Comparative Activities of Three Compounds from Citrus aurantium L. var. amara Engl. to Improve Oxidized Low-Density Lipoprotein-Induced Lipid Deposition

The active ingredients of Citrus aurantium have been shown to possess a variety of biological activities, especially anti-inflammatory effects. However, its antiatherosclerotic effects need to be further investigated. The aim of this study is to identify compounds with antiatherosclerotic effects from C. aurantium and to further investigate their mechanisms. Three compounds were separated, and then their antiatherosclerotic effect on foam cells induced by oxidized low-density lipoprotein (ox-LDL) was screened by oil red O staining, BODIPY staining, and Dil-ox-LDL uptake measurement. Cholesterol uptake, cholesterol efflux, RT-PCR, and Western blot analysis were used to comprehensively and comparatively explore the potential mechanisms. Nobiletin (NOB), caffeine (CAF), and naringin (NARG), which were separated from C. aurantium, mainly inhibit the formation of foam cells in different ways. NOB reduced cholesterol uptake and enhanced cholesterol efflux and mainly regulated the expressions of ABCA1, ABCG1, and SRA1. CAF promoted cholesterol efflux, mainly by stimulating the expressions of ABCA1 and ABCG1. NARG was more effective in reducing the expression of SRA1 and CD36, which indicated that NARG mainly prevented atherosclerosis by blocking cholesterol uptake. The above results show in detail the antiatherosclerotic activity and mechanism of these compounds, making contributions to their potential applications.