Abstract
Black cumin (Nigella sativa L. [N.sativa]) seed extracts demonstrated numerous beneficial biological effects including, among others, antidiabetic, anticancer, immunomodulatory, antimicrobial, anti-inflammatory, antihypertensive, and antioxidant activity. To better understand the phytochemical composition of N. sativa seeds, methanol seed extracts were analyzed for phenolic acid and flavonoid content. Furthermore, we tested N. sativa methanol, n-hexane, and aqueous seed extracts for their inhibitory activity against butyrylcholinesterase (BChE) and catalase (CAT) as well as for antimicrobial activity against several bacterial and a yeast strains. The phenolic content of N. sativa was analyzed using ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS). The inhibition of BChE was assessed by modified Ellman's method, and the inhibition of CAT was determined by monitoring hydrogen peroxide consumption. The extracts were tested against Bacillus subtilis, Staphylococcus aureus, Salmonella enterica, and Escherichia coli using the agar diffusion method. The UHPLC-MS/MS method allowed the identification and quantification of 23 phenolic compounds within 15 minutes. The major components found in N. sativa seed extract were sinapinic acid (7.22 ± 0.73 µg/mg) as a phenolic acid and kaempferol (11.74 ± 0.92 µg/mg) as a flavonoid. All extracts showed inhibitory activity against BChE, with methanol seed extract demonstrating the highest inhibitory activity (inhibitory concentration 50% [IC50] 79.11 ± 6.06 µg/ml). The methanol seed extract also showed strong inhibitory activity against CAT with an IC50 value of 6.61 ± 0.27 µg/ml. Finally, the methanol extract exhibited considerable inhibitory activity against the tested microbial strains. Overall, this is the first study to investigate the ability of black cumin seed extracts to inhibit CAT. Our results indicate that N. sativa seed can be considered as an effective inhibitor of CAT activity.
Highlights
Plants are natural producers of chemical compounds, many of which are used to promote health and fight diseases, and are marketed as food or herbal medicines [1]
The UHPLC-MS/MS method used in this study for the identification of phenolic compounds in N. sativa seed extracts showed better performance compared to other chromatographic methods
Sinapinic acid and kaempferol were the two major phenolic components in the N. sativa seed extracts detected by UHPLC-MS/MS method
Summary
Plants are natural producers of chemical compounds, many of which are used to promote health and fight diseases, and are marketed as food or herbal medicines [1]. Bioactive compounds commonly found in plants have been shown to have health benefits mainly because they inhibit oxidative. Recent studies revealed a wide spectrum of pharmacologically active components in N. sativa. It is an annual plant, commonly known as black cumin, and is native to the Middle East, North Africa, and Western Asia, and cultivated in many countries worldwide. Black cumin has long been used as a natural medicine for the treatment of many acute, as well as chronic conditions, acting as diuretic, diaphoretic, stomachic, and liver tonic [4].
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