PROBLEM TO BE SOLVED: To provide a novel peroxide scavenger that is oxidized by peroxides such as reactive oxygen species which are generated in mitochondria due to an oxidative stress and localized in mitochondria, and increases fluorescence intensity thereof.SOLUTION: The invention provides a phosphine compound represented by formula [I] and a peroxide scavenger comprising the phosphine compound, wherein Ar is an allylene group； R is an aliphatic hydrocarbon group； Y is P, N or Bi； and all of R-R, Zand Zare cyclic groups.【課題】酸化ストレスによりミトコンドリア中に発生し、ミトコンドリア中に局在する活性酸素種などの過酸化物によって酸化され、その蛍光強度を増加できる新規な過酸化物捕捉剤を提供。【解決手段】式[I]で表されるホスフィン化合物及び該ホスフィン化合物からなる過酸化物捕捉剤。（Ａｒはアリレン基；Ｒは脂肪族炭化水素基；ＹはＰ、Ｎ又はＢｉ；Ｒ１～Ｒ３、Ｚ１及びＺ２はいずれも基）【選択図】なし
