Anti-leishmanial Effect and Cytotoxicity of Hydroalcoholic Extract of <i>Laser trilobum</i>: An in vitro Evaluation

Background: With the hope of finding a less expensive, safe, and common drug for leishmaniasis, this study aimed to evaluate the leishmanicidal activity and cytotoxicity of Laser trilobum hydroalcoholic extract in vitro conditions. Methods: The fruit extract of L. trilobum was prepared and examined for cytotoxic activity against RAW264.7 macrophages using the colorimetric MTT assay. The hydroalcoholic extract was evaluated against Leishmania major promastigote and amastigote stages. The infectivity rate and the number of amastigotes inside macrophages were investigated and compared with no treatment (control) and glucantime (reference drug) groups. Results: Laser trilobum exhibited significant leishmanicidal activity against both promastigote and amastigote forms compared to the control groups. The inhibitory concentration (IC50) values of the plant on uninfected RAW264.7 cells were 1727 μg/mL. Herbal lethality against promastigotes was observed from 15 ± 7.4% for 37 μg/mL up to at least 79 ± 7.8% for 5000 μg/mL. The percentage of infected macrophages and the number of amastigotes in macrophages significantly declined at concentrations of 1000, 1250, and 1500 μg/mL (P < 0.05, P = 0.001, and P = 0.000, respectively) over 24 to 72 h compared to control groups. The infected macrophage rates between 1500 μg/mL extract and 5 µg/mL glucantime were not statistically significant at each time point. The crude extract at 1000, 1250, and 1500 μg/mL was significantly more effective on the number of amastigote forms in treated macrophages than the 5 µg/mL glucantime (P < 0.05, P = 0.001, and P = 0.000, respectively), whereas its 1250 μg/mL was not statistically significant with 10 μg/mL glucantime at 48 - 72 h post-incubation. Additionally, the percentage of amastigote viability in treated macrophages was equal between 1500 μg/mL crude extract and 15 µg/mL glucantime at each time point, so the mean number of amastigotes/100 macrophages was 2.67 ± 1.58 for this concentration versus 2.67 ± 0.58 for 15 μg/mL glucantime, and also 7.33 ± 1.53 for 10 μg/mL glucantime after 48 h of incubation. Conclusions: Considering the remarkable leishmanicidal effects and absence or very low cytotoxicity, we can introduce the plant as a valuable natural source for further studies on the treatment and control of leishmaniasis.