Bioaccesssibility and bioactivity of polyphenols extracted from six cherry cultivars

Introduction There is a possible association between consumption of fruit and vegetables and reduced risk of cancer, particularly cancer of the digestive tract. This anti-cancer activity has been attributed in part to polyphenols present in foods [1]. Cherries in particular are a rich source of polyphenols, especially anthocyanins and hydroxycinnamic acids [2]. Method Cherries from six different cultivars (Durone della Marca, Celeste, Durone Nero I, Bigarreau, Lapins and Moretta) were in vitro digested with a procedure that mimicked the physiochemical conditions of the gastro-intestinal tract [3]. After digestion, polyphenol-rich extracts were obtained by preparative chromatography on C18 column. Polyphenols were also extracted from un-digested cherries with methanol-water-formic acid solution (70:28:2 v/v) and chromatographed on C18 column. Total polyphenols and anthocyanins concentration were determined by Folin-Ciocalteau assay and pH differential method, respectively [3]. Polyphenols were identified using liquid chromatography mass spectrometry. The digested and un-digested preparations were assessed for their cytotoxic and anti-proliferative activities using two human colon adenocarcinoma cell lines (Caco-2 and SW480) and IC50 values of anti-proliferative activity were determined. Results / Discussion / Conclusion The total polyphenol concentration in the un-digested samples varied from 70.2mg/100g of cherry in the cultivar Durone della Marca to 280.6mg/100g of cherries in the cultivar Durone Nero I. The total anthocyanin content varied from 0.12mg/100g of cherry in the cultivar Durone della Marca to about 17mg/100g of cherry in the two darker cultivars (Lapins and Moretta). In vitro digestion resulted in a decrease in both total polyphenols and anthocyanins. Total polyphenols decrease ranged from 56 to 80%, whereas total anthocyanin decrease was more than 90% in all the tested cultivars. Mass spectrometry showed that the gastro-intestinal digestion decreased the content of hydroxycinnamic acids and anthocyanins. Other classes of polyphenols are more stable to digestion. Breakdown products of polyphenols are also present. Digested and un-digested polyphenol-rich extracts showed no cytotoxic activity. Un-digested polyphenol-rich extract from the cultivar Bigarreau showed the highest anti-proliferative effect (IC50 of 7.1 ± 1.1 µg polyphenols/mL) on the SW480 cells. The in vitro digestion increased the anti-proliferative activity of cherry extracts. Polyphenol-rich extracts from digested Durone della Marca and Celeste were the most active with IC50 values of 1.7 ± 0.8 and 3.5 ± 1.2 µg polyphenols/mL, respectively. All of the tested extracts showed no anti-proliferative activity on Caco-2 cells. Our results showed that cherry polyphenols were effective anti-proliferative agents on the more undifferentiated colon adenocarcinoma cells SW480 and that their digestion increased the effect. The increase may be due to the formation of polyphenol metabolites. A great difference was observed between the cultivars used. Further research is required to identify the compounds responsible for the observed anti-proliferative effect.