Ultrasound-assisted extraction, optimization, characteristics and antioxidant activity of Piper nigrum L. polysaccharides

The process conditions, content of ingredients and in vitro antioxidant activity of Piper nigrum L. polysaccharides (PNP) by ultrasound-assisted extraction (UAE) and PNP by hot water extraction (HWE) were compared. The findings demonstrated that the UAE produced greater polysaccharides content (74.41 %) with the yield of PNP (2.9 %) than HWE. The ideal conditions were 324 W of ultrasonic power, 36 mL/g of liquid to material ratio, 70 min of ultrasonic time, and 78 °C of temperature. Structural analysis showed UAE-PNP was the α-type polysaccharides with a pyran ring structure, which were mainly neutral polysaccharides. In addition, UAE-PNP had great antioxidant activity, especially in its ability to scavenge ABTS free radicals. According to the experimental results, the UAE method was an efficient way to extract PNP. This experiment showed for the first time the structure and antioxidant activity of HWE-PNP and UAE-PNP, which provided some theoretical proof for the application of PNP in food additives and biopharmaceuticals.