It is recognized that minor dietary components
polyphenols have anticancer effects on digestive tract, lung,
leukemia, and other
cancers, while
polyphenols also can covalently or noncovalently interact with major dietary components
proteins such as
casein,
soybean proteins,
whey proteins, and
bovine serum albumin. Thus, whether the noncovalent interaction between the molecules of two
polyphenols (
quercetin and
fisetin) and two
proteins (
bovine serum albumin and
casein) has positive or negative impact on anticancer activities of the
polyphenols against human gastric
adenocarcinoma AGS cells was assessed in this study. The two
polyphenols had obvious anticancer activities to the cells, because dose levels as low as 20-160 μmol/L caused reduced cell viability of 30.0-69.4% (
quercetin) and 24.6-63.1% (
fisetin) (using a cell treatment time of 24 h), or 9.9-48.6% (
quercetin) and 6.4-29.9% (
fisetin) (using a cell treatment time of 48 h). However, the cell treatments by the
polyphenols in the presence of the two
proteins mostly caused lower
polyphenol activity toward the cells, compared with those treatments by the
polyphenols in the absence of the
proteins. Specifically, the presence of the
proteins led to reduced growth inhibition in the cells, because higher cell viability of 33.2-86.7% (
quercetin) and 29.1-77.7% (
fisetin) at 24 h, or 14.1-66.8% (
quercetin) and 7.9-59.0% (
fisetin) at 48 h, were measured in these treated cells. The two coexisting
proteins also yielded the
polyphenol-treated cells with less mitochondrial membrane potential loss, less formation of
reactive oxygen species, and decreased cell apoptosis. Thus, it is highlighted that the noncovalent interaction between dietary
polyphenols and
proteins resulted in weakened anticancer ability for the
polyphenols to the
gastric cancer cells.