Traditional detoxification of Jatropha curcas L. seeds

Abstract

Ethnopharmacological relevance: Jatropha curcas L. is a plant with high cultural significance for quilombola communities of Oriximiná (Pará State, Brazil). Although the plant is highly toxic, its seeds are used in these communities to treat tuberculosis and related diseases and symptoms.

Aim of the study: This study was designed to provide a scientific rationale for the traditional detoxification method and use of J. curcas seeds in quilombola communities of Oriximiná.

Materials and methods: J. curcas seeds were manually separated into testa, tegmen, endosperm, and embryo, and then methanolic extracts of each sample were prepared. The traditional preparation of J. curcas seeds consists of a water extract of endosperms that is known as "milk of pinhão-branco". The content of phorbol esters (PEs) in the extracts was analyzed by High-Performance Liquid Chromatography with Diode-Array Detection (HPLC-DAD). The cytotoxic activity was evaluated in human monocytic cell line THP-1 by Resazurin Reduction Assay, and antimycobacterial activity was assessed by determining Minimal Inhibitory Concentration (MIC) values against H37Rv and BCG strains using the Resazurin Microtiter Assay (REMA).

Results: The content analysis revealed that the distribution of PEs within the seeds is not homogeneous. High contents were found in tegmens (4.22 ± 0.25-15.52 ± 0.06 mg/g) and endosperms (1.61 ± 0.07-5.00 ± 0.42 mg/g), while concentrations found in testas and embryos were all below 0.5 mg/g. The traditional preparation derived from the endosperm of J. curcas contained significantly less PEs than the endosperms (0.01 ± 0.005 mg/g). Against THP-1 cells, all the parts of the seed showed cytotoxic activity, while the traditional preparation was considered non-cytotoxic. Nevertheless, only the tegmen and endosperm of J. curcas were considered active against M. tuberculosis and M. bovis (MIC = 200 μg/mL).

Conclusion: The results of this study indicated that the traditional processing performed by the quilombola people from Oriximiná is effective in reducing the toxicity of J. curcas seeds. Although inactive against mycobacteria, the extensive use of the traditional preparation and its low toxicity encourage further studies to investigate other biological activities.

Keywords: Cytotoxicity; Ethnotoxicology; Jatropha curcas; Phorbol esters; Tuberculosis.