Phytochemical Screening, Mineral Content, Antioxidant Potential and Antibacterial Activity of the Leaves Extract of <i>Alstonia boonei</i>

Abstract

This study evaluated the phytochemical constituents, antioxidant potential, mineral content and antibacterial activity of the ethyl acetate  extract of Alstonia boonei leaves. The results of the phytochemical screening revealed the presence of phenolics, eugenols, steroids,  alkaloids and reducing sugars. While the mineral content for sodium, potassium, calcium, magnesium, copper iron and zinc were found  to be5.61 mg/kg, 120.63 mg/kg, 15.61 mg/kg, 2.63 mg/kg, 0.01 mg/kg, 7.15 mg/kg and 1.62 mg/kg respectively. The antioxidant potential examined using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay at 250, 200, 150, 100 and 50 μg/ml gave the IC₅₀ of 2.89  μg/ml and 2.52 μg/ml for the extract and standard, respectively. Determination of the zone of inhibition of the bacterial isolates using  agar well diffusion method revealed that the isolates showed varying sensitivity towards the extract. Pseudomonas aeruginosa had the  highest value at 35 mm and subtilis had the lowest sensitivity value at 26.5 mm. The minimum inhibitory concentration (MIC) values were  found to be 25 mg/ml for Pseudomonas aeruginosa and 12.5 mg/ml for Klebsiella pneumoniae, Escherichia coli, Staphylococcus aureus and  Bacillus subtilis. The minimum bactericidal concentration (MBC) values were found to be 12.5 mg/ml for Klebsiella pneumoniae, 50 mg/ml  for Escherichia coli and Staphylococcus aureus, 25 mg/ml for Pseudomonas aeruginosa while Bacillus subtilis was above 50mg/ml. The results  provided a useful insight into the medicinal uses of the plant extract against oxidative stress and microbial infections.