Oxidoreductase involved in lignan biosynthesis (PubMed:11606193). Catalyzes the NADPH-dependent reduction of phenylcoumaran benzylic ethers (PubMed:11606193). Converts dehydrodiconiferyl alcohol (DDC) to isodihydrodehydrodiconiferyl alcohol (IDDDC) (PubMed:11606193). (-)-dehydrodiconiferyl alcohol + H(+) + NADPH = (S)-isodihydrodehydrodiconiferyl alcohol + NADP(+) (+)-dehydrodiconiferyl alcohol + H(+) + NADPH = (R)-isodihydrodehydrodiconiferyl alcohol + NADP(+) May cause an allergic reaction in human (PubMed:11606193). Binds to IgE from patients allergic to pear fruit (PubMed:11606193). Induces histamine release from basophils of patient allergic to the pear fruit protein Pyr c 5 (PubMed:11606193). Exhibits cross-reactivity with IgE from patients allergic to other fruits, vegetables and birch pollen (PubMed:11606193). May be a minor allergen of pear fruit (PubMed:11606193). Belongs to the NmrA-type oxidoreductase family. Isoflavone reductase subfamily.