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Kinetic evaluation of the ciliotoxicity of methyl- and propyl-p-hydroxybenzoates using factorial experiments
Abstract:
The ciliotoxicity of methyl-p-hydroxybenzoate (methyl paraben, MHB) and propyl hydroxybenzoate (propyl paraben, PHB) was investigated. It is shown that at the concentrations used (0.28 and 0.38 mM) PHB exerted only mild toxicity. The MHB solutions used (1.18 and 2.36 mM) were much more ciliotoxic. There was, however, an order of magnitude difference in the concentrations used as a result of constraints imposed by their differing aqueous solubilities. There was no evidence of synergism in the ciliotoxicity of the two compounds when the MHB concentration was raised from 1.18 to 2.36 mM and the PHB concentration was raised from 0.28 to 0.38 mM in a 2(2) factorial experiment. At those levels the two compounds showed additive effects. On the other hand, clear synergism was evidenced by the fact that the ciliotoxicity of both MHB and PHB was dependent on whether the cilia were exposed to each hydroxybenzoate singly or in combination. The results combined with those of an earlier study, indicate that it is not possible to improve the selectivity of antimicrobial activity without also increasing ciliotoxicity.
Insights
Methyl paraben (MHB) is more toxic to cilia than propyl paraben (PHB). While additive at tested levels, MHB and PHB exhibit synergistic ciliotoxicity when combined, indicating a trade-off between antimicrobial activity and toxicity.
Area of Science:
- Toxicology
- Biochemistry
- Cell Biology
Background:
- Parabens, including methyl-p-hydroxybenzoate (MHB) and propyl hydroxybenzoate (PHB), are widely used preservatives.
- Assessing the safety of parabens involves understanding their potential toxic effects on biological systems, such as cilia.
Purpose of the Study:
- To investigate and compare the ciliotoxicity of methyl paraben (MHB) and propyl paraben (PHB).
- To determine the interaction effects (additive or synergistic) of MHB and PHB on ciliotoxicity.
Main Methods:
- Ciliotoxicity assays were performed using varying concentrations of MHB (1.18 and 2.36 mM) and PHB (0.28 and 0.38 mM).
- A 2(2) factorial experiment was employed to assess the combined effects of MHB and PHB.
- Cilia exposure was varied to include single compound and combined exposures.
Main Results:
- Propyl paraben (PHB) demonstrated mild ciliotoxicity at the tested concentrations.
- Methyl paraben (MHB) exhibited significantly higher ciliotoxicity compared to PHB.
- No synergistic ciliotoxicity was observed when concentrations were incrementally increased within the tested range; effects were additive.
- Synergistic ciliotoxicity was evident when comparing single exposures to combined exposures, indicating a complex interaction.
Conclusions:
- The study highlights that methyl paraben is considerably more ciliotoxic than propyl paraben.
- The interaction between MHB and PHB suggests that their combined use can lead to synergistic toxicity, even if individual components show additive effects at certain levels.
- Findings imply a potential challenge in enhancing antimicrobial selectivity of parabens without concurrently increasing their ciliotoxicity.