Nigella sativa L. is a medicinal herb with high antioxidant activity. However, the substances linked with this biological activity are infrequently documented. This study assessed the antioxidant potentials of extracts and essential oil (EO) of N. sativa and identified their phytochemical constituents. A chemometric application was used to classify them according to their relationship to antioxidant properties. The results showed that the EO of N. sativa exhibited the highest antioxidant potentials (IC50 ABTS = 17.96 and IC50 DPPH =189.53 μg/ml). Compared with hexane, ethyl acetate, chloroform, and water extracts, this sample also displayed the highest total phenolic (123.23 mg GAE/100 g extract) and flavonoid contents (34.51 mg QE/100 g extract). The gas chromatography-mass spectrometry analysis revealed that 2,3-dimethyl hydroquinone (44.79%), eugenol (3.61%), and thymol (3.05%) were the major components of EO. Particle component analysis (PCA) successfully classified the tested samples into three groups. EO was classified as having high antioxidant activity, while ethyl acetate and chloroform extracts were medium. The final group, the low antioxidant activity, involved water and hexane extracts. Moreover, PCA indicated some compounds, such as 2,3-dimethyl hydroquinone, 6-octadecenoic acid-methyl ester, thymoquinone, and carbonic acid-2-methoxyethyl phenyl ester, to have a positive correlation with the antioxidant activity of N. sativa.
Key words: Nigella sativa, principal component analysis (PCA), GC-MS, chemical profile, antioxidant activity
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