Heteroglycan of Annona muricata leaves: Extraction, characterization, modulation of the inflammatory response in raw 264.7 macrophages and peripheral Blood mononuclear cells

Abstract

The natural products contained in Annona muricata leaves are characterized by their ability to effectively enhance the immune response without exhibiting toxicity. The immunomodulatory effect of natural polysaccharides is considered one of the most important bioactive functions. In this study, we investigated the antioxidant activities and immunological properties of heteroglycans extracted from A. muricata leaves using hot water followed by ethanol precipitation. The polysaccharide was characterized for its physicochemical properties (UV spectroscopy, FTIR, gas chromatography), antioxidant potential (scavenging properties, chelating ability, reducing capability, and protection against DNA damage), immunomodulatory activities, and production of pro-inflammatory cytokines using peripheral blood mononuclear cells (PBMCs) and RAW 264.7 cells. The results indicated that the heteroglycans consisted of Glu-Man-GalA-GluA-Xyl and GluA-Man-Glu, respectively, for low and high molecular weight water-soluble polysaccharides coded as LWPC and HWPC. They exhibited strong metal chelating and scavenging activities. Additionally, each sample provided protection against DNA damage induction, with LWPC exhibiting up to 73.1 % protection. LWPC and HWPC significantly down-regulated the expression of pro-inflammatory cytokines TNF-α, IL-1β, IL-6, and COX-2, as well as NO production. At 200 µg/mL, only LWPC increased the production of IL-1β and IL-6 in PBMCs. Therefore, LWPC and HWPC hold promise for inhibiting radical-induced and inflammatory disorders.