Chemical properties[edit]
Structurally, chlorogenic acid is the ester formed between caffeic acid and L-quinic acid.[4]
Isomers of chlorogenic acid include 4-O-caffeoylquinic acid (cryptochlorogenic acid or 4-CQA), 5-O-caffeoylquinic acid(neochlorogenic acid or 5-CQA). The epimer at position 1 has not yet been reported.[3]
Isomers containing two caffeic acid molecules are called isochlorogenic acid. It can be found in coffee.[5] There are several isomers such as 3,4-dicaffeoylquinic acid and 3,5-dicaffeoylquinic acid[6] Cynarine (1,5-dicaffeoylquinic acid) is an other isomer with two caffeic acid molecules..