Antioxidant and prebiotic activity of five peonidin-based anthocyanins extracted from purple sweet potato (Ipomoea batatas (L.) Lam.)

Abstract

Twelve kinds of anthocyanins from the Chinese purple sweet potato cultivar (Ipomoea batatas (L.) Lam.) were extracted and identified using LC-MS/MS, which had a high content of peonidin-based anthocyanins. Five peonidin-based anthocyanin monomers (P1, P2, P3, P4 and P5) were isolated by preparative liquid chromatography with structural analyses using an Impact II Q-TOF MS/MS. Then, the functional properties of the anthocyanin monomers, such as the antioxidant activities, proliferative effects on probiotics, and their inhibition on harmful bacteria in vitro, were investigated. The peonidin-based components in purple sweet potato anthocyanins (PSPAs) showed good properties regarding scavenging 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals and superoxide anions, and had good potential in reducing the total power activity and Fe²⁺ chelating ability. While the order of the antioxidant abilities was as follows: P4 > P5 > P3 > P2 > P1 > PSPAs. Microbial cultivations showed that P1, P2, P3, P4, P5 and PSPAs could induce the proliferation of Bifidobacterium bifidum, Bifidobacterium adolescentis, Bifidobacterium infantis and Lactobacillus acidophilus, and they inhibited the growth of Staphylococcus aureus and Salmonella typhimurium, suggesting the anthocyanins might have prebiotic-like activity through the modulation of the intestinal microbiota. Our results indicate that peonidin-based anthocyanins could be further utilized in health foods and pharmaceutical developments.

Figure 1

HPLC profile of the anthocyanins extracted from PSP (a), and preparative chromatographic separation of anthocyanins in PSP by gradient elute at 520 nm (b).

Figure 2

Mass spectrometric data and chemical structure of peonidin-based anthocyanins. (a) HPLC-TOF-MS spectrum of P1 (peak 2), (b) HPLC-TOF-MS/MS spectrum of P1 (peak 2), (c) chemical structure of P1 (peak 2).

Figure 3

In vitro antioxidant activities of PSPAs and peonidin-based anthocyanin monomers (P1, P2, P3, P4 and P5). (a) DPPH radical-scavenging ability, (b) superoxide anion radical (O₂⁻·) scavenging ability, (c) total reducing power, (d) chelating ability. Vc was used as positive control in DPPH radical-scavenging ability, superoxide anion radical (O₂⁻·) scavenging ability and total reducing power evaluations. EDTA was used as positive control in the chelating ability evaluation. Different lowercase letters indicate significant differences (P < 0.05) among PSPAs and peonidin-based anthocyanin monomers at same concentration. Different capital letters indicate significant differences (P < 0.05) among different sample concentrations in each sample group.

Figure 4

The inhibitory effect of PSPAs and peonidin-based anthocyanin monomers (P1, P2, P3, P4 and P5) on (a) Staphylococcus aureus, (b) Salmonella typhimurium, respectively. Data were obtained from three independent experiments and represented as mean values.