Antimicrobial and antioxidant properties of African medicinal plants

Objective:To study antioxidant and antimicrobial properties ofTerminalia catappa,Psidium guajava,Alstonia boonei,Morinda lucida (M. lucida) andSpondias mombin leave extracts using ethanol, petroleum-ether and aqueous media. <br> Methods: The free radical 2, 2-diphenyl-1-picrylhydroazyl was used to measure scavenging activities of extracts, while phenolic and flavonoid content were estimated by spectrophotometry. Antibacterial screening of extracts was done by determining zone of inhibition using disc diffusion method. Plant extracts were tested against five strains of Gram-positive and Gram-negative bacteria. After sterilization, the discs were loaded with concentrations of broad spectrum ciprofloxacin, and prepared extract solutions of different concentrations were refrigerated for 24 h. Determination of minimum inhibitory concentration of extracts in the screening assay was according to micro-broth dilution, while determination of minimum bactericidal concentration was carried out by agar diffusion. <br> Results: The highest radical scavenging effect was found in petroleum ether extracts of all the plants withM. lucida andPsidium guajava having the highest and lowest values respectively. Aqueous solvent recorded highest phenolic content in all extracts with the exception ofM. lucida. Flavonoid content was extracted better fromAlstonia boonei andM. lucida with ethanol, while aqueous solvent extracted more from the other plants. With exception of extracts from petroleum ether, all others exhibited varying levels of antibacterial activities againstE. coli,Pseudomonas aeruginosa,Salmonella typhi,Vibrio cholera andStaphylococcus aureus. <br> Conclusions:This study proved that all crude extracts showed strong antioxidant and antimicrobial potentials, which qualified them as nutraceuticals in fish feed production.