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Reduced nitrogen supply enhances the cellular antioxidant potential of phenolic extracts through alteration of the phenolic composition in lettuce ( Lactuca sativa L.)
Author(s) -
Zhou Weiwei,
Liang Xin,
Zhang Yimo,
Li Kejie,
Jin Bingjie,
Lu Lingli,
Jin Chongwei,
Lin Xianyong
Publication year - 2019
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.9721
Subject(s) - lactuca , antioxidant , chemistry , chlorogenic acid , food science , reactive oxygen species , biochemistry , quercetin , oxidative stress , nitrogen , reactive nitrogen species , phenols , composition (language) , enzyme , oxidative phosphorylation , botany , biology , organic chemistry , linguistics , philosophy
BACKGROUND Nitrogen availability is an important environmental factor that determines the production of phenolic compounds in vegetables, but the relationship between low nitrogen‐induced alterations of phenolic compounds in vegetable crops and the cellular antioxidant activities of these compounds remains unclear. This study investigated the effect of reduced nitrogen supply (0.05 mmol L −1 nitrate) on phenolic metabolism in lettuce and the protective role of phenolic extracts against H 2 O 2 ‐induced oxidative stress in Caco‐2 cells by determining cell damage, reactive oxygen species (ROS) content and antioxidant enzyme activities. RESULTS Reduced nitrogen supply significantly improved the accumulation of phenolic compounds in lettuce, which was partially correlated with the upregulation of genes related to the phenolic synthesis pathway. Phenolic extracts from lettuce cultivated in low‐nitrogen medium exhibited a better protective effect against H 2 O 2 ‐induced oxidative damage in Caco‐2 cells than those from lettuce cultivated with adequate nitrogen. These extracts act by increasing the activities of antioxidant enzymes and, subsequently, by inhibiting ROS overproduction, which leads to a decrease in mitochondrial membrane and DNA damage. The results of HPLC and correlation analyses implied that the improvement in the protective capacity of lettuce extracts after low‐nitrogen treatment may be related, not only to the increased content of phenolic compounds, but also to the increased percentage contribution of chlorogenic acid and quercetin derivatives to the total phenolic content. CONCLUSION Reduction in nitrogen supply can be a powerful strategy to modify phenolic metabolism and composition in lettuce and, consequently, to improve their antioxidant capacity. © 2019 Society of Chemical Industry