Affiliations: Department of Food Science and Technology, School of
Agricultural Biotechnology, Seoul National University, Seoul 151-742, South
Korea | Department of Food Science and Technology, Cornell
University, Geneva, NY 14456, USA
Note: [] Address for correspondence: Professor Hyong Joo Lee, Department
of Food Science and Technology, Seoul National University, Shinlim-dong,
Kwanak-ku, Seoul 151-742, South Korea. Tel.: +82 2 880 4853; Fax: +82 2 873
5095; E-mail: [email protected]
Abstract: The present study investigated antioxidant and antitumor-promoting
activities of major phenolic phytochemicals of apples. The contents of each
antioxidant in Empire apples was quantified and their contributions to total
antioxidant activity of apples were determined using assay for inhibition of
12-O-tetradecanoylphorbol-13-acetate-induced superoxide radical generation in
cell culture model and expressed in vitamin C equivalent antioxidant capacity
(VCEAC). The estimated contribution of major phenolics and vitamin C to total
anitoxidant capacity of 100 g fresh Empire apples is as follows: quercetin
(60.05 VCEAC) > chlorogenic acid (12.32) > phloretin (7.41) >
procyanidin B_2 (7.22) > vitamin C (6.61) >
epicatechin (5.10) in superoxide radical scavenging assay. Recent reports
suggest that the mechanism of carcinogenic process of hydrogen peroxide
(H_2O_2) may be associated with the
inhibition of gap-junctional intercellular communication (GJIC), which is
involved in tumor promotion process. Apple extracts showed the protective
effects against the inhibition of GJIC by
H_2O_2 in a dose-dependent manner.
Quercetin exerted the strongest protective effects among major antioxidants in
apples on H_2O_2-induced inhibition of
GJIC, following epicatechin, procyanidin B_2, and vitamin C,
while chlorogenic acid and phloretin had no effects. Our results indicate that
cancer chemopreventive activity of apples is associated with the combined
antioxidant capacity and antitumor-promoting activities of diverse
antioxidants.
