Phylobioactive hotspots identified through multidimensional profiling of botanical drugs used to treat Chagas disease in Bolivia and Dioscorides’ De Materia Medica
Authors: Salm Andrea , Krishnan Sandhya R. , Collu Marta , Danton Ombeline , Hamburger Matthias , Leonti Marco , Almanza Giovanna , Gertsch Jürg 
Published: December 2019

Globally, more than six million people are infected withTrypanosoma cruzi, the causative protozoan parasite of the vector-borne Chagas disease (CD). In Bolivia, CD is hyperendemic and a major health problem among indigenous communities. Although botanical drugs are used widely among different ethnic groups in Bolivia, studies challenging the hypothesis that effective antitrypanosomal medicinal agents were identified empirically are lacking. We conducted a cross-sectional ethnopharmacological field study in Bolivia among different ethnic groups in the Chaco, Chiquitanía and Inter-Andean valleys. We compared botanical drugs used in Bolivia in the context of CD with botanical drugs from unrelated indications from the MediterraneanDe Materia Medica (DMM) compiled by Dioscorides two thousand years ago. A total of 775 ethyl acetate plant extracts with and without ethnomedical indications for CD treatment were profiled againstT. cruziepimastigote and procyclicT. bruceiproliferation, parasite release fromT. cruzitrypomastigote infected cells, as well as for host cell cytotoxicityin vitro. Inhibition of parasite release was monitored using a flow cytometry-based celluar assay. At 25 µg/mL, less than 5% of all extracts exhibited selective toxicity forT. cruzi. We found no evidence that ethnomedicine-inspired bioprospecting significantly increased the probability of finding selective antichagasic botanical drugs. The ethnomedical data further indicate a discrepancy between local and scientific concepts about CD among the studied ethnic groups. Intriguingly, the phylobioactive anthraquinone hotspot identified in this study matched the antichagasic activity ofSenna chloroclada, the taxon with the strongest consensus for treating CD among the Izoceño-Guaraní. Selected antitrypanosomal plant extracts fromDMMwere subjected to HPLC-based activity profiling and targeted isolation of active compounds yielding sesquiterpene lactones, naphtoquinones and anthraquinones. Because the anthraquinone emodin selectively and potently inhibitedT. cruziin host cell infection, we performed a preliminary structure-activity relationship analysis for the 9,10-anthracenedione scaffold, exploring the impact of differential hydroxylation. This study shows that the multidimensional phylobioactivity-guided identification of antichagasic natural products enables comparative bioprospecting and is suitable to challenge ethnopharmacological hypotheses.

Author summary

Chagas disease (CD) is a parasitic disease caused by the protozoanTrypanosoma cruzi. In Bolivia, CD is a major health problem among indigenous communities, which frequently use traditional medicine to treat the chronic symptoms of the disease related to cardiomyopathy. However, the ethnomedical context of the use of such remedies is largely unclear and it remains unknown whether the botanical drugs have any effect on parasitemia. In a field study among different ethnic groups in the Chaco, Chiquitanía and Inter-Andean valleys the authors collected ethnobotanical and ethnopharmacological information. Later, they profiled and compared the CD botanical drug extract library from Bolivia with a botanical drug extract library from the MediterraneanDe Materia Medica with no association to CD. Using phylogenetic and biological information, they identified bioactive hotspots among different taxa and isolated antichagasic natural products. This led to a first structure-activity relationship study of the natural product class called anthraquinones. While there was no overall statistical difference between the libraries, it is noteworthy that the botanical drug derived fromSenna chlorocladawith the highest consensus among the Guaraní communities, also belonged to the anthraquinone cluster, potentially providing a molecular explanation for its use.