In enzymology, a leucoanthocyanidin reductase (LAR, aka leucocyanidin reductase or LCR) is an enzyme that catalyzes the chemical reaction The 3 substrates of this enzyme are (2R,3S)-catechin, NADP+, and H2O, whereas its 3 products are 2,3-trans-3,4-cis-leucocyanidin, NADPH, and H+. This enzyme belongs to the family of oxidoreductases, specifically those acting on CH or CH2 groups with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is (2R,3S)-catechin:NADP+ 4-oxidoreductase. This enzyme is also called leucocyanidin reductase. This enzyme participates in flavonoid biosynthesis. The enzyme can be found in the plant Hedysarum sulphurescens and in Vitis vinifera (grape).