Antioxidant Activity, Antiproliferation of Colon Cancer Cells, and Chemical Composition of Grape Pomace

Chardonnay and Tinta Cao grape pomaces were generated by the winemaking process. The pomaces were extracted with 50% acetone and tested for antioxidant capacities using the oxygen radical absorbance capacity (ORAC) assay, DPPH□EC50 , and ABTS.+ scavenging capacity tests. Cytotoxicity and antiproliferative activities against Caco-2 and HT-29 human colon cancer cell lines were also analyzed. The quantitative detection of caspase-3 activity during the early apoptotic process was evaluated by fluorometric immunosorbent enzyme assay (FIENA). Induction of late stage apoptosis was analyzed by DNA fragmentation. Total phenolic content (TPC), individual phenolic acids, total oil, and fatty acid profile were also analyzed. The Tinta Cao pomace had the highest antioxidant capacity in all tests with an ORAC value of 386.5 μmol trolox equivalents (TE) per g pomace (μmol TE/g), its DPPH□EC50 value was 94.6 mg equivalents/L, and its ABTS.+ value was 806.7 μmol TE/g, which was more than twice as high as the Chardonnay. Both Tinta Cao and Chardonnay grape pomace extracts appear to contain components that inhibit the proliferation of Caco-2 and HT-29 cancer cells, at least in part, by triggering apoptosis. Expression of caspase-3 was induced by Tinta Cao and Chardonnay pomace extracts at 3 g/L after 4 hours of treatment with a 308% and 229% increase compared to control, respectively. An increase in DNA fragmentation was also observed with both grape pomace treatments. This study demonstrated that these tested grape pomaces were potent scavengers of free radicals and may provide some level of protection against certain cancers.