The potential role and apoptotic profile of three medicinal plant extracts on Leishmania tropica by MIT assay, macrophage model and flow cytometry analysis

Introduction: Treatment of leishmaniasis with conventional synthetic drugs is a major global challenge. This study was designed to explore the leishmanicidal activity and apoptotic profile of three leaf extracts on Leichmania tropica stages. Methods: The plants of Quercus velutina, Calotropis procera and Nicotiana tabacum were gathered from Anbarabbad county, in the southeastern part of Kerman province and extracted by maceration method using methanol alcohol. Various concentrations of the extracts (1, 10, 100 and 1000 mu g/mL) were used against L tropica stages to evaluate the inhibitory effect by colorimetric assay, macrophage model and flow cytometry. The MIT assay was conducted to determine the IC50 and CC50 values in promastigotes and J774-A1 macrophages, respectively. For infra-macrophage amastigotes, the leishmanicidal activity was evaluated by calculating the mean number of amastigotes in each macrophage and also IC50 values. The promastigote or amastigote stages with no drug and complete medium without organisms were considered as positive and negative controls, respectively. Meglumine antimoniate (Glucantime) was also used as standard drug. Also, annexin V was used to assess the apoptotic profile. All treatment settings were incubated for a standard time of 72 h in triplicates. Data were analyzed by t-test and ANOVA. Results: The findings showed that all plant extracts inhibited the proliferation rate of promastigotes and amastigotes (P < 0.001); especially, Q. velutina represented the lowest IC50 in both stages. Besides, Q. velutina showed the least number of amastigotes in each macrophage compared to the other groups (4.5 mu g/mL). The percentage of parasitic apoptosis at 1000 mu g/mL of Q. velutina, C. pmcera, N. tabacum and Glucantime (R) were 37.4, 18.6, 8.5 and 52.4, respectively. Amastigotes (clinical stage) were significantly more susceptible to extracts and also Glucantime (R) than promastigotes (P < 0.001). Conclusions: This study revealed that all three extracts of Q. velutinu, C. procera and N. tabacum exhibited an effective antileishmanial activity and induced apoptosis against the L tropica promastigotes. Further investigations are essential to isolate and analyze the chemical compositions and their biological properties. (C) 2021 Published by Elsevier Ltd on behalf of World Federation of Parasitologists.