Physicochemical Properties and Biological Activities of Polysaccharides from Dendrobium officinale Leaves in Response to Different Extraction Methods

Extraction techniques play a crucial role in determining the structural attributes and biological functions of polysaccharides. This study aimed to evaluate the physicochemical and biological properties of <i>Dendrobium officinale</i> leaf polysaccharides (DLPs) extracted using various methods, including hot water, acidic, alkali, ultrasound-assisted, and enzyme-assisted extraction. The results indicated that the extraction methods significantly influenced the yield, content, molar ratios of monosaccharides, molecular weight, and structural features of the polysaccharides, as well as their in vitro adsorption, antioxidant, and immunostimulatory activities. Among these extraction methods assessed, enzyme-assisted extraction yielded the highest amount of polysaccharides, characterized by a substantial galacturonic acid residue and exceptional scavenging capability towards free radicals. In contrast, hot water extraction and ultrasound-assisted extraction preserved a triple helix conformation, enabling the polysaccharides to exhibit superior adsorption capabilities for cholesterol and nitrite, as well as significantly increasing the release of nitric oxide and the secretion of TNF-α, IL-6, and IL-1β in RAW264.7 macrophages. These findings suggest that enzyme-assisted, ultrasound-assisted, and hot water extraction are effective approaches to extract DLPs with pronounced biological activity. The selection of the extraction method for DLPs should be tailored to align with the specific requirements of practical applications.