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Abstract Background Diseases caused by microorganisms and parasites remain a major challenge globally and particularly in sub-Saharan Africa to man and livestock. Resistance to available antimicrobials and the high cost or unavailability of antimicrobials complicates matters. Many rural people use plants to treat these infections. Because some anthelmintics e.g. benzimidazoles also have good antifungal activity we examined the antifungal activity of extracts of 13 plant species used in southern Africa to treat gastrointestinal helminth infections in livestock and in man. Methods Antifungal activity of acetone leaf extracts was determined by serial microdilution with tetrazolium violet as growth indicator against Aspergillus fumigatus, Cryptococcus neoformans and Candida albicans. These pathogens play an important role in opportunistic infections of immune compromised patients. Cytotoxicity was determined by MTT cellular assay. Therapeutic indices were calculated and selectivity for different pathogens determined. We proposed a method to calculate the relation between microbicidal and microbistatic activities. Total activities for different plant species were calculated. Results On the whole, all 13 extracts had good antifungal activities with MIC values as low as 0.02 mg/mL for extracts of Clausena anisata against Aspergillus fumigatus and 0.04 mg/mL for extracts of Zanthoxylum capense, Clerodendrum glabrum, and Milletia grandis, against A. fumigatus. Clausena anisata extracts had the lowest cytotoxicity (LC50) of 0.17 mg/mL, a reasonable therapeutic index (2.65) against A. fumigatus. It also had selective activity against A. fumigatus, an overall fungicidal activity of 98% and a total activity of 3395 mL/g against A. fumigatus. This means that 1 g of acetone leaf extract can be diluted to 3.4 litres and it would still inhibit the growth. Clerodendrum glabrum, Zanthoxylum capense and Milletia grandis extracts also yielded promising results. Conclusions Some plant extracts used for treatment of parasitic infections also have good antifungal activity. Because it is much easier to isolate antifungal compounds by bioassay guided fractionation, this approach may facilitate the isolation of anthelmintic compounds from active plant extracts. The viability of this approach can be tested by isolating the antifungal compounds and then determining its anthelmintic activity. Some of these plant extracts may also be useful in combating fungal infections.

Abstract Background The poultry industry due to intensive methods of farming is burdened with losses from numerous infectious agents, of which one is the fungus Aspergillus fumigatus. In a preliminary study, the extracts of Loxostylis alata A. Spreng, ex Rchb. showed good activity in vitro against A. fumigatus with a minimum inhibitory concentration of 0.07 mg/ml. For this study crude, a crude acetone extract of L. alata leaves was evaluated for its acute toxicity in a healthy chicken model and for efficacy in an infectious model of aspergillosis (A. fumigatus). Results At a dose of 300 mg/kg, the extract induced some toxicity characterised by decreased feed intake and weight loss. Consequently, 100 and 200 mg/kg were used to ascertain efficacy in the infectious model. The plant extract significantly reduced clinical disease in comparison to the control in a dose dependant manner. The extract was as effective as the positive control ketoconazole dosed at 60 mg/kg. Conclusions The results indicate that a crude extract of L. alata leaves has potential as an antifungal agent to protect poultry against avian aspergillosis.

Abstract Background Several herbs are traditionally used in the treatment of a variety of ailments particularly in the rural areas of South Africa where herbal medicine is mainly the source of health care system. Many of these herbs have not been assessed for safety or toxicity to tissue or organs of the mammalian recipients. Methods This study evaluated the cytotoxicity of some medicinal plants used, inter alia, in the treatment of diarrhoea, and stomach disorders. Six selected medicinal plants were assessed for their antibacterial activities against ampicillin-resistant and kanamycin-resistant strains of Escherichia coli by the broth micro-dilution methods. The cytotoxicities of methanol extracts and fractions of the six selected plants were determined using a modified tetrazolium-based colorimetric assay (3-(4, 5-dimethylthiazol)-2, 5-diphenyl tetrazolium bromide (MTT) assay). Results The average minimum inhibitory concentration (MIC) values of the plants extracts ranged from 0.027 mg/mℓ to 2.5 mg/mℓ after 24 h of incubation. Eucomis autumnalis and Cyathula uncinulata had the most significant biological activity with the least MIC values. The in vitro cytotoxicity assay on human hepatocarcinoma cell line (Huh-7) revealed that the methanol extract of E. autumnalis had the strongest cytotoxicity with IC50 of 7.8 μg/mℓ. Ethyl acetate and butanol fractions of C. uncinulata, Hypoxis latifolia, E. autumnalis and Lantana camara had lower cytotoxic effects on the cancer cell lines tested with IC50 values ranging from 24.8 to 44.1 μg/mℓ; while all the fractions of Aloe arborescens and A. striatula had insignificant or no cytotoxic effects after 72 h of treatment. Conclusions Our results indicate that the methanol fraction of E. autumnalis had a profound cytotoxic effect even though it possessed very significant antibacterial activity. This puts a query on its safety and hence a call for caution in its usage, thus a product being natural is not tantamount to being entirely safe. However, the antibacterial activities and non-cytotoxic effects of A. arborescens and A. striatula validates their continuous usage in ethnomedicine.