Immunosuppressant activity and morphological changes in Leishmania amazonensis treated with extracts from seeds of Lonchocarpus cultratus

TL;DR

This study shows that extracts from Lonchocarpus cultratus seeds can kill Leishmania parasites, have low toxicity, and reduce immune cell activity in lab tests.

Contribution

The study demonstrates the leishmanicidal, low cytotoxic, and immunosuppressive properties of Lonchocarpus cultratus seed extracts in vitro.

Findings

Dichloromethane, hexane, and methanolic extracts inhibited Leishmania amazonensis promastigote and amastigote growth with low IC50 values.

Hexane and methanolic extracts showed low toxicity to macrophages and high selectivity against parasites.

All three extracts reduced nitric oxide secretion in macrophages, indicating immunomodulatory activity.

Abstract

The first-line drugs used for treating leishmaniasis are highly costly and aggressive. Extracts from Lonchocarpus cultratus have trypanocidal activity and possess several compounds with biological activities. This study sought to observe the in vitro anti-Leishmania amazonensis action of extracts from seeds of L. cultratus. Furthermore, the immunomodulatory and antioxidant characteristics of the extracts were determined.

Sequential extraction with hexane, dichloromethane, and methanol was performed to obtain extracts from L. cultratus seeds, which were characterized via 1H NMR. Promastigotes, intracellular amastigotes, and murine macrophages were treated with increasing concentrations of the extracts, and the inhibition rates were determined by scanning electron microscopy (SEM) analysis of the extracellular forms of the extracts. The immunomodulatory activity of the extract was determined against stimulated RAW macrophages.

Isocordoin and lonchocarpine were identified in dichloromethane and hexane extracts. Dichloromethane (LDS), hexane (LHS), and methanolic (LMS) extracts inhibited promastigote cell growth (IC50 values of 5.18±1.18, 5.25±1.47, and 33.89±1.62 μg/ml, respectively) and decreased the number of amastigotes in the macrophages (IC50 values of 1.41±0.31, 6.33±1.42, and 5.87±1.37 μg/ml, respectively). Hexane and methanolic extracts showed low toxicity in macrophages, resulting in a high selectivity index against promastigotes and amastigotes. In addition, the three extracts immunomodulated macrophages, reducing nitric oxide (NO) secretion.

The results revealed that the activities of the L. cultratus extracts included leishmanicidal effects, low cytotoxicity to macrophages, and immunosuppression in vitro.

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