A potent trypanocidal component from the fungus Lentinus strigosus inhibits trypanothione reductase and modulates PBMC proliferation

Abstract

The fungus Lentinus strigosus (Pegler 1983) (Polyporaceae, basidiomycete) was selected in a screen for inhibitory activity on Trypanosoma cruzi trypanothione reductase (TR). The crude extract of L. strigosus was able to completely inhibit TR at 20 µg/ml. Two triquinane sesquiterpenoids (dihydrohypnophilin and hypnophilin), in addition to two panepoxydol derivatives (neopanepoxydol and panepoxydone), were isolated using a bioassay-guided fractionation protocol. Hypnophilin and panepoxydone displayed IC 50 values of 0.8 and 38.9 µM in the TR assay, respectively, while the other two compounds were inactive. The activity of hypnophilin was confirmed in a secondary assay with the intracellular amastigote forms of T. cruzi, in which it presented an IC 50 value of 2.5 µM. Quantitative flow cytometry experiments demonstrated that hypnophilin at 4 µM also reduced the proliferation of human peripheral blood monocluear cells (PBMC) stimulated with phytohemaglutinin, without any apparent interference on the viability of lymphocytes and monocytes. As the host immune response plays a pivotal role in the adverse events triggered by antigen release during treatment with trypanocidal drugs, the ability of hypnophilin to kill the intracellular forms of T. cruzi while modulating human PBMC proliferation suggests that this terpenoid may be a promising prototype for the development of new chemotherapeutical agents for Chagas disease. Key words: fungal natural products -Chagas disease -drug discovery -immunomodulators -BasidiomycotaChagas disease is caused by the protozoan parasite Trypanosoma cruzi and affects millions of people in Latin America, having an enormous economic and social impact in the endemic areas. These patients rely on treatment with nitrofuran (nifurtimox; Bayer) or nitroimidazol (benznidazole; Roche), medicines that display little or no activity in chronic infections, in spite of their beneficial effect during the acute phase of the disease (Cançado 2002, Coura & Castro 2002. However, significant differences in the therapeutic effectiveness are observed between these two drugs, especially when considering distinct geographical areas, which is probably due to the occurrence of naturally resistant and susceptible T. cruzi strains (Filardi & Brener 1987, Toledo et al. 2003. Furthermore, both drugs cause several side effects that contribute to their reduced use in clinical medicine (Cançado 1985). Thus, new compounds are needed to develop more effective medicines to treat Chagas disease, espe- cially in its chronic phase, is needed (Schmidt & KrauthSiegel 2002, Nwaka & Ridley 2003. However, due to low profit prospects, the development of new trypanocidal drugs is not attractive to the pharmaceutical industry (Nwaka & Ridley 2003). Thus, this endeavor is being conducted mainly in academic laboratories (Fairlamb 1999).Among the many different strategies for drug discovery, screening the local biodiversity for bioactive natural products using appropriate bioassays is an interesting alternative for researchers in affec...

In vitro activity of hypnophilin from Lentinus strigosus: a potential prototype for Chagas disease and leishmaniasis chemotherapy

“…(voucher code UFMGCB975) as previously described (12). All spectral data (MS, IR, 1H-, and 13C-NMR) of the crystals obtained for this study were in agreement with that published for panepoxydone and hypnophilin (12) (Figure 1). The compounds were dissolved in dimethylsulfoxide (DMSO), diluted in RPMI and added to the culture at the desired final concentrations.…”

“…We have been investigating the biological activities of hypnophilin and panepoxydone, natural products isolated from L. strigosus (12), focusing on identifying new drugs for the treatment of leishmaniasis and Chagas disease. We demonstrate here that hypnophilin is an effective in vitro anti-Trypanosoma and anti-Leishmania compound, with minor toxicity against human PBMC.…”

“…We initially screened more than 3000 extracts of plants and fungi and observed that the extract of Lentinus strigosus, a Basidiomycete fungus belonging to the Polyporaceae family (11,12), contained the most promising drug activity because of its strong TR-inhibitory activity. This TR-bioguided assay led to a detailed investigation of two secondary metabolites produced by the fungus L. strigosus named panepoxydone and hypnophilin (12).…”

“…This TR-bioguided assay led to a detailed investigation of two secondary metabolites produced by the fungus L. strigosus named panepoxydone and hypnophilin (12).…”

Leishmanicidal, trypanocidal, and cytotoxic activities of endophytic fungi associated with bioactive plants in Brazil

“…In previous studies, we showed that the fungi isolated from Brazilian ecosystems are able to produce bioactive secondary metabolites against pathogenic microorganisms (23,24), Trypanosoma cruzi, and human tumour cells (5,25). In connection with our program to discover bioactive fungal metabolites, this study focuses on the ability of endophytic fungi recovered from the pharmacological plants A. myriadenia, P. tetraphylla, P. adiantoides, and T. vauthieri to produce secondary metabolites with cytotoxic, leishmanicidal, and trypanocidal activities.…”