Influence of biotic stress induction on the antimicrobial and biochemical parameters of Nigella sativa

The traditionally used indigenous medicinal plant Nigella sativa was germinated under fungal induced stress for the evaluation of its antifungal activity against Aspergillus niger, Trichoderma harzianum, Fusarium solani, Helmenthosporium myedis, Rizopus solani and its antibacterial effects on Bacillus subtilis, Pasturella multocida, Escherichia coli and Staphylococcus aureus. The biochemical parameters related to stress were also studied. Crude phosphate buffer (pH: 7.0) extracts of different days post inoculation (dpi) showed significantly high antimicrobial activity (disk diffusion method) against the selected strains at 237.5µg/mL The strongest antimicrobial activity was found against S. aureus and F. solani as compared to other bacterial and fungal strains. While comparing the activity at various dpi, stronger antibacterial activity was found at dpi 4, suggesting the induction of bioactive compounds of N. sativa was due to biotic stress. On the other hand, dpi 3 showed the highest antifungal activity against the selected strains. Biochemical parameters such as peroxidases (POD), catalases (CAT), superoxide dismutase (SOD) and proteases were recorded at different dpi. The highest specific activities were obtained at dpi 3 and 4. The highest total phenolic contents (gallic acid equivalent) were also found at dpi 3. This study demonstrates that the therapeutic activity of medicinal plants should be explored multifactoriously for the treatment of different human infections diseases.

Acknowledgement: Higher Education Commission, Government of Pakistan for funding the grant for this under the PYI programme.