Evaluation of anti theilerial activity of a lipophilic root bark extract of stereospermum kunthianum against theileria parva
Background: naphthoquinones are common compounds found in several species of bignoniaceae and exhibit anti plasmodial activity hence can serve as potential sources of lead compounds for discovery and development of antitheilerial drugs. previous studies indicate that plants with good antiplasmodial activity are also very good candidates for development of anti theilerial drugs. though considered effective if treatment is started early, the conventional drugs currently used in the treatment of east coast fever (ecf) are very expensive and not readily available in rural areas. methods: the detection of naphthoquinones in the different extracts of stereospermum kunthianum ( fam. bignoniaceae) was possible with uv light at 254 nm using uv lamp and then at 365nm after spraying the spots seen at 254 nm with 10 % methanolic – potassium hydroxide reagent. the antitheilerial activity of the lipophilic root bark extract against theileria parva was evaluated by observing visual colour changes to establish growth of the organism under the defined conditions, counting mean number of cells with dead macroschizonts per slide, counting the mean number of dividing cells per slide and calculating the percentage of cells infected by t. parva after 48 hrs and 10 days following treatment. the medium effective concentration of the extract was determined by linear regression analysis. results: sixteen unknown naphthoquinones in both the lipophilic and hydrophilic extracts of the leaf, stem bark and root bark of s. kunthianum were screened. the lipophilic root bark extract of s.kunthianum caused death of macroschizonts of t.parva with 18 % mean percentage activity at a start experimental dose of 1 μg/l. the mean percentage activity against macroschizonts of t. parva increased with increase in the concentration of the lipophilic root bark extract of s. kunthianum. the in vitro median effective concentration, ic50 of 1.6μg/l as compared to the ic50 of 0.3 μg/l for buparvaquone, a known hydroxy naphthoquinone used in the treatment of ecf. conclusions: the presence of naphthoquinones in the leaf and stem bark of stereospermum kunthianum ( fam.bignoniaceae) has been established for both the hydrophilic and lipophilic extracts and validation of their presence in the root bark extracts has been done confirming earlier reports of presence of naphthoquinones in the lipophilic root bark extract of stereospermum kunthianum. the activity of lipophilic root bark extract of stereospermum kunthianum against theileria parva has also been established with in vitro median inhibitory concentration, ic50 of 1.6μg/l as compared to the reported ic50 of 0.3 μg/l for buparvaquone.