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| Author(s): |
Humberto Enrique Ortega Dominguez
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Ribeirão Preto. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Ciências Farmacêuticas de Ribeirão Preto (PCARP/BC) |
| Defense date: | 2018-12-10 |
| Examining board members: |
Monica Tallarico Pupo;
Roberto Gomes de Souza Berlinck;
Hosana Maria Debonsi;
Felipe Christoff Wouters
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| Advisor: | Monica Tallarico Pupo |
| Abstract | |
There is a quadripartite symbiosis in the fungus-growing ant ecosystem between three mutualist (Attine ant, fungal garden and symbiotic actinomycetes) and one parasite (specialized pathogenic fungus Escovopsis sp). The actinobacteria associated to the ant host produce secondary metabolites to inhibit this pathogen but not the crop fungus. Interesting natural products have been reported from these bacteria with a wide spectrum of biological activities. In this thesis, several actinobacteria were isolated from the exoskeleton and garden of fungus-growing ants to isolate active compounds against different targets such as Leishmania donovani and Escovopsis. The known antibiotic and cytotoxic compounds griseorhodin A (1), griseorhodin C (2), griseorhodin G (3) and dinactin (4) were produced in solid ISP-2 culture by Streptomyces puniceus AB10, which was isolated from the leaf-cutter ant Acromyrmex rugosus rugosus. The absolute configurations of 1 and 2 were unambiguously established as 6S,6aS,7S,8S and 6R,6aS,7S,8R, respectively, using vibrational circular dichroism (VCD) and density functional theory (DFT) calculations. The bacterium Streptomyces puniceus AB10 produced in broth A-medium only one family of antibiotics as dinactin (4). Compound 4 showed inhibition against Escovopsis and a higher activity against L. donovani promastigotes and intracellular amastigotes than miltefosine. Two stereoisomers strepchazolin A (5) and strepchazolin B (6), the antibiotic streptazolin (7), its E-isomer (8), and the inorganic compound cyclooctasulfur (9) were produced in solid ISP-2 culture by Streptomyces chartreusis AC70, which was isolated from the fungal garden of the leaf-cutter ant Acromyrmex subterraneus brunneus. Compound 9 showed antagonist activity against the specialized pathogenic fungus Escovopsis sp. This is the first report of 8 as natural product. The absolute configurations of 5 and 6 were unambiguously established as 5S,6S,9R and 5S,6S,9S, respectively, using vibrational circular dichroism (VCD) and density functional theory (DFT) calculations. The bacterium Candidatus Streptomyces philanthi ICBG292, isolated from the exoskeleton of a worker of a Cyphomyrmex colony, produced the antibiotics Mer-A2026B (10), piericidin-A1 (11) and nigericin (12). Compounds 10-12 showed activity against Escovopsis sp and against L. donovani. Compound 12 showed higher activity against L. donovani promastigotes and intracellular amastigotes than miltefosine. Compound 10 was also active against the fungus Trichoderma sp. Streptomyces sioyaensis ICBG311, isolated from winged male ants of Cyphomyrmex colonies, produced a new naphtoquinone named cyphoquinone (13), two new antifungal compounds named cyphomycin (14) and epoxycyphomycin (15), and the known antifungal GT-35 (16). Compounds 14-16 displayed activity against several strains of Escovopsis sp and Candida albicans K1 with a MIC of 1.0, 0.5 and 0.25 ?g/mL, and a higher activity against L. donovani promastigotes and intracellular amastigotes than miltefosine, while 13 a weak activity against L. donovani. Cyphomycin (14) also showed potent in vitro activity against the resistant human pathogens Aspergillus fumigatus 11628 (echinocandin resistance), C. glabrata 4720 (triazole resistance), and C. auris B11211 (echinocandin, triazole, and amphotericin B resistance), with MIC of 0.5, 0.5 and 4 ?g/mL, respectively. A single-dose study of cyphomycin (14) in a neutropenic mouse disseminated candidiasis model exhibited a dose-like response with 0.56 and 0.66 log reduction of infectious burden when treated with 20 and 40 mg/kg cyphomycin (14), respectively, and epoxycyphomycin (15) exhibited 0.53 log ii reduction with 40 mg/kg, demonstrating clinical relevance and effectiveness of 14 and 15 in this industry-standard model of Candida infection. On the other hand, GT-35 (16) killed the mice 1 hr post dose at 40 mg/kg. (AU) | |
| FAPESP's process: | 14/14095-6 - Bacterial symbionts isolated from fungus-growing ants collected in remaining hotspots of biodiversity in São Paulo State as sources of antiparasitic compounds |
| Grantee: | Humberto Enrique Ortega Dominguez |
| Support Opportunities: | Scholarships in Brazil - Doctorate (Direct) |