COMPLEXATION OF ACTIVE INGREDIENT THYMOQUINONE OF NIGELLA SATIVA (BLACK SEED) WITH CHROMIUM(VI)

Abstract

Thymoquinone is a principal and active ingredient of Nigella sativa (Black seed). In the present research its complexation with Cr(VI) has been studied using cyclic voltammetry. Mentioned electrochemical study was carried out at glassy carbon as working electrode, platinum as auxiliary and saturated calomel as reference electrode. Whole practical work was performed at 25 ± 1?C in aqueous medium using NaCl as supporting electrolyte. Comparison of the voltammograms of metal, ligand and the complex suggest presence of pre - equilibrium charge transfer process in Cr(VI)-thymoquinone complex. In addition present study reflects effects of scan rates on the complex showing that the complex follows quasi-reversible electron transfer process. E? of complex is found to be 0.260 ± 0.01 V whereas diffusion coefficient was 3.37x10-5 cm2 s -1 . The values of transfer coefficients (? and ?) were also determined. The value of ? was found to be 0.593 ± 0.02 - 1.231 ± 0.01 whereas values of ? were found in the range of 0.750 ± 0.01 – 1.171 ± 0.01. Since present research confirms complex formation between thymoquinone and Cr(VI), it is suggested that current research could be beneficial in eliminating Cr (VI) toxicity. This can be done either by complex formation between the thymoquinone and Cr(VI) or by reduction of Cr(VI) to Cr(III) by thymoquinone. In the former case Cr(VI) in complexed form will be no more harmful whereas in the later case it would be converted into useful form.