Enhancement of paraben-fungicidal activity by sulforaphane, a cruciferous vegetable-derived isothiocyanate, via membrane structural damage in Saccharomyces cerevisiae

Abstract

Parabens have been widely used as antimicrobial preservatives in cosmetics, pharmaceuticals, foods and beverages. Commonly, methyl-, ethyl-, propyl- and butylparaben are used independently or in combination to maintain the quality of industrial products, and they are considered to have low toxicity. However, recent evidence has suggested that parabens are toxic in mammalian cells, and parabens have been associated with allergic-contact dermatitis, breast cancer and changes in testosterone levels. Sulforaphane, a cruciferous vegetable-derived isothiocyanate, was effective in decreasing the growth inhibitory concentrations of ethyl-, propyl-, butyl- and methylparaben in the yeast Saccharomyces cerevisiae. The sulforaphane-enhanced fungicidal effects of methylparaben were deemed to be caused by drastic cell membrane damage and the leakage of internal substances, such as nucleotides, from S. cerevisiae cells. Moreover sulforaphane markedly decreased the minimum concentration of methyl- and ethylparaben required to inhibit the growth of various microbes, such as the pathogenic yeast that causes severe mycosis, Candida albicans; the filamentous fungi Aspergillus niger; and the Gram-negative bacterium Escherichia coli. Enhanced antimicrobial activity from the beneficial components of edible plants may increase paraben efficacy at low concentrations and minimize preservative-induced side effects in consumers. SIGNIFICANCE AND IMPACT OF THE STUDY: Sulforaphane, a natural and beneficial cruciferous vegetable-derived isothiocyanate, increased the ability of parabens to disrupt fungal cell membranes. Paraben-containing products have been reported to cause allergic contact dermatitis and drug hypersensitivity; therefore, methods to preserve organic products that may reduce the concentrations of parabens are both timely and necessary. In this study, we found that the combined antimicrobial effects of sulforaphane and parabens had the potential to reduce the paraben concentration needed to preserve organic products, thereby indicating that paraben toxicity may be reduced without affecting its activity as a preservative.

Keywords: amplification; antimicrobial activity; parabens; preservatives; sulforaphane.