Cytotoxicity, antibacterial and antifungal activities of five plant species used by agro-pastoral communities in Mbulu district, Tanzania.

Gymnema sylverstre, Phytolacca dodecandra, Cynoglossum geometrium, Leonotis nepetifolia and Ocimum filamentosum plant species are traditionally used by agro-pastoral communities in Mbulu, Tanzania for treatment of various plant, human and veterinary diseases. Extracts from plants were investigated for antibacterial and antifungal activities using agar well diffusion and broth macrodilution methods. Extracts were tested in vitro for cytotoxicity using Brine Shrimp Lethality test method. Cytotoxic activities against Brine Shrimps of all plants extracts were greater than that of Potassium permanganate standard. P. dodecandra leaf extract showed the highest cytotoxicity with an LC50 of 4.57 µg/ml. Roots of O. filamentosum, P. dodecandra and C. geometrium were potent against brine shrimps with LC50 values of 28.08, 34.74 and 71.09 µg/ml, respectively. Antibacterial activities of plants extract ranged between 25% and 75% of gentamycin standard activity with C. geometrium exhibiting the highest activity against Escherichia coli (ATCC 25922) at minimum inhibitory concentration (MIC) of 37.5 mg/mL. Antifungal activities of plants ranged from 0% to 55% of fluconazole standard activity with P. dodecandra leaves showing the highest activity against Cryptoccoccus neofomans (ATCC 66037) at an MIC of 9.4 mg/mL. Phytochemical screening of the plant species indicated the presence of alkaloids, terpenes, tannins, phenols, flavonoids, saponins and glycocides. The observed bioactivities could be associated with presence of these phytochemicals in plant species and lend credence to traditional use of these plant species in curing various plants, human and veterinary diseases.