Antibacterial activity and acute toxicity of herbs used in treatment of water borne diarrheal diseases in Butaleja District

Abstract

Uganda is still negatively impacted by a huge burden of water borne diseases, the heaviest being diarrhoeal diseases. This may result in high morbidity and mortality rates if left unattended to. The study documented herbs used in Butaleja district to treat water borne diarrhoeal diseases and evaluated their antibacterial efficacy and safety. This was achieved by: conducting an ethnobotanical survey employing observation, focus group discussions, informal, field & in-depth interviews; Evaluating in vitro antibacterial activity for crude ethanol, petroleum ether and aqueous extracts of six preferred medicinal plants against selected bacteria species: Bacillus cereus, Staphylococcus aureus and Clostridium perfringens (gram positives) and Shigella dysenteriae, Salmonella typhi, Escherichia coli (gram negatives) using agar well diffusion, minimal inhibitory concentration (MIC) values determined using a microplate serial dilution technique and consequently minimum bactericidal concentration (MBC) values; Evaluating oral acute toxicity of three preferred plant extracts in BALB/c mice of 5-7 weeks using old Lorke’s method. Ethnobotanical data was summarized using descriptive statistics, antibacterial assay data analysed using one-way analysis of variance and then tukey tests, acute toxicity data was subjected to probit analysis to determine median lethal doses. Fifty-six plant species from 31 families were reported, most dominant family was Fabaceae with eight plant species, 40% were sourced from wild and home gardens, tree life forms (33%) were most dominant, most dominant plant parts were leaves (37%), most dominant mode of preparation was decoction (40.9%) and most frequently cited plants were Microglossa pyrifolia & Tamarindus indica with a 5% frequency of citation. The preferred plant species basing on informant consensus were Erythrina abyssinica, Zanthoxylum leprieurii, Hydnora abyssinica, Cryptolepis Sanguinolenta, Diospyros natalensis, Securidaca longipedunculata. Five out of six preferred plant species exhibited antibacterial activity in at least some extracts with variable potency with MIC values ranging from 0.039 mg/mL to 2.5 mg/mL whereas MBC values ranged from 0.313 mg/mL to 5.0 mg/mL of crude extract. All three most effective plant extracts showed LD50 values above 5000 mg/kg of body weight, therefore, exhibited safety margins so people may use them without any doubts though more studies are required to isolate active compounds. The best solvent people should use is alcohol because they extract out active ingredients best which can be used to provide leads for drug discovery and among the selected plant species, Cryptolepis sanguinolenta was most effective.