Leucocyanidin is a colorless chemical compound that is a member of the class of natural products known as leucoanthocyanidins.

[1] Molar equivalents of synthetic (2R,3S,4R or S)-leucocyanidin and (+)-catechin condense with exceptional rapidity at pH 5 under ambient conditions to give the all-trans-[4,8]- and [4,6]-bi-[(+)-catechins] (procyanidins B3, B6) the all-trans-[4,8:4,8]- and [4,8:4,6]-tri-[(+)-catechins] (procyanidin C2 and isomer).

Its gene expression has been studied in developing grape berries and grapevine leaves.

[3] Its activity has also been measured in leaves, flowers, and seeds of the legumes Medicago sativa, Lotus japonicus, Lotus uliginosus, Hedysarum sulfurescens, and Robinia pseudoacacia.

[4] The C-4 stereochemistry of leucocyanidin substrates affects anthocyanidin synthase (ANS) products.