Potential roles of dietary flavonoids from Citrus aurantium L. var. amara Engl. in atherosclerosis development
Dietary consumption of flavonoids correlated positively with lower risk of cardiovascular disease. However, the precise roles of flavonoids from blossoms of Citrus aurantium Linn variant amara Engl (CAVA) in atherosclerosis (AS) were still poorly understood. This study aimed to ﬁnd novel ﬂavonoid-type skeletons with protection against AS. Total flavonoids (CAVAF), homoeriodictyol (HE) and hesperetin-7-O-β-D-glucopyranoside (HG) were isolated from blossoms of Citrus aurantium Linn variant amara Engl. by chromatography. Their suppressive effects on lipopolysaccharide (LPS)-induced inflammatory responses and ox-LDL-induced foam cell formation were systematically and comparatively investigated using macrophage RAW264.7 cells. HE was more powerful than HG in inhibiting LPS-induced production of nitric oxide (NO), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), interleukin-1 beta (IL-1β) and gene expression in RAW264.7 cells. HE and HG exhibited different responses to extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), P38, P65, IκBα, IκKα/β phosphorylation, and nuclear factor-kappa B (NF-κB) nuclear translocation. HE and HG also differentially decreased oxidized low-density lipoproteins (ox-LDL)-induced foam cell formation by regulating peroxisome proliferator-activated receptor-gamma (PPARγ), phospholipid ATP-binding cassette transporters A1 (ABCA1), phospholipid ATP-binding cassette transporters G1 (ABCG1), scavenger receptor class B type I (SRB1), scavenger receptor class A type I (SRA1) and cluster of differentiation 36 (CD36) expression at gene and protein levels in RAW264.7 cells. HG showed weaker potential than HE in preventing AS development. Their chemical differences might partially explain their bioactivity discrepancy. In conclusion, HE and HG might be developed into novel therapeutic agents against inflammation and AS-associated diseases.