Insoluble dietary fiber (IDF) and soluble dietary fiber (SDF) from Auricularia cornea var. Li. were extracted by alkaline or enzymatic extraction. Our aim was to compare the effects of the two extraction methods on the structural, physicochemical and functional properties of dietary fiber. Scanning electron microscopy (SEM) analysis showed that dietary fiber extracted by enzymatic extraction method had a looser and more complex structure. Fourier transform infrared spectroscopy (FTIR) indicated that all samples showed the characteristic absorption peaks of sugar. X-ray diffraction analysis (XRD) showed that enzymatically extracted dietary fiber had lower crystallinity. Thermogravimetric analysis (TGA) demonstrated that alkaline extracted dietary fiber had higher stability. Enzymatically extracted dietary fiber had waterholding capacity of 10.68–20.79 g/g, oil-holding capacity of 2.05–3.72 g/g, swelling power of 2.85–12.14 mL/g, glucose content of 4.92–7.95 μg/g and cholesterol-adsorbing capacity of 3.89–8.19 mg/g, which were significantly higher than those of dietary fiber extracted by alkaline method, and it had a stronger inhibitory effect on α-amylase (45.43%–66.71%) and pancrelipase (21.50%–36.52%). These results reveal that the dietary fiber of A. cornea var. Li. can be used as a functional food ingredient. This study provides a theoretical basis for further exploring the nutritional value of A. cornea var. Li..

This study was implemented in order to explore the effect of ultrasound-assisted H₂O₂-Vitamin C (VC) degradation on ginseng polysaccharides (GPS). GPS were extracted from ginseng by water extraction followed by alcohol precipitation and separated and purified by DEAE-52 cellulose and Sephadex G-100 column chromatography. Fraction GPS-1A was degraded into a low-molecular-mass polysaccharide DGPS-1A under the following conditions: sample concentration 4.2 mg/mL, H₂O₂-VC concentration 10.3 mmol/L and ultrasound power 1006 W. Meanwhile, the structural characteristics of GPS-1A and DGPS-1A, their inhibitory effects on major starch digestive enzymes and their antioxidant activities were studied. The results showed that the relative molecular masses of GPS-1A and DGPS-1A were 135 and 77.8, respectively, but the composition of monosaccharides did not change after ultrasound-assisted H₂O₂-VC degradation. The Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectra also showed that the major functional groups of the polysaccharide were not damaged after degradation. In addition, DGPS-1A showed stronger in vitro antioxidant and hypoglycemic activities than did GPS-1A. At the maximum concentration (6 mg/mL), the inhibition rates of α-glucosidase and α-amylase and the scavenging rates of 1,1-diphenyl-2-trichrophenylhydrazine radical (DPPH) and hydroxyl radical by DGPS-1A were (90.83 ± 3.04)%, (78.03 ± 2.29)%, (89.56 ± 1.17)% and (76.85 ± 1.63)%, compared to only (65.16 ± 2.53)%, (54.04 ± 1.97)%, (31.77 ± 2.42)% and (30.85 ± 2.29)% with GPS-1A, respectively. Moreover, the reducing power of DGPS-1A was 2.03 times higher than that of GPS-1A. These results indicate that ultrasound-assisted H₂O₂-VC degradation of ginseng polysaccharides has potential application in the development of functional foods with antioxidant and hypoglycemic activities.

In this study, the fermentation supernatant, cells and disrupted cell supernatant of five strains of lactic acid bacteria (LAB) were screened for tyrosinase inhibitory activity and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity. The results showed that the tyrosinase inhibitory activity of the fermentation supernatant was much higher than that of the cells and the disrupted cell supernatant. The percentage inhibition of tyrosinase activity by the fermentation supernatant of strain MNJ-9 was 68.9% compared to only 50.9% with the cells and 34.8% with the disrupted cell supernatant. The fermentation supernatant of strain MNJ-9 scavenged 93.1% of DPPH radical. Meanwhile, MNJ-9 was identified by 16S rDNA gene sequencing. The major components of the fermentation supernatant of MNJ-9 were investigated using untargeted metabolomics based on liquid chromatography-mass spectrometry (LC-MS). The tyrosinase inhibitory activity and DPPH radical scavenging capacity of 10 of the major components were measured. The results showed that 5-aminovaleric acid had the highest tyrosinase inhibitory activity and DPPH radical scavenging capacity. The cytotoxicity of 5-aminovaleric acid on mouse melanoma cells (B16F10), and its impact on the melanin content and tyrosinase activity of B16F10 cells were determined to evaluate its whitening ability. The results showed that the cell survival rate was equal to or over 80% after culture for 72 h with 70 μg/mL of 5-aminovaleric acid, indicating no apparent cytotoxicity. At 5-aminovaleric acid concentrations of 10-70 μg/mL, the intracellular melanin content and tyrosinase activity were 85.4%-45.2% and 76.53%-40.5%, respectively. This indicates that 5-aminovaleric acid has some whitening ability.