PROBLEM TO BE SOLVED: To provide a fluorescent dyestuff excellent in quantum yield whether a fluorescent wavelength is long or short to provide a fluorescent reagent containing the fluorescent dyestuff and to provide a method for diagnosing an affected part of a living body, a method for identifying a target cell and a method for detecting a target substance, the methods each using the fluorescent reagent.SOLUTION: Since each of benzoxanthones each having such a structure that one benzene ring is added to only one side of a xanthone skeleton and dibenzoxanthones each having such another structure that one benzene ring is added to both sides of the xanthone skeleton has generally the quantum yield higher than that of a linear type compound of each of naphtho fluoresceins each having such a different structure that one benzene ring is added to both sides of a xanthene skeleton and naphtho rhodamines, the state of a viable tissue can be observed excellently in diagnostic imaging of the affected site of the living body, and analytical precision of the target cell or the target substance can be improved in measurements with an instrument such as in flow cytometry by using the fluorescent dyestuff containing at least one of the benzoxanthones and the dibenzoxanthones.COPYRIGHT: (C)2014,JPO&INPIT【課題】蛍光波長が長波長か短波長かを問わず量子収率に優れる蛍光色素、この蛍光色素を含む蛍光試薬、この蛍光試薬を用いる生体患部の診断方法、標的細胞の特定方法及び標的物質の検出方法を提供する。【解決手段】キサントン骨格の片側のみにベンゼン環を1つ付加した構造のベンゾキサントン類、及び、キサントン骨格の両側にベンゼン環を1つずつ付加した構造のジベンゾキサントン類は、キサンテン骨格の両側にベンゼン環を1つずつ付加した構造のナフトフルオレセイン類及びナフトローダミン類のうち直線型の化合物よりも概して量子収率が高いので、前記ベンゾキサントン類及び前記ジベンゾキサントン類の少なくとも1つを含む蛍光色素を用いることにより、生体患部の画像診断では生体組織の状態観察が良好に行え、フローサイトメトリー等の機器測定では標的細胞や標的物質の分析精度の向上が図られる。【選択図】なし
