The
antioxidant activity of
anthocyanins has been well characterized in vitro; many cases has been postulated to provide an important exogenous mediator of oxidative stress in the gastrointestinal tract. The objective of this study was to evaluate the efficacy of
anthocyanin protection against
peroxyl radical (
AAPH)-induced oxidative damage and associated cytotoxicity in Caco-2
colon cancer cells. Crude blackberry extracts were purified by gel filtration column to yield purified
anthocyanin extracts that were composed of 371 mg/g total
anthocyanin, 90.1%
cyanidin-3-glucoside, and 4.9 mmol
Trolox equivalent/g (ORAC) value. There were no other detectable phenolic compounds in the purified
anthocyanin extract. The
anthocyanin extract suppressed
AAPH-initiated Caco-2 intracellular oxidation in a concentration-dependent manner, with an IC50 value of 6.5+/-0.3 microg/ml.
Anthocyanins were not toxic to Caco-2 cells, but provided significant (P<0.05) protection against
AAPH-induced cytotoxicity, when assessed using the CellTiter-Glo assay.
AAPH-induced cytoxicity in Caco-2 cells was attributed to a significant (P<0.05) reduction in the G1 phase and increased proportion of cells in the sub G1 phase, indicating apoptosis. Prior exposure of Caco-2 cells to
anthocyanins suppressed (P<0.05) the
AAPH-induced apoptosis by decreasing the proportion of cells in the sub-G1 phase, normalized the proportion of cells in other cell cycle phases. Our results show that the
antioxidant activity of
anthocyanins principally attributed to cyanidin-3-O-glucoside and common to blackberry, are effective at inhibiting
peroxyl radical induced apoptosis in cultured Caco-2 cells.