Evaluation of Antibacterial Efficacy of Ocimum gratissimum n-Hexane Extract against Staphylococcus aureus
Umar Muazu
*
Department of Biotechnology, Faculty of Computing and Sciences, Mewar International University Nigeria, Masaka, Nasarawa State, Nigeria and Department of Food Technology and Value Addition, National Cereals Research Institute, Badeggi, Niger State, Nigeria.
Sa'adatu Idris
Department of Biotechnology, Faculty of Computing and Sciences, Mewar International University Nigeria, Masaka, Nasarawa State, Nigeria.
Amina Ahmed Saleh
Department of Biotechnology, Faculty of Computing and Sciences, Mewar International University Nigeria, Masaka, Nasarawa State, Nigeria.
Aisha Labaran Aliyu
Department of Biotechnology, Faculty of Computing and Sciences, Mewar International University Nigeria, Masaka, Nasarawa State, Nigeria.
Amina Muhammad Abara
Department of Biotechnology, Faculty of Computing and Sciences, Mewar International University Nigeria, Masaka, Nasarawa State, Nigeria.
Nabila Jamilu Zarewa
Department of Biotechnology, Faculty of Computing and Sciences, Mewar International University Nigeria, Masaka, Nasarawa State, Nigeria.
Hafsah Ibraheem
Department of Biotechnology, Faculty of Computing and Sciences, Mewar International University Nigeria, Masaka, Nasarawa State, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Background: Ocimum gratissimum is a medicinal plant widely used in traditional medicine for the treatment of various infections due to its antimicrobial properties.
Aim: This study evaluated the antibacterial activity of n-hexane leaf extract of Ocimum gratissimum against Staphylococcus aureus.
Methodology: The plant leaves were collected, air-dried, and ground into powder before extraction using n-hexane as the solvent (50 g in 250 mL). The extract obtained was concentrated and subsequently dissolved using Dimethyl Sulfoxide to obtain a uniform solution. The antibacterial activity of the extract was determined using the agar well diffusion method with a 0.5 McFarland standard (~1.5 × 10⁸ CFU/mL), 6 mm wells, 100 μL per well, and incubation at 37℃ for 24 hours. MIC was determined by broth dilution from 100% to 6.25%, and MBC was assessed by subculture.
Results: The n-hexane leaf extract of Ocimum gratissimum exhibited concentration-dependent antibacterial activity against Staphylococcus aureus, with zones of inhibition of 12-22 mm. In broth dilution, no turbidity was observed at 100% and 50% concentrations, while turbidity was observed at 25%, 12.5%, and 6.25%; hence, the MIC was 50%. For MBC determination, only concentrations up to 50% were subcultured because the extract volume at 100% concentration was insufficient. Growth was observed at 50%; hence, the MBC was not achieved within the tested range (MBC >50%), indicating bacteriostatic activity at ≤50%.
Conclusion: These findings indicate that Ocimum gratissimum possesses preliminary in vitro antibacterial activity against Staphylococcus aureus and may serve as a candidate for the development of plant-based antimicrobial agents against antibiotic-resistant pathogens.
Keywords: Ocimum gratissimum, Staphylococcus aureus, n-hexane extract, antibacterial activity, agar well diffusion, minimum inhibitory concentration, minimum bactericidal concentration, medicinal plant, dimethyl sulfoxide, gentamicin