Acetobacter syzygii CCTCC M 2022983 was isolated and characterized from Tibetan kefir grains, which is utilized as a functional food with diverse bioactive properties. After 6 days of fermentation by A. syzygii, Acetobacter fermented extract (AFE) showed significantly higher antioxidant, anti-tyrosinase, and anti-melanin effects compared to the unfermented yeast extract (UFY). Western blotting confirmed that AFE reduced melanogenesis-related proteins (MITF, TYR, TRP-1, TRP-2). LC-MS/MS analysis identified 4-hydroxybenzoic acid as abundant in AFE, contributing to its antioxidant capacity. Succinic acid and citric acid emerged as the major compound and a type of mixed inhibitor against mushroom tyrosinase, with IC50 values of 2.943 mM and 1.615 mM, respectively. Fluorescence spectra analysis revealed that these acids caused conformational changes in tyrosinase. Moreover, succinic acid and citric acid prevented L-DOPA from auto-oxidation with IC50 values of 0.355 mM and 0.261 mM, respectively. Molecular docking analysis suggested that these acids interacted with the association of the H and L subunits of tyrosinase, thereby reducing its stability. In B16-F10 cells, succinic and citric acids significantly reduced melanin production in a dose-dependent manner. Thus, succinic acid and citric acid revealed promising potential for applications in the food and medicine industries as melanogenesis inhibitors due to their safety.

Taxifolin, a natural flavonoid, consistently exerts cytoprotective effects against various oxidative stresses. In this study, we systematically evaluated its photoprotective efficacy and underlying mechanisms against ultraviolet B (UVB)-induced injury in human immortalized keratinocytes (HaCaT). Cell viability and apoptosis were assessed by MTT, fluorescence staining, and flow cytometry, while integrative transcriptomic and proteomic analyses were employed to identify core pathways and key mediators. Taxifolin exhibited antioxidant capacity comparable to that of ascorbic acid under identical in vitro radical-scavenging assays. Moreover, it displayed a strong absorption peak at 289 nm that overlaps the UVB spectrum (280–320 nm), enabling it to act as a chemical sunscreen. In UVB-challenged HaCaT cells, taxifolin markedly reduced intracellular reactive oxygen species (ROS) and attenuated JNK/p38 MAPK activation, as evidenced by Western blot, thereby breaking the ROS-MAPK vicious cycle. Multi-omics revealed that taxifolin was associated with attenuation of UVB-imposed G1/S arrest concomitant with restored Cyclin expression, while up-regulating MYC, FOXQ1, HMOX1 and AP-1 components c-Jun/c-Fos and thereby switching on a pro-survival transcriptional program. Consequently, apoptosis was suppressed and survival was significantly improved. Collectively, taxifolin integrated chemical filtration, ROS scavenging and signaling modulation to support a multi-target photoprotective network, which provides mechanistic insight into taxifolin-mediated cytoprotection and identifies candidate molecular nodes for further validation.

Meconopsis quintuplinervia is traditionally used in Tibetan medicine for diseases of the lung and liver. This study investigated the antioxidant and anti-inflammatory activities of its extract (MQ extract), analyzed its chemical composition, and explored the potential therapeutic mechanisms against chronic obstructive pulmonary disease (COPD) and non-alcoholic fatty liver disease (NAFLD) using network pharmacology. MQ extract demonstrated effective scavenging of DPPH and ABTS radicals, with activity comparable to ascorbic acid and Trolox. In cellular assays, the extract dose-dependently reduced ROS levels in H₂O₂-induced B16-F10 and RAW264.7 cells and significantly inhibited NO production in LPS-stimulated RAW264.7 macrophages. Quantitative analysis showed total phenolic content of 90.54 ± 0.91 mg/g and total flavonoid content of 44.48 ± 0.43 mg/g. LC-MS/MS analysis identified taxifolin as the predominant constituent at approximately 2.39%. Network pharmacology and molecular docking studies revealed that flavonoids including catechin, isorhamnetin, kaempferol, luteolin, naringenin, nobiletin, quercetin, and taxifolin interacted with therapeutic targets for COPD and NAFLD. These compounds likely exerted effects by inhibiting NF-κB signaling, downregulating pro-inflammatory cytokines (TNF-α, IL-6, IL-1β), and enhancing antioxidant enzyme activities (SOD), while also reducing hepatic lipid accumulation through SREBP-1 suppression. Our findings elucidated why Tibetan medicine traditionally uses M. quintuplinervia to treat pulmonary and hepatic disorders.