Bioactive potentials of Vitellaria paradoxa stem bark extract on bacterial isolates associated with human infections.
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Date
2016
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Microbiology,Obafemi Awolowo University
Abstract
This study extracted the crude extract from stem bark of Vitellaria paradoxa, investigated the antibacterial potentials and mechanisms of action of potent fractions of the extract on susceptible bacterial isolates. It also assessed the phytochemical constituents and antioxidant properties of the plant. This was with a view to tackling problem of multidrug resistance development by microorganisms.
The stem bark of V. paradoxa was harvested from Ijagbo, Kwara State, Nigeria, and oven-dried at 40°C using hot-air oven and ground into fine powder. The powdered sample was cold extracted using methanol and sterile distilled water in ratio 3:2 (v/v). The mixture obtained was concentrated in vacuo using a rotary evaporator and then lyophilized. The crude extract collected was screened for antimicrobial activity against selected bacterial isolates associated with human infections. The crude extract was later partitioned into fractions using different organic solvents in the order of their polarity. The antimicrobial potentials of the crude extract and along with the fractions were determined using agar-well diffusion method. The active fractions were further partially purified by combination of thin layer and column chromatography. The antimicrobial activity of the resulting samples was tested against the bacterial strains previously used. The rate of killing, protein, nucleotide and potassium leakages were determined using Staphylococcus aureus and Escherichia coli as representatives of Gram positive and Gram negative bacteria respectively. The most active fraction of the partially purified butanol fraction was analysed using GC-MS.
The stem bark extract of V. paradoxa and various fractions obtained from it exhibited varying degrees of antibacterial activities. Phytochemical screening revealed the presence of alkaloids, flavonoids, saponins, tannins, reducing sugar and cardiac glycosides. The minimum inhibitory concentration of the crude extract ranged between 0.545 mg/mL and 2.187 mg/mL while those of aqueous, butanol and ethylacetate fractions ranged between 0.31 mg/mL and 5.00 mg/mL, 0.31 mg/mL and 2.50 mg/mL and 0.31 mg/mL and 2.50 mg/mL respectively. The time kill assay showed that the percentage of the cells killed increased with increasing concentrations of the fractions, as well as, contact time intervals. Leakages of protein, potassium ions and nucleotides followed the same trend observed for killing rate. Vitellaria paradoxa extract exhibited 50% inhibition at 0.008777 mg/mL, whereas ascorbic acid used as standard had IC50 of 0.078777 mg/mL. The major active constituent of the purified sample was identified as 14-methylhexadecanoic acid.
The study concluded that V. paradoxa stem bark extract which possessed antioxidant properties exhibited appreciable antimicrobial activities against the test pathogens.
Description
xix, 164p
Keywords
Bioactive pontentials, Vitellara paradox, Stem bark, Bacterial isolate, Human infections.
Citation
Olasunkanmi,O.O(2016). Bioactive potentials of Vitellaria paradoxa stem bark extract on bacterial isolates associated with human infections. Obafemi Awolowo University