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Theogallin is a trihydroxybenzoic acidglycoside, a type of polyphenolic compound found in tea where it has been characterised as an umami enhancing compound. The compound can also be found in Arbutus unedo fruits.
In rats, theogallin, or its metabolite quinic acid, can move through the blood-brain barrier and can have cognition enhancing activities.
References
Cartwright, R. A.; Roberts, E. A. H. (1954). "Theogallin, a polyphenol occurring in tea". Journal of the Science of Food and Agriculture. 5 (12): 593. doi:10.1002/jsfa.2740051207.
Dimpfel, Wilfried; Kler, Adolf; Kriesl, Erwin; Lehnfeld, Romanus (2007). "Theogallin and l-theanine as active ingredients in decaffeinated green tea extract: II. Characterization in the freely moving rat by means of quantitative field potential analysis". Journal of Pharmacy and Pharmacology. 59 (10): 1397–403. doi:10.1211/jpp.59.10.0010. PMID17910815.