Structure-Toxicity Relationships for Aliphatic Isothiocyanates to Tetrahymena pyriformis

Schultz, T.W.; Comeaux, J L

doi:10.1007/s001289900093

Cited by 20 publications

(14 citation statements)

References 10 publications

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“…Penetration, therefore, n S av was not a limiting step in soft electrophilic toxicity. This observation is consistent with the findings of Schultz et al [5] and Schultz and Comeaux [39] for alkenones and isothiocyanates, respectively, toxicants also considered to be soft electrophiles.…”

Section: Discussionsupporting

confidence: 92%

Structure–activity Relationships for Pimephales and Tetrahymena: A Mechanism of Action Approach

Bearden¹,

Schultz²

1997

Environ Toxicol Chem

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Abstract-The toxicity data of 74 chemicals tested in both the 96-h fathead minnow (Pimephales promelas) mortality assay and the 2-d Tetrahymena pyriformis (a protozoan) growth inhibition assay were evaluated using quantitative structure-activity relationships (QSARs). Each chemical was a priori assigned a mechanism of acute toxic action from either nonpolar narcosis, polar narcosis, weak acid respiratory uncoupling, soft electrophilicity, or proelectrophilicity. The polar narcotics were further split into a phenol group and an aniline group. The relationship between bioreactivity and the importance of penetration to the site of action in both systems was studied. Bioreactivity showed a trend to be inversely proportional to the value of the hydrophobicity term. The data were examined to investigate how different molecular descriptors modeled the mechanisms of action. Models were produced for nonpolar narcotics and anilines for both species with the 1-octanol/water partition coefficient (log K ow ) alone. Soft electrophiles were best predicted by the average acceptor superdelocalizability ( ), whereas proelectrophiles were modeled by log K ow and n S av . The weak acid uncouplers modeled with either log K ow or log K ow plus the ionization constant (pK a ) for Pimephales and n S av Tetrahymena, respectively. Phenols yielded predictive models using a either a combination of log K ow with or lowest unoccupied n S av molecular orbital, for fathead minnow and protozoan, respectively.

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Section: Discussionsupporting

confidence: 92%

Structure–activity Relationships for Pimephales and Tetrahymena: A Mechanism of Action Approach

Bearden¹,

Schultz²

1997

Environ Toxicol Chem

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show abstract

“…Penetration, therefore, was not a limiting step in soft electrophilic toxicity. This observation is consistent with the findings of Schultz et al [5] and Schultz and Comeaux [39] for alkenones and isothio‐cyanates, respectively, toxicants also considered to be soft electrophiles.…”

Section: Discussionsupporting

confidence: 93%

Structure‐activity relationships for Pimephales and Tetrahymena: A mechanism of action approach

Bearden

Schultz

1997

Enviro Toxic and Chemistry

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The toxicity data of 74 chemicals tested in both the 96‐h fathead minnow (Pimephales promelas) mortality assay and the 2‐d Tetrahymena pyriformis (a protozoan) growth inhibition assay were evaluated using quantitative structure‐activity relationships (QSARs). Each chemical was a priori assigned a mechanism of acute toxic action from either nonpolar narcosis, polar narcosis, weak acid respiratory uncoupling, soft electrophilicity, or proelectrophilicity. The polar narcotics were further split into a phenol group and an aniline group. The relationship between bioreactivity and the importance of penetration to the site of action in both systems was studied. Bioreactivity showed a trend to be inversely proportional to the value of the hydrophobicity term. The data were examined to investigate how different molecular descriptors modeled the mechanisms of action. Models were produced for nonpolar narcotics and anilines for both species with the 1‐octanol/water partition coefficient (log Kow) alone. Soft electrophiles were best predicted by the average acceptor superdelocalizability (Snav), whereas proelectrophiles were modeled by log Kow and Snav. The weak acid uncouplers modeled with either log Kow or log Kow plus the ionization constant (pKa) for Pimephales and Tetrahymena, respectively. Phenols yielded predictive models using a either a combination of log Kow with Snav or lowest unoccupied molecular orbital, for fathead minnow and protozoan, respectively.

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“… Structures and selected properties of the two isothiocyanates investigated. Data from material safety data sheets, except the vapor pressure which is from Vaughn and Boydston [28] and log K OW which is from Schultz et al [29] and Schultz and Comeaux [30]. …”

Section: Methodsmentioning

confidence: 99%

Degradation and sorption of 2‐propenyl and benzyl isothiocyanate in soil

Gimsing

Strobel

Hansen

2009

Enviro Toxic and Chemistry

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Isothiocyanates of natural origin produced by the hydrolysis of plant-produced glucosinolates have the potential to control soil pests, but getting sufficiently high isothiocyanate concentrations in soil is difficult. Furthermore, the isothiocyanates have proven toxic to a wide range of organisms and hence may also harm nontarget organisms. Knowledge of the sorption and degradation of the isothiocyanates is essential to optimize the use of natural isothiocyanates for pest control while minimizing the environmental impact. We have conducted studies on the sorption and degradation of two isothiocyanates of natural origin, 2-propenyl isothiocyanate and benzyl isothiocyanate. The experiments show the isothiocyanates degrade very quickly (t(1/2) = 0.93-4.25 h) in a 1:1 soil water slurry at 25 degrees C and they are sorbed by the organic matter in soil. From an environmental point of view, a fast degradation is desirable, but if the natural isothiocyanates are to be utilized for pest control, a fast degradation may imply they are not present long enough to have the desired effect on pests.

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Structure-Toxicity Relationships for Aliphatic Isothiocyanates to Tetrahymena pyriformis

Cited by 20 publications

References 10 publications

Structure–activity Relationships for Pimephales and Tetrahymena: A Mechanism of Action Approach

Structure–activity Relationships for Pimephales and Tetrahymena: A Mechanism of Action Approach

Structure‐activity relationships for Pimephales and Tetrahymena: A mechanism of action approach

Degradation and sorption of 2‐propenyl and benzyl isothiocyanate in soil

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