Tannins
Tannins
two major types: condensed - proanthocyanidins and hydrolyzable tannins
500-2500 MW, bind to proteins, used to make leather
not all phenolic materials are tannins
(for example, gallic acid, chlorogenic acid, (+)-catechin, are not tannins).
biosynthesis of condensed tannins has only recently been elucidated
flavan-3,4-diols
flavan-3-ols
procyanidin dimers - usually a C-4 in the upper group
more highly condensed units
quebracho and wattle are mostly condensed tannins
C-4 to C-8 and C-4 to C-6 are the most common linkages
procyanidins ----> H+ ----> anthocyanidins
Hydrolyzable tannins
gallic acid esters of sugars, mostly glucose
hexahydroxydiphenic acid ----> ellagic acid
see handout sheet
enzymes to β-pentagalloylgucose are now mostly known
these are found in evolutionarily advanced families
Biological activity
binding to proteins
some proteins are not deactivated by this binding
others are deactivated, the role in animal diets
proline-rich proteins
digestive enzymes
acridids -some actually require tannins in the diet
cost of tannins - similar to protein ... procyanidins
makes "N" available by liberation from phenylalanine in biosynthesis
the phenylalanine-cinnamic acid pathway is a major sink for carbon compounds in plants
with N-limited, carbon compounds usually accumulate
Medical properties
antitumor, anticancer
tannin analysis
tea and throat cancer ... tea and anticancer properties?
Catechins and Compounds Associated with Tannins
β-Pentagalloylglucose and Tannin Relatives
Biosynthesis of β-Penta-O-galloyl-D-glucose
Miscellaneous Proanthocyanidins
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.
