Ultrasound-assisted extraction of novel ancient tea polysaccharide NATP-60a: Process optimization, structural characterization, and mechanism of alleviating DSS-induced colitis in mice.

Plant-derived polysaccharides are considered potentially effective treatments for colitis due to their safety and anti-inflammatory properties. This study used leaves ofancient tea trees endemic to southwestern China as raw materials, established an optimized ultrasound-assisted extraction (UAE) process, subsequently isolated and purified a novel polysaccharide NATP-60a, and systematically investigated its alleviating effect on colitis induced by oral administration of dextran sulfate sodium (DSS) in mice. The results showed that under the optimal UAE process conditions, the yield of crude polysaccharide was 3.84 ± 0.15%. Subsequently, preliminary screening was performed to obtain the crude polysaccharide NATP-60, which was further purified via DEAE-52 cellulose anion-exchange chromatography to ultimately acquire the bioactive polysaccharide fraction NATP-60a. NATP-60a was a polymer with a molecular weight of 8.4 kDa. Its main chain structure was: T-β-Rhap-1 → 3-α-D-Manp-1 → 6-α-D-Manp-1 → 3,6-β-Galp-1 → 5-α-L-Araf-1 → 4-β-D-Xylp-1 → 6-β-Galp-(1 → . NATP-60a significantly alleviated DSS-induced colitis symptoms in mice, restored gut microbiota homeostasis, increased the abundance of beneficial bacteria such as Muribaculum, and reversed DSS-induced depletion of short-chain fatty acids. Metabolomics results showed that NATP-60a mainly corrected metabolic disorders by regulating amino acid metabolism, especially tryptophan metabolism and tyrosine metabolism. The above results demonstrate that NATP-60a improves DSS-induced colitis by modulating gut microbiota and metabolic reprogramming, making it a potential prebiotic for colitis treatment.