Page 20 - Nutrinsight-3

NutrInsight • Do we need dietary polyphenols for health?
MECHANISMS OF ACTION OF POLyPHENOLS: 3 MECHANISMS OF ACTION OF POLyPHENOLS:
NEWLy EMERGING EVIDENCE NEWLy EMERGING EVIDENCE
by Dr Francesco Visioli
The antioxidant activity of polyphenols potentially explains all the results from epidemiology and trials described in Chapter 2 and, for many years, this has been assumed to be their major mechanism of action. However, although there are many studies showing in vitro antioxidant effects of polyphenols often at high and not physiological concentrations (>10 μM), solid scientific evidence of their in vivo antioxidant activities is scant and the biological relevance of direct antioxidant of polyphenols is being questioned [Visioli et al., 2011; Hollman et al., 2011].
So, how do polyphenols improve cardiovascular prognosis? This chapter will explain that the mechanisms of action of polyphenols are manifold and include anti-inflammatory, and detoxifying activities and that the antioxidant activities may be more indirect than previously thought (Figure 9).
Microbiota
Anti-aggregants
(platelets)
Anti-inflammatory
Metal chelators
(e.g. food during digestion)
Polyphenols
Anti-oxidants
?Grey area as yet to be investigated
Activators of Phase II Enzymes
Figure 9: Some of the manifold activities of polyphenols
The activities of polyphenols are complex: from antioxidant effect already well-studied to prebiotic effects on the gut flora
Source: From F. Visioli
20
Some of the manifold activities of polyphenols