Comparative study of ultrasonic-assisted and hot water extraction of polysaccharides from waste leaves of vine tea: Based on extraction mechanisms and green efficiency analysis

Vine tea harvesting and processing generate massive quantities of waste leaves. The resource utilization of these agricultural byproducts to produce high value-added products such as polysaccharides represents a key strategy for balancing economic benefits and environmental protection. This study optimized the ultrasound-assisted extraction (UAE) process for vine tea polysaccharides (VTP) using response surface methodology, and employed multi-dimensional characterization techniques (Fourier-transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy) to systematically compare UAE and hot water extraction (HWE) in terms of their extraction mechanisms, the physicochemical characteristics of the polysaccharides, and their in vitro biological activities. Mechanistic investigations showed that, compared with HWE, UAE disrupted vine tea cell walls through acoustic cavitation and mechanical action, significantly improving the extraction yield of polysaccharides while reducing energy consumption. Comparative analyses demonstrated that UAE-derived VTP possessed lower molecular weights, higher uronic acid content, and better thermal stability, along with more prominent in vitro biological activities. This work provides an important theoretical basis and technical support for the optimization of VTP extraction procedures, the elucidation of their structure-activity relationships, and the promotion and application of VTP in the food and pharmaceutical industries.