PROBLEM TO BE SOLVED: To provide an amyloid β aggregation inhibitor composition, a BACE1 inhibitor composition, and an anti-Alzheimer composition containing them, which are safe and have high activity, have a low risk of side effects and can be administered for a long time. SOLUTION: The amyloid β aggregation inhibitor composition, BACE1 inhibitor composition and anti-Alzheimer composition of the present invention are one or more compounds contained in one or both of the pericarp and the fruit of a plant belonging to the family Rhinoceros, preferably Contains an extract of one or both of a peel and a fruit or one or more compounds separated from the extract as an active ingredient, and has an activity of inhibiting amyloid β aggregation associated with symptoms of Alzheimer's dementia and amyloid β. It has an activity of inhibiting BACE1 which is an enzyme involved in production. [Selection diagram] Figure 1【課題】安全で高い活性を有し、副作用のリスクが低く長期投与が可能なアミロイドβ凝集阻害剤組成物、ＢＡＣＥ１阻害剤組成物及びそれらを含む抗アルツハイマー組成物を提供する。【解決手段】本発明のアミロイドβ凝集阻害剤組成物、ＢＡＣＥ１阻害剤組成物及び抗アルツハイマー組成物は、ヒシ科に属する植物の果皮及び果実の一方又は双方に含まれる１又は複数の化合物、好ましくは果皮及び果実の一方又は双方の抽出物又は該抽出物より分離される１又は複数の化合物を有効成分として含み、アルツハイマー型認知症の症状に関連するアミロイドβ凝集を阻害する活性及びアミロイドβの生成に関与する酵素であるＢＡＣＥ１を阻害する活性を有している。【選択図】図１
