Patent ID: 7524974

Claim:
A fluorescent probe which is represented by the following formula (I): wherein, R 1 and R 2 each independently represents hydrogen atom, or a substituent for trapping proton, a metal ion, or an active oxygen species, provided that both of R 1 and R 2 do not simultaneously represent hydrogen atoms, or R 1 and R 2 may combine to each other to form a ring structure for trapping proton, a metal ion, or active oxygen species; R 3 is a lower alkyl group or a lower alkoxy group; R 4 and R 5 each independently represents hydrogen atom or a halogen atom; R 6 represents hydrogen atom, an alkylcarbonyl group, or an alkylcarbonyloxymethyl group, provided that a combination of R 1 , R 2 , and R 3 provides: (1) substantially high electron density of the benzene ring to which said groups bind so that the compound represented by the formula (I) is substantially no fluorescent before the trapping of proton, a metal ion, or an active oxygen species, and (2) substantially reduced electron density of the benzene ring to which said groups bind so that a compound after the trapping, which is derived from the compound represented by the formula (I), is substantially highly fluorescent after the trapping of proton, a metal ion, or an active oxygen species.