Casein phosphopeptide (CPP) is a bioactive phosphorylated peptide derived from the hydrolysis of cow’s milk casein, which has superior chelating properties. In this study, CPP was used as a carrier to prepare selenium-chelating CPP (CPP-Se) for use as a novel selenium supplement. The structure of CPP-Se was characterized by spectroscopy and thermodynamics. Molecular docking was used to simulate the binding interaction between Se and CPP and the immunoregulatory and anti-inflammatory activities of CPP-Se were studied in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells. The results showed that the Se content of CPP-Se prepared under peptide/selenium mass ratio of 2:1, 35.48 ℃ and pH 7.0 was 5578.66 μg/g. Ultraviolet (UV) and Fourier transform infrared spectroscopy (FTIR) demonstrated that CPP chelated Se through carbonyl, carboxyl, and phosphate groups. Circular dichroism (CD) spectroscopy indicated that the proportion of β-sheet was higher in CPP-Se than in CPP. Thermogravimetric (TG) analysis indicated that CPP-Se was more stable than CPP. Furthermore, isothermal titration calorimetry (ITC) combined with molecular docking revealed that the chelating site between peptide and selenium was hydrogen bonds in glutamic acid and serine, with a distance of 2.6 Å and a binding energy of –7.53 kJ/mol, mainly driven by hydrophobic interactions. For the same selenium concentration, the safe range of CPP-Se for RAW264.7 macrophages was two times larger than that of sodium selenite, and CPP-Se increased the phagocytic capacity of macrophages by 25%. The inhibitory effect of CPP-Se on the secretion and release of NO, tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in LPS-stimulated RAW264.7 macrophages was more pronounced than that of sodium selenite. In summary, CPP-Se can be used as a new safe selenium supplement. This study provides new ideas for the widespread application of CPP.

This study employed conventional methods to systematically analyze the moisture, ash, total protein, fat, carbohydrate, minerals, vitamins B, amino acids, starch nutritional fractions, and bioactive components of finger millet (Eleusine coracana (L.) Gaertn.). The in vitro antioxidant activity of the bioactive components obtained using solvents of different polarities was evaluated, and the strong antioxidant components were identified using ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The results showed that the contents of moisture, ash, protein, fat, and carbohydrates in finger millet were 10.06%, 1.92%, 12.98%, 1.67%, and 73.31%, respectively. Slowly digestible starch and resistant starch totally accounted for 83.87% of the total starch. Finger millet was rich in calcium, manganese, iron, zinc elements, and vitamin B₁. The total amino acid content was 53.27 mg/g, containing all 20 common amino acids, with essential amino acids accounting for 37.4% of the total amino acids. The total polyphenol, total flavonoid and total saponin contents of finger millet were 571, 533 and 251 mg/100 g, respectively. The ethyl acetate extractable fraction had the strongest antioxidant activity, and UPLC-MS/MS detected 59 phenolic acid compounds and 74 flavonoid compounds. The majority of the top 30 most abundant components were found to have strong biological activity. The above results indicate that finger millet has rich nutritional components, and its extracts have good antioxidant activity. This new food resource has broad application prospects.

In this study, the total flavonoid composition and bioactivity of finger millet was analyzed. Eleusine coracana flavonoids (ECFs) were obtained through sequential 70% ethanol extraction, ethyl acetate extraction, and purification with D101 macroporous resin. The total flavonoid content was determined using the NaNO₂-Al(NO₃)₃-NaOH colorimetric method, and the flavonoid composition using ultra-high performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS). The in vitro antioxidant activity of ECFs was evaluated using chemical assays, and the anti-aging activity using C. elegans as a model organism. The results demonstrated that the total flavonoid content of ECFs was 82.6%, with 16 major components being identified, including flavonoid glycosides and catechin. In vitro antioxidant tests showed that ECFs exhibited half-maximal inhibitory concentrations (IC₅₀) of 45.34 and 22.75 μg/mL against 1, 1-diphenyl-2-picrylhydrazyl(DPPH) and 2, 2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) cation radicals, respectively, with the IC₅₀ against ABTS cation radicals being lower than that of the positive control vitamin E (29.25 μg/mL). At a concentration of 200 μg/mL, ECFs increased catalase activity in C. elegans by 53.98%, superoxide dismutase activity by 30.64%, and glutathione levels by 51.06%, while decreasing malondialdehyde (MDA) content by 11.82%. ECFs extended the lifespan of C. elegans by 17.86%, and improved its mobility compared to the control group, indicating improved vitality. ECFs had no significant effect on C. elegans fecundity suggesting no promoting effect on its reproductive function. Additionally, ECFs reduced the level of lipofuscin by 53.91%. These findings demonstrated that ECFs had significant antioxidant effects both in vitro and in vivo as well as remarkable anti-aging activity in C. elegans, which could provide a foundation for the functional application of finger millet.