Ultrasound-assisted enzyme extraction of Citri Exocarpium Rubrum (Juhong) polysaccharides and its structural characteristics and evaluation of improving Parkinson’s disease through HDAC6/NLRP3 pathway

Citri Exocarpium Rubrum (CER) has been utilized in food and medicine for over 2000 years both domestically and internationally. This study investigated the polysaccharide extraction process, structural characteristics, and biological activity of CER using ultrasonic-assisted enzyme extraction (UAE). The sugar yield of UCERP extracted via UAE, was 14.23 ± 0.12 %, with optimal extraction conditions of 70°C, 50 min of ultrasonic enzyme hydrolysis, 4.0 % cellulase, a solid-to-liquid ratio of 20: 1 mL/g, and ultrasonic power of 240 W. The monosaccharide composition of UCERP1-1, purified by isolation, includes rhamnose, arabinose, galactose, glucose, and galacturonic acid (ratio of 0.042: 0.202: 0.242: 0.06: 0.454). Moreover, the structural analysis revealed that UCERP1-1's fractions are primarily linked by a repeating unit: →[4)-α-D-GalAp-(1]₆ → [4)-α-D-GalAp-(1]₅ → [4)-β-D-Galp-(1]₃ → 3)-α-L-Rhap-(1 → 4)-β-D-Galp-(1 → 4)-β-D-Galp-(1 → . In vivo, a Parkinson's disease (PD) model was established in mice using MPTP to assess the therapeutic effects of UCERP1-1. It significantly alleviated PD symptoms, improved behavioral deficits, increased the number of TH-positive cells, reduced dopaminergic neuron loss in MPTP-treated mice, and decreased SH-SY5Y cell death induced by MPP⁺. Further analysis via ELISA, Western blot and Cellular thermal shift assay revealed that UCERP1-1 reduced inflammatory markers and alleviated oxidative stress in PD mice. UCERP1-1 also regulated the HDAC6/NLRP3 pathway in PD mice. These findings provide a theoretical foundation for the potential use of UCERP1-1 as a functional food for PD or related diseases.