Isolation, Structural Characterization and Macrophage Activation Activity of an Acidic Polysaccharide from Raspberry Pulp

Abstract

The discovery of safe and effective plant polysaccharides with immunomodulatory effects has become a research hotspot. Raspberry is an essential commercial fruit and is widely distributed, cultivated, and consumed worldwide. In the present study, a homogeneous acidic polysaccharide (RPP-2a), with a weight-average molecular weight (Mw) of 55582 Da, was isolated from the pulp of raspberries through DEAE-Sepharose Fast Flow and Sephadex G-200 chromatography. RPP-2a consisted of rhamnose, arabinose, galactose, glucose, xylose, galacturonic acid and glucuronic acid, with a molar ratio of 15.4:9.6:7.6:3.2:9.1:54.3:0.8. The results of Fourier transform infrared spectroscopy (FT-IR), gas chromatography-mass spectrometer (GC-MS), 1D-, and 2D-nuclear magnetic resonance (NMR) analyses suggested that the backbone of RPP-2a was primarily composed of →2)-α-L-Rhap-(1→, →2,4)-α-L-Rhap-(1→, →4)-α-D-GalAp-(1→, and →3,4)-α-D-Glcp-(1→ sugar moieties, with side chains of α-L-Araf-(1→, α-L-Arap-(1→, and β-D-Galp-(1→3)-β-D-Galp-(1→ residues linked to the O-4 band of rhamnose and O-3 band of glucose residues. Furthermore, RPP-2a exhibited significant macrophage activation activity by increasing the production of nitric oxide (NO), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β), and the expression of inducible nitric oxide synthase (iNOS) and cytokines at the transcriptional level in RAW264.7 cells. Overall, the results indicate that RPP-2a can be utilized as a potential natural immune-enhancing agent.

Structural Characteristics, Antioxidant, and Immunostimulatory Activities of an Acidic Polysaccharide from Raspberry Pulp

“…In this study, a novel homogeneous acidic polysaccharide named RPP-3a was isolated from the raspberry pulp. Its structure was different from another acidic polysaccharide RPP-2a, which was also separated from the pulp of raspberry in our previous study [ 13 ]. RPP-3a was composed of rhamnose, arabinose, galactose, glucose, mannose, and galacturonic acid, among which the galacturonic acid content was the highest.…”

“…Information on methylated sugar, mass fragment information, glycosyl linkage patterns, and molar ratios is summarized in Table 1. Among these connection modes, the molar ratios of 13 C-NMR signals were assigned according to correlations in the 2D-NMR spectra to interpret the structure of RPP-3a. As shown in Figure 6a, proton spectrum signals were mainly concentrated between 3.0 and 5.5 ppm, and the signals of the anomeric proton were distributed in the δ H 4.4-5.2 ppm region.…”

“…A heteropolysaccharide (RCP I) and a degraded polysaccharide (DRCP I) were obtained from raspberry fruits, both of which displayed high antioxidant activity [ 12 ]. In our recent study, a novel acidic polysaccharide named RPP-2a was isolated from raspberry pulp and exhibited significant macrophage activation activity [ 13 ]. These results indicated that the polysaccharides derived from raspberries have great potential for in-depth development and utilization.…”

“…NMR spectra and proposed structure of RPP-3a 1. H NMR (a),13 C NMR (b), DEPT-135 (c), HMBC (d), NOESY (e), HSQC (f), COSY (g), and the structure of RPP-3a (h). Figure6.…”

Removal of Methylene Blue from Aqueous Solutions Using a New Natural Lignocellulosic Adsorbent—Raspberry (Rubus idaeus) Leaves Powder

“…They are used to treat cardiovascular and degenerative diseases, obesity, and cancer. Raspberry leaves, although used on a smaller scale than fruits, contain organic acids, flavonoids, tannins, and vitamin C and have the following many therapeutic properties: astringent, disinfectant, healing, antidiarrheal, antihemorrhagic, and hormone-regulating [ 24 , 25 , 26 , 27 ].…”