Anti-Inflammatory Effects of Flavonoids in Common Neurological Disorders Associated with Aging

Aging reduces homeostasis and contributes to increasing the risk of brain diseases and death. Some of the principal characteristics are chronic and low-grade inflammation, a general increase in the secretion of proinflammatory cytokines, and inflammatory markers. Aging-related diseases include focal ischemic stroke and neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD). Flavonoids are the most common class of polyphenols and are abundantly found in plant-based foods and beverages. A small group of individual flavonoid molecules (e.g., quercetin, epigallocatechin-3-gallate, and myricetin) has been used to explore the anti-inflammatory effect in vitro studies and in animal models of focal ischemic stroke and AD and PD, and the results show that these molecules reduce the activated neuroglia and several proinflammatory cytokines, and also, inactivate inflammation and inflammasome-related transcription factors. However, the evidence from human studies has been limited. In this review article, we highlight the evidence that individual natural molecules can modulate neuroinflammation in diverse studies from in vitro to animal models to clinical studies of focal ischemic stroke and AD and PD, and we discuss future areas of research that can help researchers to develop new therapeutic agents.

Automated summary

Aging leads to reduced homeostasis, increased risk of brain diseases, and death. Chronic inflammation, increased secretion of proinflammatory cytokines, and inflammatory markers are key characteristics of aging. Several neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease are associated with aging. Flavonoids, commonly found in plant-based foods, have been studied for their anti-inflammatory effects in vitro and in animal models of stroke and neurodegenerative diseases. However, evidence from human studies is limited. This review highlights the potential of individual natural molecules to modulate neuroinflammation and discusses future research directions for developing new therapeutic agents.