From gloom to bloom: osmanthus black tea essential oil alleviates anxiety in mice via modulation of the nose-brain axis.

Aromatherapy exerts mood-regulating effects primarily through inhalation, with the nasal microbiota playing a critical yet mechanistically undefined role in the nose-brain axis, especially in anxiety-related neurological disorders. In this study, osmanthus black tea essential oil (OBT) was examined for anxiolytic effects and potential mechanisms linked to the nose-brain axis. Volatile compounds with known anxiolytic properties, such as linalool, limonene, and α-terpineol, were identified in OBT. In a chronic restraint stress-induced anxiety mouse model, OBT inhalation significantly improved anxiety-like behaviors, restored hippocampal neurotransmitter balance by elevating γ-aminobutyric acid (GABA) and 5-hydroxytryptamine (5-HT) levels while reducing glutamate (Glu), alleviated neuronal damage, and attenuated inflammation by promoting macrophage polarization. Notably, OBT reshaped the nasal microbiota structure in anxious mice by promoting beneficial bacteria such as Delftia and Herbaspirillum and suppressing anxiety-associated genera like Comamonas and Klebsiella. Correlation analysis revealed significant associations between volatile compounds in OBT and specific microbial taxa as well as neurotransmitter levels, implying an interconnected mechanism contributing to the anxiolytic effect. Overall, OBT exerts its anti-anxiety activity by modulating both neurotransmitter systems and the nasal microbiota, highlighting its potential as a functional product for anxiety relief.