Optimized Degradation and Inhibition of α-glucosidase Activity by Gracilaria lemaneiformis Polysaccharide and Its Production In Vitro

Abstract

Gracilaria lemaneiformis polysaccharide (GLP) exhibits good physiological activities, and it is more beneficial as it is degraded. After its degradation by hydrogen peroxide combined with vitamin C (H2O2-Vc) and optimized by Box–Behnken Design (BBD), a new product of GLP-HV will be generated. While using GLP as control, two products of GLP-H (H2O2-treated) and GLP-V (Vc-treated) were also produced. These products chemical characteristics (total sugar content, molecular weight, monosaccharide composition, UV spectrum, morphological structure, and hypolipidemic activity in vitro) were assessed. The results showed that the optimal conditions for H2O2-Vc degradation were as follows: H2O2-Vc concentration was 18.7 mM, reaction time was 0.5 h, and reaction temperature was 56 °C. The total sugar content of GLP and its degradation products (GLP-HV, GLP-H and GLP-V) were more than 97%, and their monosaccharides are mainly glucose and galactose. The SEM analysis demonstrated that H2O2-Vc made the structure loose and broken. Moreover, GLP, GLP-HV, GLP-H, and GLP-V had significantly inhibition effect on α-glucosidase, and their IC50 value were 3.957, 0.265, 1.651, and 1.923 mg/mL, respectively. GLP-HV had the best inhibition effect on α-glucosidase in a dose-dependent manner, which was the mixed type of competitive and non-competitive. It had a certain quenching effect on fluorescence of α-glucosidase, which may be dynamic quenching.

Structural characterization and hypolipidemic activity of Gracilaria lemaneiformis polysaccharide and its degradation products

“…The concentrated solution was precipitated, dialyzed (7 kDa) and freeze-drying. Then GLP was obtained ( Long et al, 2021b ).…”

“…GLP was degraded by H 2 O 2 -Vc (mole ratio of H 2 O 2 and Vc was 1:1). In brief, GLP (5 mg/mL) and 18.7 mM of H 2 O 2 -Vc reacted at 56 ℃ for 0.5 h according to previous research ( Long et al, 2021b ). The degradation reaction was terminated by adjusting pH to neutral.…”

“…Extraction rate was referred to the mass ratio of lyophilized polysaccharide to raw material. The content of galacturonic acid and glucuronic acid were detected by high performance liquid (HPLC) ( Long et al, 2021b ).…”

“…Moreover, vitamins C (Vc) facilitates this process by reinforcing H 2 O 2 to produce hydroxyl groups ( Yan et al, 2021 ). The polysaccharide of G. lemaneiformis treated by H 2 O 2 -Vc showed the best hypoglycemic activity in vitro , and the molecular weight became lower and reducing sugar reinforced after degradation, compared with polysaccharide ( Long et al, 2021b ). In addition, polysaccharide manifested the better antioxidant and anti-tumor activities after degraded by H 2 O 2 -Vc, reported by Chen et al, 2020 , Shen et al, 2019 , respectively.…”

Physicochemical Characterization of Fucoidans from Sargassum henslowianum C.Agardh and Their Antithrombotic Activity In Vitro

“…According to the method reported by Long et al [ 45 ], the composition of monosaccharides was determined by high performance liquid chromatography (HPLC, Agilent 1100, Santa Clara, CA, USA) with ZORBAX Eclipse column as XDB-C18 column (4.6 × 250 mm, 5 μm). Fucoidan was added with 1 mL trifluoroacetic acid and sealed immediately after being filled with nitrogen and hydrolyzed at 110 °C for 8 h. Then, it was dried with nitrogen, and 1 mL of ultra-pure water was added to obtain the polysaccharide solution.…”