RESUMO
Biochar (BC) is a carbonaceous material obtained by pyrolysis at 200-1000 °C in the limited presence of O2 from different vegetable and animal biomass feedstocks. BC has demonstrated great potential, mainly in environmental applications, due to its high sorption ability and persistent free radicals (PFRs) content. These characteristics enable BC to carry out the direct and PFRs-mediated removal/degradation of environmental organic and inorganic contaminants. The types of PFRs that are possibly present in BC depend mainly on the pyrolysis temperature and the kind of pristine biomass. Since they can also cause ecological and human damage, a systematic evaluation of the environmental behavior, risks, or management techniques of BC-derived PFRs is urgent. PFRs generally consist of a mixture of carbon- and oxygen-centered radicals and of oxygenated carbon-centered radicals, depending on the pyrolytic conditions. Here, to promote the more productive and beneficial use of BC and the related PFRs and to stimulate further studies to make them environmentally safer and less hazardous to humans, we have first reviewed the most common methods used to produce BC, its main environmental applications, and the primary mechanisms by which BC remove xenobiotics, as well as the reported mechanisms for PFR formation in BC. Secondly, we have discussed the environmental migration and transformation of PFRs; we have reported the main PFR-mediated application of BC to degrade inorganic and organic pollutants, the potential correlated environmental risks, and the possible strategies to limit them.
RESUMO
Biochar (BC), also referred to as "black gold", is a carbon heterogeneous material rich in aromatic systems and minerals, preparable by the thermal decomposition of vegetable and animal biomasses in controlled conditions and with clean technology. Due to its adsorption ability and presence of persistent free radicals (PFRs), BC has demonstrated, among other uses, great potential in the removal of environmental organic and inorganic xenobiotics. Bamboo is an evergreen perennial flowering plant characterized by a short five-year growth period, fast harvesting, and large production in many tropical and subtropical countries worldwide, thus representing an attractive, low-cost, eco-friendly, and renewable bioresource for producing BC. Due to their large surface area and increased porosity, the pyrolyzed derivatives of bamboo, including bamboo biochar (BBC) or activated BBC (ABBC), are considered great bio-adsorbent materials for removing heavy metals, as well as organic and inorganic contaminants from wastewater and soil, thus improving plant growth and production yield. Nowadays, the increasing technological applications of BBC and ABBC also include their employment as energy sources, to catalyze chemical reactions, to develop thermoelectrical devices, as 3D solar vapor-generation devices for water desalination, and as efficient photothermal-conversion devices. Anyway, although it has great potential as an alternative biomass to wood to produce BC, thus paving the way for new bio- and circular economy solutions, the study of bamboo-derived biomasses is still in its infancy. In this context, the main scope of this review was to support an increasing production of BBC and ABBC and to stimulate further studies about their possible applications, thus enlarging the current knowledge about these materials and allowing their more rational, safer, and optimized application. To this end, after having provided background concerning BC, its production methods, and its main applications, we have reviewed and discussed the main studies on BBC and ABBC and their applications reported in recent years.
RESUMO
Chagas disease therapy still relies on two nitroderivatives, nifurtimox and benznidazole (Bz), which have important limitations and serious adverse effects. New therapeutic alternatives for this silent disease, which has become a worldwide public health problem, are essential for its control and elimination. In this study, 1,2,3-triazole analogues were evaluated for efficacy against T. cruzi. Three triazole derivatives, 1d (0.21 µM), 1f (1.23 µM), and 1g (2.28 µM), showed potent activity against trypomastigotes, reaching IC50 values 10 to 100 times greater than Bz (22.79 µM). Promising candidates are active against intracellular amastigotes (IC50 ≤ 6.20 µM). Treatment of 3D cardiac spheroids, a translational in vitro model, significantly reduced parasite load, indicating good drug diffusion and efficacy. Oral bioavailability was predicted for triazole derivatives. Although infection was significantly reduced without drug pressure in a washout assay, the triazole derivatives did not inhibit parasite resurgence. An isobologram analysis revealed an additive interaction when 1,2,3-triazole analogs and Bz were combined in vitro. These data indicate a strengthened potential of the triazole scaffold and encourage optimization based on an analysis of the structure-activity relationship aimed at identifying new compounds potentially active against T. cruzi.
RESUMO
The application of the oxidative system composed of a heterogeneous triazolium pre-catalyst, iron(ii) phthalocyanine and air is described for the selective conversion of 5-hydroxymethylfurfural (HMF) into the added-value 5-hydroxymethyl-2-furancarboxylic acid (HMFCA). The disclosed one-pot two-step procedure involved sequential oxidative esterifications of HMF to afford a polyester oligomer having hydroxyl and carboxyl terminal groups (Mw = 389-1258), which in turn was hydrolyzed by a supported base (Ambersep 900 OH) to yield HMFCA in 87% overall yield. The same strategy was adopted for the effective synthesis of ester and amide derivatives of HMFCA by nucleophilic depolymerization of the oligomeric intermediate with methanol and butylamine, respectively. The utilization of the disclosed oxidative system for the direct conversion of HMF and furfural into their corresponding ester, amide, and thioester derivatives is also reported.
