Abstract
Oviductus ranae, an animal-based traditional Chinese medicinal material listed in Chinese Pharmacopeia is widely consumed as tonic, approximately twenty Oviductus ranae-related functional foods have been approved on the market by National Medical Products Administration in China. Proteins are well-defined bioconstituents in Oviductus ranae, little information is availabe on its polysaccharides. In present work, a Polysaccharide-Rich fraction (POR-3) was fractionated from Oviductus ranae based on antioxidant activity-guided isolation and its structure was partially characterized as well as its immunomodulatory potential was explored. POR-3 belonged to a heteropolysaccharide-protein fraction mainly consisted of Man, GlcN, GalA, Gal and Fuc at a molar ratio of 1: 2.28: 2.40: 3.00: 2.23 with binding proteins content of 6.42±0.16%. POR-3 possessed polydisperse property with MW of 999.586 kDa and PDI of 4.09. The UV and FT-IR analysis demonstrated that structures of POR-3 correspond with the characteristics of polysaccharide-protein complex. POR-3 elicited higher scavenging capacities against hydroxyl and DPPH radicals and exerted potent in vitro immunomodulatory activity via promoting macrophages phagocytosis and via stimulating NO production as well as appeared no proliferation on macrophages. POR-3 possesses high potentials to be consumed as a medicine or functional food with antioxidant and immune modulator properties.
Highlights
Reactive Oxygen Species (ROS) play a dual role on immune system
It has been reported that uronic acids enable polysaccharides negatively charged (Sun et al, 2018) and Polysaccharides from OR (POR)-3 contained more uronic acids than that of POR-2 (Table 1), which may be the reason that fractionation of POR-3 required relatively higher concentration of NaCl solution as eluent
The IC50 value of POR-3 against DPPH radical was 0.73±0.01 mg/mL, still markedly lower (P < 0.01) than that of POR-2 (1.15±0.03 mg/mL), but higher (P < 0.01) than that of Vitamin C (VC) (0.037±0.004 mg/mL). These results indicated that POR-3 outperforms POR2 on scavenging activities against hydroxyl and DPPH radicals, which might be contributed partially by the relatively higher content of uronic acids in POR-3 (Table 1), due to the fact that uronic acids are well acknowledged as an important role in antioxidant activity (He et al, 2016)
Summary
Reactive Oxygen Species (ROS) play a dual role on immune system. Low ROS production induced by the activation of phagocyte NADPH oxidase 2 complex is considered to regulate immune response and cell proliferation and to control T-cell autoreactivity (Lam et al, 2010). Excessive accumulation of ROS caused by harmful environmental stresses such as overconsumption of smoking and alcohol, long-term exposure to organic pollutants and heavy metals as well as X-ray irradiation could induce oxidative stress, thereby impairing the activated T cell and destroying the membrane structure of immune cell to cause immune disorder (Amir Aslani and Ghobadi, 2016; Hildeman et al, 2003; Srivastava et al, 2017). Endogenous antioxidants, including glutathione, superoxide dismutase, glutathione peroxidase and catalases usually exert certain scavenging capacities against ROS to decrease the damaging effects of oxidative stress (Ighodaro and Akinloye, 2018). Levels of these endogenous antioxidants are always lower than the minimum concentrations demanded for scavenging ROS (Szuroczki et al, 2016). It is of importance to supplement antioxidants exogenously, owing to their beneficial effects on oxidative stress-related disorders, for immune dysfunction
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