Antioxidant Activity of Vitis davidii Foex Seed and Its Effects on Gut Microbiota during Colonic Fermentation after In Vitro Simulated Digestion

Abstract

Vitis davidii Foex whole seed (VWS) is a by-product during the processing of grape products, which is rich in bioactive compounds that have great potential in the food industry. In this study, the bioactive compounds and antioxidant activity of VWS were determined, and their dynamic changes during in vitro colonic fermentation were also investigated after VWS subjected to in vitro simulated digestion. Results showed that VWS were rich in polyphenols (23.67 ± 0.52 mg GAE/g), flavonoids (13.13 ± 1.22 mg RE/g), and proanthocyanidins (8.36 ± 0.14 mg CE/g). It also had good DPPH and ABTS radical scavenging activity, which reached 82.10% and 76.10% at 1000 μg/mL. The alteration trend of the antioxidant activity during in vitro fermentation for 24 h was consistent with that of the content of bioactive substances, such as polyphenols, with the extension of fermentation time. The bioactive compounds and antioxidant activity showed a trend of increasing and then decreasing, reaching the highest value at 8 h. The high-throughput sequencing analysis of the regulatory effect of VWS on intestinal micro-organisms revealed that VWS influenced intestinal microbiota diversity. The relative abundance of beneficial microbiota, such as Blautia and Parabacteroides, increased by 4.1- and 1.65-fold after 24 h of fermentation compared with that of the control group. It also reduced Escherichia-Shigella by 11.23% and effectively reduced host inflammation, while increasing the contents of acetic acid, propionic acid, and other metabolites. Taken together, these results reveal the value of VWS utilization and provide new insights into the nutritional and microbiota modulation effects of VWS, which could therefore serve as a nutraceutical ingredient in health promotion.

Keywords: Vitis davidii Foex seed; antioxidants; bioactive substances; in vitro digestion; in vitro fermentation; short-chain fatty acids.

Figure 1

Diagram of VWS digestion and fermentation in vitro.

Figure 2

Active substance content of VWS.

Figure 3

In vitro antioxidant activity of VWS. (A) DPPH radical scavenging activity; (B) ABTS radical cation scavenging activity; (C) Ferric reducing antioxidant power; (D) Hydroxyl radical scavenging activity.

Figure 4

In vitro antioxidant activity of fermentation broth during in vitro fermentation. (A) ABTS and DPPH radical scavenging activity; (B) Hydroxyl radical scavenging activity and ferric reducing antioxidant power. Means with different letters in figures were significantly different at p < 0.05.

Figure 5

LEfSe analysis (A) LEfSe evolutionary branching diagram (red nodes indicate enrichment in C24, while green nodes indicate enrichment in G24) (B) Histogram of LDA value distribution (LDA > 4).

Figure 6

Changes in the relative abundance of intestinal microbiota. (A) Species distribution map at the phylum level; (B) species distribution map at the genus level; (C) analysis of differences in microbial composition at the phylum level for 24 h in vitro fermentation; (D) analysis of differences in microbial composition at the genus level for 24 h in vitro fermentation (p < 0.05).

Figure 7

Heatmap of the correlation between TPC, TFC, and OPC in group GS and changes in intestinal micro-organisms during fermentation.

Figure 8

Change of pH during in vitro fermentation. Means with different letters in figures were significantly different at p < 0.05.

Figure 9

Change of SCFAs concentration during in vitro fermentation. (A) Formic acid concentration; (B) Acetic acid concentration; (C) Propionic acid concentration; (D) Butyric acid concentration. Means with different letters in figures were significantly different at p < 0.05, * p < 0.05.