https://www.sciencedirect.com/science/article/pii/B9780128053768000198
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Flavanols, specifically monomeric flavanols (catechin, epicatechin, epigallocatechin, gallocatechin, and their gallate derivatives) and their polymerization products (proanthocyanidine), are present in noteworthy concentrations in cocoa powder and chocolate, teas, and grapes. In black teas, teaflavin and tearubigin also can be found in significant concentrations.
Catechins are the most readily absorbable flavonoids because they are the only form not bound to sugars (flavonoids glicosides are more easily absorbed after transformation in aglycan form).
Compounds of this class have high antioxidant activity, common food sources, and possible beneficial biological functions.
Grape and grape juice (rich in catechin and epicatechin) seem capable of reducing glutamate excitotoxicity and exert powerful antioxidant activity and thus ameliorate endothelial function and reduce platelet aggregation and low-density lipoprotein (LDL) oxidation. These effects are a good basis from which to approach reducing the risk of onset or progression of cerebrovascular damage, even if they come from indirect evidence (grape juice and not a single micronutrient administration).
Results from preclinical and human studies on flavanol - rich cocoa administration (in which epicatechin is the most represented flavanol) have shown that it could result in the reduction of age-related cognitive decline, the risk of AD, and depression. Moreover, as previously described for the flavonoid class, this substance seems capable of improving cerebral blood flow, synaptic plasticity, and mitochondrial function.
A high-flavanol dietary supplement administered to elder adults was found to enhance activity in brain regions involved in age-related cognitive decline (dentate gyrus, assessed by functional MRI) and to improve performance at cognitive testing.
Epigallocatechin gallate, the most abundant flavanol in green and black tea, has shown promising preclinical results in reducing AD and cognitive decline induced by vascular damage.
