Evaluation of antioxidant activity and antiproliferative effect of fruit juices enriched with Pycnogenol® in colon carcinoma cells. The effect of in vitro gastrointestinal digestion.

The aim of this study was to examine the effect of in vitro gastrointestinal digestion on the antioxidant and antiproliferative effect of fruit juices enriched with Pycnogenol® (0.5 g/L) on a colon carcinoma cell line (Caco-2). The total phenolic concentration (TPC), antioxidant activity and inhibition cell growth were studied in fresh and digested pineapple juice and red fruits juice (both enriched with pine bark extract and not). After in vitro digestion the level of detectable phenolic compounds (expressed as gallic acid equivalent) was higher in both pineapple and red fruits juices enriched with Pycnogenol® than in non-enriched commercial juices (155.6 mg/100 mL vs 94.6 mg/100 mL and 478.5 mg/100 mL vs 406.9 mg/100 mL, respectively). Increased antioxidant activity (measured by 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and oxygen radical absorbance capacity assay (ORAC) methods) was observed in digested enriched juices with respect to the same samples before digestion. Pycnogenol® enrichment led to a high antiproliferative effect between 24 and 72 h of incubation with undigested pineapple juice compared with the non-enriched juice. It can be concluded that enrichment of fruit juices with Pycnogenol® provides a source of phenolic compounds with high stability to in vitro gastrointestinal conditions; however, the antioxidant properties of fruit juices were affected to a different extent.