Phytochemical constituents and antibacterial activity of Nigella sativa seeds against some pathogenic bacteria

Document Type : Original Article

Authors

Department of Microbiology, Faculty of Life Sciences, Ahmadu Bello University, Zaria Nigeria

Abstract

Background:  This research investigates the antibacterial activity of Nigella sativa seeds against some bacteria isolated from clinical samples of patients attending Ahmadu Bello University Medical Centre, Zaria- Nigeria. Aim: This work aimed at determining the antibacterial activities of aqueous and methanolic extracts of Nigella sativa seeds against Salmonella species, Escherichia coli and Staphylococcus aureus. Methods: Ten (10) clinical isolates of Salmonella species, Escherichia coli and Staphylococcus aureus each were collected from Microbiology Laboratory of Ahmadu Bello University Medical Centre and were reconfirmed using culture, microscopy and some biochemical tests. The seed samples of Nigella sativa were purchased from herbal point Zaria, Kaduna State, Nigeria. Results: The phytochemical analysis of the extracts revealed the presence of carbohydrate, steroids, cardiac glycosides, saponins, flavonoids and alkaloids in both extracts. The highest antibacterial activity for aqueous extract of Nigella sativa seeds against Salmonella species was found to be 7.70±1.82 mm and for methanolic extracts was found to be 9.00±3.61 mm respectively. The highest antibacterial activity for aqueous extract of Nigella sativa seeds against Escherichia coli was found to be 8.10±2.17 mm and for the methanolic extract was found to be 6.00±0.00 mm indicating that it was not effective. Both methanolic and aqueous extracts of Nigella sativa seeds were not effective against Staphylococcus aureus (6.00±0.00mm). The minimum inhibitory concentration (MIC) of the aqueous extract of Nigella sativa seeds against Escherichia coli was 25mg/mL and the Minimum Bactericidal concentration (MBC) was 100mg/mL. While the minimum inhibitory concentration (MIC) of the methanolic extract Nigella sativa seeds against Salmonella species was 12.5mg/mL and the minimum bactericidal concentration (MBC) was 50mg/mL. Conclusion: Aqueous Nigella sativa seeds extract has antibacterial activity against Salmonella species and Escherichia coli but no activity against Staphylococcus aureus.

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