Ether-linked Phenolic Acids Research Articles

In Situ Rumen Degradation Characteristics and Bacterial Colonization of Corn Silages Differing in Ferulic and p-Coumaric Acid Contents.

In plant cell wall, ferulic acid (FA) and p-coumaric acid (pCA) are commonly linked with arabinoxylans and lignin through ester and ether bonds. These linkages were deemed to hinder the access of rumen microbes to cell wall polysaccharides. The attachment of rumen microbes to plant cell wall was believed to have profound effects on the rate and the extent of forage digestion in rumen. The objective of this study was to evaluate the effect of bound phenolic acid content and their composition in corn silages on the nutrient degradability, and the composition of the attached bacteria. Following an in situ rumen degradation method, eight representative corn silages with different FA and pCA contents were placed into nylon bags and incubated in the rumens of three matured lactating Holstein cows for 0, 6, 12, 24, 36, 48, and 72 h, respectively. Corn silage digestibility was assessed by in situ degradation methods. As a result, the effective degradability of dry matter, neutral detergent fibre, and acid detergent fibre were negatively related to the ether-linked FA and pCA, and their ratio in corn silages, suggesting that not only the content and but also the composition of phenolic acids significantly affected the degradation characteristics of corn silages. After 24 h rumen fermentation, Firmicutes, Actinobacteria, and Bacteroidota were observed as the dominant phyla in the bacterial communities attached to the corn silages. After 72 h rumen fermentation, the rumen degradation of ester-linked FA was much greater than that of ester-linked pCA. The correlation analysis noted that Erysipelotrichaceae_UCG-002, Olsenella, Ruminococcus_gauvreauii_group, Acetitomaculum, and Bifidobacterium were negatively related to the initial ether-linked FA content while Prevotella was positively related to the ether-linked FA content and the ratio of pCA to FA. In summary, the present results suggested that the content of ether-linked phenolic acids in plant cell walls exhibited a more profound effect on the pattern of microbial colonization than the fibre content.

Phytochemical composition and effects of commercial enzymes on the hydrolysis of gallic acid glycosides in mango (Mangifera indica L. cv. 'Keitt') pulp.

A detailed characterization of mango pulp polyphenols and other minor phytochemicals was accomplished for the first time in the cultivar 'Keitt' whereby the identification and semiquantification of five hydroxybenzoic acids, four cinnamic acids, two flavonoids, and six apocarotenoids was accomplished. Among the most abundant compounds were two monogalloyl glucosides (MGG) identified as having an ester- or ether-linked glucose, with the ester-linked moiety present in the highest concentration among nontannin polyphenolics. Additionally, the impact of side activities of three commercial cell-wall degrading enzymes during 'Keitt' mango pulp processing was evaluated to determine their role on the hydrolysis of ester- and ether-linked phenolic acids. The use of Crystalzyme 200XL reduced the concentration of ester-linked MGG by 66%, and the use of Rapidase AR 2000 and Validase TRL completely hydrolyzed ether-linked MGG after 4 h of treatment at 50 °C. Fruit quality, in vivo absorption rate, and bioactivity of mango phytochemicals rely on their chemical characterization, and characterizing changes in composition is critical for a complete understanding of in vivo mechanisms.

Relative amounts of tissues in mature wheat ( Triticum aestivum L.) grain and their carbohydrate and phenolic acid composition

Hand dissection of mature grains from two common wheats ( Triticum aestivum L., cv. Caphorn and cv. Crousty) were performed to quantitatively assess their tissue composition and to obtain homogeneous samples of embryonic axis, scutellum, starchy endosperm, aleurone layer, hyaline layer, outer pericarp and a composite layer made up of testa+hyaline layer+inner pericarp. Polymeric neutral sugar and phenolic acid contents of the samples were determined and used to identify specific composition patterns in each tissue irrespective of the cultivar. The scutellum and embryonic axis showed the lowest amount of carbohydrates with similar relative amounts of arabinose and xylose (Ara+Xyl), but the scutellum differed from the embryonic axis in its high phenolic acid, in particular ferulate dehydrodimer, content. The peripheral layers of the grains were mainly composed of cell wall polysaccharides, chiefly arabinoxylans but with differing structures. The hyaline layer was mostly composed of arabinoxylan with extremely low Ara/Xyl ratio (0.1), with high amounts of ferulic acid monomers and hence very weakly crosslinked. The aleurone layer differed from the outer pericarp by its much lower Ara/Xyl ratio and lower amounts of ferulic acid dimers and trimers. High proportions of ether-linked phenolic acids (released by alkali at 170 °C) were detected specifically in the seed coat and tissues in the crease region. The possible application of biochemical markers found in the various tissues to monitor wheat grain fractionation processes is discussed.

Detection of major phenolic acids from dried mesocarpic husk of mature coconut by thin layer chromatography

This is a report of extraction and identification of phenolic acids present in the dried mesocarpic husks of mature coconut fruit. The total phenolic content of the husk material was 13.0 mg/g dry wt. 4-Hydroxybenzoic acid (4-HBA) and ferulic acid contents were identified and analysed in the husk fractions extracted by mild alkali hydrolysis (with 0.1 M NaOH). Detection of ether-linked phenolic acids (by treatment with 2 M NaOH) yielded 2.2 mg/g dry wt. of 4-HBA and 0.1 mg/g dry wt. of ferulic acid. Our results demonstrate that mesocarpic husk materials can form an alternative source of 4-HBA.

Quantitative determination of hydroxycinnamic acids in wheat, rice, rye, and barley straws, maize stems, oil palm frond fiber, and fast-growing poplar wood.

A new method has been developed for the quantitative determination of hydroxycinnamic acids participating in ester or ether linkages to the cell wall polymers. The method is based on mild alkaline hydrolysis followed by acid hydrolysis or mild alkaline hydrolysis, which partially removed esterified phenolic acids, and high-temperature concentrated alkaline treatment, which cleaved both the ester and ether linkages. It was found that traditional mild alkaline hydrolysis and acid hydrolysis released only part of the ester- and ether-linked phenolic acids, respectively. Approximately half (44.0-47.9%) of the total ester-linked p-coumaric acid and 18.2-32.6% of the total esterified ferulic acid remained ester-linked to the mild alkali-soluble lignin polymers, and 55.0-72.0% of the total ether-linked p-coumaric acid and 37.5-53.8% of the total ether-linked ferulic acid remained ether-linked to the solubilized lignin molecules after the acid hydrolysis. To correct this, a second mild alkaline hydrolysis of the alkali-soluble lignin preparations and acid hydrolysis of the solubilized lignin fractions, obtained from the first acid hydrolysis of the cell wall materials, was investigated. On the basis of this new method, a majority of the cell wall p-coumaric acid (55.8-81.5%) was found to be ester-linked to cell wall components, mainly to lignin, and about half of the cell wall ferulic acid is etherified through its phenolic oxygen to the cell wall lignin component, whereas the remainder is esterified to the cell wall hemicelluloses and/or lignin in different plant materials.

Brown midrib mutant maize with reduced levels of phenolic acids ether-linked to the cell walls

Cell wall composition and rumen degradability of leaf blade, leaf sheath and stem of normal and brown midrib mutant 3 (bmr3) maize ( Zea mays L.) phenotypes were determined in this study. Concentrations of ether-linked phenolic acids were determined by acid and alkaline hydrolysis of whole cell wall materials. The bmr3 maize had higher rumen degradability and lower contents of cellulose, lignin, ferulic and p-coumaric acids esterified and/or etherified to the cell walls, and a lower ratio of xylose to arabinose residues as compared with the normal phenotype. Cellulose degradability was inversely correlated with the acetyl bromide lignin, but not with the acid detergent lignin or Klason lignin. The contents of ether-linked ferulic and p-coumaric acids, whether determined by acid or by alkaline hydrolysis, were inversely correlated with degradability. The bmr3 mutation is characterized not only by a lower lignin content, but also by a reduced level of total ether-linked ferulic acid which is thought to play an important role in cross-linking lignin and cell wall polysaccharides.

Pyrolysis mass spectrometry and pyrolysis gas chromatography-mass spectrometry of ester- and ether-linked phenolic acids in coastal bermudagrass cell walls

Coastal bermudagrass cell walls were treated with 2 M NaOH at room temperature and subsequently with 4 M NaOH at 170° to determine the amounts of esterified and etherified phenolic acids, respectively. In addition, total phenolic acids were determined by direct treatment of the cell walls with the 4 M treatment. Treatment with 2 M NaOH removed ester-linked p-coumaric, ferulic, truxillic and truxinic acids. Further treatment of the cell wall residue with 4 M NaOH at elevated temperature removed ether-linked phenolic acids. Pyrolytic methylation gas chromatography-mass spectrometry of the residue after 2 M NaOH treatment showed the presence of a small amount of ether-linked truxillic and truxinic acids. Data from the sequential sodium hydroxide and direct 4 M sodium hydroxide treatments showed that a total of 13.3% of the p-coumaric acid and 45.4% of the ferulic acid was ether-linked. A substantial portion of these ether-linked acids was present as a base-soluble fraction of the 2 M treatment.

Ester- and ether-linked phenolic acids in orchardgrass (Dactylis glomerata L.) and their digestion from cell walls when fed to sheep

Ester- and ether-linked p-coumaric (PCA) and ferulic acids (FA) in cell wall materials from orchardgrass (Dactylis glomerata L.), hays harvested at the heading stage and feces samples from sheep fed the orchardgrass hays were analyzed. Results showed that ether-linked PCA and FA were more resistant to ruminant digestion and enzymatic degradation than ester-linked PCA and FA. Key words: p-coumaric acid, esters, ethers, ferulic acid, orchardgrass, sheep digestion