Green Tea Catechins as Neuroprotective Agents: Systematic Review of the Literature in Animal Pre-Clinical Trials

Abstract

Alzheimer's Disease (AD) is a neurodegenerative disorder and the most common form of dementia, with symptoms and manifestations that progressively get worse with increasing age. Therefore, with the ageing of the population worldwide, the prevalence of AD is increasing. There is no current cure for AD and, as a result, there has been a recent rise in interest in plant bioactive compounds that may prevent or improve symptoms of the disease. Currently, the nootropic potential of plant derived compounds that can combat damage posed by free radicals is being investigated. Antioxidants, in particular, the Green Tea Catechins (GTC), have been shown significant interest due to their exceptionally strong antioxidant and anti-inflammatory properties. The aim of this paper was to perform a systematic review based on the PRISMA guidelines in order to evaluate the effectiveness of GTC as a potential treatment to suppress or delay the onset of AD in pre-clinical animal trials. The paper reports on three animal pre-clinical trials in which rat or mice models of AD were used to test the effects of GTC or the pure form of the predominant GTC, Epigallocatechin gallate (EGCG), administered orally or by injection. The reviewed papers show that GTC extracts or pure EGCG had preventative effects on AD in the various animal models used, including the enhancement of learning and memory, possibly through the reduction in oxidative stress, β-amyloid plaque build up and Tau protein phosphorylation. Therefore, GTC extracts or EGCG in its pure form may serve as nootropic options in the prevention or treatment of neurodegeneration-associated diseases such as AD.