Extraction, modification, analysis and antioxidant activity of white pepper polysaccharide

Polysaccharides, as key bioactive components in pepper, remain poorly understood in terms of their structure, activity, and even their functions. In this experiment, a neutral crude polysaccharide was extracted from Piper nigrum L. by ultrasound-assisted extraction (UAE), and the Piper nigrum L. polysaccharides (PNLP) were isolated and purified to obtain PNLP-1 A, and PNLP was modified by sulphation to obtain sulfated PNLP (S-PNLP). The physicochemical properties and in vitro antioxidant activities of PNLP-1 A and S-PNLP were compared. NMR and HPLC were taken to attribute the C/H of PNLP-1 A, indicating that PNLP-1 A is an α-glucan with 1→4,6 glycosidic linkages. The molecular weight (Mw) of PNLP-1 A is 8.957 kDa, indicating that it is a homogeneous polysaccharide with a relatively small Mw. This seems to suggest that it is more capable of entering cells and exerting its biological activity. PNLP-1 A does not possess a triple-helical structure, and its microstructure suggests a tighter conformation. S-PNLP showed a significant increase in hydroxyl radical scavenging activity and DPPH radical scavenging activity compared to PNLP, suggesting that sulphation modification could improve some of the antioxidant activities of PNLP. The above experiments provided the experimenters with further understanding of the structure and antioxidant activity of PNLP, and provided a basic research theory for the structure-activity relationship study of PNLP.