Inhibition of Calcium Oxalate Formation and Antioxidant Activity of Carboxymethylated Poria cocos Polysaccharides

Abstract

Three carboxymethylated Poria cocos polysaccharides (PCP-C1, PCP-C2, and PCP-C3) with -COOH contents of 6.13%, 10.24%, and 16.22%, respectively, were obtained by carboxymethylation of the original polysaccharide (PCP-C0), which has a molecular weight of 4 kDa and a carboxyl (-COOH) content of 2.54%. The structure of the PCP-Cs was characterized by FT-IR, 1H NMR, and 13C NMR spectra. The four PCP-Cs exhibited antioxidant activity, and their ability to scavenge radicals (hydroxyl and DPPH) and chelate ferrous ions was positively correlated with the degree of carboxymethylation. As the content of -COOH groups in the PCP-Cs increases, their ability to regulate the growth of calcium oxalate (CaOx) crystals was enhanced, thus inhibiting the growth of calcium oxalate monohydrate (COM) crystals and inducing the formation of more calcium oxalate dihydrate (COD) crystals. The formed CaOx crystal was more round and blunt, the absolute value of the Zeta potential on the crystal surface increased, and the aggregation between crystals was inhibited. Thermogravimetric analysis curves showed that the proportions of PCP-C0, PCP-C1, PCP-C2, and PCP-C3 incorporated into the crystal were 20.52%, 15.60%, 10.65%, and 9.78%, respectively, in the presence of 0.4 g/L PCP-Cs. PCP-C protection resisted oxidative damages of human kidney proximal tubular epithelial cells (HK-2) caused by oxalate, resulting in increased cell viability and superoxide dismutase activity and decreased reactive oxygen species levels, malondialdehyde content, and 8-hydroxy-deoxyguanosine expression. Hence, PCP-Cs, especially PCP-C3, can inhibit the formation of CaOx crystals and may have the potential to be an alternative antistone drug.

Carboxymethylation of Corn Silk Polysaccharide and Its Inhibition on Adhesion of Nanocalcium Oxalate Crystals to Damaged Renal Epithelial Cells

“…The higher the degree of carboxymethylation, the higher the carboxyl content and the better the performance of the antioxidant activity. 49 Our previous studies 26 showed that corn silk polysaccharide showed the strongest antioxidant activity when its molecular weight was 6.0 kDa (in the range of 2.0−124 kDa), and it could inhibit the transformation of calcium oxalate dihydrate (COD) crystals into calcium oxalate monohydrate (COM) crystals. In this study, the performance of corn silk polysaccharide is similar to that of Poria cocos polysaccharide.…”

Extraction optimization, physicochemical characterization, and antioxidant activity of polysaccharides from Rhodosorus sp. SCSIO-45730

“…Henceforth, the chelating influence on ferrous ions has been lately broadly used to assess some antioxidant activity of polysaccharides (Huang et al 2021 ). The iron-chelating ability of polysaccharides may be associated with the formation of cross-bridges between the carboxyl group in uronic acid and the divalent ions (Li et al 2021 ). The chelating rate of a novel heteropolysaccharide obtained from A. pubescens root was close to our present investigation at 2.0 mg mL −1 (Yuan et al 2020b ).…”

Structural Elucidation, Modification, and Structure-Activity Relationship of Polysaccharides in Chinese Herbs: A Review

“…After carboxymethylation, the molecular weight of polysaccharide from Cyclocarya paliurus decreased and correspondingly the molar ratio of monosaccharide composition changed ( 144 ). Among carboxymethylated polysaccharides, the antioxidant activity aims to terminate free radicals against oxidation reactions from occurring by increasing the ability of chelating transition metal ions and providing single electron or hydrogen atoms with the increased content of -COOH ( 145 ). It is worth mentioning that there is a positive correlation between antioxidant activity and the degree of carboxymethylation within a certain range ( 146 ).…”