黄芩多糖的磷酸化修饰及其体外降血糖活性

Phosphorylation modification of polysaccharide from Scutellaria baicalensis Georgi and its hypoglycemic activity in vitro

摘要:

以黄芩多糖（SBP）为原料，综合磷酸根含量与体外降血糖活性的加权值（Q）为考察指标，通过单因素试验优选黄芩多糖磷酸化的工艺参数，比较磷酸化修饰前后黄芩多糖的理化特性和体外降血糖活性。结果表明，在多糖与磷酸化试剂摩尔比1:10，80 ℃磷酸化修饰2 h后黄芩多糖的Q值达最大。在此条件下，平行3组进行验证试验，磷酸化黄芩多糖（SBP-P）的Q值分别为50.25、49.29、49.62，偏差为0.006，在允许误差范围之内。修饰后黄芩多糖SBP-P在IR谱图1237 cm-1处出现了P=O基团的伸缩振动吸收峰，磷酸根含量为（2.74±0.07）%，其它多糖典型特征吸收峰基本保持，说明磷酸化修饰成功且没有影响黄芩多糖的基本结构。相比SBP，磷酸化修饰黄芩多糖SBP-P的分子量增大至4 225 615 g/moL，粒径减小为（307.87±63.06） nm，Zeta电位的绝对值增加至（16.63±1.37）mV，微观形貌从光滑的薄片状变为粗糙的块状堆积。在测试浓度范围内，磷酸化修饰黄芩多糖SBP-P的降血糖活性明显增强（p <0.05），且呈浓度依赖性。当多糖浓度为 4 mg/mL 时，SBP和SBP-P对α-淀粉酶和α-葡萄糖苷酶的抑制率分别为65.13 %、65.19 %和89.39 %、90.29 %，IC50分别为0.676、0.654 mg/mL和0.085、0.080 mg/mL，SBP-P的IC50更接近于阳性对照阿卡波糖（0.021和0.042 mg/mL）。可见，磷酸化修饰可能通过改变黄芩多糖的分子量、粒径、Zeta电位和微观结构等理化特性以增强其水溶性、分散性和稳定性，进而提升其降血糖活性，SBP-P有潜力作为一种餐后血糖调节因子被开发利用在食品、医药等领域。

Abstract:

Using Scutellaria baicalensis polysaccharide (SBP) as the raw material, the weighted value (Q) of the phosphate content and the hypoglycemic activity in vitro was used as the evaluation index. The process parameters for the phosphorylation of SBP were optimized through single-factor experiments, and the physicochemical properties and hypoglycemic activity in vitro before and after the phosphorylation modification of SBP were compared. The results showed that when the molar ratio of polysaccharide to phosphorylation reagent was 1:10 and the phosphorylation modification was carried out at 80 ℃ for 2 h, the Q value of SBP reached its maximum. Under these conditions, three parallel validation experiments were conducted, and the Q values of phosphorylated polysaccharide SBP-P were 50.25, 49.29, and 49.62, respectively, with a deviation of 0.006, which was within the allowable error range. After modification, an absorption peak of the P=O group stretching vibration appeared at 1237 cm-1 in the IR spectrum of SBP-P, with a phosphate content of (2.74±0.07)%. The typical characteristic absorption peaks of polysaccharides were basically maintained, indicating that the phosphorylation modification was successful and did not affect the basic structure of SBP. Compared with SBP, the molecular weight of SBP-P increased to 4 225 615 g/mol, the particle size decreased to (307.87±63.06) nm, the absolute value of the Zeta potential increased to (16.63±1.37) mV, and the micro-morphology changed from a smooth flake shape to a rough blocky aggregation. Within the tested concentration range, the hypoglycemic activity of SBP-P was significantly enhanced (p <0.05), showing a concentration-dependent effect. When the polysaccharide concentration was 4 mg/mL, the inhibition rates of SBP and SBP-P on α-amylase and α-glucosidase were 65.13%, 65.19%, and 89.39%, 90.29%, respectively, with IC50 values of 0.676, 0.654 mg/mL and 0.085, 0.080 mg/mL, in which SBP-P were close to the IC50 of the positive control acarbose (0.021 and 0.042 mg/mL). It can be seen that phosphorylation modification enhances the water solubility, dispersibility, and stability of SBP by changing its molecular weight, particle size, Zeta potential, and microstructure, thereby enhancing its hypoglycemic activity. SBP-P has the potential to be developed and utilized as a postprandial blood sugar regulatory factor in the fields of food and medicine.