European Journal of Medicinal Plants

Objective: To evaluate anti-plasmodial potency of extracts of Toddalia asiatica and Carica papaya when used in combinations.

Methods: The plants, were collected from Homa-Bay County in Kenya and dried under shade to constant weight then ground into fine powder. Extraction was then done using organic solvent. Extracts were tested against Plasmodium falciparum in vitro at a starting concentration of 100µg/mL, which was then serially diluted 2-fold in growth medium to generate the test concentration ranges.  The assay plate was incubated at 37⁰C for 72h in a sealed gas chamber under 3% O₂ and 4% CO₂ with the balance being N₂.  The remaining population of parasites at each concentration of the test compound was determined by comparing the absorbance of each well to the absorbance of a well containing the drug-free control. Survival was plotted against concentration and the IC50-values were obtained using a non-linear dose response curve fitting analysis. Phytochemical screening of the extracts of the was also done.

Results:  The study established that the plant extracts were reasonably active, yielding IC50 values between approximately 2 and 11 µg/mL. When the two plants extracts were used in combination with each other it was established that, addition of Carica papaya to Toddalia asitica seems to improve its potency across most concentrations as reflected in the shift in IC50 of Toddalia. However, the opposite is true for Carica, Best results were however seen with higher ratios of the Carica papaya extract was paired with smaller levels of the Toddalia extract. 

Conclusion: The shift in Toddalia asitica's IC50 values indicates that adding Carica papaya extract to Toddalia asitica extract generally seems to increase its potency.