Yujuan Xu

Marine-derived bioactive peptides are promising natural enzyme inhibitors, but their functional robustness and inhibition behavior require experimental validation. Golden pompano (Trachinotus anak) muscle proteins were subjected to ultrasound-assisted neutral protease–papain hydrolysis, activity-guided ultrafiltration, LC–MS/MS identification, and synthetic-peptide validation. The 2+ chelation) and was selected for LC–MS/MS. Five candidate peptides were synthesized after stepwise prioritization. VTPPHVE showed the lowest IC₅₀ value for tyrosinase inhibition (113.41 μM) and exhibited the strongest apparent Cu²⁺-chelating activity among the synthesized peptides (141.54 μM). VTPPHVE retained comparable inhibitory activity after pH 2–10 treatment and heating at 20–100 °C, and showed detectable apparent activity after simulated gastrointestinal treatments, although the digested samples were not normalized to an equivalent peptide concentration at the assay stage and digestion-fluid blanks were not included. Enzyme kinetics indicated mixed-type inhibition, with a concentration-dependent decrease in apparent Vmax and an increase in apparent Km. Molecular docking placed VTPPHVE in an inter-chain surface region spanning H-subunit chains A and B, while a 100 ns molecular dynamics simulation supported the dynamic persistence of the docking-derived model after initial conformational adjustment. These results identify VTPPHVE as a marine fish-derived tyrosinase-inhibitory peptide and extend its characterization from sequence-level discovery to functional activity retention, enzyme kinetics, and exploratory structural modeling.

Finger Citron (Citrus medica L. var. sarcodactylis Swingle) holds significant potential as both a culinary ingredient and a traditional medicinal remedy; however, its precise molecular mechanisms of action remain largely unexplored. This study investigates the anti-inflammatory properties of Finger Citron extract (FCE) in RAW 264.7 macrophages stimulated by lipopolysaccharide (LPS). Using UPLC-ESI-QTF-MS, we analyzed the extract’s composition, revealing a rich presence of polyphenols and polysaccharides, with hesperidin, melitidin, and hesperetin as the predominant polyphenolic compounds. Additionally, the study elucidated the monosaccharide composition profile of polysaccharides in the extract. Furthermore, Finger Citron extract markedly suppressed the production of key inflammatory mediators, including TNF-α, IL-6, and NO. The inhibition of protein phosphorylation levels of inhibiting the mitogen-activated protein kinase (MAPK) and nuclear factor kappa-B (NF-κB) signaling was also observed, indicating that the anti-inflammatory effects of Finger Citron extract may involve the NF-κB and MAPK signaling pathway. Given these findings, Finger Citron extract has the potential to act as a natural product with anti-inflammatory activity.

Citri Grandis Exocarpium (CGE), is renowned for its dual use in medicine and food, being well-known for its beneficial antioxidant and anti-inflammatory effects. However, the changes of chemical composition and antioxidant activity of CGE during the storage (aging) process are still unclear. In this study, We examined the changes in metabolites of CGE samples aged for 1 year (CG1), 3 years (CG3) and 5 years (CG5), mainly through comprehensive metabolomics techniques. The results indicated that analysis of CGE extracts by ultra-high-performance liquid chromatography-quadrupole/time of flight mass spectrometry (UHPLC-QTOF-MS/MS) resulted in the detection of 1249 metabolites. A total of 57 differential metabolites were identified as potential markers for distinguishing CGEs of different aging years by chemometrics methods, including naringin, among others. The KEGG annotation, enrichment and topology analysis revealed that the biosynthesis of flavonoids was a key metabolic pathway during the aging process of CEG, involving 14 flavonoids determined as differential metabolites. Total flavonoids, naringin, naringenin, butin, 7’,4-dihydroxyflavone, and phlorizin have been identified as potential metabolites associated with antioxidant activity. These results clarified the effects of aging time on the flavonoids accumulation and antioxidant activity of CGE, and provided a scientific basis for understanding the mechanism of CGE aging process.

Generally, the extraction method has a great influence on the quality of pectin. However, there is little study on the effect of extraction method on the properties of Choerospondias axillaris fruit pulp pectin (CAPP). Accordingly, the physicochemical, structural, and functional properties of CAPP extracted by hot water (HWE), hydrochloric acid (HAE), ultrasound (UAE), and ultrahigh pressure (UPE) were investigated. Among these four CAPPs, UPE had the highest yield (15.79%) and GalA content (60.44%). UAE showed the most abundant side chains and RG-I region (55.12%). The lowest molecular weight (233.13 kDa) and yield (8.64%) were found in HAE. Though HWE exhibited better yield than HAE, its Mw was the highest. Different from physicochemical characteristics, the extraction method had a small effect on the structure of CAPP. The crystalline structure and functional group composition of different CAPPs were similar, while the surface structure of UAE and UPE had irregular circular holes in comparison with HWE and HAE. Furthermore, the extraction method also showed a great impact on the function. Compared with HWE and HAE, UAE and UPE presented better thermal stability and emulsifying properties. Meanwhile, HAE and UAE showed better antioxidant ability and prebiotic properties among these four CAPPs. The above results indicated that UAE showed better yield and functional properties. Hence, ultrasound extraction could be used as an effective method to extract CAPP.

Pomelo sponge layer (PSL) had been considered as a potential source of soluble dietary fiber (SDF), while they were mostly disposed of as waste. To promote high-value utilization of pomelo wastes, this study extracted SDF from PSL of six varieties of pomelo, and their physicochemical, structural and functional properties were investigated. Results indicated that all PSL-SDFs showed good physicochemical and functional properties. Among them, PSL-SDF from grapefruit (GRSDF) showed better water holding capacity and swelling capacity, whereas Shatian pomelo PSL-SDF and Guanxi pomelo PSL-SDF had the highest thermal stability and oil holding capacity, respectively. Furthermore, compared with other PSL-SDFs, GRSDF displayed the lowest hydrolysis degree coupled with the best antioxidant and probiotic growth-promoting abilities. Finally, the correlation analysis showed that multiple beneficial effects of PSL-SDFs were markedly associated with their molecular weight and the concentrations of total phenolic, total flavonoids, rhamnose, galacturonic acid, glucose and arabinose. Collectively, these findings contributed to a better understanding of the physicochemical and functional properties of SDFs extracted from different PSLs, which provided a scientific basis for the development of PSL-SDFs into functional foods.

Flavonoids are essential substances with antioxidant properties and high medicinal value. Citrus reticulata ‘Chachi’ peel (CRCP) is rich in flavonoids and has numerous health benefits. The different maturity periods of CRCP can affect the flavonoid contents and pharmacological effects. In this study, we successfully performed UPLC-ESI-MS/MS-based metabolic analysis to compare the metabolites of CRCP at different harvesting periods (Jul, Aug, Sep, Oct, Nov, and Dec) using a systematic approach. The results revealed the identification of a total of 168 flavonoid metabolites, including 61 flavones, 54 flavonols, 14 flavone C-glycosides, 14 dihydroflavones, 9 flavanones, 8 isoflavones, 3 flavanols, 3 dihydroflavonols, and 2 chalcones. Clustering analysis and PCA were used to separate the CRCP samples collected at different stages. Furthermore, from July to December, the relative contents of isoflavones, dihydroflavones, and dihydroflavonols gradually increased and flavanols gradually decreased over time. The relative content of flavonoid C-glycosides showed an increasing and then decreasing trend, reaching the highest value in August. This study contributes to a better understanding of flavonoid metabolites in CRCP at different harvesting stages and informs their potential future utilization.

In this study, the influences of pomelo cultivars on physicochemical properties, functional characteristics, and volatile compounds of juices were investigated. Among these six varieties, the highest juice yield (73.22%) was obtained in grapefruit. Sucrose and citric acid were the main sugar component and organic acid of pomelo juices, respectively. The results showed that the cv. Pingshanyu pomelo juice and grapefruit juice had the highest sucrose (87.14 g L⁻¹, 97.69 g L⁻¹) and citric acid content (14.49 g L⁻¹, 13.7 g L⁻¹), respectively. Moreover, the naringenin was the main flavonoid of pomelo juice. Additionally, the total phenolics, total flavonoids, and ascorbic acid concentrations of grapefruit and cv. Wendanyu pomelo juice were higher than those of other varieties of pomelo juices. Furthermore, 79 volatile substances were identified from the juices of six pomelo cultivars. Hydrocarbons were the predominant volatile substances, and the limonene was the characteristic hydrocarbon substance of pomelo juice. In addition, the pulp content of pomelo juice also presented great effects on its quality and volatile compounds composition. Compared to low pulp juice, the corresponding high pulp juice had higher sucrose, pH, total soluble solid, acetic acid, viscosity, bioactive substances and volatile substances. The effects of cultivars and variation in turbidity on juice are highlighted. It is useful for pomelo breeders, packers and processors to understand the quality of the pomelo they are working with. This work could provide valuable information on selecting suitable pomelo cultivars for juice processing.

Headspace gas chromatography–ion mobility spectrometry and partial-least-squares discriminant analysis (PLS-DA) were adopted to analyze the rule of change in flavor substances for different varieties of green plums at different levels of maturity (S1—immature, S2—commercially mature, and S3—fully mature). The results showed that 68 kinds of volatile flavor substances were identified in all green plum samples. The types and contents of such volatile substances experienced a V-shaped trend with an increasing degree of green plum maturity. During the S1 and S2 stages, aldehydes, ketones, and a small amount of alcohols were the main volatile flavor substances in the green plum samples. During the S3 stage, esters and alcohols were the most important volatile flavor components in the green plum pulp samples, followed by terpenes and ketones. YS had the most types and highest contents of volatile flavor substances in three stages, followed by GC and DZ. By using the PLS-DA method, this study revealed the differences in flavor of the different varieties of green plums at different maturity stages, and it identified eight common characteristic volatile flavor substances, such as ethyl acetate, 3-methylbutan-1-ol, and 2-propanone, produced by the different green plum samples during the ripening process, as well as the characteristic flavor substances of green plums at each maturity stage (S1–S3).