Modulation of Proinflammatory Cytokines by Flavonoids in the Main Age-related Neurodegenerative Diseases

Aging is a process associated with distinctive changes in physiological functions and physical appearance that result from progressive tissue degeneration, harming the structure and function of vital organs. Illnesses that are particularly frequent in people 65 years of age and older are generally grouped as age-related diseases or aging-related diseases and include neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD), which are caused by progressive degeneration and/or neuronal death to produce debilitating conditions, and they have no cure. For these illnesses, the most important risk factor is aging. Aging involves changes in neuroendocrine and inflammatory responses and presents a stage with chronic and low-grade inflammation, characterized by a general increase in the production of proinflammatory cytokines, inflammatory markers, and cellular senescence. Herbal medicine, as well as various components of the human diet, including vegetables, cereals, and fruits, contain widely varied phytochemicals including flavonoids, which are the most common polyphenolic compounds. Epidemiological studies suggest that a higher intake of flavonoid-rich foods and beverages is associated with better cognitive outcomes, lower dementia rates, and reduced risk of neurodegenerative diseases. Moreover, numerous preclinical studies have shown that these compounds have a therapeutic effect on animal models of human degenerative diseases and highlight the anti-inflammatory effect of flavonoids by decreasing the activated glial cells and several proinflammatory mediators. Much modern scientific research has focused on establishing biological activities of purified single compounds to provide an evidence base for the rationale of traditional practice, and also to integrate these into modern medical practice.