ARS | Publication request: P-COUMAROYLATED SYRINGYL UNITS IN MAIZE LIGNIN: IMPLICATIONS FOR BETA- ETHER CLEAVAGE BY THIOACIDOLYSIS

Submitted to: Phytochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 29, 1996
Publication Date: N/A

Interpretive Summary: Fiber makes up 15 to 90% of the dry weight of plants. Fiber is composed primarily of two types of polymers, polysaccharides and lignin. Polysaccharides can be degraded to simple sugars by enzymes. These sugars are an important source of energy for humans and for livestock. These sugars may also be converted into ethanol for use in automobile fuels. Polysaccharides in fiber are poorly degraded into simple sugars because of their association with lignin. Our research is trying to understand how lignin prevents polysaccharides from being degraded by enzymes. This study was done to help us understand how the building blocks of lignin (coniferyl alcohol, sinapyl alcohol, and p-coumaric acid) are put together in plants. Lignin from corn was chemically degraded by a procedure known as thioacidolysis. Analysis of the degradation products revealed that p- coumaric acid was primarily attached to sinapyl alcohol. We will use the results of this and other studies to help us modify lignin in plants so that polysaccharides can be more efficiently converted into food and fuel energy.

Technical Abstract: The existence of p-coumarate esters at the gamma-position of lignin sidechains suggests that p-hydroxycinnamyl alcohol lignin monomers are enzymatically pre-acylated prior to incorporation into grass lignins. Thioacidolysis/desulfuration experiments have revealed that p-coumarate is attached primarily to syringyl and less frequently to guaiacyl moieties in maize lignin. These results indicate that sinapyl p-coumarate is the primary precursor of p-coumarate esters in maize lignin and, probably, in other grass lignins.