The diet and health linkages are well defined and many research studies carried out in animal and humans provided evidences that dietary modules are best strategy in preventing many ailments e.g. cardiovascular disorders and diabetes mellitus [
4].
Nigella sativa is famous in Asian countries owing to its potential role in prevention of different ailments. In this regard, Sultan et al. [
8] carried out the safety assessment of
Nigella sativa fixed and essential oil (NSFO & NSEO). In the present research, further efforts were made to study the effects of NSFO and NSEO on hepatic enzymes, antioxidant status and immunopotentiating potential of
Nigella sativa in oxidative stressed Sprague dawley rats. The protocols followed in the present research were based on the studies conducted by scientists [
20,
21].
In the present study, we fed the groups of rats on experimental diets containing
N. sativa fixed and essential oils along with control for a period of 8 weeks. The addition of
N. sativa fixed and essential oil increased feed and water intakes as compared to control group that certainly be due to the remedial action of experimental diets thus resulting in restoration of normal metabolism and body homeostasis [
22‐
24]. Oxidation and its complexities results in uncontrolled free radicals production that become lethal leading to oxidative stress. In this regard, these reactive oxygen species (ROS) overcomes the antioxidant capacity of the target cells and tissues. In stress-induced conditions, supplementation of antioxidants may evoke certain protective roles in the body against various health discrepancies [
25]. In the instant study, total antioxidant capacity (TAC) of the body decreased significantly in control group, while values for serum MDA and conjugated dienes levels increased indicating more oxidative damage. However, diets containing
N. sativa fixed and essential oils assuaged the damage by improving total antioxidant capacity by 1.5 and 2.0 folds, respectively. Moreover, serum MDA level decreased significantly by 20.58 and 51.62 % in fixed and essential oils groups, respectively. The conjugated dienes levels also decreased significantly i.e. 15.98 and 34.35 %, respectively. However, levels of serum MDA and conjugated dienes were higher as compared to normal rats owing to injection of potassium bromate used for induction of oxidative stress [
8]. Total antioxidant capacity (TAC) is primarily dependent on antioxidants defence system capabilities and secondly on antioxidants ingested as a part of the diet. Moreover, it also relies on total free radical trapping potential of the body in both normal and oxidative stress conditions. The decreased TAC in oxidative stressed rats can be due to depletion of antioxidants present in the body and increased free radical production. Correlation also provided the evidence that MDA and conjugated dienes were negatively associated with TAC. The investigations conducted by Al-Othman et al. [
26] proved that black cumin supplementations hold potential to improve the antioxidant capacity of the body. Antioxidant status i.e. glutathione, α- and γ-tocopherols were improved consequently with experimental diets. Level of glutathione decreased in control by 25.23 %, while increased by 4.30 and 21.82 % in
N. sativa fixed and essential oils groups, respectively. The restoration of glutathione to near normal ranges is hallmark of the present study. Glutathione along with tocopherols were in linear linkage with antioxidant capacity, while inverse association with that of oxidative damage. These findings further validated our stance that supplementation of diets rich in tocopherols and antioxidant ameliorate the adverse consequences of oxidative stress. Production of free radicals results in lipid peroxidation thus resulting in extensive oxidative damage as indicated by high level of MDA & conjugated dienes. These indicators were modulated in groups of rats consuming fixed and essential oil based diets. According to Alenzi et al. [
27], the oils of black cumin and thymoquinone served a protective mechanism against toxicity induced by cyclophosphamide and prevent incidence of necrosis. Formerly, Meral and Kanter [
28] observed reduced level of MDA, improved antioxidant capacity and restoration of glutathione because of black cumin supplementation that strengthened the present results.
Lipid peroxides and associated moieties are products of lipid peroxidation that are harmful in progression of diseases such as atherosclerosis and brain damage. However, experimental diets attenuated the damage that certainly be attributed to their rich nutritional profile. In this context, El-Desoky et al. [
29] suggested the potential role of tocopherols and nutraceuticals in scavenging free radicals and ameliorating their toxic effects for normal functionality of the body. In another research investigation, Sánchez-Reus et al. [
30] reported that oxido-reduction or GSH/GSSG ratio is important in controlling the antioxidant potential of the body. In the present study, NSFO and NSEO modulated the hepatic enzymes activity. The aforementioned results indicated the involvement of complex mechanism in which specialized processes involving glutathione and tocopherols scavenge the oxidants like MDA, lipid peroxides, hydro-peroxides and conjugated dienes. The expressions of hepatic enzymes enhance the antioxidant capacity in the groups of rats fed on experimental diets. In this context, glutathione reductase (GR), glutathione peroxidase (GPx) and glutathione transferase (GST) are important biological catalyst to control peroxides and free radicals production through glutathione cyclic transformation [
31].
Role of enzymes in amelioration of oxidative stress is indispensable. Casalino et al. [
32] supported the present findings that antioxidant supplementation could avert the hepotocellular damage as a consequences of oxidative stress. The enhanced level of these metabolites triggers cascade of events that results in malfunctioning of the body and even in severe cases death may be the possible penalty. The supplementations of diets with appropriate antioxidant or formulation containing bioactive compounds are useful in reversing the sequential distortion due to free radicals. Some other studies also suggested that active ingredients present in
N. sativa fixed and essential oils protect the body from nephrotoxicity and hepatotoxicity [
4].
N. sativa fixed and essential oils ameliorate oxidative stress and maintain body homeostasis by regulating several hematological and serological attributes. The present exploration concluded that
N. sativa fixed and essential oils have potential to improve the antioxidant status of the body. The diet supplemented with the
N. sativa oils with special reference to essential oil can act as safeguard against oxidative stress and allied disorders. Future perspectives include testing their effectiveness as nutraceuticals in maladies characterized by oxidative stress like arthritis and osteoporosis.