Comparative studies on the in vitro antioxidant and antibacterial activity of methanolic and hydro-ethanolic extracts from eight edible leafy vegetables of Ghana

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Epidemiological studies indicate that consumption of fruits and vegetables has the ability to inhibit the damaging activities of free radicals and other pathogens in the human body. Eight edible leafy vegetables of Ghana namely: Xanthosoma sagittifolium, Hibiscus sabdariffa, Solanum macrocarpon, Talinum triangulare, Corchorus olitorius, Laportea aestuans, Ipomoea batatas, and Amaranthus cruentus were assessed for their in vitro antioxidant and antibacterial properties. The experimental results indicate that hydro-ethanol is an effective solvent for extracting the phytoconstituents of the leafy vegetables. The total antioxidant capacity (TAC) and total phenol content (TPC) in the methanol extracts (METE) and hydro-ethanol extracts (HETE) from the selected leafy vegetables within the measured concentration range (0.1 - 3.0 mg/mL) decreased in the order X. sagittifolium > I. batatas > L. aestuans > T. triangulare > H. sabdariffa > C. olitorius > S. macrocarpon > A. cruentus. A high and positive correlation was observed between TPC and TAC in both the METE and HETE from all the selected leafy vegetables. The selected leafy vegetables showed strong antioxidant properties with respect to their free radical scavenging activity and Fe3+ reduction ability with hydro-ethanol extracts indicating higher antioxidant potential compared with their respective methanol extracts. In addition, the extracts from the selected leafy vegetables exhibited a strong antibacterial activity against the growth of Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus with the exception of extracts from H. sabdariffa, C. olitorius, S. macrocarpon, and A. cruentus which showed no activity against the growth of B. subtilis.
A Thesis Submitted to the Department of Chemistry,Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfillment of the requirements for the award of the Master of Philosophy Degree in Chemistry,