Structural Characterization of Acidic Polysaccharides from Scutellaria baicalensis Georgi and Its Protection Against Acute Lung Injury

Acute lung injury (ALI) seriously impairs health and well-being. Although Scutellaria baicalensis Georgi (SBG) extract has been shown to alleviate ALI, the effects of SBG acidic polysaccharides on ALI have not been revealed. In this study, a homogeneous acidic polysaccharide (SBGP1) was purified and characterized, and its impact on ALI was evaluated. Our findings illustrated that the average molecular weight of SBGP1 was 40764.6 Da, and it was mainly composed of GalA (53.14%), Ara (26.99%), Gal (7.75%), Glc (5.95%), and Rha (6.17%). The main chain of SBGP1 consisted of →4)-α-GalpA-6-OMe-(1→ and →4)-α-GalpA-(1→. Furthermore, SBGP1 exhibited a significant alleviating effect on ALI, as evidenced by decreased levels of TNF-α, IL-1β, IL-6, GSSG, and MDA, and increased levels of IL-4, IL-10, GSH, and SOD. Mechanistically, SBGP1’s role in alleviating ALI may be associated with the activation of the Rap1 signaling pathway. SBGP1 improved intestinal homeostasis, manifested as increased abundance of beneficial bacteria (Lactobacillus and norank_f_Muribaculaceae) and decreased abundance of harmful bacteria (Adlercreutzia, Ligilactobacillus, Massiliomicrobiota, and Mucispirillum). Interestingly, SBGP1-derived Lactobacillus johnsonii and propionic acid evidently improved the inflammatory response and oxidative stress in ALI mice. Overall, this study provides novel insights into SBGP1 as a potential therapeutic option for ALI.