Coumarins
Coumarins
δ-lactones or internal esters
two major types - coumarins and furanocoumarins
four are very common: coumarin, umbelliferone, esculetin, and scopoletin
about 300 compounds of this series known
often occur as glycosides
some simple coumarins are prenylated
phenylalanine ---->PAL ----> p-hydroxycinnamic acid or cinnamic acid ----> 2'-hydroxylase ----> O-glucosyltransferase and
UDP-glucose ----> 2-O-glucosylcinnamic acid or p-hydroxy... ----> light Z-2-O-glucosylcinnamic acid etc. ----> coumarin or
umbelliferone
coumarin ----> moldy forage ----> dicoumarol (13)
coumarins are formed in the cytoplasm, not in the chloroplast as once was reported
the glycosides are accumulated in the vacuole/ β-glycosides in intercellular spaces
umbelliferone is the precursor to most other coumarins
Furanocoumarins or furocoumarins
prenylation is followed by cleavage of three carbons in many compounds
at C-6 or C-8, to give two distinct series with different properties angular/linear
phe ----> cinnamic acid ----> p-coumaric acid ----> umbelliferone ----> furanocoumarins
(coumarin and scopoletin are usually not incorporated)
Petroselinum hortense (parsley) cell cultures have only traces of furanocoumarins until fungal elicitors are added
furan ring from mevalonate
biosynthesis of psoralen, a common furanocoumarin
Limited distribution
found in about 19 plant families
Asteraceae (Composite) (uncommon), Moraceae, Apiaceae (Umbelliferae) (common), Rutaceae (common)
angular furanocoumarins only in Apiaceae and a few Fabaceae
linear furanocoumarins inhibit viruses, bacteria, fungi, insects, nematodes etc.
UV-A 320-400 nm
reported to crosslink DNA, but the evidence for this is weak
supposed to join pyrimidine bases
phytoalexins in many Apiaceae
herbivory
foods
medical uses, psoriasis
Stilbenes and Related Compounds
Lecture Slides
© David S. Seigler, Integrative Biology 425, Plant Secondary Metabolism, Department of Plant
Biology, 265 Morrill Hall, 505 S. Goodwin Ave., University of Illinois, Urbana, Illinois 61801, USA.
217-333-7577. seigler@life.uiuc.edu.
