Quantitative major polyacetylenes of carrots (falcarinol and falcarindiol) and American ginseng roots (falcarinol and panaxydol) were isolated and tested in human intestinal epithelial cells of normal (FHs 74 Int.) and cancer (Caco-2) origin. A hormesis effect was seen for all isolated polyacetylenes when added to Caco-2 cells in concentrations ranging from 1 ng/mL to 20 μg/mL. The relative inhibitory potency was falcarinol > panaxydol > falcarindiol. No hormesis effect was observed when adding the polyacetylenes to FHs 74 Int. cells. Instead, an inhibitory growth response was observed above 1 μg/mL. The relative inhibitory potency was panaxydol > falcarinol > falcarindiol. Maximal inhibition at 20 μg/mL corresponded to approximately 95% and 80% inhibition of cell proliferation in normal and cancer cells, respectively. Combinations of falcarinol and falcarindiol added to normal and cancer cells showed a synergistic response for the inhibition of cell growth. Furthermore, the oxidized form of falcarinol, falcarinon, showed a significantly less growth inhibitory effect in intestinal cells of both normal and cancer origin; hence, a hydroxyl group at C-3 may be important for activity of falcarinol-type polyacetylenes. Extracts of carrots, containing different amounts of falcarinol, falcarindiol, and falcarindiol 3-acetate had significant inhibitory effects on both normal and cancer cell proliferation. In cancer cells, the extract containing the highest concentration of falcarinol tended to have the highest growth inhibitory effect, in accordance with a higher potency of falcarinol than falcarindiol. The present study demonstrates that aliphatic C17-polyacetylenes are potential anticancer principles of carrots and related vegetables and that synergistic interaction between bioactive polyacetylenes may be important for their bioactivity.
The decomposition kinetics of hexabromocyclododecane (HBCD), a flame retardant used in foamed polystyrene, were studied by monitoring the rate of HBr formed at temperatures between 180-240°C. Samples from five suppliers, and from two lots from three of the suppliers, were evaluated. There were significant differences in the decomposition rates, which appeared to be related to the finishing end of the manufacturing process.Samples showing the highest levels of labile bromine containing compounds (probably allylic bromides), as indicated by reactivity towards the silver nitrate, also showed the greatest rates of decomposition.
The thermal decomposition of a series of commercial FR agents used in polyurethane was studied in dilute solution in bibenzyl at temperatures commonly found in the center of large, slab stock buns. At 216°C all of the haloalkyl phosphates containing the XCH 2 CYHOgroups, where X is Cl or Br and Y is H or ClCH 2 -, decomposed at similar rates, i.e., they all gave first order rate constants between 1.0 and 5.8 x 10 -4 min -1 . The addition of toluene diamine to the solution increased the rate of acid evolution from the reacting mixture by a factor of at least ten and in one case by a factor of sixty. The amine is postulated to attack the C-X bond to produce a secondary amine hydrohalide salt which releases hydrogen halide at elevated temperatures.Pentabromodiphenyl oxide was found to be stable under both sets of conditions. Tris (2,3-dibromopropyl) phosphate, in contrast, undergoes decomposition via a free radical mechanism similar to that of vicinal dibromoalkanes.
The thermal decomposition kinetics of several aliphatic FR agents contain ing vicinal bromines were studied under temperature conditions, i.e., 200-226 °C., commonly found in extruders. The reactions were monitored by the rate of HBr evolution and by the formation of trans-stilbene in dilute (1.8-10 wt.% agent) bibenzyl solutions. The measured reaction rate constants ( kHBr) were found to include a free radical component ( kHBr1) and an ionic com ponent ( kHBr2) resulting from the homolytic cleavage of a carbon-bromine bond and from an iron or zinc induced reaction, respectively. Of the primary agents used in polystyrene, pentabromochlorocyclohexane was found to decompose at about three times the rate of hexabromocyclodo decane at any given temperature.
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