A voltammetric approach for the quantification of thymoquinone in Nigella Sativa products

Thymoquinone (TQ), a bioactive compound found in Nigella sativa seed oil, has been widely studied for its therapeutic potential. In this study, a new, sensitive, and cost-effective method was developed for TQ determination using square-wave voltammetry (SWV) with an environmentally friendly carbon paste electrode. Due to the morphology of the TQ oxidation signals, three calibration curve construction methods were tested, namely, based on: current height, peak area and cumulative voltammetry concept. The broadest linear range was established when calibration curve was constructed on the basis of TQ peak current height (LOD 8.9 nmol·L^{- 1}, LOQ 29.8 nmol·L^{- 1}). This method was validated through the analysis of real samples, including Nigella sativa seed oil and dietary supplement, with the results showing a strong correlation to those obtained by the HPLC reference method. The developed method represents a significant advancement in the electrochemical detection of TQ, offering practical benefits in terms of simplicity, precision, and cost-effectiveness.