Umbellic acid (2,4-dihydroxycinnamic acid) is a hydroxycinnamic acid. It is an isomer of caffeic acid.

It is a precursor in the umbelliferone biosynthesis pathway. Umbelliferone is a phenylpropanoid and as such is synthesized from L-phenylalanine, which in turn is produced via the shikimate pathway. Phenylalanine is lysated into cinnamic acid, followed by hydroxylation by cinnamate 4-hydroxylase to yield 4-coumaric acid. The 4-coumaric acid is again hydroxylated by cinnamate/coumarate 2-hydroxylase to yield 2,4-dihydroxy-cinnamic acid followed by a bond rotation of the unsaturated bond adjacent to the carboxylic acid group. Finally an intramolecular attack from the hydroxyl group of C2' to the carboxylic acid group closes the ring and forms the lactone umbelliferone.

L-phenylalanine   Cinnamic acid  para-Coumaric acid  2,4-Dihydroxycinnamic acid  Umbelliferone

The enzyme 4-hydroxycinnamate decarboxylase, induced in bacteria species such as Klebsiella oxytoca, works also with p-coumaric acid analogs such as E-2,4-dihydroxycinnamic acid.[1]

References

  1. ^ Hashidoko, Y; Tanaka, T; Tahara, S (2001). "Induction of 4-hydroxycinnamate decarboxylase in Klebsiella oxytoca cells exposed to substrates and non-substrate 4-hydroxycinnamate analogs". Bioscience, Biotechnology, and Biochemistry. 65 (12): 2604–12. doi:10.1271/bbb.65.2604. hdl:2115/15847. PMID 11826954.

External links

The dictionary definition of umbellic acid at Wiktionary