Antimicrobial and Antioxidant Properties of Aqueous Garlic (Allium sativum) Extract against Staphylococcus aureus and Pseudomonas aeruginosa

Abstract

Aim: To investigate the antimicrobial and antioxidant properties of aqueous garlic (Allium sativum) extract against Staphylococcus aureus and Pseudomonas aeruginosa. Methods: Determination of Proximate Composition, DPPH radical-scavenging activities, qualitative and quantitative analysis of the aqueous garlic extract (AGE) were carried out using standard methods. The antimicrobial activity was evaluated by agar well diffusion method. MIC, MBC and other microbial analyses were also determined using standard methods. Results: The proximate composition of the garlic indicate that they contain carbohydrate (66.8%), oil (2.6%), moisture (14.5%), total ash (1.3%) and protein (14.8%). The Phytochemical analysis of aqueous extract of Allium sativum shows the presence of secondary metabolites like tannins, terpenoids, steroids, saponins, phenol, protein and reducing sugar. The amount of total phenol content present was 0.285±0.0226 mg/ml while that of flavonoid content was 28.74±8.23 mg QUE/ml. The DPPH scavenging activity of the extract range from 4.47% to 92.44% for the garlic extract with corresponding to concentration range from 3 to 40 mg/ml while the IC50 value was 25.3 mg/ml. Agar well diffusion method was used to determine the antimicrobial activity of the garlic extract. It was characterized by inhibition zones of 25.6±2.4 mm for S. aureus and 28.1±1.8 mm for P. aeruginosa. Pseudomonas aeruginosa was tested against 10 standard antimicrobial agents, of these; chloramphenicol, ciprofloxacin, septrin, pefloxacin, streptomycin, gentamicin, amoxacillin, and sparfloxacin were sensitive while augmentin and tarivid were resistant to the tested organism. Staphylococcus aureus were susceptible to pefloxacin, amoxacillin, ciprofloxacin, streptomycin, and septrin. Resistance to gentamicin, ampiclox, zinnacef, rocephin and erythromycin were also observed with the same organism. The minimum inhibitory concentration (MIC) for P. aeruginosa was 40 mg/ml while S. aureus has a value of 80 mg/ml. The extract has a minimum bacteriocidal concentration (MBC) of 88 mg/ml for P. aeruginosa and 104 mg/ml for S. aureus. The extract has strong potency against these microorganisms with P. aeruginosa being the most susceptible.