The screening of medicinal plants traditionally used to treat ...

155Pillay et al., 2001). In this study remedies to treat diarrhoea were preparedaccording to traditional practice except those that were extracted usingmethanol and acetone and tested for antibacterial activity. The greatestadvantages of acetone are the volatility, miscibility with polar and non-polarsolvents and its relatively low toxicity to the test organism. Due to the ease ofhandling extract fractions at subsequent stages, acetone is probablepreferable to methanol and more hydrophilic compounds were tested becauseacetone extracted highly polar components.All the plants reported by people to have the potential to treat diarrhoea testedpositive for antibacterial activity (those sourced at homesteads, as well asthose bought at the muthi market). In this study, Staphylococcus aureus wasmostly inhibited by all the different plant extracts. The micro-organisms thatwere the least inhibited were Shigella sonnie, Shigella flexnerie andSalmonella typhii. The results of the disk-diffusion were confirmed by theagar-well diffusion assay. The measurements of the zone of inhibition for boththe methods ranged from 10 mm to about 30 mm in diameter. The lowestMIC value of the plant extracts was 1 mg/ml and 0.4 mg/ml. From the resultsthat were obtained in this study it is believed that plants which are rich in awide variety of secondary metabolites belonging to chemical classes such astannins and alkaloids are generally better in their antimicrobial activities andthis corroborates with what has been investigated by Cowan (Cowan, 1999).This suggests that the strength of antimicrobial activity of a plant depends onthe diversity and quantity of chemical component it contains.The results lend some support to traditional knowledge and can serve as abasis for selecting the most active medicinal plants to use in traditionalmedicine practices in the future. These plants include: Acacia robusta, Aloearborescens, Baccharoides adoensis, Chromolaena odarata, fhlaza, Uppiajavanica, Psidium guajava, Schotia brachypeta/a, Syzygium cordatum,Tetradenia riparia and Vemonia tigna. The inhibitory effects of most of theplant extracts from the above results can be considered as goodantidiarrhoeal agents. Further work needs to be done in order to isolate andidentify antimicrobial compounds from the plant extracts. This finding lends