Phenolic acid content and fibre in Nigerian wholegrains; their metabolism, and potential cardiovascular benefits

Student thesis: Doctoral Thesis

Abstract

Wholegrains consumption is advantageous for the prevention of cardiovascular diseases, partly due to their polyphenolic and fibre content. In this study, 14 raw wholegrains (Nigeria and UK grown) were screened for their phenolic acids (PAs) and fibre content. PAs were extracted into soluble and bound fractions and analysed for 26 PAs using Ultraperformance Liquid Chromatography-Tandem Mass Spectrometry (UPLC-MS/MS). Based on the PA screening of raw grains, selected grains from Nigeria were cooked and subjected to in vitro digestions, PA content of cooked and digested samples were determined. Subsequently, freeze- dried digestate of selected grains were fermented over a 24 h period using an in vitro colonic model. Fermented samples were analysed for their PA contents using UPLC MS/MS and their microbial DNA content using 16s rRNA Next Generation Sequencing. Based on PA results from in vitro studies, a selection of commercially obtained pure PAs were used for cell mechanistic studies in HUVEC cells, to see their impact on the nitric oxide pathway as a model of endothelial function. Cells treated with PAs or controls were assessed for their nitric oxide levels using diaminofluorescein-2 diacetate (DAF-2DA) fluorescence probe and superoxide production using ferricytochrome c reduction assay. ELISA methods were used to assay for cGMP production, Akt1 and eNOS activation in treated cells. Lastly, scratch assay was performed to assess the impact of treatments on wound healing in HUVEC monolayer using microscopic techniques. Total PAs in raw grains ranged from 22.2.5 ± 34.9 ng/mg to 132.2 ± 12.1 ng/mg. Cooking and digestion significantly affected the PAs in all grains (p0.05) but gap closure in PA treated cells were significantly different (p
Date of Award31 May 2023
Original languageEnglish
Awarding Institution
  • University of Roehampton
SponsorsSchlumberger Foundation Faculty for the Future Fellowship
SupervisorGiulia Corona (Director of Studies), Adele Costabile (Co-Supervisor) & Yolanda Calle (Co-Supervisor)

Keywords

  • Phenolic acid
  • cardiovascular health
  • LC-MS
  • cell migration
  • colonic fermentation
  • ELISA
  • gut microbiota
  • nitric oxide signalling
  • HUVEC

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