NADH-dependent flavin oxidoreductase; part of the gene cluster that mediates the biosynthesis of ilicicolin H, a 4-hydroxy-2-pyridonealkaloid that has potent and broad antifungal activities by inhibiting the mitochondrial respiration chain (PubMed:30905148). IccA to iccE are sufficient for ilicicolin H biosynthesis and the roles of the remaining enzymes, iccF, iccG and iccH within the pathway have still to be determined (PubMed:30905148). The biosynthesis of ilicicolin H starts with formation of the tetramic acid by the hybrid PKS-NRPS synthetase iccA with the partnering trans-enoyl reductase iccB since iccA lacks a designated enoylreductase (ER) domain. The cytochrome P450 monooxygenase iccC then catalyzes the ring expansion of the tetramate to the acyclic 2-pyridone. The pericyclase iccD further converts the acyclic 2-pyridone into 8-epi-ilicicolin H. Finally, the epimerase iccE converts 8-epi-ilicicolin H into ilicicolin H via epimerizationd (PubMed:30905148) (Probable). Mycotoxin biosynthesis. Belongs to the short-chain dehydrogenases/reductases (SDR) family.