Effects of in vitro simulated digestion on the α-glucosidase inhibitory activity, structure, and prebiotic activity of a polysaccharide from Anemarrhena asphodeloides Bunge

Abstract

This study explored the changes in the structure and α-glucosidase inhibitory activity of a non-starch polysaccharide derived from Anemarrhena asphodeloides Bunge, AABP-1B, during digestion in vitro and its effect on host intestinal microbiota. Simulations of digestion in the upper digestive tract showed that the reducing sugar content and molecular weight of AABP-1B changed slightly, though no monosaccharides were detected. AABP-1B was resistant to degradation in the simulated upper gastrointestinal environments, retained strong α-glucosidase inhibitory activity after digestion, which may be related to the lack of structural changes. In in vitro fermentation, AABP-1B enhanced the growth of commensal microorganisms, including Bacteroides, Megasphaera, and Prevotella, while inhibiting the proliferation of pathogenic bacteria, such as Escherichia-Shigella. Fermentation of AABP-1B by gut microbes resulted in a notable increase in short-chain fatty acid contents and a decrease in pH levels. Our findings showed that AABP-1B promotes intestinal health and may serve as a prebiotic in the development of functional food.

Keywords: Anemarrhena asphodeloides Bunge polysaccharide; digestive property; intestinal microbiota; structure; α-glucosidase.

Figure 1

(A) Changes in Mw of AABP-1B during simulated digestion in saliva; (B) stomach; (C) and intestinal fluid; (D) changes in free monosaccharide contents during digestion.

Figure 2

Changes in reducing sugar contents in simulated digestion. Values were mean ± SD (n = 3). Different superscript letters within columns indicate differences (p < 0.05).

Figure 3

Inhibitory activity of AABP-1B on α-glucosidase before and after digestion; Values represent mean ± standard deviation. Different superscript lowercase letters indicated significance (p < 0.05) in each column.

Figure 4

Variations in pH during fermentation of AABP-1B; values represent mean ± standard deviation; different superscript lowercase letters indicated significance (p < 0.05) in each column.

Figure 5

Variations in SCFA concentrations during fecal fermentation; values were mean ± SD (n = 3); different superscript letters within columns indicate differences (p < 0.05).

Figure 6

(A) Rank abundance; (B) Shannon curves; (C) hierarchical clustering tree based on OTUs; (D) PCoA.

Figure 7

Phylum-level distribution of gut microbiota. OR was blank medium fermentation for 0 h; BLK-6, BLK-12, BLK-24, IN-6, IN-12, IN-24, AABP-1B-6, AABP-1B-12 and AABP-1B-24 were blank medium, Inulin medium, AABP-1B medium fermentation for 6 h, 12 h and 24 h, respectively.

Figure 8

Gut microbiota analysis of AABP-1B during in vitro fermentation based on heat map at genus level; OR was blank medium fermentation for 0 h; BLK-6, BLK-12, BLK-24, IN-6, IN-12, IN-24, AABP-1B-6, AABP-1B-12 and AABP-1B-24 were blank medium, Inulin medium, AABP-1B medium fermentation for 6 h, 12 h and 24 h, respectively.

Figure 9

The differences in gut microbes were compared based on LEfSe; LEfSe among Blank 0 (OR), Blank 24 (BLK-24), Inulin 24 (IN-24) and AABP-1B 24 (AABP-1B-24) at OTUs level; Blank 0 was blank medium fermentation for 0 h, Blank 24, Inulin 24, AABP-1B 24 was blank medium, Inulin medium, AABP-1B medium fermentation for 24 h, respectively.

Figure 10

LDA score; LDA among Blank 0 (OR), Blank 24 (BLK-24), Inulin 24 (IN-24) and AABP-1B 24 (AABP-1B-24) at OTUs level; Blank 0 was blank medium fermentation for 0 h, Blank 24, Inulin 24, AABP-1B 24 was blank medium, Inulin medium, AABP-1B medium fermentation for 24 h, respectively.