Determination of cell wall ferulic and p-coumaric acids in sugarcane bagasse

To completely determine ferulic and p-coumaric acids and related phenolic compounds in the cell walls of sugarcane bagasse (SCB), a second mild alkaline hydrolysis of the alkali-soluble lignin preparations and acid hydrolysis of the 90% acidic dioxane-soluble lignin fractions were performed, which released 48.8% of the total ester-linked p-CA and 43.8% of the total esterified FA from the alkali-soluble lignin fractions, and 38.8% of the total ether-linked p-CA and 38.5% of the total ether-linked FA from the 90% acidic dioxane-soluble lignin preparations, respectively. Based on the dry weight, it has been found that the SCB contained 1.76% p-CA and 1.29% FA as well as minor quantities of related phenols. Further study of the solubilized lignin samples by combining with UV and FT-IR spectroscopy, and H-1 and C-13 NMR spectroscopy confirmed that a predominant amount of p-CA (69.5-76.4%) is ester-linked to the cell wall components, mainly to lignin. On the other hand, about half of the FA (44.0-55.0%) is esterified to the cell wall hemicelluloses, and the remaining half of the FA is also be etherified through the phenolic oxygen to lignin component in the cell walls of SCB. (c) 2005 Elsevier B.V. All rights reserved.