Fig 1.
HPLC chromatogram of the black rice extract detected at 520 nm.
Peak 1, cyanidin-3,5-diglucoside; Peak 2, not identified; Peak 3, cyanidin-3-glucoside; Peak 4, cyanidin-3-rutinoside; Peak 5, peonidin-3-glucoside; and Peak 6, peonidin-3-rutinoside.
Fig 2.
MS, MS/MS spectra of the six peaks in the HPLC analysis and the chemical structure of the anthocyanin monomers detected in the black rice extract.
a (Peak 1), cyanidin-3,5-diglucoside; b (peak 2), not identified; c (peak 3), cyanidin-3-glucoside; d (peak 4), cyanidin-3-rutinoside; e (peak 5), peonidin-3-glucoside; and f (peak 6), peonidin-3-rutinoside.
Fig 3.
Purification and verification of C3G.
(a) Pre-HPLC chromatogram of black rice anthocyanin extract; (b) HPLC chromatogram of C3G purified by Pre-HPLC; (c) MS spectrum of C3G purified by Pre-HPLC; (d) HPLC chromatogram of C3G standard.
Fig 4.
Effect of BRAE and C3G on the pH of diverse bacterial media under anaerobic conditions at 37 °C for 48 h.
(a) B. bifidum; (b) B. adolescentis; (c) B. infantis; (d) L. acidophilus. Data were obtained from three independent experiments and represent the mean values and SD. Different lowercase letters indicate significant differences (P < 0.05) in the media pH values with different concentrations of the same microorganism.
Table 1.
Numbers (log10 cell/mL) of Bifidobacteria and Lactobacilli groups in anaerobic fermentation broth containing C3G and BRAE at 37 °C for 48 h.
Fig 5.
Proposed metabolic pathway of C3G based on the metabolites detected in the Bifidobacteria and Lactobacilli fermentation broth.
Blue metabolites were detected, and grey metabolites were not detected in the GC-MS experiment.
Table 2.
C3G metabolites produced by Bifidobacteria and Lactobacilli through GC-MS after BSTFA derivatization.
Table 3.
Relative content of C3G metabolites produced by Bifidobacteria and Lactobacilli at different incubation times in anaerobic conditions at 37 °C.