Reduces FMNH(2) to FMN, with NADPH as reductant. It also reduces nitroaromatic compounds, quinones and azo dyes. FMNH2 + NADP(+) = FMN + 2 H(+) + NADPH Homodimer. Catalysis proceeds by a classical ping-pong bi-bi reaction mechanism. NADPH is more effective as an electron donor than NADH. Belongs to the flavin oxidoreductase frp family.