Comparative Studies on the In Vitro Antioxidant and Antimicrobial Properties of Methanolic And Hydro-Ethanolic Plant Extracts from Five Medicinal Plant Parts of Ghana

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Studies show that consumption of plant products has the potential to inhibit the damaging activities of free radicals in the human body. Five medicinal plant parts of Ghana namely: the seed of Okuobaka aubrevillei, leaves of Annona muricata, leaves of Theobroma cacao, the false stem and root Cymbopogon citratus were assessed for their antioxidant properties and antimicrobial properties. The experimental results indicate that hydro-ethanol is an effective solvent for extracting the phytoconstituents of the medicinal plants. The total antioxidant capacity (TAC) and total phenol content (TPC) in the methanol extracts (METE) and hydro-ethanol extracts (HETE) from the selected medicinal plants within the measured concentration range (0.1 - 3.0 mg/ml) decreased in the order T. cacao > A. muricata > root of C. citratus > false stem of C. citratus > O. okuobaka. A high and positive correlation was observed between TPC and TAC in both the METE and HETE from all the selected medicinal plants. The selected medicinal plant 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. All extracts of the plants tested showed varying degree of antibacterial activities against the test bacterial species (S. aureus, E. coli and B. substlis). The hydro-ethanol extracts showed higher activity than the methanol extracts. However, the hydro - ethanol extract of the root of C. citratus showed no activity against S. aureus, E. coli at lower concentrations.
A Thesis Submitted to the Department Of Chemistry, College of Science and the School Of Graduate Studies, Kwame Nkrumah University of Science and Technology In Partial Fulfilment of the Requirement for the Award of the Degree of Master of Philosophy (Analytical Chemistry), June-2013