Antimicrobial activity of aqueous, ethanolic extracts and crude extracted phytoconstituents of Nigella sativa seeds

Nigella sativa seeds (black seed; Kalonji) have been used in traditional medicine for the treatment of a variety of diseases. In this study, the antibacterial and antifungal effects of ethanol and aqueous extracts of seeds as well as crude extracted phytoconstituents against two gram positive (Bacillus subtilis, Staphylococcus aureus) and two gram negative strains of bacteria (Escherichia coli, Pasturella multocida) and one strain of fungi (Aspergillus niger) have been investigated and compared with standard drug i.e chloramphenicol. Percentage of phytoconstituents in the seed was also determined. The inhibitory effects of extracts and phytoconstituents were assessed using disk diffusion method at three different concentrations i.e 50mg/mL, 100mg/mL and 15omg/mL. Results showed that the aqueous extract did not show any effect against Pasturella multocida and against Aspergillus niger of fungi, However against all bacterial strains Nigella sativa showed inhibition zone between the range of 20 and 23mm. Ethanolic extract showed inhibition zone between the range of 15 and 28mm against all the four bacterial strains. Against fungi 15mm inhibition zone was observed. Phytoconstituents showed varying degree of inhibition against all the four bacteria and fungi. Alkaloids showed no inhibition against Escherichia coli and Pasturella multocida. Steriods and triterpenoids against Staphylococcus aureus, Tannic acids against Staphylococcus aureus and Bacillus subtilis also showed no inhibition. All the extracts and phytoconstituents showed varying degree of inhibition.