The intracellular antioxidant activities of diosmetin were evaluated by cellular antioxidant activity (CAA) assay, 2,2-azobis(2-amidinopropane) dihydrochloride (AAPH)-induced erythrocyte hemolysis assay and cupric chloride (CuCl2)-induced plasma oxidation assay. The results showed that diosmetin exhibits strong cellular antioxidant activity (EC50 = 7.98 μmol, CAA value = 58 μmol QE/100 μmol). It was also found that diosmetin treatment could effectively attenuate AAPH-induced erythrocyte hemolysis (91.0% inhibition at 100 μg/mL) and CuCl2-induced plasma oxidation through inhibition of intracellular reactive oxygen species (ROS) generation. Diosmetin could significantly restore AAPH-induced increase of intracelluar antioxidant enzyme (SOD, GPx, and CAT) activities to normal levels, as well as inhibit intracellular malondialdehyde (MDA) formation. Thus, the intracellular antioxidant detoxifying mechanism of diosmetin is associated with both nonenzymatic and enzymatic defense systems.

A novel polysaccharide, here named DP1, was isolated from the fruiting body of Dictyophora indusiata using a water extraction method. Structure characterization revealed that DP1 had an average molecular weight of 1132 kDa and consisted of glucose (56.2%), galactose (14.1%), and mannose (29.7%). The main linkage type of DP1 were proven to be (1 → 3)-linked α-l-Man, (1 → 2,6)-linked α-d-Glc, (1 → 6)-linked β-d-Glc, (1 → 6)-linked β-d-Gal, and (1 → 6)-linked β-d-Man by periodate oxidation-Smith degradation and nuclear magnetic resonance analysis. The immunostimulating assay indicated that DP1 could significantly promote macrophage NO, TNF-α, and IL-6 secretion in murine RAW 264.7 cells involving complement receptor 3 (CR3). The immune activities of DP1 were quite stable under thermal processing (100, 121, and 145 °C). Besides, DP1 retained stability after acidic/alkline treatment (pH 4.0-10.0), which enabled it to be an ideal complementary medicine or functional food for therapeutics of hypoimmunity and immunodeficiency diseases.

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In this study, walnut meal hydrolysates (WMH) and dephenolized walnut meal hydrolysates (DWMH) were found to effectively decrease the serum uric acid level and protect the renal function in potassium oxonate-induced hyperuricemic rats in vivo as well as inhibit xanthine oxidase in vitro. Two novel antihyperuricemic peptides including WPPKN (640.8 Da) and ADIYTE (710.7 Da) were purified from DWMH via Sephadex G-15 gel filtration and reverse-phase high-performance liquid chromatography and identified by LC-ESI-MS/MS. These peptides displayed high in vitro xanthine oxidase inhibition (XOI) activity with IC values of 17.75 ± 0.12 mg mL (WPPKN) and 19.01 ± 0.23 mg mL (ADIYTE). Based on the results of molecular simulation, WPPKN entered into the hydrophobic channel and even obstructed the interaction between xanthine and xanthine oxidase (XO), while ADIYTE was positioned on the surface of the B-chain and blocked the entrance of the substrate to the hydrophobic channel. Therefore, the two peptides are partially responsible for the antihyperuricemic properties of DWMH.