Antileishmanial activities of leaf latex and compound isolated from Aloe ghibensis Sebsebe & Friis

Abstract

Aloe ghibensis Sebsebe & Friis is traditionally used in Ethiopia for the treatment of various ailments including skin problem, wounds and malaria. Phytochemical constituents and antileshimanial properties of the leaf latex of A. ghibensis have not been reported. The objective of this study was, therefore, to determine the phytochemical constituents and in vitro antileishmanial activities of the leaf latex of A. ghibensis and its major compounds against two Leishmania species. Preparative TLC was used to isolate compounds from the leaf latex of A. ghibensis and spectroscopic techniques including 1D- and 2D-NMR as well as ESI-MS were employed to elucidate structures of the isolated compounds. In vitro antileishmanial activity was performed against promastigotes and axenically cultured amastigotes of Leishmania aethiopica and Leishmania donovani clinical isolates using Alamar Blue assay. Phytochemical investigation led to the isolation of two major anthrones, identified as aloin A/B and 7-hydroxyaloin A/B. Both the leaf latex of A. ghibensis and isolated compounds showed antileishmanial activity with IC₅₀ values ranging from 1.6 ± 0.43 to 3.64 ± 0.09 µg/ml and 1.87 ± 0.21 to 3.72 ± 0.12 against promastigotes and axenically cultured amastigotes of L. aethopica and L. donovani, respectively. Moreover, the test substances were found to be less toxic (LC₅₀ = 145 ± 0.72 to 156 ± 0.08 µg/ml) than amphotericin B (LC₅₀ = 12.11 ± 0.51 µg/ml) towards human monocytic cell line (THP-1). The present study revealed that the latex and pure compounds possess genuine antileishmanial activity with high selectivity indices (SIs). Therefore, the isolated compounds can be used as a scaffold for the development of effective drugs for leishmaniasis.