Theabrownin from Dark Tea Attenuates Age-Related Cognitive Decline in Naturally Aged Mice by Modulating Gut Microbiota and Metabolites

Dietary factors play an important role in cognitive health during aging. Dark tea has shown potential cognitive benefits, but its key bioactive component and underlying mechanisms remain unclear. In a naturally aged C57BL/6J mouse model, instant dark tea (IDT) samples with different fermentation degrees were evaluated together with behavioral outcomes using composition–effect relationship analysis. This analysis identified theabrownin (TB) as the component most strongly associated with improved cognitive performance. Compared with aged controls, TB increased Y-maze spontaneous alternation from 51.91% to 71.59% and reduced escape latency on day 5 of the Morris water maze from 44.84 s to 26.59 s. In contrast, the corresponding TB-depleted fraction produced no comparable cognitive improvement. TB also alleviated hippocampal injury and neuroinflammation. Antibiotic treatment abolished the cognitive benefits of TB, whereas fecal microbiota transplantation partially restored them. Multi-omics analyses suggested that TB treatment was associated with gut microbiota remodeling and increased serum acetate and 3-hydroxybutyrate; both metabolites partially recapitulated these benefits. Together, these findings show that TB attenuates age-related cognitive decline in naturally aged mice and suggest that modulation of gut microbiota and metabolites may contribute to this effect, supporting its potential as a functional food ingredient for healthy brain aging.