Relationship Between the Structure and Immune Activity of Components From the Active Polysaccharides APS-II of Astragali Radix by Enzymolysis of Endo α-1,4-Glucanase

Ke Li; Xue-Qin Li; Guang-Xin Li; Lian-Jie Cui; Xue-Mei Qin; Zhen-Yu Li; Yu-Guang Du; Yue-Tao Liu; Ai-Ping Li; Xing-Yun Zhao; Xin-Hui Fan

doi:10.3389/fphar.2022.839635

Relationship Between the Structure and Immune Activity of Components From the Active Polysaccharides APS-II of Astragali Radix by Enzymolysis of Endo α-1,4-Glucanase

Front Pharmacol. 2022 Feb 25:13:839635. doi: 10.3389/fphar.2022.839635. eCollection 2022.

Authors

Ke Li^{1

2

3

4}, Xue-Qin Li^{1

3

4}, Guang-Xin Li⁵, Lian-Jie Cui^{1

3

4}, Xue-Mei Qin^{1

3

4}, Zhen-Yu Li^{1

3

4}, Yu-Guang Du², Yue-Tao Liu^{1

3

4}, Ai-Ping Li^{1

3

4}, Xing-Yun Zhao^{1

3

4}, Xin-Hui Fan^{1

3

4}

Affiliations

¹ Modern Research Center for Traditional Chinese Medicine, Shanxi University, Taiyuan, China.
² Institute of Process Engineering, Chinese Academy of Sciences, Beijing, China.
³ The Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Shanxi University, Taiyuan, China.
⁴ Shanxi Key Laboratory of Active Constituents Research and Utilization of TCM, Shanxi University, Taiyuan, China.
⁵ College of Agriculture, Shanxi Agricultural University, Taiyuan, China.

Abstract

Astragali Radix polysaccharides (APSs) have a wide range of biological activities. Our preliminary experiment showed that APS-Ⅱ (10 kDa) was the main immunologically active component of APSs. However, the characteristic structure related to activity of APS-Ⅱ needs further verification and clarification. In this study, APS-II was degraded by endo α-1,4-glucosidase. The degraded products with different degrees of polymerization [1-3 (P1), 3-6 (P2), 7-14 (P3), and 10-18 (P4)] were obtained using a polyacrylamide gel chromatography column. The structural features of the different products were characterized by HPGPC, monosaccharide composition, Fourier transform infrared spectrum, GC-MS, nuclear magnetic resonance, and UPLC-ESI-QTOF-MS analysis. Specific immune and non-specific immune cell tests were used to identify the most immunogenic fractions of the products. The backbone of P4 was speculated to be α-D-1,4-linked glucans and rich in C2 (25.34%) and C6 (34.54%) branches. Immune screening experiments indicated that the activity of P4 was better than that of APS-II and the other three components. In this research, the relationship between the structure of APS-Ⅱ and the immune activity from the degradation level of polysaccharides was studied, laying a foundation for the quality control and product development of APSs.

Keywords: APS-Ⅱ; enzymolysis; immune activity; structure analysis; structure-activity relationship.