Inhibitory effects of ß-ionone on amyloid fibril formation of ß-lactoglobulin.

ß-Lactoglobulin (ß-LG) is the major constituent of whey food, which has been shown to interact with a wide range of aroma compounds. In the present work, a model aroma compound, ß-ionone, is used to investigate the influence of aroma compounds on the urea-induced unfolding of ß-LG at pH 7.0. ß-Ionone is observed to enhance the stability of ß-LG at pH 7.0. Moreover, the amyloid fibrils are observed when ß-LG at pH 7.0 is incubated for 12-20 days at 37 °C in the presence of 3-5M urea. However, the formation of amyloid fibrils is inhibited when ß-ionone is added into the samples and the inhibitory effects follow a concentration-dependent fashion. There is a clear correlation between Cm and lag time. The correlation demonstrates that protein stability affects the amyloid fibril formation of ß-LG. The results highlight the critical role of protein stability and provide an approach to prevent the formation of amyloid fibrils in vitro.

Antioxidant and antitumor activities of 4-arylcoumarins and 4-aryl-3,4-dihydrocoumarins.

Five 4-arylcoumarins (1c-g) and twelve 3,4-dihydro-4-arylcoumarins (2a-l) were synthesized and tested for antioxidant activity, antitumor activity, toxicity and structure-activity relationships analysis. 4-Arylcoumarins and 3,4-dihydro-4-arylcoumarins that possess two hydroxyl groups in ortho position, such as 1d, 1f, 2a, 2f, 2g and 2h had stronger radical scavenging properties than that of vitamin C (Vit C) in ABTS(+) assay. Kinetic traces of scavenging ABTS(+) and DPPH radicals showed that all the reaction could reached endpoint in 1 min, which was similar with Vit C. 4-Arylcoumarins with 3'-hydroxyl-4'-methylphenyl structural show more efficient NO radical scavenging activity. Three compounds 2e, 1f and 2a, in particular had superior EC50 for NO scavenging than did Vit C. MTT assay indicated that one compound in particular had a potential antitumor effect, inhibiting proliferation of BGC-823 cells and almost completely killing them at a concentration 62.5 mg/L. With same concentration 100 µg/mL, hemolytic analysis in rabbit red blood cells showed that only two compounds had hemolytic activity with a little more than 5% hemolysis. Injection and oral toxicity tests on Galleria mellonella larvae showed that none of the tested 4-arylcoumarins significantly affected their appetite, viability and mortality.