The present study deals with the safety evaluation of two commonly used
synthetic preservatives, i. e., germaben II (methyl-4-hydroxybenzoate) and euxyl K100
(a mixture of benzyl alcohol + methyl chloroisothiazolinone + methyl isothiazolinone)
for cosmetic products. The safety of the essential oils of thyme white, thyme red and
tea tree was also evaluated as susbstituents for the synthetic preservatives.
Therefore, the activities of some enzymes of rat organs, i. e., alanine
aminotransferase (AL T), aspartate aminotransferase (AST) , alkaline phosphatase
(ALP), ribonuclease (RNase) and deoxyribonuclease (DNase) and rat serum contents,
i. e., urea, total lipids, total proteins, total cholesterol, uric acid, bilirubin and creatinine
were determined for rats administered both synthetic and natural preservatives under
study. In addition, histopathological studies were carried out in order to emphasis the
results of biochemical determination for liver and kidney functions. In general, the
natural preservatives induced little changes in rat enzyme activities and serum
contents. On the contrary, the synthetic preservatives caused remarkable alterations
in some rat enzyme activities and serum constituents.