Evaluation of antileishmanial activity of South Indian medicinal plants against Leishmania donovani

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

PURPOSE

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.

METHODS

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.

RESULTS

The chloroform extract of Averrhoa carambola leaf (ACCEX) (IC50 = 50.76 ± 1.7 µg/mL) exhibited the highest activity, followed by the ethyl acetate, hexane, and methanol extracts. ACCEX has also exhibited lower toxicity towards host macrophages. ACCEX 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 ACCEX were identified from the National Institute of Standards and Technology (NIST) database and from a literature review.

CONCLUSIONS

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

A review on new natural and synthetic anti-leishmanial chemotherapeutic agents and current perspective of treatment approaches

Leishmaniases are considered among the most neglected yet dangerous parasitic diseases worldwide. According to the recent WHO report (Weekly Epidemiological Record, Sep, 2021), 200 countries and territories reported leishmanises cases in 2020; of which 89 (45%) for CL, and 79 (40%) for VL were endemic. Indian subcontinent (India, Bangladesh and Nepal), one of the three eco-epidemiological hotspots of VL, currently reported 18% of the total cases of VL worldwide. Eastern Mediterranean region and the Region of the Americas together reported >90% of the new CL cases, of which >80% were from Afghanistan, Algeria, Brazil, Colombia, Iraq, Pakistan and the Syrian Arab Republic. While considering the current therapeutic options, conventional anti-leishmanial drugs have long been proved to be toxic and/or expensive and have resulted in extensive drug resistance in India. Recent searches for novel anti-leishmanial drugs have led to find out the prime cellular targets and metabolic pathways to bridge the gap between the known facts and unexplored data. Cutting edge knowledge based drug designing has simplified the search for novel molecules with leishmanicidal efficacy by identifying ligand-receptor interactions and has accelerated the cost effective primary discovery of molecules through computational validation against Leishmaniases. This review focuses on the limitations of conventional drugs, and discusses the chemotherapeutic potential of many novel natural and synthetic anti-leishmanial agents reported since the last decade. It is also interpreted that some of the reported molecules might be tested singly or as a part of combinatorial therapy on pre-clinical and clinical level.

Antileishmanial potential of species from the family Lamiaceae: chemical and biological aspects of non-volatile compounds

Leishmaniasis is a neglected tropical disease present in more than 90 countries and annually affects about 1 million people worldwide. It is caused by the genus Leishmania protozoa that are transmitted to humans by insect bites. This disease is a serious public health problem, which can cause death, disability, and mutilation. The drugs used in treatment have high toxicity, low efficiency, high costs, and possible antiparasitic resistance. Medicinal plant-based treatments have been used for leishmaniasis by population from endemic areas. Among the main botanical families used against leishmaniasis, in different parts of the world, the family Lamiaceae stands out. In this review, the antileishmanial activity of extracts, fractions, and non-volatile compounds of Lamiaceae species are presented. Leishmania species present in the Old and New World were evaluated and discussed. Altogether there are forty-two Lamiaceae species, belonging to twenty-six genera, and ninety-one constituents, isolated from eighteen species of this family, verified in antileishmanial assays. Chemical and biological aspects of extracts, fractions and non-volatile constituents are discussed in order to define a profile of antileishmanial plants of this family, based on the antileishmanial activities results. Notes are presented to guide future investigations to expand chemical and biological knowledge of Lamiaceae species and highlight its most promising antileishmanial agents.