In Vitro Antiprotozoal Activity of the Leaf Latex of Caralluma speciosa Against Two Leishmania Species

Abstract

The alarming growth of parasite resistance has increased the urgency of finding novel therapeutic compounds for the treatment of protozoal diseases such as leishmaniasis. Previous studies have demonstrated that several plants belonging to the genus Caralluma possess antiprotozoal activity against malaria, trypanosomiasis and leishmaniasis. In the present study, the antiprotozoal activity of the methanolic extract of the leaf latex obtained from the Ethiopian plant Caralluma speciosa N. E. Br. (family Asclepiadaceae) was evaluated by in vitro testing against Leishmania aethiopica and L. donovani. Antileishmanial activity test was carried out using the Alamar Blue assay on promastigotes and axenic cultured amastigotes of L. aethiopica and L. donovani clinical isolates, and cell viability was fluorometrically determined. Amphotericin B was used as a positive control, and 1% dimethyl sulfoxide (DMSO) and the media were employed as a negative control. Results of the study indicated that the latex possessed good activity against both parasites with IC50 values of 18.32 ± 0.85 and 26.21 ± 0.90 μg/ml against promastigotes, and 25.72 ± 0.76 and 25.33 ± 0.65 μg/ml against axenically cultured amastigotes of L. aethiopica and L. donovani, respectively. Furthermore, the latex showed selectivity indices (SIs) of 7.88 and 5.51 toward promastigotes and 5.61 and 5.70 toward amastigotes, while amphotericin B demonstrated SIs of 10.32 and 10.55 toward promastigotes and 9.76 and 10.10 toward amastigotes of L. aethiopica and L. donovani, respectively. The findings of this investigation attest that the latex of C. speciosa is endowed with promising antileishmanial activity against and L. aethiopica and L. donovani warranting further investigations into the active constituents.