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

The aim of this study was to determine the chemical and intracellular antioxidant activities of ${\beta}$-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 ${\beta}$-carotene, as calculated by QSAR. Chemical antioxidant activities of ${\beta}$-carotene, lycopene, and Trolox were examined by measuring ferric reducing antioxidant power (FRAP) and 2,2'-diphenyl-1-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 ${\beta}$-carotene (P<0.05), and the two carotenoids had similar antioxidant activities in DPPH radical scavenging activity assay. Trolox had the greatest chemical antioxidant activities (P<0.05). When RAW264.7 cells were treated with lipopolysaccharide (LPS) (100 ng/mL) for 20 h, intracellular ROS and DNA fragmentation significantly increased (P<0.05). RAW 264.7 cells pretreated with ${\beta}$-carotene ($4{\mu}M$) and lycopene ($0.4{\sim}2{\mu}M$) 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 $2{\mu}M$ lycopene produced less intracellular ROS than those treated with ${\beta}$-carotene (P<0.05). DNA fragmentation of cells with ${\beta}$-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 ${\beta}$-carotene in the QSAR, FRAP, and intracellular ROS assays (P<0.05). ${\beta}$-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.

β-Carotene과 Lycopene의 양자역학 및 화학적 항산화능과 세포 내 산화적 스트레스 보호 효과의 비교

본 연구는 ${\beta}$-carotene과 lycopene의 양자역학 및 화학적 항산화능과 세포 내 항산화 효과를 분석하였다. ${\beta}$-Carotene과 lycopene의 항산화능을 양자역학적으로 비교한 결과 lycopene의 항산화능이 ${\beta}$-carotene보다 높은 것으로 나타났으며, 이러한 항산화능의 차이는 FRAP로 측정하였을 때도 유사하게 관찰되었다. Trolox와 비교했을 때 ${\beta}$-carotene과 lycopene의 FRAP 수치는 유의적으로 낮았으나 LPS에 의한 세포 내 ROS 생성을 낮추는 데는 두 카로티노이드가 더 우수한 것으로 나타났다. 그러므로 본 연구에서 비교한 ${\beta}$-carotene과 lycopene의 양자역학적 항산화능은 화학적 항산화능을 일부 반영하지만, 실제 세포 내 ROS에 의한 산화스트레스 저하 효과와는 차이가 있는 것으로 나타났다.