Cognitive-Enhancing and Antioxidant Activities of Quercetin Liposomes in Animal Model of Alzheimer's Disease

Problem statement: Recent findings demonstrated the crucial role of oxidative stress on the pathophysiology of Alzheimer’s Disease (AD). Antioxidant intake is beneficial to delay or inhibit the progression of this disease. Quercetin, a bioflavonoid in fruits and vegetables, has a powerful antioxidant activity both in vitro and in vivo. Claims that quercetin has many biological activities. However, quercetin is rapidly metabolized and limited ability to cross the blood-brain-barrier are obstacles to its use for treatment of AD. Liposomes have been used as an effective delivery system to the brain. Advantages associated with the nasal administration over oral route include higher bioavailability due to no first pass hepatic metabolism and rapid absorption leading to shorter time to onset of effect. Based on this information, the effects of quercetin liposomes via nasal route on improving cognitive behavior and biochemical markers of oxidative stress, Superoxide Dismutase (SOD), catalase, glutathione and Malondialdehyde (MDA) in the hippocampus in animal model of AD were investigated. Approach: Male Wistar rats were pretreated with quercetin liposomes, containing 0.5 mg of quercetin in 20 μL (dose = 20 μg), via intranasal route once daily continually for 2 weeks before and 1 week after AF64A administration. Learning and memory was evaluated using the Morris water maze test at 7 days after the AF64A administration and then the rats were sacrificed for determining the content of MDA and the activities of SOD, catalase and glutathione in the hippocampus. Results: Quercetin liposomes via nasal administration significantly improved memory impairment by inhibiting the oxidative damage in hippocampus. The possible underlying mechanisms might be partly associated with the decrease the level of MDA whereas increase the activity of SOD, catalase and glutathione. Conclusion: Our studies demonstrated that quercetin liposomes via nasal administration may have a therapeutic importance in the clinical management of AD.