Increasing evidence supports the beneficial effects of
polyphenol-rich diets, including the traditional
Mediterranean diet, for the management of
cardiovascular disease,
obesity and
neurodegenerative diseases. However, a common concern when discussing the protective effects of
polyphenol-rich diets against diseases is whether these compounds are present in systemic circulation in their intact/parent forms in order to exert their beneficial effects in vivo. Here, we explore two common classes of dietary
polyphenols, namely
isoflavones and
lignans, and their gut microbial-derived metabolites for gut and blood-brain barrier predicted permeability, as well as protection against neuroinflammatory stimuli in murine BV-2 microglia.
Polyphenol microbial metabolites (PMMs) generally showed greater permeability through artificial gut and blood-brain barriers compared to their parent compounds. The parent
polyphenols and their corresponding PMMs were evaluated for protective effects against
lipopolysaccharide-induced
inflammation in BV-2 microglia. The
lignan-derived PMMs,
equol and
enterolactone, exhibited protective effects against
nitric oxide production, as well as against pro-inflammatory
cytokines (IL-6 and TNF-α) in BV-2 microglia. Therefore, PMMs may contribute, in large part, to the beneficial effects attributed to
polyphenol-rich diets, further supporting the important role of gut microbiota in human health and disease prevention.