Antioxidant and Anti-Inflammatory Effects of Inhaled Ginkgo biloba Leaf Essential Oil in a Chronic Stress Mouse Model: Insights from Neuroimmune, Metabolic, and Gut Microbiota Remodeling

Chronic stress induces behavioral abnormalities through coordinated neuroendocrine, inflammatory, oxidative, metabolic, and gut microbial disturbances. Plant-derived volatile fractions may modulate stress-related neurobehavioral responses, yet their antioxidant and anti-inflammatory effects and associated neurobiological mechanisms remain insufficiently characterized. In this study, Ginkgo biloba leaf essential oil (GbO) was extracted from air-dried leaves by hydrodistillation, chemically characterized by GC–MS, and evaluated in a chronic unpredictable mild stress (CUMS) mouse model using behavioral, biochemical, molecular, hippocampal metabolomic, and gut microbiota analyses. HS-SPME–GC–MS tentatively identified 70 volatile constituents detected in at least two independent extraction batches, including 65 constituents consistently detected. In CUMS mice, inhaled GbO, particularly at the higher exposure level, attenuated depression- and anxiety-like behavioral abnormalities without altering general locomotor activity. GbO reduced serum corticosterone and peripheral and hippocampal pro-inflammatory cytokines, alleviated hippocampal oxidative imbalance, and decreased Iba-1 and GFAP signals. These changes were accompanied by reduced NF-κB activation, enhanced Nrf2/HO-1-related antioxidant signaling, and improved BDNF/TrkB/CREB-related neurotrophic signaling and PSD95-associated synaptic integrity. Hippocampal metabolomics further showed partial correction of stress-associated disturbances in neurotransmitter, lipid, inflammatory, and energy/redox metabolism, while 16S rRNA sequencing revealed partial restoration of gut microbial diversity and community structure. Collectively, these findings indicate that inhaled GbO exerts antioxidant and anti-inflammatory effects in CUMS mice in association with coordinated neuroimmune, neurotrophic, metabolic, and gut microbial remodeling.