Comparison of Quantitative Structure-Activity Relationship and Chemical Antioxidant Activity of p-Carotene and Lycopene and Their Protective Effects on Intracellular Oxidative Stress

摘要

The aim of this study was to determine the chemical and intracellular antioxidant activities of P-carotene and lycopene and to compare their quantitative structure-activity relationship (QSAR). In our previous study, the second ionization energy of lycopene was higher than that of P-carotene, as calculated by QSAR. Chemical antioxidant activities of p-carotene, lycopene, and Trolox were examined by measuring ferric reducing antioxidant power (FRAP) and 2,2'-di-phenyl-l-picrylhydrazyl (DPPH) radical scavenging activity. Intracellular antioxidant activities were evaluated by intracellular reactive oxygen species (ROS) and DNA fragmentation. The FRAP of lycopene was higher than that of P-caro-tene (P<0.05), and the two carotenoids had similar antioxidant activities in DPPH radical scavenging activity assay. Trolox had the greatest chemical antioxidant activities (PO.05). When RAW264.7 cells were treated with lipopolysac-charide (LPS) (100 ng/mL) for 20 h, intracellular ROS and DNA fragmentation significantly increased (P<0.05). RAW 264.7 cells pretreated with P-carotene (4 pM) and lycopene (0.4 ~ 2 uM) for 4 h formed significantly less intracellular ROS than LPS-treated control cells (P<0.05), whereas cells with Trolox did not reduce production of intracellular ROS. In addition, cells pretreated with 2 pM lycopene produced less intracellular ROS than those treated with p-carotene (PO.05). DNA fragmentation of cells with P-carotene and lycopene was similar to that of LPS-treated control cells as measured by Hoechst staining. The antioxidant ability of lycopene was greater than that of p-carotene in the QSAR, FRAP, and intracellular ROS assays (P<0.05). p-Carotene and lycopene had lower antioxidant activities as measured by FRAP (P<0.05) but higher intracellular protective effects against LPS-induced oxidative stress in comparison with Trolox.