Caffeic acid is present in a variety of fruits, vegetables and seasonings, predominantly in
the form of ester conjugates, inc1uding chi orogenie acids (esters of caffeic acid and quinic
acid) and related compounds. These conjugates may be hydrolysed upon ingestion, leading
to variable uptakes of caffeic acid. Table 1 summarizes the levels of caffeic acid and its
conjugates in various fruits and vegetables, as determined by thin-Iayer chromatography
following enzyic, acid and/or alkaline hydrolysis.