Enrichment of brewer’s spent grain polyphenols and assessment of their role in inhibition of cholinesterases, amylase and glucosidase

Birsan, Rares (2022) Enrichment of brewer’s spent grain polyphenols and assessment of their role in inhibition of cholinesterases, amylase and glucosidase. Doctoral thesis, University of East Anglia.

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Polyphenols are important components of the human diet and are studied for their antioxidant properties and health benefits. Brewer’s spent grain (BSG) is a valuable source of polyphenols, such as phenolic acids and flavonols, and is readily available. To use these polyphenol-rich BSG reservoirs as health promoters, efficient extraction and enrichment methodologies must be developed, followed by in vitro testing and chromatographic analysis.

Here, several classic and novel solid-liquid extraction technologies were explored to extract polyphenols from three types of BSG. This was followed by liquid-liquid partitioning and flash chromatography to obtain polyphenol rich fractions, which were then identified and quantified using LC-MS/MS. The ability of these BSG extracts and fractions to inhibit the enzymatic activities of acetylcholinesterase, butyrylcholinesterase, α-amylase and α-glucosidase, associated with Alzheimer's disease and diabetes, respectively was assessed in vitro.

The results showed that saponification with 0.75% sodium hydroxide is the best method to extract bound phenolic acids from BSG, and 60% aqueous-acetone solution to extract free phenolics. Among the organic solvents tested to obtain rich-phenolic extracts, diethyl ether and ethyl acetate showed the highest recovery. LC-MS/MS analysis showed that BSG bound phenolic extracts are abundant in hydroxycinnamic acids, i.e. ferulic acid, p-coumaric acid, including dimers and trimers of ferulic acid, and 4-hydroxibenzoic acid. On contrary, BSG free phenolic extracts were abundant in the flava-3-ol catechin. BSG Dark polyphenol rich extracts, its flash chromatography fractions presented a higher inhibitory capacity for acetyl- and butyrylcholinesterase activities compared to the other tested samples, as well as for α-amylase and α-glucosidase. BSG diethyl ether fractions showed that the decarboxylated di-ferulic acid exhibited a significant contribution towards anticholinesterase activities.

This work highlighted the potentials of using BSG polyphenols for these degenerative diseases and pave way for further research towards their nutraceutical and phytopharmaceutical benefits.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Chris White
Date Deposited: 05 Apr 2023 07:17
Last Modified: 05 Apr 2023 07:17
URI: https://ueaeprints.uea.ac.uk/id/eprint/91737


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