Flavonoids: Their putative neurologic roles, epigenetic changes, and gut microbiota alterations in Parkinson’s disease

Parkinson's Disease (PD), a neurodegenerative disorder, is characterized by the degeneration of progressive dopaminergic (DA) neurons in the substantia nigra region of the human midbrain. Although just what causes PD remains a mystery, it is known that oxidative stress (OS) as well as mitochondrial dysfunction, neuro-inflammation, and insufficient neurotrophic support play a role in the disease's pathophysiology. Phytochemicals are a diverse small molecule group derived from plants that can be classified into numerous classes on the basis of their biological activities and chemical structure. Of these groups of phytochemicals, the most abundant, which has well-established anti-Parkinson's effects, are polyphenols. Flavonoids, including naringin and naringenin, genistein, kaempferol, anthocyanins, epigallocatechin-3-gallate, and baicalein are plant-based biologically active polyphenols, which have been shown to exhibit therapeutic potential when used as treatment for a variety of pathological illnesses, such as neurodegenerative diseases (NDs) and PD. Recently, it was reported that flavonoids have beneficial effects on PD, such as the protection of DA neurons, improvement of motor and cognitive abilities, regulation of signaling pathways, and modulation of OS and neuro-inflammation. In addition, by changing the composition of bacteria in gut microbiota, flavonoids reduce pathogenic strains and promote the growth of beneficial strains. In this context, the current paper will provide a literature review on the neurological roles that flavonoids play, as one of the most abundant phytochemical families, in PD.