Ultrasound-assisted extraction and antioxidant activity of polysaccharides from Tenebrio molitor

Tenebrio molitor, which is rich in various nutrients, and its polysaccharides, as significant bioactive substances, exhibit strong antioxidant effects. This study utilized defatted T. molitor as raw material and employed an ultrasound-assisted extraction method. The factors considered include extraction temperature, time, ultrasound power, and liquid-to-feed ratio, with the yield of T. molitor polysaccharides as the response value. Based on single-factor experiments and response surface methodology, the optimal extraction parameters for T. molitor polysaccharides were determined. Following purification, protein removal, and dialysis to eliminate impurities, the structure of the extracted polysaccharides was preliminarily investigated using infrared spectroscopy. Their antioxidant activities were explored by measuring their DPPH·, OH·, and ABTS⁺· radical scavenging abilities and Fe³⁺ reducing power. The results indicated that the optimal conditions for ultrasound-assisted extraction were an extraction temperature of 75 °C, an extraction time of 150 min, an ultrasound power of 270 W, and a liquid-to-feed ratio of 15:1 mL/g, yielding a polysaccharide extraction rate of 9.513%. Infrared spectroscopy analysis revealed the presence of pyranose sugars with main functional groups including C-O, C=O, and O-H. Antioxidant activity tests showed that within a certain concentration range, the higher the polysaccharide concentration, the stronger its radical scavenging abilities. Compared with Vitamin C(Vc), the polysaccharides had stronger scavenging abilities for DPPH· and OH·, some scavenging ability for ABTS^+·, and Fe³⁺ reduction ability, and corresponding to IC₅₀ values of 0.9625, 9.1909, and 235.69 mg/mL respectively. The Fe³⁺ reducing power reached a maximum absorbance of 0.38899 at a concentration of 1.6 mg/mL. T. molitor polysaccharides demonstrate promising antioxidant activity and potential as functional ingredients in food, health products, and pharmaceuticals, providing new technical references for the development and utilization of T. molitor resources.