Preliminary Phytochemical, Antioxidative and Antibacterial Screening of Selected Medicinal Plants for Possible use in the Treatment of Bacterial Diseases

Abstract

Development of cheap and reliable diagnostics is pivotal in the control of infectious diseases. Currently, one of the best strategies to tackle infectious disease is the use of natural products from plant origin, due to the perception that long term use of western medicine induces severe complications and also to stop the prevalence of antibacterial infection. This study aims at substantiating the traditional use of selected medicinal plants with antibacterial claim for possible lead for the development of more potent drugs in the treatment of bacterial infections. The preliminary phytochemical content, antioxidant and antibacterial potential of the selected medicinal plants were evaluated using standard procedures. Thirtheen plants were obtained through questionnaire administration: Garcinia kola, Costus afer, Vitellaria paradoxa, Pycnanthus angolensis, Cola acuminata Acanthospermum hipida, Aloe vera, Euadenia trifoliate, Microglossa abzelii, Moringa oleifera, Bryophyllum pinnatum, Baphia nitida and Afromonium melegueta. Thin layer chromatography (TLC) profiling of the various selected plants were carried out using two solvent system consisting of n-Hexane and ethyl acetate in varying ratio (8:2 and 7:3). Eight (8) plants, which showed good chromatographical profiling with the used solvent, were selected for further experiment (Garcinia kola, Vitellaria paradoxa, Acanthospermum hispidum, Aloe vera, Microglossa abzelii, Baphia nitida, Moringa oleifera and Bryophyllum pinnatum). These plants were subjected to qualitative phytochemistry and five plants (Moringa oleifera, Vitellaria paradoxa, Baphia nitida, Bryophyllum pinnatum and Garcinia kola) selected for quantitative phyto-screening for alkaloids, flavonoids, saponins and tannins. The antibacterial screening was carried out using Agar well diffusion and minimum inhibitory concentration (MIC) against the following isolate Staphylococcus aureus, Escherichia coli, Salmonella typhi and Bacillus subtilis. The antioxidant potential of the selected five plants were evaluated using in vitro (DPPH and FRAP) and the best plant was used for in vivo (SOD and MDA) analysis. The phytochemistry of the 13 plants revealed the presence or absence of Alkaloids, saponins, tannins, flavonoids, terpenoids, cardiac glycosides, carbohydrates and protein in the selected plants, and the best five were selected for quantitative evaluation showed they all have good quantity of alkaloids, flavonoids, saponins and tannins. The plants exhibited mild to strong antibacterial activities, having an MIC value ranging from 2.5 to >20 µg/mL when compared to ciprofloxacin (control) that is 5µg/mL. The plants showed good free radical scavenging activities and efficient ferric reducing power in a concentration dependent manner and a good enzyme activity of the superoxide dismutase (SOD) at a concentration of 100 µ/mL with a reduction in malondialdehyde (MDA) production as a marker of lipid peroxidation. The various plants have potentials for development of drugs for the treatment of infectious diseases; and a potential for further evaluation of their antibacterial claim.