Protective effects of dietary quercetin on cerebral ischemic injury: pharmacology, pharmacokinetics and bioavailability-enhancing nanoformulations

Cerebral ischemia, as an ischemic stroke-like disease, has become a health problem of global concern. Studies have found that oxidative stress, inflammation, apoptosis, and impaired blood-brain barrier (BBB) and ion channel regulation are the basis for the development of cerebral ischemia pathology. Quercetin, a flavonoid compound, commonly found in the daily diet and in some Chinese herbal medicines, including vegetables, fruits, and tea, is one of the most prominent dietary antioxidants. Modern pharmacological studies have shown that quercetin can effectively protect against cerebral ischemic injury, and its mechanisms may involve antioxidant, anti-inflammatory, anti-apoptotic, BBB protection, ion channel regulation, cell excitatory glutamate toxicity alleviation and cognitive impairment recovery activities. However, the low bioavailability of quercetin and the presence of the BBB structure limit the therapeutic efficacy. There have been studies targeting the delivery of quercetin to the injury site through nanotechnology to enhance the therapeutic effect of quercetin. This review discusses and reviews the pharmacological activity, pharmacokinetic characteristics, and targeted delivery nanosystems of quercetin in protecting against cerebral ischemic injury, and provides information on various downstream signaling pathways regulated by quercetin, such as PI3k/Akt, MAPK, and Sirt1. We hope to provide a scientific basis for the development and application of quercetin in the field of cerebral ischemia.