A Critical Appraisal of the Protecting Activity of Polyphenolic Antioxidants Against Iatrogenic Effects of Anticancer Chemotherapeutics§

Polyphenolic compounds, encompassing flavonoids (e.g., quercetin, rutin, cyanidin) and non-flavonoids (e.g., gallic acid, resveratrol, curcumin), show several health-related beneficial effects, which include antioxidant, anti-inflammatory, hepatoprotective, antiviral, and anticar-cinogenic properties, as well as the prevention of coronary heart diseases. Polyphenols have been also investigated for their counteraction against adverse effects of common anticancer chemo-therapeutics. This review examines the outcomes of clinical studies (and related preclinical data) over the last ten years, with a focus on the use of polyphenols in chemotherapy as auxiliary agents acting against oxidative stress toxicity induced by antitumor drugs. While further clinical studies are needed to establish adequate doses and optimal delivery systems, the improvement in pol-yphenols’ metabolic stability and bioavailability, through implementation of nanotechnologies currently being investigated, could improve therapeutic applications of their pharmaceutical or nutraceutical preparations in tumor chemotherapy.