Chemical structures, antioxidant capacities, and immunostimulatory activities of pectic polysaccharides from jujube fruits collected from different producing areas

Abstract

Pectic polysaccharides are well-recognized as the mainly functional components in jujube fruits, which have garnered considerable attentions to be exploited into functional food products. Nevertheless, the knowledge about the influence of the producing area on their fine structural features and biological functions is still scarce, which may restrict their rational use in the functional food sector. Therefore, the structural and biological properties of pectic polysaccharides from jujube fruits (JP) collected from different producing areas were compared. The results showed that JP's physicochemical properties (e.g., total uronic acids, total bound polyphenols, molecular mass distributions, and ratios of constituent monosaccharides) varied significantly depending on the producing area. However, the primary chemical structures of JPs obtained from various producing areas were largely similar, predominantly composing of homogalacturonan and rhamnogalacturonan-I regions. Furthermore, JP's antioxidant and immunostimulatory effects also varied remarkedly depending on the producing area, primarily attributed to variations in their physicochemical properties. Particularly, JP's antioxidant activity demonstrated a significantly positive correlation with the levels of total uronic acids and total bound polyphenols, and similarly, its immunostimulatory activity was highly dependent on the level of total uronic acids. Moreover, mechanistic investigations revealed that JP could enhance immune responses via activating the Toll-like receptor 4 mediated nuclear factor-κB signaling pathway in RAW 264.7 macrophages. Collectively, the current findings could provide valuable insights for the rational application of jujube fruits and JP in the functional food sector.