PROBLEM TO BE SOLVED: To provide a method of stabilizing piceatannol included in a water-containing solution of a plant extract, and the water-containing solution of the plant extract.SOLUTION: The method of stabilizing piceatannol included in a water-containing solution of a plant extract (excluding grape (Vitaceae) extract includes a step of controlling pH of the solution at 3.0-4.5.COPYRIGHT: (C)2015,JPO&INPIT【課題】植物抽出物の含水溶液に含まれるピセアタンノールの安定化方法、及び、植物抽出物の含水溶液を提供すること。【解決手段】植物抽出物(ただし、ブドウ(Vitaceae)抽出物を除く)の含水溶液に含まれるピセアタンノールの安定化方法として、溶液のpHを3.0~4.5とする工程を含む安定化方法とする。【選択図】図3