Antimicrobial, free radical scavenging and cytotoxic activities of Khaya grandifoliola C.DC extracts

Abstract

Aims: Khaya grandifoliola C.DC is a plant used locally in Nigeria ethno medicine for remedy of various disease conditions. However, there is little scientific evidence to support the therapeutic claims of the plant. Therefore, these investigations were conducted to determine the antimicrobial activity, antioxidant and cytotoxic potentials of the plant extracts. Methodology and results: In vitro antimicrobial activity of the leaf and stem bark extracts of K. grandifoliola against some human pathogens was done using agar diffusion method. The free radical scavenging activity and cytotoxic property of the plant materials were evaluated using 2, 2- diphenyl-1-pieryhydrazyl radical (DPPH) and brine shrimp lethality bioassay methods respectively. The yields of the plant material extracts ranged from 3.57±0.06 to 6.49±0.01% and 4.76±0.02 to 9.17±0.06% for the leaf and stem bark extracts respectively. The minimum inhibitory concentration (MIC) of KG-A and KG-E ranged from 2.5 to 200 mg/mL and recorded remarkable activity against the growth of Staphylococcus aureus, Escherichia coli, Salmonella typhi, Pseudomonas aeruginosa, Trichophyton rubrum and Aspergillus flavus. However, Strepcoccus pneumoniae, Staphylococcus epidermidis, Klebsiella pneumoniae, and T. rubrum were resistant to the KG-W. The plant extracts demonstrated high DPPH free radical scavenging activity when compared with ascorbic acid used as control in the assay and, also exhibited lethality against brine shrimp larvae with LC50 values ranging from: leaf extracts (0.67 to 1502 ppm) and stem bark extracts (0.91 to 1431 ppm). Conclusion, significance and impact of study: The results show that the KG-A and KG-E have great potentials as antimicrobial agent and may be used in the treatment of infectious diseases caused by the susceptible organisms.