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Influence of Brewer’s Spent Grain Compounds on Glucose Metabolism Enzymes

  • With a yearly production of about 39 million tons, brewer’s spent grain (BSG) is the most abundant brewing industry byproduct. Because it is rich in fiber and protein, it is commonly used as cattle feed but could also be used within the human diet. Additionally, it contains many bioactive substances such as hydroxycinnamic acids that are known to be antioxidants and potent inhibitors of enzymes of glucose metabolism. Therefore, our study aim was to prepare different extracts—A1-A7 (solid-liquid extraction with 60% acetone); HE1-HE6 (alkaline hydrolysis followed by ethyl acetate extraction) and HA1-HA3 (60% acetone extraction of alkaline residue)—from various BSGs which were characterized for their total phenolic (TPC) and total flavonoid (TFC) contents, before conducting in vitro studies on their effects on the glucose metabolism enzymes α-amylase, α-glucosidase, dipeptidyl peptidase IV (DPP IV), and glycogen phosphorylase α (GPα). Depending on the extraction procedures, TPCs ranged from 20–350 μg gallic acid equivalents/mg extract and TFCs were as high as 94 μg catechin equivalents/mg extract. Strong inhibition of glucose metabolism enzymes was also observed: the IC50 values for α-glucosidase inhibition ranged from 67.4 ± 8.1 μg/mL to 268.1 ± 29.4 μg/mL, for DPP IV inhibition they ranged from 290.6 ± 97.4 to 778.4 ± 95.5 μg/mL and for GPα enzyme inhibition from 12.6 ± 1.1 to 261 ± 6 μg/mL. However, the extracts did not strongly inhibit α-amylase. In general, the A extracts from solid-liquid extraction with 60% acetone showed stronger inhibitory potential towards α-glucosidase and GPα than other extracts whereby no correlation with TPC or TFC were observed. Additionally, DPP IV was mainly inhibited by HE extracts but the effect was not of biological relevance. Our results show that BSG is a potent source of α-glucosidase and GPα inhibitors, but further research is needed to identify these bioactive compounds within BSG extracts focusing on extracts from solid-liquid extraction with 60% acetone.

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Author:Daniela Becker, Tamara Bakuradze, Marcel Hensel, Simone Beller, Carolina Corral Yélamos, Elke RichlingORCiD
URN (permanent link):urn:nbn:de:hbz:386-kluedo-66141
ISSN:2072-6643
Parent Title (English):Nutrients
Publisher:MDPI
Document Type:Article
Language of publication:English
Publication Date:2021/08/04
Year of Publication:2021
Publishing Institute:Technische Universität Kaiserslautern
Date of the Publication (Server):2021/10/08
Issue:2021, 13(8)
Number of page:21
Source:10.3390/nu13082696
Faculties / Organisational entities:Fachbereich Chemie
DDC-Cassification:5 Naturwissenschaften und Mathematik / 540 Chemie
Collections:Open-Access-Publikationsfonds
Licence (German):Zweitveröffentlichung