Phenolic acid esters motifs have been found in bioactive natural products, for example, the NF?? k B inhibitors CAPE,[1]1. Natarajan , K. , Singh , S. , Burke , TR Jr. , Grunberger , D. and Aggarwal , BB 1996. Caffeic acid phenethyl ester is a potent and specific inhibitor of activation of nuclear transcription factor NF?螃?B. Proc. Natl. Acad. Sci. USA, 93: 9090–9095. [CrossRef], [PubMed], [Web of Science ®], [CSA] View all references the honeybee propolis contact allergen ...