Hops (Humulus lupulus) Extract Enhances Redox Resilience and Attenuates Quinolinic Acid-Induced Excitotoxic Damage in the Brain

Background: Humulus lupulus (Hops) possesses a diverse array of bioactive compounds with reported antioxidant, anti-inflammatory, antibacterial, and neuroprotective properties. However, most studies have focused on isolated components, whose purification is costly and yields limited quantities. Objective: In this study, we aimed to evaluate whether a complete Hops extract could exert antioxidant and neuroprotective effects. Methods: First, the ability of Hops extract’s free radical scavenging capacity against superoxide, hydroxyl radical, and peroxynitrite was discovered using combinatorial chemical assays. Moreover, the used Hops extract prevented both DNA and protein degradation induced by hydroxyl radicals. Next, rats were orally administered with three different doses of Hops extract (10, 15, and 20 mg/kg/day) for 7 consecutive days. Results: Ex vivo analyses of brain tissues revealed that Hops pre-treatment attenuated FeSO4-induced lipid peroxidation, increased the GSH/GSSG ratio and downregulated both glutathione peroxidase and reductase activities. Additionally, the expression of the nuclear factor erythroid 2-related factor (Nrf2) gene was significantly elevated in the striatum of Hops-treated animals. To further explore neuroprotection, we evaluated the effect of Hops (15 mg/kg/day) in an in vivo model of excitotoxicity induced by quinolinic acid (QUIN). Pre-treatment with the Hops extract reduced QUIN-induced circling behavior, increased the translocation of NRF2 to the nucleus and decreased apoptosis in the striatum. Conclusion: These findings suggest that the whole Hops extract enhances redox resilience in the brain and confers protection against oxidative and excitotoxic insults.