the total amount of both polyphenols and vitamin C were major contributors to the total antiproliferative capacity of Actinidia fruit.
Though many studies have shown an antiproliferative activity in phenolics extracts [27], the mechanisms of action are not yet clearly determined. Possible mechanisms include interference with the metabolite activation of promutagen, as blocking agents and formation of adducts with ultimate mutagens, scavenging of free radicals and suppression of tumor cell invasiveness via the inhibition of matrix metalloproteinase-2/-9 activity [28]. In this study, the positive effects of the antioxidants found in each Actinidia extract could contribute toward the antiproliferative activities of HT-29 and HepG2 tumor cells. Alternatively, taking into consideration the complexity of the mechanisms proposed for their chemopreventative properties, it is likely that anticarcinogenic effects attributed to polyphenols may be based on synergistic, additive, or antagonistic interactions of many compounds present in these extracts [29].
Figure 6. (a) Inhibition of HT-29 cell proliferation by the treatments of different concentrations of Actinidia extracts for 48 h; (b) Inhibition of HepG2 cell proliferation by the treatments of different concentrations of Actinidia extracts for 48 h; (c) EC50 values of antiproliferative activity of three Actinidia extracts on HepG2 and HT-29 (mean ±SD, n = 3).