Auricularia auricula Peptides Nutritional Supplementation Delays H2O2-Induced Senescence of HepG2 Cells by Modulation of MAPK/NF-κB Signaling Pathways.

Auricularia auricula is a traditional medicinal and edible mushroom with anti-aging effects. Many studies focused on polysaccharides and melanin. However, the anti-aging effects and mechanism of the nutritional supplementation of Auricularia auricula peptides (AAPs) were not elucidated. In this study, AAPs were prepared by enzymolysis of flavor protease and the protective effects on H2O2-induced senescence of HepG2 cells were explored for the first time. The potential mechanism was also investigated. AAPs were mostly composed of low molecular weights with less than 1000 Da accounting for about 79.17%, and contained comprehensive amino acids nutritionally, including seven essential amino acids, aromatic, acidic, and basic amino acids. AAPs nutritional supplementation could significantly decrease the levels of intracellular reactive oxygen species (ROS) and malondialdehyde (MDA), and increase the activities of antioxidant enzymes (SOD, CAT, and GSH-Px). In addition, the senescence-associated-ß-galactosidase (SA-ß-gal) activity was restrained, and the expression levels of senescence-associated secretory phenotype (SASP) (IL-6, IL-8, IL-1ß, and CXCL2) were also decreased. Ribonucleic acid sequencing (RNA-Seq) was carried out to screen the differentially expressed genes (DEGs) between different groups. GO and KEGG enrichment analysis showed that the mechanism was related to the MAPK/NF-κB signaling pathways. Quantitative real-time PCR (qRT-PCR) analysis and Western blot were carried out to verify the key genes and proteins in the pathways, respectively. AAPs nutritional supplementation resulted a significant down-regulation in key the genes c-fos and c-jun and up-regulation in DUSP1 of the MAPK signaling pathway, and down-regulation in the key genes CXCL2 and IL-8 of the NF-κB signaling pathway. The results of Western blot demonstrate that AAPs nutritional supplementation could inhibit MAPK/NF-κB pathways by reducing the expression levels of IKK, IκB, P65, and phosphorylation of ERK, thus decreasing the inflammatory reaction and delaying cell senescence. It is the first time that AAPs nutritional supplementation was proved to have protective effects on H2O2-induced oxidative damage in HepG2 cells. These results implicate that dietary AAPs could be used as nutrients to reduce the development or severity of aging.

Reducing toxic constituents of ginkgolic acid content and improving bioactive flavonoid content from Ginkgo biloba leaves by high-temperature pretreatment processing.

High-temperature pretreatment was developed in this article to remove the main toxic constituents of ginkgolic acids (GAs) from Ginkgo biloba leaves (GBLs) and improve the bioactive flavonoid content by water extraction. To optimize the effects of high-temperature pretreatment process parameters on removing toxic GAs to a limited level and improving the content of bioactive flavonoids, a Box-Behnken design (BBD) combined with response surface methodology (RSM) was also conducted. The results showed that the content of GAs could be reduced to 4.11 ppm and the highest content of flavonoids could reach 3.51% under the optimized conditions of high-temperature pretreatment process of 177°C with water extraction at 96°C at a liquid-to-solid ratio of 56:1. The content of toxic GAs substantially decreased by 83.50% while the content of bioactive flavonoids increased by 44.30% compared with the conventional water extraction method. Moreover, the new process was more efficient, environmentally friendly, and could get avoid a subsequent multi-step process of removing toxic GAs. The crude extracts were then purified by macroporous resin to obtain the 60% ethanol fraction. After purification, the flavonoid content increased to 43.50% while the GAs were not detected. The main compounds of 60% ethanol fraction were identified by UPLC-QTOF-MS/MS. Antioxidant activities including reducing powder, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, and OH· scavenging assays all showed that the 60% ethanol fraction was better than the butylated hydroxytoluene (BHT) standard.