Ultrasound-assisted low-temperature extraction of polysaccharides from Lavandula angustifolia Mill.: optimization, structure characterization, and anti-inflammatory activity

Lavandula angustifolia Mill. is a traditional Chinese medicinal herb with high economic and pharmacological value. In this study, we optimized the conditions for low-temperature ultrasound-assisted extraction of L. angustifolia Mill. polysaccharides using response surface methodology (RSM), and two homopolysaccharides LAP-W-1 (33.6 kDa) and LAP-S-1 (95.9 kDa) were obtained after isolation and purification by DEAE-650 M and SuperdexTM 200 chromatography. The primary structure of LAP-S-1 was determined using "partial acid hydrolysis, methylation, two-dimensional (2D NMR) spectroscopy" as the core method. The results revealed that LAP-S-1 is a heteropolysaccharide whose main chain consists of [-1)-(3-Galp-(6-*1)-alpha-Araf-(5-*]3-1-alpha-Araf(3-*1)-alpha-Araf-(5-*[1)-(3-Galp-(6-*1)-alpha-Araf-(5-*]3-1-alpha-Araf-(5-*1)-alpha-Araf-(5-*[-1)-(3-Galp-(6-*1)-alpha-Araf-(5-*]3. In vitro experiments revealed that LAP-W-1 and LAP-S-1 significantly reduced the production of the inflammatory cytokines Interleukin-1(3 (IL-1(3), Interleukin-6 (IL-6), and Tumor Necrosis Factor (TNF), as well as the expression of Nitric Oxide Synthase 2 (NOS2) and release of nitric oxide (.NO) free radical in the inflammatory model established by lipopolysaccharide (LPS) stimulated RAW264.7. Besides, the zebrafish inflammatory model, stimulated by CuSO4, was employed to assess the impact of polysaccharides on neutrophil migration, indicating a notable decrease in zebrafish neutrophils and confirming their potential anti-inflammatory activity. These results indicate that polysaccharides from L. angustifolia Mill. be used in the development of functional foods and pharmaceutical products.