Problem: to provide an activator for activating intracellularATP production. Solution: use of a 5-deazaflavin compoundrepresented by the following formula (I):Chemical formula 1:(wherein, R1 represents a hydrogen atom, an alkyl group, ahalogen-substituted alkyl group, a carboxy-substituted alkylgroup, or a phenyl group, R2 represents an alkyl group, acycloalkyl group, a phenyl-substituted lower alkyl group, aphenyl group, a phenyl group substituted by one of a halogenatom, a lower alkyl group, or a lower alkoxy group, or alower alkyl disubstituted phenyl group, and R3 and R4 eachrepresent a hydrogen atom, a lower alkyl group, a halogenatom, a hydroxyl group, a nitro group, a cyano group, a loweralkoxy group, a phenyl-substituted lower alkoxy, a loweralkylamino group, a phenyl-substituted lower alkylamino group,or a lower alkylsulfonyl group).
