Oxidoreductase involved in lignan biosynthesis. Catalyzes the NADPH-dependent reduction of phenylcoumaran benzylic ethers. Converts dehydrodiconiferyl alcohol (DDC) to isodihydrodehydrodiconiferyl alcohol (IDDDC), and dihydrodehydrodiconiferyl alcohol (DDDC) to tetrahydrodehydrodiconiferyl alcohol (TDDC). Plays an important role in the biosynthesis of secondary metabolites. In addition to the 8-5'-linked neolignan DDC, can reduce the 8-8'-linked lignans, pinoresinol, and lariciresinol, but with lower activities. (-)-dehydrodiconiferyl alcohol + H(+) + NADPH = (S)-isodihydrodehydrodiconiferyl alcohol + NADP(+) (+)-dehydrodiconiferyl alcohol + H(+) + NADPH = (R)-isodihydrodehydrodiconiferyl alcohol + NADP(+) (2R,3S)-dihydrodehydrodiconiferyl alcohol + H(+) + NADPH = (S)-tetrahydrodehydrodiconiferyl alcohol + NADP(+) (2S,3R)-dihydrodehydrodiconiferyl alcohol + H(+) + NADPH = (R)-tetrahydrodehydrodiconiferyl alcohol + NADP(+) Expressed in apical meristem and cotyledon veins of young seedlings. Expressed in vascular tissues of roots, leaves, stems and petals. Expressed in pollen grains. Expressed at low levels in cauline leaves and siliques. Induced by wounding. Belongs to the NmrA-type oxidoreductase family. Isoflavone reductase subfamily.