Freising, October 27, 2021 - Gallic acid is a secondary plant ingredient found in wine or green tea. An Austrian-German team of scientists led by Veronika Somoza, has now found evidence that gallic acid influences gastric acid release by activating a bitter receptor. The study results provide new insights into the still unknown functions of bitter receptors in interaction with taste-active food ingredients.
Veronika Somoza is deputy head of the Department of Physiological Chemistry at the Faculty of Chemistry, University of Vienna, and director of the Leibniz Institute for Food Systems Biology at the Technical University of Munich (LSB). For a long time, she has been researching the physiological effects of taste-active substances naturally present in foods. These include gallic acid, which gives white or red wine, for example, an astringent taste, i.e., produces a slightly rough, dry sensation on the tongue and in the mouth. Although controversial, some studies suggest that gallic acid also tastes bitter.
Gallic acid interesting for research
This makes gallic acid interesting for research. After all, more and more scientific work is showing that bitter substances and their receptors are not only important for taste perception. "Bitter receptors are indeed found on the tongue. But other organs such as the stomach, the heart or the lungs also have these taste receptors," says first author Sonja Sterneder, who is doing her doctorate at the Faculty of Chemistry in Vienna. However, the physiological functions they perform there have not yet been adequately researched, the nutrition scientist adds. The current study now contributes to adding another piece of the puzzle on the overall functional picture of bitter compounds and their receptors.
As Veronika Somoza's team first determined in sensory tests, gallic acid dissolved in water tastes more bitter than tap water, and this is true even at a very low dose (10 micromolar; 1.7 mg/L). Similarly, the team observed that the bitter taste is concentration-dependent and increases with increasing dose (up to 1,000 micromolar).
Plant compound stimulates acid secretion
The team of scientists then used a cellular assay system to study how gallic acid affects gastric cells, which naturally possess different types of bitter receptors. They observed that the plant substance stimulated gastric cells to secrete acid, regardless of whether the researchers had added it to the culture medium dissolved in water or in red wine.
Further extensive molecular biology investigations by the team also suggest that gallic acid exerts this effect via the taste receptor TAS2R4. Computer-based structural analyses of the receptor and virtual docking experiments conducted by the Leibniz Institute support this assumption.
"Already our previous studies on the effects of caffeine indicate that the bitter receptor TAS2R43 is involved in the regulation of gastric acid secretion. Now we have found evidence for the involvement of another bitter receptor that is equally found on the tongue as well as on gastric cells," says Veronika Somoza. In the future, Somoza's team will continue to investigate the molecular relationships between bitter substances and bitter receptors, with the aim of improving the digestibility of foods.
Publication: Sterneder S, Stoeger V, Dugulin CA, Liszt KI, Di Pizio A, Korntheuer K, Dunkel A, Eder R, Ley JP, Somoza V (2021) J Agric Food Chem, 69(36):10550-10561, DOI: 10.1021/acs.jafc.1c03061. Astringent gallic acid in red wine regulates mechanisms of gastric acid secretion via activation of bitter taste sensing receptor TAS2R4, pubs.acs.org/doi/10.1021/acs.jafc.1c03061
The Symrise AG, based in Holzminden, Germany, and the Federal College and Research Institute for Viticulture and Pomology, Klosterneuburg in Austria were involved in the study.
Humans have 25 different bitter receptor types. Some of them recognize only a small selection of bitter substances. Others, on the other hand, are able to detect a wide range of different bitter substances.
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or: Liszt KI, Ley JP, Lieder B, Behrens M, Stöger V, Reiner A, Hochkogler CM, Köck E, Marchiori A, Hans J, Widder S, Krammer G, Sanger GJ, Somoza MM, Meyerhof W, Somoza V (2017) Proc Natl Acad Sci, 114(30):E6260-E6269, DOI: 10.1073/pnas.1703728114. Caffeine induces gastric acid secretion via bitter taste signaling in gastric parietal cells, https://www.pnas.org/content/114/30/E6260
Expert contact and director at LSB:
Prof. Dr. Veronika Somoza
Leibniz Institute for Food Systems Biology
at the Technical University of Munich (LSB)
Responsible for PR at the LSB:
Dr. Gisela Olias
Knowledge Transfer, Press and Public Relations
Phone: +49 8161 71-2980
Information about the LSB
The Leibniz Institute for Food Systems Biology at the Technical University of Munich comprises a new, unique research profile at the interface of Food Chemistry & Biology, Chemosensors & Technology, and Bioinformatics & Machine Learning. As this profile has grown far beyond the previous core discipline of classical food chemistry, the institute spearheads the development of a food systems biology.
Its primary research objective is to develop new approaches for the sustainable production of sufficient quantities of food whose biologically active effector molecule profiles are geared to health and nutritional needs, but also to the sensory preferences of consumers. To do so, the institute explores the complex networks of sensorically relevant effector molecules along the entire food production chain with a focus on making their effects systemically understandable and predictable in the long term.
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