VARIATION IN THE EXTRACTABILITY OF ESTERIFIED P-COUMARIC AND FERULIC ACIDS FROM FORAGE CELL-WALLS

Extraction conditions that may affect yield of esterified phenolics from forage cell walls were examined. Esterified p-coumaric and ferulic acids were extracted from alfalfa, smooth bromegrass, and switchgrass samples with various concentrations of NaOH. Forage fiber samples were prepared prior to alkaline extraction by enzymatic removal of starch and alcohol extraction (AIR), extraction with neutral detergent (NDF), or extraction with neutral detergent followed by ball-milling to reduce particle size (BM-NDF). The forage species had different phenolic acid contents, with alfalfa having the lowest and switchgrass the greatest. An interaction was observed for sample preparation method and alkali concentration. The AIR and NDF gave maximal yields of p-coumaric and ferulic acids from alfalfa with use of 2 M NaOH for extraction, whereas the yield from grasses peaked at 1 M. Recovery of p-coumaric and ferulic acids was greater from the AIR preparation than NDF for all forages. NaOH at 4 M concentration was needed for maximal yield from BM-NDF of grasses, and 6 M concentration was best for alfalfa BM-NDF. Immature and mature growth stage samples of forages behaved differently in response to extraction conditions. The molar ratio of p-coumaric to ferulic acids extracted from forage samples changed in response to different preparation conditions and alkali concentrations. Recommendations are given for maximizing yields of extractable phenolic acid esters from forage cell walls. © 1990, American Chemical Society. All rights reserved.