Experimental Calculations of Metals Content in Skin-Whitening Creams and Theoretical Investigation for Their Biological Effect Against Tyrosinase Enzyme

The demand for skin-whitening creams (SWCs) has increased rapidly worldwide due to sharp rise in product advertisements in the media and the growing awareness. Metals are present either as impurities or added intentionally in creams and may have toxic effects on users. The present study was carried out to determine the content of metals such as mercury (Hg), cadmium (Cd), lead (Pb), arsenic (As), chromium (Cr), nickel (Ni), cobalt (Co), copper (Cu), zinc (Zn), and iron (Fe) in fifteen skin-whitening creams marketed at local shops in Islamabad, Pakistan. The concentrations of metals were analyzed by inductive coupled plasma-optical emission spectrometer (ICP-OES) after digestion with a mixture of HNO3, HCl, and H2O2. The skin-whitening creams were found to have metal concentrations in parts per million (ppm) in the following range: Hg (1.0-18,210 ppm), Co (0.1992-1.9931 ppm), Cr (1.0453-2.7455 ppm), Cu (0.6987-0.1997 ppm), Fe (8.8868-28.6213 ppm), Ni (0.7487-1.5958 ppm), Pb (0.2997-4.7287 ppm), and Zn (7819.2-39,696.7 ppm). As and Cd were not detected in any of the fifteen skin-whitening creams. Only one cream (L'Oreal Paris White Perfect) was found in safe limits defined by the Food and Drug Administration for cosmetics. In order to elucidate the mechanism of lower production of melanin in presence of heavy metals, a molecular docking study was carried out by using Molecular Operating Environment (MOE) software. A good correlation was observed between experimental findings and molecular docking studies.