Studies of Bioactive Potentials of the Root Extracts of Elaeis guineensis Jacq. against Pathogens Implicated in Wound Infections

Abstract

This study was carried out at the Department of Microbiology, Obafemi Awolowo University, Ile-Ife, Nigeria, between April and October, 2014. It was designed to investigate the antimicrobial activities of the root extract of Elaeis guineensis Jacq. on some bacteria implicated in wound infection. This was with a view to obtaining the root extract of E. guineensis and testing its in vitro bactericidal effects, the modes of action on various strains of Staphylococcus aureus, Pseudomonas aeruginosa and Klebsiella pneumoniae implicated in wound infections as well as to determine the phytochemical components present in the plant extract that are responsible for the bioactivity. The root of E. guineensis was harvested from Akinlalu area, Ile-Ife, Nigeria in the month of April, 2014. The plant sample was dried in hot air oven at 45ºC and then ground to fine powder. The powered root was cold extracted using methanol and distilled water (3:2 v/v). The methanolic extract obtained was concentrated in vacuo using rotary evaporator and then lyophilised. The methanolic crude extract was screened for phytochemicals and tested for antimicrobial activity against all the bacterial isolates associated with wound infection. The extract was later partitioned using different organic solvents in the increasing order of polarity starting from n-hexane, chloroform, ethyl acetate and butanol. The antimicrobial potentials of the crude extract and that of the partitioned fractions were determined by agar-well diffusion method. The minimum inhibitory concentrations (MIC) and the minimum bactericidal concentrations (MBC) of the crude extract and the ethyl acetate fraction were also determined. Finally, the rate of kill, potassium ions and nucleotides leakages were determined using Staphylococcus aureus and Pseudomonas aeruginosa as representatives of Gram-positive and Gram-negative organisms. The crude extract and the ethyl acetate fraction exhibited varying degrees of antimicrobial activity while other fractions did not show appreciable antimicrobial activities. The MIC of the crude extract ranged between 0.78 and 12.50 mg/mL and that of the ethyl acetate fraction ranged between 0.63 and 5.00 mg/mL. Phytochemical screening of the crude extract showed the presence of tannins, saponins, steroids and flavonoids. The time-kill assay revealed that the percentage of the cells killed increased with increase in the concentrations of the fractions as well as contact time intervals. A 100% kill was achieved by ethyl acetate fraction on Staphylococcus aureus at 3 x MIC within 120 minutes, whereas 100% kill was achieved by the same fraction on Pseudomonas aeruginosa at 3 x MIC within 30 minutes. Varying amounts of potassium ions as well as nucleotides were leaked by the ethyl acetate fraction from selected bacterial isolates leading to their death. The leakages of these materials were monophasic. This study concluded that the crude extract along with the ethyl acetate fraction obtained from it exhibited appreciable bactericidal activities at minimal contact time and low concentrations. It also established the root extract of E. guineensis as a potential source of broad spectrum antibacterial drugs in the treatment of wound infections.