Alcalóide bisindólico de origem natural com atividade indutora de apoptose

Investigadores do Instituto de Investigação do Medicamento (iMed.ULisboa), da Faculdade de Farmácia da Universidade de Lisboa, em colaboração com o Centro de Estudos Moçambicanos e de Etnociências (CEMEC), descobriram que um alcaloide bisindólico, isolado da espécie Tabernaemontana elegans Stapf, provoca a morte de células de cancro do cólon e hepático, sugerindo que este composto poderá ser uma molécula promissora para o desenvolvimento de novos fármacos.

A grande diversidade estrutural e as propriedades biológicas dos produtos naturais proporcionam a base da atual indústria farmacêutica, sendo que a maioria dos fármacos anticancerígenos são de origem natural, em particular isolados a partir de plantas.

O género Tabernaemontana, da família Apocynaceae, compreende numerosas espécies distribuídas por regiões tropicais e subtropicais, incluindo África. As suas plantas são ricas em alcaloides indólicos responsáveis por diversas atividades biológicas, nomeadamente atividade antitumoral.

Este estudo utiliza uma estratégia promissora para o desenvolvimento de medicamentos anticancerígenos capazes de reverter a resistência a múltiplos fármacos, que passa por induzir a morte das células tumorais utilizando compostos extraídos de fontes naturais.  

Autores e Afiliações:

Angela Paterna^a1, Sofia E. Gomes^a1, Pedro M. Borralho^a, Silva Mulhovo^b, Cecília M. P. Rodrigues^a and Maria-José U. Ferreira^a*

^a Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal

^b Centro de Estudos Moçambicanos e de Etnociências (CEMEC), Faculty of Natural Sciences and Mathematics, Pedagogical University, 21402161 Maputo, Mozambique

Abstract:

Abstract Ethnopharmacological relevance: Tabernaemontana elegans Stapf. (Apocynaceae) is a medicinal plant traditionally used in African countries to treat cancer. Aims of the study: To discover new apoptosis inducing lead compounds from T. elegans and provide scientific validation of the ethnopharmacological use of this plant. Materials and methods: Through fractionation, (3’R)-hydroxytaberanelegantine C (1), a vobasinyl-iboga bisindole alkaloid, was isolated from a cytotoxic alkaloid fraction of the methanol extract of T. elegans roots. Its structure was identified by spectroscopic methods, mainly 1D and 2D NMR experiments. Compound 1 was evaluated for its ability to induce apoptosis in HCT116 and SW620 colon and HepG2 liver carcinoma cells. The cell viability of compound 1 was evaluated by the MTS and lactate dehydrogenase (LDH) assays. Induction of apoptosis was analyzed through Guava ViaCount assay, by flow cytometry, caspase-3/7 activity assays and evaluation of nuclear morphology by Hoechst staining. To determine the molecular pathways elicited by 1 exposure, immunoblot analysis was also performed. Results: (3’R)-hydroxytaberanelegantine C (1) displayed strong apoptosis induction activity as compared to 5-fluorouracil (5-FU), the most used anticancer agent in colorectal cancer treatment. In the MTS assay, compound 1 exhibited IC50 values similar or lower than 5-FU in the three cell lines tested. The IC50 value of 1 was also calculated in CCD18co normal human colon fibroblasts. The lactate dehydrogenase assay showed increased LDH release by compound 1, and the Guava ViaCount assay revealed that 1 significantly increased the incidence of apoptosis to a further extent than 5-FU. Moreover, the induction of apoptosis was corroborated by evaluation of nuclear morphology by Hoechst staining and caspase-3/7 activity assays of 1 treated cells. As expected, in immunoblot analysis, compound 1 treatment led to poly(ADP-ribose) polymerase cleavage. This was accompanied by decreased anti-apoptotic proteins Bcl-2 and XIAP steady state levels in all three cancer cell lines tested. Conclusions: Compound 1 showed remarkable induction of apoptosis in HCT116, SW620 and HepG2 cells. Together, the results suggest that compound 1 is a promising lead structure for inducing apoptosis.

Revista: Journal of Ethnopharmacology

Link: http://dx.doi.org/10.1016/j.jep.2016.09.020