A comparative analysis of cutin monomers from cereal brans and fruit peels: isolation and characterization

Authors: LI, YUANYUAN - Zhejiang University; Yadav, Madhav; MOREAU, ROBERT - Former ARS Employee; Powell, Michael; Simon, Stefanie; Sarker, Majher; QIU, SHUANG - Zhejiang University

Submitted to: Journal of Cereal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2024
Publication Date: 2/15/2024
Citation: Li, Y., Yadav, M.P., Moreau, R.A., Powell, M.J., Simon, S., Sarker, M.I., Qiu, S. 2024. A comparative analysis of cutin monomers from cereal brans and fruit peels: Isolation and characterization. Journal of Cereal Science. 116:103873. https://doi.org/10.1016/j.jcs.2024.103873.
DOI: https://doi.org/10.1016/j.jcs.2024.103873

Interpretive Summary: Plant cuticles are the outermost film layer on plants. They mainly consist of lipid polymers and provide protection against desiccation and external environmental stresses. They also provide protection from pathogens and insects and stresses such as drought, heat, and excess solar radiation. The importance of these polymers prompted us to determine the monomeric composition of the cuticular polymers fractionated from three cereal fibers: corn bran, wheat bran and sorghum bran and compared them with the well-studied cuticular polymers present in fruit peels (apple and tomato peels). In this study the cuticular polymers of apple peel, tomato peel, wheat bran, corn bran and sorghum bran were isolated, and chemically analyzed. The total cuticular contents in apple and tomato peels were higher (ranging from 54.5 % to 54.8 %) than the cuticular monomers content in sorghum bran (7.14 %), corn bran (3.92 %) and wheat bran (5.92). The amount of cuticle monomers in corn bran was comparatively lower than the cuticle monomers present in other cereal brans and fruit peels, which may be due to differences in the structure of their outer layers. The fruit peels (apple and tomato peels) and cereal brans show a remarkable difference in the kind of phenolic compounds present in them. Knowing the nutraceutical compounds in these brans will be beneficial to cereal bran producers.

Technical Abstract: Plant cuticles, mainly consist of lipid polymers (cutin), provide protection against desiccation and external environmental stresses. Monomeric compositions of the cuticular polymer fractions of three cereal fibers: corn bran, wheat bran and sorghum bran, as well as hemicellulose/cellulose fractions isolated from sorghum bran were investigated and compared with cuticular content isolated from apple and tomato peel samples. Total cuticular contents in apple and tomato were the highest, ranging from 54.5 % to 54.8 %, while cuticular material content in sorghum bran (7.14%) was higher than corn bran and wheat bran (3.92% and 5.92% respectively). Hexadecanoic acid (C16), octadecanoic acid (C18), '-hydroxy fatty acids, with midchain functionalities such as enoic, epoxy and hydroxyl groups were identified in all cutin samples. The percentage of p-coumaric acid in apple and tomato peel samples represented 84.0% and 78.7% of the total phenolic acids respectively, whereas ferulic acid content was 94.1%, 92.8% and 88.0% in corn, sorghum and wheat brans respectively.