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To develop and validate HPLC and UV-visible spectroscopy methods for the determination of Thymoquinone (TMQ) content in different solvent extracts of N. sativa L. seed. The evaluation of the free radical scavenging effect of different solvent extracts of TMQ was investigated. Extraction of solvent was done by adding 20 mL of the solvent (hexane, methanol, ethanol, ethyl acetate, and water) to 1 g of blackseed and in a conical flask, respectively. The mixtures were then incubated in a water bath at 40°C for 2 and 4 h, respectively. The mixtures were then centrifuged at 4000 rpm for 10 min at 4°C. The extracts were then quantitatively analyzed using HPLC and UV-visible spectrophotometry. The free radical scavenging activity of TMQ extracts was studied using 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. The results obtained from HPLC indicate that TMQ extracted using hexane at 4 h (0.075 mg/mL, P <0.05) was significantly higher compared to other extraction solvents used. The results obtained from UV-vis spectroscopy analysis indicate that the methanol extract at 4 h (0.00957 mg/mL, P <0.05) was significantly higher compared to other extraction solvents used. Methanol extracts at 2 h showed the highest free radical scavenging activity (95.8%) compared to other extraction solvents. The results obtained show that hexane extracted the most TMQ at 4 h. Methanol extract demonstrated the highest free radical scavenging activity. [ABSTRACT FROM AUTHOR]

The study aimed to investigate the effects of different extraction methods on the content of thymoquinone using UV-Vis spectroscopy and the antioxidant activities of thymoquinone by measuring the free radical scavenging activity. One gram of powdered Nigella sativa L. black seed was added to 20 mL of solvents (hexane and methanol) into a conical flask and mixed. The mixtures were extracted by different methods which were maceration, percolation, and ultrasonic-assisted extraction. In the percolation method, the mixtures were placed in a water bath of 40°C for 4 h whereas, for maceration, the mixtures were left at room temperature for 4 h. On the other hand, the mixtures were replaced in an ultrasonic bath at room temperature for 2 h in ultrasonic-assisted extraction. The extracts were centrifuged at 4000 rpm at 4°C for 10 min and filtered. The extracts were then analyzed qualitatively and quantitatively by a validated method (UV-Vis spectroscopy). On the other hand, the antioxidant activity was measured by DPPH radical scavenging. In UV analysis, the percolation method with methanol extracted the most content (0.9102%) of thymoquinone. The free radical scavenging activity was observed highest (95.6891%) in the methanol extracts by percolation method. The results in the present study show that methanol extract by percolation method is the best method to extract the main bioactive component, thymoquinone from N. sativa seed. Furthermore, the N. sativa seed extracts exhibit antioxidant activity. [ABSTRACT FROM AUTHOR]