ELECTROCHEMICAL STUDIES OF THYMOQUINONE WITH COBALT(II)

Abstract

In the present research complexation of thymoquinone with Co(II) has been investigated using cyclic voltammetry. In this electrochemical study glassy carbon, platinum and saturated calomel electrodes were used as working, auxiliary and reference electrodes respectively. During whole work temperature was 25±1?C and NaCl was used as supporting electrolyte. Comparison of the voltammograms of Co(II), thymoquinone and their complex suggest existence of pre - equilibrium charge transfer process in the formation of Co(II)-thymoquinone complex. Effects of scan rates and successive cyclic scans on complex have also been examined. Results revealed quasi-reversible electron transfer process. E? of complex is found to be 0.275±0.01 V whereas diffusion coefficient was 2.412x10-5 cm2 s -1 . The values of transfer coefficients, ? and ?, were found to be in the range of 0.667±0.01- 0.873±0.01 and 0.738±0.01 – 1.091±0.01 respectively. Successive cyclic scans showed that no adsorption or deposition of complex occurred on the electrode surface. Present study confirms complex formation between thymoquinone, which is an active constituent of Nigella sativa (Black seed), and cobalt successfully. Former is used frequently in our food and confectionary items whereas later is used in the form of vitamin B12. Hence this research reveals that simultaneous intake of cobalt mineral and Nigella sativa seeds may result in cobalt deficiency due to complexation of thymoquinone with cobalt. Therefore their intake should not be simultaneous.