Parabens are esters of p-hydroxybenzoates that are commonly found in everyday consumer products as well as pharmaceuticals. They are often used in commercial products to prevent bacterial growth as well as to provide extended shelf life, but they have been shown to activate estrogen receptors in vivo, a contributing factor in human breast cancer proliferation. Our lab has previously generated a multitude of paraben derivatives that do not exhibit estrogenic activity. Many of these derivatives may have other safety concerns, but gallate esters appear to have the least hazardous properties. The estrogenic, antimicrobial, and antioxidant properties of the gallate ester family are unclear; therefore, our lab has synthesized several non-commercially available gallate esters through a DCC coupling reaction. To determine the viability of gallates as preservatives, minimum inhibitory concentrations (MIC) were obtained against Staphylococcus epidermidis, Staphylococcus aureus, and Serratia marcescens and were found to be comparable to traditional parabens. Estrogenic activity was compared via MTT proliferation, LDH cytotoxicity, and estradiol colorimetric competition ELISA assays, indicating gallate esters do not upregulate estrogenic activity, while traditional parabens show increased cell proliferation and upregulation of estradiol. Finally, through cyclic voltammetry and DPPH colorimetric assays, gallate esters were determined to act as antioxidants through the reduction of free radicals, where traditional parabens do not. These findings suggest gallate esters could be a suitable antioxidative alternative for traditional parabens. Further work should be completed to determine the magnitude of binding to the estrogen receptor and the extent of the associated antagonistic properties of gallate esters.
Reeves, Marcia, "Synthesis and evaluation of gallate esters as alternatives to traditional parabens" (2022). Longwood Senior Theses. 12.