Antioxidant capacity of flavonoids from Folium Artemisiae Argyi and the molecular mechanism in Caenorhabditis elegans

Folium Artemisiae Argyi (FAA) is one kind of Chinese herbal medicine with a long history. It has widespread pharmacological activities such as antibacterial, anti-inflammatory, antioxidative, and hemostatic, among others. FAA is traditionally used for the treatment of eczema, respiratory diseases and gynecological diseases for hundreds of years. Flavonoids are reported as the main components of them. Recent studies focused on the antioxidant effect of its flavonoids in vitro, while few studies focused on the antioxidant effect in vivo, and the underlying mechanisms have not yet been elucidated.The aim of this study was to evaluate the antioxidant activity of Folium Artemisia Argyi flavonoids (FAAF) and explore its possible molecular mechanism in Caenorhabditis elegans. The research and development of its medicinal value will beneficial to the resource utilization of FAA.Firstly, FAAF was prepared, purified and then qualitatively and quantitatively analyzed using LC-DAD-MS. Then, 1,1-diphenyl-2-trinitrophenylhydrazine (DPPH), 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS), hydroxyl radical and ferric reducing antioxidant power (FRAP) assays were applied to investigate the antioxidant effect of FAAF in vitro. Meanwhile, a stress resistance assay was carried out to evaluate the antioxidant effect of FAAF in vivo. Moreover, superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities and reactive oxygen species (ROS) accumulation were determined to ascertain whether FAAF can increase the oxidant defense system of nematodes and reduce the accumulation of ROS. Lipofuscin and protein carbonylation assays were employed to test whether FAAF can increase the antioxidant capacity of nematodes to resist the growth health indicators related to antioxidation. At last, quantitative real-time polymerase chain reaction (qRT-PCR) was performed to evaluate the expression of genes related to antioxidation. The expression of green fluorescent protein (GFP) was further investigated using a fluorescence microscope in transgenic strains (SOD-3::GFP, GST-4::GFP, and HSP-16.2::GFP).FAAF exhibited a strong antioxidant capacity and enhanced stress resistance in C. elegans. FAAF reduced ROS accumulation and improved the antioxidant defense system under acute stress. Moreover, FAAF prevented the accumulation of lipofuscin and protein carbonylation in C. elegans. FAAF also upregulated the gene expression levels of hsp-16.2, gst-4, sod-3, skn-1, daf-16, ctl-2, hsf-1 and increased SOD-3::GFP and GST-4::GFP expression.These results demonstrated that FAAF exerted antioxidant activity in C. elegans. It was perhaps regulated by the insulin/insulin-like growth factor-1(IGF-1) signaling pathway.