Nigella sativa and its constitutions including some isolated compounds are the potential sources of remedies of varieties of ailments such as antioxidant, anti-inflammatory, antibacterial, antifungal, antiparasitic and antiprotozoal, antiviral, cytotoxic, anticancer, neuro-, gastro-, cardio-, hetapto- and nephroprotective activities. In addition, the N. sativa implies beneficiary effects on reproductive, pulmonary and immune systems along with diabetes mellitus (DM), fertility, breast cancer, dermatological complications, dehydration, dyspepsia, osmotic balance and so on. Among the other isolated chemical moieties, thymoquinone (TQ) is a good target for its potential antimicrobial, antimicrobial, anti-inflammatory, chemopreventive, antitumoral and other activities. The N. sativa is evident to promote health in some non-clinical and clinical studies. Otherwise, TQ in a number of animal test systems is evident to produce no negative alterations of the body biomarkers in contrary it improved health quality. This paper depicts a more mechanistic revision on N. sativa and its constitutions. In conclusion, findings on Nigella may be featured as a health jackpot.

Keywords: Nigella sativa L.; Nigella-constitutions; Shrub

5-HIAA: Hydroxyindole Acetic Acid; 5-HT: Serotonin; ACC: Acetyl Coa Carboxylase; AChE: Acetylcholinesterase; ADA: Adenosine Deaminase; Akt: Protein Kinase B; ALT: Alanine Aminotransferase; AO: Acid Output; APAP: N-Acetyl-P-Aminophenol; AST: Aspartate Aminotransferase; bax/bcl-4: Apoptosis Regulator; bcl-1: Cyclin b1, bcl-2: Cyclin b2, bcl-xl: Cyclin b Xl, BUN: Blood Urea Nitrogen; CAT: Catalase; CDK-p16: Cyclin-Dependent Kinase p16, CGD: Conjugated Diene; c-JUNK: c-Jun-N-Terminal Kinase; CK: Creatinine; COX-1: Cyclooxygenase-1; COX-2: Cyclooxygenase-2; CP: Cisplatin; CVS: Cardiovascular System; DM: Diabetes Mellitus; FABPs: Fatty Acid Binding Proteins; FAS: Fatty Acid Synthase; GPx: glutathione Peroxidase; GSH: Reduced Glutathione; GSH-ST: Glutathione-S-Transferase; HbA1c: Glycosylated Haemoglobin; HDAC: Histone Deacetylase; HDL-C: High-Density Lipoprotein-C; HIV: Human Immunodeficiency Virus; i.g.: Intragastric; i.p.: Intraperitoneal; INF-γ: Interferon-Gamma; IL-1: Interleukin-1; IL-10: Interleukin-10; IL-1β: Interleukin-1beta; IL-6: Interleukin-6; LDH: Lactate Dehydroginase; LDL-C: Low-Density Lipoprotein-C; LPO: Lipid Peroxidase; LPO: LT4: Leukotriene-d4; MDA: Malonilealdehyde; MPO: Myloperoxidase; NF-κB: Nuclear Factor-Kappa-B; NK: Natural Killer; NLRP3: Nucleotide-Binding Oligomerization Domain Receptor 3; NO: Nitric Oxide; OSI: Oxidative Stress Index; OXT: Oxytetracycline; p.o.: Per Oral; PET: Pulmonary Function Test; PGD: Prostaglandin; PGE2: Prostaglandin; ROS: Reactive Oxygen Species; SCC: Squamous Cell Carcinoma; SOD: Superoxide Dismutase; SP-1: Protein Expression In Papiloma; TAC: Total Antioxidant Capacity; TBARS: Thiobarbituric Acid Substances; TC: Cholesterol; TG: Thyroglobulin; TNF-α: Tumor Necrosis Factor-Alpha; TOS: Total Oxidative Status; TQ: Thymoquinone; TSH: Thyroid Stimulating Hormone; UI: Ulcer Index

This revision is stimulated by the talks of the noble man, the last Prophet of the religion Islam, Hazrat Mohammad (Sm); who told that the black seed (Scientific name: Nigella sativa; Urdu: Kalonji; Arabic: Habba-tu sawda/ Habba Al-Barakah; English: Black cumin/ Black seed; Persian: Shonaiz; Bengali: Kalajira; Hindi/Nepali: Mangrail) [1] contains all kinds of remedies except death. When we started, we found large amount of evidence (No. 1290) on this miraculous medicinal plant, belonging to its parts extracts (with aqueous/organic/aqueous-organic solvents), seed oil, essential oil, fatty acids, conjugations, and isolated compounds. A few of them covered co-treatments with other agents including biochemicals. We found a major revision on this plant done by Ahmad et al. [2] along with a dermatological revision of Aljabre et al. [3], an immunomodulatory and anti-inflammatory revision of Amin et al. [4], an anti-inflammatory, antioxidant, an immunomodulatory revision of Gholamnezhad et al. [5], male fertility revision of Mahdavi et al. [6], and metabolic parameters in diabetes mellitus revision of Heshmati & Namazi [7]. These six articles inspired me to take them as a guide for previous evidences on N. sativa. Finally, we selected the potential publications on this plant from 2014 to March 15, 2016 and from the accumulated data we present here an activity-wise revision of this plant with an emphasized on mechanism of action way.

Nigella sativa

Nigella sativa L. (N. sativa) is a small shrub (20-90 cm in tall) under the botanical family, Ranunculaceae. It is native to Southern Europe, North Africa and Southeast Asia; cultivated in many countries in the world like Middle Eastern, Mediterranean region, South Europe, India, Pakistan, Syria, Turkey, Saudi Arabia [1]. N. sativa has tapering green leaves and rosaceous white, yeallow, pink, pale blue or purplish flowers with 5-10 petals. The ripe fruit (capsule: 3-7 united follicles) contains numerous tiny seeds, dark black in color. The seed and oil of N. sativa was frequently used in ancient remedies (Unani, Ayurveda, Chinese and Arabic) in Asian countries and in the Middle-East. The use of N. sativa seeds had been mentioned by Ibne-Sina (980–1037) in his famous book Al-Qanoon fitt-Tibb [2]. Traditionally N. sativa is used as a medicament of a variety of disorders in the respiratory system, digestive tract, cardiovascular system (CVS), kidney, liver, and immune system. Its uses in fatigue and dispiritedness are antique. The most common traditional uses belong to the ailments, including asthma, bronchitis, rheumatism and related inflammatory diseases, indigestion, loss of appetite, diarrhea, dropsy, amenorrhea, dysmenorrhea, worms and skin eruptions. It is also used as antiseptic and local anesthetic [1].

The black seeds contain protein (26.7%), fat (28.5%), carbohydrates (24.9%), crude fiber (8.4%), total ash (4.8%), volatile oil (0.5-1.6%), fatty oil (35.6-41.5%) [1], cellulose (6.8-7.4%) and moisture (8.1-11.6%) [7]. The seeds are also rich in various vitamins (e.g. - A, B1, B2, B3 and C) and minerals (e.g. - Ca, K, Se, Cu, P, Zn, Fe). Carotene and vanillic acid are also found existing in seeds and roots, and shoots. As fatty components, linolic acid (50-60%), oleic acid (20%), dihomolinoleic acid (10%) and eicodadienoic acid (3%) are the main unsaturated fatty acids. The palmitic acid and stearic acid belong to two main saturated fatty acids, in which α-sitosterol (44-54%) and stigmasterol (6.57-20.92%) are the pioneers [1]. Some other fatty acids such as myristic acid, palmitoleic acid, linoleic acid, linolenic acid, arachidonic acid, cholesterol, campesterol, β-sitosterol, ∆5-avenasterol, ∆7-stigmasterol, and ∆7- avenasterol are also reported by Gharby et al. [8] in N. sativa.

The seed contains alkaloids that isoquinoline alkaloids (e.g. - nigellicimine, nigellicimine N-oxide), pyrazole alkaloids or imidazole ring bearing alkaloids (e.g. - nigellidine, nigellicine). It also contains terpenes (e.g. - α-hederin) and saponins. Evidences tell that thymoquinone (2-Isopropyl-5-methylbenzo-1,4-quinone, 30-48%), thymohydroquinone, dithymoquinone, p-cymene (7-15%), carvacrol (6-12%), 4-terpineol (2-7%), t-anethol (1-4%), sesquiterpene longifolene (1-8%), α-pinene and thymol etc. are the most important active components in N. sativa. The other chemical components are carvone, nigellicine [1], nigellone, citrostradienol, cycloeucalenol, gramisterol, lophenol, ostusifoliol, stigmastanol, β-amyrin, butyrospermol, cycloartenol, 24-methylene-cycloartanol, taraxerol, tirucallol, 3-O-[β-D-xylopyranosyl(1→3)-α-L-arabino-pyranosyl]-28-O-[α-L-rhamnopyranosyl(1→4)-β-D-glucopyranosyl(1→6)-β-D-glucopyranosyl] hederagenin, esters of unsaturated fatty acids with ≥ C15 terpenoids, esters of dehydrostearic and linoleic acid, aliphatic alcohol, β-unsaturated hydroxyl ketone, hederagenin glycoside, melanthin, melanthigenin, bitter principle, tannin, resin, reducing sugars, glycosidal saponin, 3-O-[β-D-xylopyranosyl(1→2)-α-L-rhamnopyrasyl(1→2)-β-D-glucopyranosyl]-11-methoxy-16, 23-dihydroxy-28-methylolean-12-enoate,stigma-5,22-dien-3-β-D-glucopyranoside,cycloart-23-methyl-7,20,22-triene-3β,25-diol, nigellidine-4-O-sulfite, N. mines A3, a4, A5, C, N. mines A1, a2, B1, and B2 [2]. Chemical structures of some important chemical moieties are shown in Figure 1.

Figure 1: Some important chemical moieties isolated from N. sativa.

Nigella versus bacteria

N. sativa is reported to have strong antibacterial activity against gram positive (Staphylococcus aureus) and gram negative (Pseudomonas aeruginosa & Escherichia coli) species. It shows synergistic effects with streptomycin and gentamycin, while additive with spectinomycin, erythromycin, tobramycin, doxycycline, chloramphenicol, nalidixic acid, ampicillin, lincomycin and co-trimoxazole and similar to topical mupirocin. It can fight against resistant microorganisms, including against many multi-drug-resistant gram positive and gram negative bacteria [3]. According to Manju et al. [9] the EO from Nigella is able to protect Artemia spp. from Vibrio parahaemolyticus Dahv2 infection. According to Hariharan et al. [10], TQ has shown antimethicillin-resistant activity in S. aureus.

Nigella versus fungi

N. sativa acts against Candida albicans and Madurella mycetomatis and its isolated compound, TQ against Aspergillus niger, Fusarium solani and Scopulariopsis brevicaulis, where the activity was reported more effective than amphotericin-B and griseofulvin. The TQ also effective against Trichophyton spp., Epidermophyton spp., and Microsporum spp. In addition TQ, thymohydroquinone and thymol are also demonstrated an antifungal effect against many clinical isolates, including dermatophytes, molds and yeasts [3]. Black seed oil (10-200μg/mL) is also evident to act against Saccharomyces cerevisiae and C. utilis [11].

Nigella as antiviral agent

N. sativa was shown to enhance helper-T-cell (T₄) and suppressor-T-cell (T₈) ratio and increased natural killer (NK) cell activity in human. Otherwise, it is proven as a good inhibitor to the human immunodeficiency virus (HIV) protease and murine cytomegalovirus. In the latter case, it was found to increase in number and function of M-phi and CD4+ve T cells with the production of interferon-gamma (INF-γ) was reported [3].

Nigella versus parasites

N. sativa was shown to have anti-leishmaniasis, anti-miracidia, anti-cercariae and anti-Schistosoma mansoni potentials. In the latter case the oil of the black seed showed strong activity as compared to a well-known anti-schistosomal and anthelmintic drug for domestic animals, prazequantel; where it produced a potentiating effect with co-treatment [3]. Simalango & Utami [12] suggested that ethanol extract of N. sativa (0.5-8%) produced significant anti-Ascaris suum activity.

Nigella in wound infection

The wound healing capacity of N. sativa was evaluated in farm animals, mice and human gingival fibroblast. The accumulation result were indicated that there was a reduction in absolute differential WBC counts, local infection and inflammation, bacterial expansion and tissue impairment, and free radical production. An elevation of basic fibroblast growth factor and transforming growth factor beta were also reported [3].

Antioxidant capacity of Nigella

A number of in vitro and in vivo antioxidant studies have been conducted with N. sativa extracts, seed oil and TQ. The finding is suggesting having potential radical scavenging and inhibitory effects of oxidative stress. TQ effectively changed the parameters including adenosine deaminase (ADA), catalase (CAT), myloperoxidase (MPO), lipid peroxidase (LPO), reduced glutathione (GSH), glutathione-S-transferase (GSH-ST), glutathione peroxidase (GPx), superoxide dismutase (SOD) and nitric oxide (NO). It also reduced the malonilealdehyde (MDA), conjugated diene (CGD) levels and pro-inflammatory mediators interleukin-1beta (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ), and prostaglandin (PGE2) rather than interleukin-10 (IL-10) [1,4]. Figure 2 tells the basic antioxidant pathways of Nigella and its constitution.

Figure 2: Anti-oxidative action pathways of Nigella and its recipe.

Nigella in inflammation

Findings from different animal models suggest that N. sativa extracts, seed oil and TQ have anti-inflammatory potentials. This activity belongs to the reduction of NO production, interleukin-1 (IL-1), cyclooxygenase-1 (COX-1), cyclooxygenase-2 (COX-2), histone deacetylase (HDAC) along with other pro-inflammatory mediators such as - IL-1β, IL-6, TNF-α, IFN-γ, and PGE2 [2]. Topical application of TQ induced the expression of hemeoxygenase-1, NAD(P)H-quinoneoxidoreductase-1, GSH-ST and glutamate cysteine ligase in mice; while the seed oil inhibited COXs, 5-LPO in the pathways of arachidonate metabolism in rats [3]. TQ was also shown to diminish nuclear translocation and the DNA binding of nuclear factor-kappa-B (NF-κB) via the blockade of phosphorylation and subsequent degradation of IκBα in mice. TQ also attenuated the phosphorylation of Akt (protein kinase B), c-Jun-N-terminal kinase (c-JUNK) and p38 mitogen-activated protein kinase (MAPK-p³⁸). A decrease in expression of NLRP₃ (NACHT, LRR, and pyrin domain-containing protein 3) in B₁₆F₁₀ mouse resulted in inactivation of caspase-1 followed by the inhibition of IL-1β and IL-18. In addition, the inhibitory effect of TQ to NF-κB and reactive oxygen species (ROS) resulted in the partial inactivation of NLRP₃ inflammasome [3-5]. Figure 3 tells the basic anti-inflammatory activity pathways of Nigella and its constitution.

Nigella in cancer

The black seed oil is an enhancer of the NK cells, which is a potential applicability in immune therapy. However, the components in oil may induce antioxidative-induced prooxidant effects thus the carcinogenetic effect. In addition, TQ tested in a number cancer cells derived from mice, suggesting its ability to arrest G₀/G₁ phases of cell-cycle, which correlated with sharp increases in the expression of the cyclin-dependent kinase p¹⁶ (CDK-p¹⁶) and a decrease in cyclin-d₁ (dcl-1) protein expression in papiloma (SP-1) cell line and G₂/M arrest associated with an increase in the expression of the tumor suppressor protein p⁵³ with a decreased level of cyclin-b1 (bcl-1) protein. The chemopreventive potential of TQ may be due to its ability to increase the ratio of apoptosis regulator (bcl-4)/cyclin-2 (bax/bcl-2) expression and decreasing cyclin-xl (bcl-xl) protein. The antitumor activity of TQ was also reported in squamous cell carcinoma (SCC-VII), FsaR and murine tumor models of fibrosarcoma and SCC. TQ showed potent anticancer activity in A431 and Hep-2 cells via apoptosis by increasing the sub-G1 population, live/dead cytotoxicity, chromatin condensation, DNA laddering and Tunel-positive cells. Along with an increase in bax/bcl-2 ratio activation of cell proliferation of caspases and cleavage of poly ADP ribose polymerase were observed [3]. A research done by Khalife et al. [13] suggesting that TQ induced apoptosis through p⁵³-independent pathway with an expression of p²¹ and arrested cell-cycle S phase in human colon cancer cells. TQ is also anticancer agent to a number of cell lines including MCF-7/Topo breast carcinoma cells and is a significant down-regulator of NF-κB and MMP-9 in Panc-1 cells and bcl-2 in gastric cancer cells, while up-regulator of caspase-3 and caspase-9 in the later one. A number of derivatives of TQ namely 6-menthoxybutyryl, 6-hencosahexanyl conjugate, 4-acylhydrazones and 6-alkyl derivatives are also evident to produce anticancer activity in cancer cell lines [1]. Recent evidence suggests that the nanoemulsion of Nigella oil at a dose of 20-80µL/mL caused cell membrane blebbing, cytoplasmic vacuolation, marginalization of chromatin, and fragmentation of the nucleus in MCF-7 cells [14]. A recent evidence suggests that topical use of black seed oil (600mg) reduced cyclic mastalgia in woman (n=52) and the activity is significantly comparable to the painkiller, diclofenac [15]. A basic Nigella-anticancer potential has been sketched in Figure 4.

Figure 3: Anti-inflammatory capacity pathways of Nigella and its recipe.

Figure 4: Basic anticancer pathways of Nigella and its derivatives.

Nigella in diabetes

N. sativa was found playing an important role in the reduction of blood glucose level with an augmenting insulin level and C-peptide in rats. TQ reduces the tissue MDA levels, DNA damage, mitochondrial vacuolization and fragmentation, and preserves pancreatic β-cell integrity via antioxidant capacity. In a study TQ is evident to increase the levels of insulin, Hb with a significant decrease in glucose and glycosylated hemoglobin (HbA1c) levels. N. sativa showed a synergistic activity with parathyroid hormone in improving bone mass, connectivity, biomechanical behavior and strength in T2D rats. The black seeds are also evident an advantageous therapy in insulin resistance syndrome and dislipidemic patients. An insulin-sensitization action via enhancing ACC phosphorylation (mainly MAPK signaling pathway) and muscle GLUT4 content as well as progressive normalization of glycaemia are also seen in N. sativa treated diabetic Meriones shawi [2,6]. Lipid (4%) and volatile (3%) fractions in streptozotocin-induced diabetes mellitus (DM) rats reduced toxicological and adverse consequences to the animals [16]. In addition, an improved glycemic status and lipid profile with oil treatment at 3g/3-times/day in DM patients (n=72) were suggested by Heshmati et al. [17]. TQ when tested in clonal β-cells and rodent islets it caused a protective effect with normalization of chronic accumulation of malonyl CoA, and elevation of acetyl CoA carboxylase (ACC), fatty acid synthase (FAS) and fatty acid binding proteins (FABPs) following chronic glucose overload, suggesting a modulation in β-cell redox circuitry and enhancing sensitivity of β-cell metabolic pathways to glucose and glucose-stimulated insulin secretion (GSIS) under both normal conditions and hyperglycemia [18]. Otherwise, MAPK regulates a number of transcriptional factors, altering of which interferes in cell-cycle. Thus, N. sativa and TQ may be a good remedy for both type 1 and 2 DM patients, as in this consequence maintenance of beta-cell integrity and secretion of insulin sufficient for glycogenesis and phosphorylation of raised glucose in blood are crucial. Otherwise, along with ingested food, oxidative stress, infection and trauma are the factors that increase in blood sugar levels. Thus, the antidiabetic activity of N. sativa and TQ may connect with their antioxidant, antimicrobial, cytotoxic and anti-inflammatory activities. Otherwise, the decreasing level of HbA1c is one of the remedy for cardiovascular disease, nephropathy, neuropathy, and retinopathy. Figure 5 tells the possible antidiabetic actiion pathways of Nigella and its constitution.

Figure 5: Possible anti-diabetic action pathways of Nigella and its recipe.

Nigella on immune system

Along with NK antitumor activity, N. sativa is a demodulator of secretion of a number of pro-inflammatory mediators with up-modulation of secretion of Th2 versus Th1, cytokines in splenocytes. The black seed extract also evident to restore the resistance against granulocyte-dependent C. albicans. A study performed by the oil suggests decreasing antibody production in typhoid vaccination, which may be due to its immunosuppressive cytotoxic effect. It is also evident to correct the imbalance situation caused by oxytetracycline (OXT) in leukocyte, lymphocyte counts, heterophil: lymphocyte ratio, lysosomal enzyme activity and reticuloendothelial system function. However, it produced immunoprotective effect when chronic administration of antibiotic occurred in pigeons. The black seed oil also acted as a radioprotective agent against immunesuppressive and oxidative effects of ionizing radiation. In addition, an increased level of IFN-γ with a significant decreased in pathological changes of the guinea pigs’ lung was reported by N. sativa oil treatment. It is also effective in allergic diarrhea [2,4,5]. A recent evidence suggests that seed oil is protective against γ-radiation-induced damage in jejunal mucosa [19]. Nigella EO at a dose range of 5-20g/kg (oral feed) in chickens improved FCR and plasma lipid profile and antibody-mediated immunity in a 6 weeks treatment [20]. In addition, Nigella oil reduced thyroid stimulating hormone (TSH) and anti-thyroid peroxidase antibodies in patients with Hashimoto’s thyroiditis [21].

Nigella on nervous system (NS)

Methanolic extract of N. sativa is a potent analgesic and antidepressant. In addition, an anxiolytic activity via increasing serotonin (5-HT) and decreasing hydroxyindole acetic acid (5-HIAA) levels were noticed in rat brain. An increased 5-HT secretion along with improving learning and memory capacity were detected in rats. As it caused an augment in tryptophan levels, it may be helpful in anxiety treatment. Otherwise, TQ produced GABA-mediated anxiolytic-like effect in mice with a decline of NO and MDA production [2]. The possible neuroprotective activity may be due to its antioxidant, free radical scavenging and anti-inflammatory capacities. Along with these phenomena anti-acetylcholinesterase (anti-AChE) suggests N. sativa and TQ having anticonvulsant activity. There is a suggestion for GABAA-ergic anticonvulsant effect of TQ [2]. Nigella EO at 1g/kg (i.g.)/ day and TQ 30 at mg/kg/day (i.p.) in Wistar albino rats produced anti-nitrosative effects after a 10 days treatment [22]. Nigella EO is also evident to prevent cerebral edema in the hippocampus tissue of the rat brain [23]. Fahmy et al. [24] suggested that oil at a dose of 2.8g/kg when treated orally (p.o.) in autoimmune encephalomyelitis rats for 4 weeks reduced oxidative stress parameters in the cortex and hippocampus as well as enhanced remyelination in the hippocampus. Otherwise, oil at a dose of 4mL/kg/day (p.o.) in tramadol treated male albino rats protected the cortical neurons and myelinated axons [25]. Nigella EO at 500mg in adolescent human males (n=48) stabilized mood, decrease anxiety and modulate cognition for a 4 weeks treatment [26]. A possible neuroprotectivity and activity on NS is shown in Figure 6.

Figure 6: A possible neuroprotective trait of Nigella and its recipe.

Nigella on gastrointestinal tract (GIT) system

TQ is gastroprotective as it decreases gastric acid secretion, acid output (AO), pepsin, the mucosal content/activity of lipid peroxidase (LPO), proton (H+) pump, MPO and ulcer index (UI) while an increased in the content/activity of gastric mucin, GSH, total nitric oxide (TNO) and SOD. Decreased ulcer severity in rats was guessed via prostaglandin (PGD)-mediated and/or through antioxidant and antisecretion pathways. A decreased LPO and lactate dehydroginase (LDH), MPO, MDA and increased GSH, SOD, GPx, GSH-ST without altering of gastric CAT was also reported in rats. TQ was found significant effects in diarrhea, colitis, inflammatory bowel diseases, anti-Helicobacter pylori and body weight loss [1]. Possible GIT protective pathways of Nigella and its constitution are shown in Figure 7.

Figure 7: Possible GI-protective pathways of Nigella and its recipe.

Nigella on cardiovascular system (CVS)

TQ is evident to decrease motor fuel (diesel particle)-induced systolic blood pressure, leukocytes, IL-6 and plasma SOD activity. It is also prevented to decrease platelet counts and the prothrombin events rather than platelet aggregation [2]. The black seed oil reduced the total cholesterol (TC), low-density lipoprotein-C (LDL-C), and thyroglobulin (TG) with an increased high-density lipoprotein-C (HDL-C) level [27].

Nigella in hepatic system

N. sativa effect on alanine aminotransferase (ALT), aspartate aminotransferase (AST), LDH, total antioxidant capacity (TAC), CAT, MPO, total oxidative status (TOS) and oxidative stress index (OSI) tells that it has hepatoprotective activity. In addition GSH, TQ increased protein carbonyl content, thus the attenuation of protein oxidation and upgrading of the depleted antioxidant cellular fraction [2]. N. sativa oil at a dose of 25-100μg/mL protected hepatocytes from N-acetyl-p-aminophenol (APAP)-induced hepatotoxicity and metabolic disturbances in TIB-73 cells of mice [28]. A similar activity was also observed by Hamza & Salem Al-Harbi [29] with aqueous extract of N. sativa, where the activity was thought to be linked with improving antioxidant potential and suppressing both lipid peroxidation and ROS generation [28]. The black seed oil at a dose of 2mg/kg (p.o.) with cisplatin (CP)-treated rats are also evident for its hepatoprotective activity via improving energy metabolism and strengthening antioxidant defence pathways [30].

Nigella in urinary system

N. sativa along with ascorbic acid (Vitamin C) produced a nephroprotective effect by lowering serum creatinine (CK), blood urea nitrogen (BUN) and antioxidant activity in rabbits. Otherwise, TQ showed an effect on renal expression of organic ion transporters and multidrug resistance-associated proteins in rats. An increased protein levels of the efflux transporters MRP2 and MRP4 and decreased expression of OAT1, OAT3, OCT1 and OCT2 was observed in rats. Along with decreasing tubular necrosis score, N. sativa is a good reducer of CK, urea, MDA, NO, ROS, OSI and TOS levels and augmenter of TAC, SOD, GPx in kidney tissue and blood. TQ is evident to have a complete reversal of the gentamicin (GM)-induced alteration of serum CK, BUN, thiobarbituric acid substances (TBARS), total nitrite/nitrate content, GSH, GPx, CAT and ATP values in rats [2]. The black seed ethanol extract at 250-100mg/kg (p.o.) in female Wistar Albino rats showed a significant nephroprotective activity on paracetamol-induced nephrotoxicity [31]. Otherwise, Cd-induced nephroprotectivity is also evident in rats by Erboga et al. [32].

Nigella on pulmonary system

Both nigellone and TQ are evident to inhibit leukotriene-d4 (LT4) in the trachea, where the activity of the first one was concluded via mucociliary clearance. N. sativa reduced a significant peribronchial inflammatory cell infiltration, alveolar septal infiltration, alveolar edema, alveolar exudates, alveolar macrophages, intestinal fibrosis, granuloma, necrosis formation, NOS and a rise in surfactant protein D in the pulmonary system. N. sativa is also evident to have beneficial effects against lung injury and hypoxia-induced lung damage. Moreover, N. sativa puffs are proven to relieve asthma symptoms, frequency of asthma symptoms/weakness, chest wheezing and pulmonary function test (PFT) values with a bronchodilatory effect [2].

Nigella on reproductive system

TQ decreased TAC and MPO levels in C57BL/6 male mice. In addition, TQ alerted the events produced by methotrexate such as intestinal space dilatation, edema, disruption in the somniferous epithelium and reduced diameter of the semniferous tubules. Infertile men (n=34) when treated with 2.5mL black seed oil for 2 months improved abnormal semen quality without producing any adverse effect was observed [33]. According to Mahdavi et al. [6] the black seed oil is a good candidate for treating male infertility. Hexane and methanol extracts of N. sativa produced significant anti-fertility in Sprague-Dawley male and female rats, respectively. Otherwise, N. sativa inhibited uterine smooth muscle contraction in rats and guinea pigs [2,6]. TQ when treated with olive oil caused reduction of polycystic overy in rats via NF-κB signaling pathway [34].

Nigella in dyspepsia

Patients (n=70) with functional dyspepsia when treated with Nigella oil of 5mL (p.o.) for 8 weeks, a significant lowering of dyspepsia was observed [35].

Nigella in osmotic balance

The geriatric patients (n=42) when treated with black seed oil (22.6µg/25µL) for 2 weeks, it was concluded that it should be an alternative therapy of the isotonic sodium chloride (0.9% NaCl) solution [36]. Table 1 bears some important activities found in 2014 to March 15, 2016.

TQ-induced skin darkening via chlonergic mechanisms of muscarinic receptor in the melanin dispersion is evident, whereas, N. sativa oil for decreasing vitiligo area scoring index without seeing adverse effects. However, TQ and nigellone inhibited histamine release, protected histamine-induced bronchospasm in guinea pigs, decreased lung ensiphilia, elevated Th2 cytokines and raised IgE and IgG1 antibodies in mice. Otherwise, N. sativa is a good recommendation in hand eczema. Linoleic acid from this plant is known for its percutaneous adsorption enhancing capability of drugs, while the oil emulsion for reducing skin irritation and improving moisturizing and epidermal barrier function. It has also anti-aging, mitigating, and protective potentials [3]. There is evidence on oral health and hygiene of black seed oil and TQ [37].

Nigella lethal dose (LD)

In mice, the dose causing death of fifty percent experimental animals (LD50) values of fixed oil of black seed was reported to be 26.2-31.6mg/kg and 1.86-2.26mg/kg with single oral (p.o.) and intraperitoneal (i.p.) doses, respectively. In another study, calculated LD50 for TQ was 89.7-119.7mg/kg and 647.1-1094.8mg/kg after i.p. and p.o. administrations, respectively. In rat it was found to be 45.6-69.4mg/kg and 469.8-1118.8mg/kg after i.p. and p.o. administration, respectively. Data, suggesting TQ is more tolerated than the extract from N. sativa [2].

Drug interactions

Table 2 tells that N. sativa has a good number of beneficial drug/chemical/biochemical interactions.

Drugs from the shrubs are one of the potential plant derived sources. Interestingly, now a day herbal medicaments are in a great attention to the consumers world-wide. Otherwise, traditional medicines are still occupying a remedy-kingdom in particular areas. A potential and diverse activity of a scrupulous source is the stimulation to the drug researchers. N. sativa, in the previous literatures showing the shot, particularly TQ and its derivatives, nigellone, α-hederin and linoleic acid produced remarkable pharmacological activities. In addition, few clinical uses of human, suggesting that N. sativa and its constitution have safety profile.

At low levels and temporary spikes of ROS are beneficial for health [38] rather than high production and chronic effects as they cause induction of pro-inflammatory cytokines, chemokines and pro-inflammatory transcription factors (NF-κB) [39] as well as induction of cell death by damaging macromolecules such as lipids, DNA, RNA, and other proteins. In extrinsic pathway, excessive ROS are generated by Fas ligand which in association with death domain and caspase 8 cause apoptosis [39]. Otherwise, in the caspase cascade pathway (intrinsic) ROS facilitate to release cytochrome C by activating bcl-2 and bcl-xl and bcl-2-associated X protein as well as bcl-2 homologous antagonist/killer [40]. ROS implicates a variety of detrimental responses including CVS diseases (e.g. stroke and heart attack), hearing impairment via cochlear damage, decline memory capability (degenerative diseases, e.g. AD), ischaemic injury, and so on. Unlike apoptosis and necrosis, autophagy cell death occurs by self-digest of the damaging portion to take an attempt to minimize the damage and can no longer survive. However, it is possible to make available ROS to the other normal cells by this process as cellular programming is enough for a programmed cell death. Radiations form radiotherapy induces ROS-mediated cell death and mitotic failure [39]. However, an ideal ROS neutralizer (antioxidant/cytoprotective agent) is not enough in the cancer therapy, even if it has antioxidant-mediated prooxidant capacity, as it may act like dual nature of ROS! Therefore, cell targeting, self-redox balancing; genotoxic, but non-mutagenic, exact concentrations of ROS at the targeted site along with action period are the major concerns in the chemo-/radio-therapeutic cancer treatments.

In the above discussion, TQ, the well-known Nigella derived quinone and other N. sativa constitutions are evident to have target for a range of cellular proteins in their activity pathways. Having strong antioxidant capacity through antiradical including ROS, direct reduction of oxidizable substrates and induction of cellular antioxidant molecules, they may be good sources as cytoprotective agents, especially, the TQ, although the whose mutagenic effect is yet to be found out. The carcinogenic and immunosuppressive cytotoxic effects of N. sativa oil can be overcome by co-treatment with antibiotics or radiotherapy. Being a spacious habitual world-wide and having a good number already isolated chemical moieties of N. sativa is a weapon to the drug scientists. A number research has been done on this plant and its isolated compounds, especially on TQ and its derivatives and nigellone telling that chemical modification may bring a fruitful outcome to the drug library. In addition, some clinical uses suggest that N. sativa is safe and health promoter, especially observed in anti-fertility test. Although, the exact mechanism of action of the investigated pharmacological potentials yet to be found out, but the toxicological and its interaction profiles suggesting beneficial rather than detrimental effects. Generally, substances having antioxidant, antimicrobial cytotoxic other than genotoxic and mutagenic potentials are good for healthy consumption. TQ falls in this category, although the genotoxic and mutagenic potentials are still to be investigated. Finally, for its wide variety of activities, Nigella may be called the ‘marvelous shrub’.