The correct quantification of lignin concentration in forages through the spectrophotometric method presumes the existence of a reference standard. This standard must have a phenolic composition similar to the cell wall lignin. The objective of this work was to verify if the lignins extracted with acidic dioxane solution to be used as reference standard would present the same variation in the phenolic composition as it occurs in the cell wall lignin. Bromegrass, corn and red clover cell wall samples were submitted to the method for extraction of lignins with an acidic dioxane solution. The phenolic composition of the extracted lignins was analyzed by alkaline nitrobenzene oxidation followed by HPLC separation. Extracted lignins confirmed that they have phenolic composition variation the same way as do intact lignins present in the cell wall and that grass lignins showed substantial presence of cinnamic acids. Concerning to phenolic composition lignins extracted by acidic dioxane may potentially be used as reference standards in the spectrophotometric analysis.
cell walls; forage crops; cinnamic acid; ferulic acid
