECTED DRAWING: None【課題】天然物由来の安全性の高いジペプチジルペプチダーゼ-IV阻害剤、血糖値上昇抑制剤および抗糖尿病剤を提供すること。【解決手段】茶葉あるいは茶殻をアルカリ溶液で抽出し、抽出液をプロテアーゼ活性を有する酵素で処理することにより得られる茶葉タンパク質分解物は、高いジペプチジルペプチダーゼ-IV阻害活性を有し、血糖値上昇を抑制することを特徴とする。【選択図】なし
