Side chain azasteroids and thiasteroids as sterol methyltransferase inhibitors in ergosterol biosynthesis

The synthesis of some novel azasteroids and thiasteroids based on a pregnan nucleus with a Δ7 double bond in two to five steps from the key aldehyde (3S,20S)-20-formylpregn-7-en-3-yl acetate has been disclosed herein. These compounds were evaluated as potential inhibitors of the enzyme Δ24-sterol methyltransferase (24-SMT), which is a key enzyme in the biosynthesis of ergosterol, and for their effects on the growth of the yeast Yarrowia lipolytica. Most of the side chain modified analogues were recognized as 24-SMT inhibitors, and in particular the 23-azasteroids 5f–5i and the 24-azasteroid 11 showed potent antifungal activity. The target enzyme could be identified unambiguously using an improved whole-cell assay combined with GC–MS analysis of the sterol pattern resulting upon incubation with the inhibitors.     

Potential for bioremediation of agro-industrial effluents with high loads of pesticides by selected fungi

Wastewaters from the fruit packaging industry contain a high pesticide load and require treatment before their environmental discharge. We provide first evidence for the potential bioremediation of these wastewaters. Three white rot fungi (WRF) (Phanerochaete chrysosporium, Trametes versicolor, Pleurotus ostreatus) and an Aspergillus niger strain were tested in straw extract medium (StEM) and soil extract medium (SEM) for degrading the pesticides thiabendazole (TBZ), imazalil (IMZ), thiophanate methyl (TM), ortho-phenylphenol (OPP), diphenylamine (DPA) and chlorpyrifos (CHL). Peroxidase (LiP, MnP) and laccase (Lac) activity was also determined to investigate their involvement in pesticide degradation. T. versicolor and P. ostreatus were the most efficient degraders and degraded all pesticides (10 mg l⁻¹) except TBZ, with maximum efficiency in StEM. The phenolic pesticides OPP and DPA were rapidly degraded by these two fungi with a concurrent increase in MnP and Lac activity. In contrast, these enzymes were not associated with the degradation of CHL, IMZ and TM implying the involvement of other enzymes. T. versicolor degraded spillage-level pesticide concentrations (50 mg l⁻¹) either fully (DPA, OPP) or partially (TBZ, IMZ). The fungus was also able to rapidly degrade a mixture of TM/DPA (50 mg l⁻¹), whereas it failed to degrade IMZ and TBZ when supplied in a mixture with OPP. Overall, T. versicolor and P. ostreatus showed great potential for the bioremediation of wastewaters from the fruit packaging industry. However, degradation of TBZ should be also achieved before further scaling up.     

Isolation of a bacterial consortium able to degrade the fungicide thiabendazole: the key role of a Sphingomonas phylotype

Thiabendazole (TBZ) is a fungicide used in fruit-packaging plants. Its application leads to the production of wastewaters requiring detoxification. In the absence of efficient treatment methods, biological depuration of these effluents could be a viable alternative. However, nothing is known regarding the microbial degradation of the recalcitrant and toxic to aquatics TBZ. We report the isolation, via enrichment cultures from a polluted soil, of the first bacterial consortium able to rapidly degrade TBZ and use it as a carbon source. Repeated efforts using various culture-dependent approaches failed to isolate TBZ-degrading bacteria in axenic cultures. Denaturating gradient gel electrophoresis (DGGE) and cloning showed that the consortium was composed of α-, β- and γ-Proteobacteria. Culture-independent methods including antibiotics-driven selection with DNA/RNA-DGGE, q-PCR and stable isotope probing (SIP)-DGGE identified a Sphingomonas phylotype (B13) as the key degrading member. Cross-feeding studies with structurally related chemicals showed that ring substituents of the benzimidazole moiety (thiazole or furan rings) favoured the cleavage of the imidazole moiety. LC-MS/MS analysis verified that TBZ degradation proceeds via cleavage of the imidazole moiety releasing thiazole-4-carboxamidine, which was not further transformed, and the benzoyl moiety, possibly as catechol, which was eventually consumed by the bacterial consortium as suggested by SIP-DGGE.

     

Characterization of the biodegradation,bioremediation and detoxification capacity of a bacterial consortium able to degrade the fungicide thiabendazole

Thiabendazole (TBZ) is a persistent fungicide used in the post-harvest treatment of fruits. Its application results in the production of contaminated effluents which should be treated before their environmental discharge. In the absence of efficient treatment methods in place, biological systems based on microbial inocula with specialized degrading capacities against TBZ could be a feasible treatment approach. Only recently the first bacterial consortium able to rapidly transform TBZ was isolated. This study aimed to characterize its biodegradation, bioremediation and detoxification potential. The capacity of the consortium to mineralize ¹⁴C-benzyl-ring labelled TBZ was initially assessed. Subsequent tests evaluated its degradation capacity under various conditions (range of pH, temperatures and TBZ concentration levels) and relevant practical scenarios (simultaneous presence of other postharvest compounds) and its bioaugmentation potential in soils contaminated with increasing TBZ levels. Finally cytotoxicity assays explored its detoxification potential. The consortium effectively mineralized the benzoyl ring of the benzimidazole moiety of TBZ and degraded spillage level concentrations of the fungicide in aqueous cultures (750 mg L^?1) and in soil (500 mg kg^?1). It maintained its high degradation capacity in a wide range of pH (4.5–7.5) and temperatures (15–37 °C) and in the presence of other pesticides (ortho-phenylphenol and diphenylamine). Toxicity assays using the human liver cancer cell line HepG2 showed a progressive decrease in cytotoxicity, concomitantly with the biodegradation of TBZ, pointing to a detoxification process. Overall, the bacterial consortium showed high potential for future implementation in bioremediation and biodepuration applications.     

Antimalarial and antitrypanosomal activity of a series of amide and sulfonamide derivatives of a 2,5-diaminobenzophenone

Here, we describe a series of readily obtainable benzophenone derivatives with antimalarial and antitrypanosomal activity. The most active compounds display submicromolar activity against Plasmodium falciparum. Micromolar activity is obtained against Trypanosoma brucei. Main problem of the compounds is low selectivity. However, there are indications that separation of antimalarial and cytotoxic activity might by possible. In addition, some compounds inhibit human ABC transporter with nanomolar activity.