Averrhoa carambola Leaf Extract Induces Apoptosis-Like Death with Increased ROS Generation in Leishmania donovani

The parasitic disease leishmaniasis is responsible for high mortality and morbidity rates worldwide. The visceral form is the most severe form of leishmaniasis (or leishmaniosis), which is caused predominantly by Leishmania donovani. Currently, clinically recommended antileishmanial drugs are not convenient because of several medical complications and resistance issues. Phytocompounds are the best candidates in this regard. The present study aimed to evaluate the antileishmanial activity of Averrhoa carambola leaf extract.

The antipromastigote activity and cytotoxicity were assessed using the MTT assay. Morphological distortions were determined using phase contrast microscopy and scanning electron microscopy (SEM). Reactive oxygen species (ROS) production, nonprotein thiol depletion and apoptotic death in promastigotes were determined via flow cytometry. UV-visible spectroscopy and energy dispersive X-ray (EDX) spectroscopy was performed for elemental analysis. Fourier-transform infrared spectroscopy (FTIR) and liquid chromatography‒mass spectrometry (LCMS) were used to characterize the phytocomponent(s) present in the extract.

The chloroform extract of Averrhoa carambola leaf (AC_CEX) (IC₅₀ = 50.76 ± 1.7 µg/mL) exhibited the highest activity, followed by the ethyl acetate, hexane, and methanol extracts. AC_CEX has also exhibited lower toxicity towards host macrophages. AC_CEX also induced morphological distortions in promastigotes, with significant generation of ROS and the concomitant apoptosis initiation followed by a decrease in the nonprotein thiol level. The major phytometabolites present in AC_CEX were identified from the National Institute of Standards and Technology (NIST) database and from a literature review.

This study suggested that Averrhoa carambola leaf extracts are rich in some classes of biologically active phytocompounds and exhibit good antileishmanial activity.