Cumin (Cuminum cyminum) and black cumin (Nigella sativa) seeds: traditional uses, chemical constituents, and nutraceutical effects

Although the seeds of cumin (Cuminum cyminum L.) are widely used as a spice for their distinctive aroma, they are also commonly used in traditional medicine to treat a variety of diseases. The literature presents ample evidence for the biomedical activities of cumin, which have generally been ascribed to its bioactive constituents such as terpenes, phenols, and flavonoids. Those health effects of cumin seeds that are experimentally validated are discussed in this review. Black seeds (Nigella sativa), which are totally unrelated to C. cyminum, have nevertheless taken the name 'Black cumin' and used in traditional systems of medicine for many disorders. Numerous preclinical and clinical trials have investigated its efficacy using the seed oil, essential oil, and its main constituent thymoquinone (TQ). These investigations support its use either independently or as an adjunct along with conventional drugs in respiratory problems, allergic rhinitis, dyspepsia, metabolic syndrome, diabetes mellitus, inflammatory diseases, and different types of human cancer. Multiple studies made in the last decades validate its health beneficial effects particularly in diabetes, dyslipidemia, hypertension, respiratory disorders, inflammatory diseases, and cancer. Nigella sativa seeds also possess immune stimulatory, gastroprotective, hepatoprotective, nephroprotective, and neuroprotective activities. TQ is the most abundant constituent of volatile oil of N. sativa seeds, and most of the medicinal properties of N. sativa are attributed mainly to TQ. All the available evidence suggests that TQ should be developed as a novel drug in clinical trials.