This study prepared high-purity Z-astaxanthin (Z-AST) by successive iodine-induced isomerization, ethanol extraction, and column chromatography. The interaction between AST and α-amylase as a key regulatory factor for blood sugar reduction was taken as a starting point to investigated the differences in the inhibitory activity of astaxanthin isomers against porcine pancreatic α-amylase (PPAA) and the underlying mechanism by enzyme inhibition assays, spectroscopic techniques and molecular docking. The results demonstrated that high-purity 9Z-AST (95.07%) and 13Z-AST (90.87%) were successfully prepared and identified. Z-AST exhibited a significantly stronger inhibitory effect on PPAA activity compared with all-E-AST (P < 0.05). Interaction studies revealed that the binding of astaxanthin isomers to PPAA caused only minor changes in the microenvironment of tryptophan (Trp) residues without significant alteration in protein conformation. Molecular docking analysis showed that the binding sites of astaxanthin isomers were located within the catalytic pocket of PPAA, coinciding with the binding site of the competitive inhibitor acarbose, and interacted with key amino acid residues at the enzyme’s catalytic center, namely Asp197, Glu233, and Asp300. This indicated that the inhibition of PPAA by astaxanthin isomers was competitive in nature. The fluorescence of PPAA was statically quenched after binding with astaxanthin isomers. Furthermore, the major interaction forces between PPAA and astaxanthin isomers were identified as van der Waals forces, hydrogen bonds, and hydrophobic interactions, and both isomers formed hydrogen bonds with the Glu233 residue. Notably, Z-AST exhibited shorter hydrogen bonds, indicating a stronger hydrogen bonding interaction. Additionally, Z-AST demonstrated higher binding affinity, interacted with more amino acid residues, and exhibited lower thermodynamic parameters compared with all-E-AST. This suggests that Z-AST possesses a stronger binding activity to PPAA, resulting in a more inhibition effect on the enzyme activity compared with all-E-AST. The findings contribute to the understanding of the differences in hypoglycemic activity between astaxanthin isomers and the potential mechanism, holding significant implications for the development of novel functional foods and hypoglycemic agents.

To simultaneously improve the extraction rate of grape pomace oil and the retention rate of active substances, this study combined acid-thermal (AT) pretreatment with low-temperature continuous phase-transition extraction (LCPE) to prepare grape pomace oil (GPO). To evaluate the extraction effectiveness, the extraction yield, physicochemical properties, contents of major active components, and in vitro antioxidant activity of GPO were determined. Furthermore, its anti-aging activity in Caenorhabditis elegans with oxidative stress induced by four factors was ascertained and its components were characterized by gas chromatography-orbitrap mass spectrometry and ultra-high performance liquid chromatography-quadrupole high-resolution mass spectrometry. The results showed that compared with LCPE, solvent extraction and AT-assisted solvent extraction, AT-LCPE resulted in higher extraction yield of GPO (96.70%) with increased contents of total phenols, total flavonoids, and total sterols (by 104.68%–184.78%, 32.74%–186.46%, and 75.76%–129.09%, respectively) and decreased half maximal inhibitory concentration (IC₅₀, by 68.48%–84.29%) against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. GPO prepared by AT-LCPE significantly prolonged the lifespan of C. elegans with oxidative stress induced by H₂O₂, paraquat, heat, and ultraviolet B radiation (UVB), extending the average lifespan by up to 33.09% (P＜0.001). Furthermore, a total of 103 and 123 compounds were identified by the above mass spectrometry techniques, respectively; the most abundant ones were fatty acids and esters, followed by terpenoids and terpenes. GPO was rich in various substances, including typical active substances such as linoleic acid, oleanolic acid, β-tocotrienol, and β-sitosterol, rare components such as squalene and ceramide, and other components such as soyasapogenol E, ganoderic acid F, and ganoderiol I, which were discovered in the oil for the first time. Therefore, AT-LCPE is an effective measure to achieve the simultaneous and efficient extraction of oils and active components, and AT-LCPE GPO has high quality and excellent efficacy. The findings provide a theoretical basis and technical support for the high-value development and utilization of grape pomace.