The effect of plant growth regulators, FeO-CTs nanoparticles and LEDs light on the growth and biochemical compounds of black seed (Nigella sativa L.) callus in vitro.

Background: black seed (Nigella sativa L.) has long been utilized in traditional medicine and as a food ingredient due to its potential therapeutic properties including its effectiveness against cancer, coronaviruses, and bacterial infections. Recently, it has garnered significant attention for its rich reservoir of beneficial secondary metabolites. In vitro culture of black seeds presents an efficient and modern approach for the large-scale production of these valuable compounds, offering advantages such as space efficiency, reduced time, and lower costs. This study aimed to develop and optimize a protocol for callus induction and the identification of key secondary metabolites, including thymoquinone (TQ), phenolic compounds, and flavonoids. To induce callus formation in seed explants, two plant growth regulators (PGRs) were applied individually or in combination and incorporated into Murashige and Skoog (MS) culture medium.

Results: The combination of Auxin, 2,4-dichlorophenoxyacetic acid (2,4-D) and cytokinin, 6-benzylaminopurine (BAP), effectively induced callus formation in most explants, with the response varying based on concentration. The highest callus fresh weight (7.02 g) was obtained on Red(R) LED lighting with FeO-CTs nanoparticles (100 mg/L), which also resulted in the highest dry weight (1.307 g) after 40 days of cultivation. Similarly, the highest levels of phenols, flavonoids and amino acids were observed under R LED with FeO-CTs nanoparticles (100 mg L), while FeO-CTs nanoparticles at 100 and 200 mg/L) exhibited significant effects on metabolite production. In contrast, the antioxidant activity against DPPH free radicals and total carbohydrate accumulation were enhanced in callus cultures treated with FeO-CTs nanoparticles (200 mg/L) under dark conditions. Additionally, GC-MS analysis revealed that FeO-CTs nanoparticles (100 mg/L) yielded the most effective enhancement of secondary metabolites under blue (B) LED light at a concentration of 295 mg/L.

Conclusion: The finding of this study highlights the potential of the proposed method for the large-scale production of secondary metabolites, total carbohydrates, amino acids, phenolic compounds, and flavonoids from black seed callus cultures in a controlled environment. This optimized approach offers a cost-effective and space-efficient strategy for enhancing bioactive compound synthesis, with potential applications in pharmaceutical and nutraceutical industries.