The in vitro and in vivo antioxidant activities of Sargassum pallidum ethanol extract and its effect on gut microbiota modulation

Sargassum pallidum (S. pallidum), a traditional Chinese herb, is a homology of medicine and food that is widely used daily. This study focused on the antioxidant activity and modulation of the gut microbiota by S. pallidum ethanol extract (SPEE). The results of component determination showed that SPEE contained flavonoids (0.398 g/100 g) and polyphenols (0.193 g/100 g). SPEE effectively eliminated 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and hydroxyl and superoxide radicals in vitro; reduced the reactive oxygen species (ROS) and malondialdehyde (MDA) contents; and increased the glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), and catalase (CAT) enzymatic activities in UVB-irradiated HaCaT cells, which indicated its in vitro antioxidant activity. In addition, the healthy mice that received SPEE treatment presented a reduced spleen index and MDA content and increased GSH-Px enzymatic activity, which indicated its in vivo antioxidant activity. Furthermore, 16S rRNA gene sequencing of fecal samples revealed that SPEE modulated the gut microbiota in mice, decreasing the abundance of harmful bacteria such as Helicobacter while increasing the abundance of beneficial bacteria such as Bifidobacterium and Akkermansia. This study systematically confirmed the antioxidant activity of SPEE, clarified its ability to modulate the gut microbiota, and elucidated the relationship between its antioxidant activity and the gut microbiota, laying a foundation for in-depth research and wider application of S. pallidum in antioxidants.