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We investigated a colorimetric chemosensor for Hg2+ based on a mixture of xylidyl blue I as an anionic organic dye and poly(diallyldimethylammonium chloride) as a cationic polyelectrolyte in an aqueous solution at pH 7.5. The addition of Hg2+ to the mixture induced a bathochromic shift in the absorption spectra with a distinct color change from red to green which was readily identifiable by the naked eye, whereas the other metal ions gave rise to insignificant color changes. By contrast, upon adding Hg2+ to xylidyl blue I alone, the solution underwent no significant change in color. Moreover, a stoichiometric ratio for the complex between xylidyl blue I and Hg2+ in the presence of poly(diallyldimethylammonium chloride) was determined to be 1:1 by the absorption titration curve and Job's plot. Thus, the mixture can be used as a selective naked‐eye colorimetric chemosensor for Hg2+ over other common metal ions. This study raises the possibility that the combination of an organic dye and an oppositely charged polyelectrolyte is a potential candidate for the easy construction of a new chemosensor system. © 2018 Society of Chemical Industry

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A new naked‐eye colorimetric sensor for detecting Co2+ in a pure aqueous solution at pH 7.0 was developed by mixing an anionic organic dye, 2‐(5‐bromo‐2‐pyridylazo)‐5‐(N‐propyl‐N‐sulfopropylamino)phenol (5‐Br‐PAPS) with a cationic polyelectrolyte, poly(diallyldimethylammonium chloride) (PDADMAC). Upon addition of Co2+, the absorption maximum exhibited a remarkable bathochromic shift from 426 to 635 nm (Δ = 209 nm) with a detectable color change from yellow, green to blue, while other metal ions did not induce such a change. The results showed that the 5‐Br‐PAPS and PDADMAC mixture can be used as a selective and sensitive naked‐eye colorimetric chemosensor for Co2+. This study afforded a simple strategy to construct a novel chemosensor by a simple mixture of an organic dye and an oppositely charged polyelectrolyte. © 2018 Society of Chemical Industry

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An artificial metabolic route to an unnatural trichothecene was designed by taking advantage of the broad substrate specificities of the T-2 toxin biosynthetic enzymes of Fusarium sporotrichioides. By feeding 7-hydroxyisotrichodermin, a shunt pathway metabolite of F. graminearum, to a trichodiene synthase-deficient mutant of F. sporotrichioides, 7-hydroxy T-2 toxin (1) was obtained as the final metabolite. Such an approach may have future applications in the metabolic engineering of a variety of fungal secondary metabolites. The toxicity of 7-hydroxy T-2 toxin was 10 times lower than that of T-2 toxin in HL-60 cells.

Fusarium graminearum causes a disease of wheat and barley known as Fusarium head blight. It contaminates the grains with trichothecene mycotoxins such as deoxynivalenol (DON). As shunt intermediates in the DON biosynthetic pathway, 7-hydroxyisotrichodermin (7-HIT) and 8-hydroxyisotrichodermin (8-HIT) are known. However, their activities have not been previously evaluated. In this study, we performed toxicity assays of these trichothecenes by using a sensitive yeast bioassay that we have recently established. The IC 50 of 7-HIT and 8-HIT were in the range of 20-40 µg/ml, while the IC 50 of DON was approximately 1.5 µg/ml. Although the toxicity of these shunt metabolites remains to be investigated in animal systems, our present data indicate that 7-HIT and 8-HIT may not be major issues that require regulation in agricultural products.