RESUMO
Second generation ethanol has the prospect of becoming an important bioenergy alternative. The development of this technology is associated with the lignocellulosic materials' use, with emphasis on agricultural and agroindustrial by-products from which fermentable sugar can be produced. The acid hydrolysis depolymerizes the hemicellulose releasing mainly xylose. Subsequently, the cellulose can be converted into glucose by enzymatic hydrolysis. However, the acid hydrolysis produces toxic compounds, such as furan derivatives, phenolics, and organic acids, which are harmful to fermentative microorganisms. This study investigated different acid concentrations in the sulfuric acid hydrolysis of sugarcane bagasse (1- 5% m/v) and the use of adsorbents with the prerogative to improve the acid hydrolysate (AH) quality for microbial ethanolic fermentation. Cell growth and fermentative yield of Saccharomyces cerevisiae (PE-2) and Scheffersomyces stipitis (NRRL Y-7124) were evaluated. AH was used as a source of pentoses (17.7 g L-1) and molasses (ME) sugarcane as source of hexoses (47 g L-1). The following adsorbents were used: activated charcoal, clay, hydrotalcite and active and inactive cells of PE-2 and NRRL Y-7124, at concentrations ranging (1 - 8% m/v). Results of cell growth and chemical characterization allowed to select the most effective adsorbents with emphasis for active cells that removed 66% furfural and 51% 5-(hydroxymethyl) furfural) (5-HMF) and alcoholic productivity of 23.5 g L-1 in AH and ME substrates, in the presence of mixed culture. These results indicate the application of active yeast cells in the detoxification of acid hydrolysates of the sugarcane bagasse previously to the fermentation.
Assuntos
Celulose/análise , Saccharomyces cerevisiae/crescimento & desenvolvimento , Saccharomycetales/crescimento & desenvolvimento , Saccharum/microbiologia , Adsorção , Hidróxido de Alumínio/química , Carvão Vegetal/química , Fermentação , Hexoses/química , Hidróxido de Magnésio/química , Pentoses/química , Saccharum/químicaRESUMO
The useful synthons sugar enones (2-benzyloxypyran-3-ones) derived from pentoses have been prepared starting from 2-acetoxyglycals or benzyl pentopyranosides. The glycals were glycosylated with benzyl alcohol in the presence of a Lewis acid (SnCl4 or InCl3) to give enantioenriched enones (eeâ¯=â¯80-90%). Under catalysis with InCl3, benzyl 2-enopyranosides gave also the enones (eeâ¯=â¯87%). On the other hand, enantiomerically pure enones were synthesized via an improved straightforward and high yielding sequence (70% overall) from benzyl pentopyranosides. However, the yields of both, the glycosylation of glycals as well as some specific reactions of the sequence from glycosides, were lowered when a p-nitro substituent was introduced into the benzyl group. These routes became impractical in the case of p-acetamidobenzyl derivatives, because of the large extent of decomposition. Therefore, alternative sequences have been developed for the synthesis of 2-(p-acetamidobenzyloxy)pyran-3-ones.
Assuntos
Cetonas/química , Cetonas/síntese química , Pentoses/química , Catálise , Técnicas de Química Sintética , Glicosilação , EstereoisomerismoRESUMO
Alzheimer's disease (AD) is becoming more common due to the increase in life expectancy. This study evaluated the effect of selenofuranoside (Se) in an Alzheimer-like sporadic dementia animal model. Male mice were divided into 4 groups: control, Aß, Se, and Aß + Se. Single administration of Aß peptide (fragments 25-35; 3 nmol/3 µL) or distilled water was administered via intracerebroventricular (i.c.v.) injection. Selenofuranoside (5 mg/kg) or vehicle (canola oil) was administered orally 30 min before Aß and for 7 subsequent days. Memory was tested through the Morris water maze (MWM) and step-down passive-avoidance (SDPA) tests. Antioxidant defenses along with reactive species (RS) were assessed. Inflammatory cytokines levels and AChE activity were measured. SOD activity was inhibited in the Aß group whereas RS were increased. AChE activity, GSH, and IL-6 levels were increased in the Aß group. These changes were reflected in impaired cognition and memory loss, observed in both behavioral tests. Se compound was able to protect against memory loss in mice in both behavioral tests. SOD and AChE activities as well as RS and IL-6 levels were also protected by Se administration. Therefore, Se is promising for further studies.
Assuntos
Acetilcolinesterase/metabolismo , Doença de Alzheimer/patologia , Inflamação , Transtornos da Memória/tratamento farmacológico , Fármacos Neuroprotetores/uso terapêutico , Compostos Organosselênicos/uso terapêutico , Estresse Oxidativo , Pentoses/uso terapêutico , Doença de Alzheimer/complicações , Peptídeos beta-Amiloides/toxicidade , Animais , Citocinas/metabolismo , Modelos Animais de Doenças , Glutationa/metabolismo , Glutationa Redutase/metabolismo , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , Transtornos da Memória/complicações , Camundongos , Estrutura Molecular , Fármacos Neuroprotetores/química , Fármacos Neuroprotetores/farmacologia , Compostos Organosselênicos/química , Compostos Organosselênicos/farmacologia , Estresse Oxidativo/efeitos dos fármacos , Pentoses/química , Pentoses/farmacologia , Fragmentos de Peptídeos/toxicidade , Espécies Reativas de Oxigênio/metabolismo , Superóxido Dismutase/metabolismoRESUMO
A practical procedure for the preparation of chiral 2-S-substituted-2H-pyran-3(6H)-ones is described. According to the reaction conditions, 1,5-anhydro-2,3,4-tri-O-acetyl-D-threo-pent-1-enitol (1) reacted with thiophenol under Lewis acid catalysis to afford the polysubstitution product 1,5-anhydro-2,3,4-tri-S-phenyl-2,3,4-trithio-D,L-threo-pent-1-enitol (2) or phenyl 2,4-di-O-acetyl-3-deoxy-1-thio-alpha- and beta-D-glycero-pent-2-enopyranoside (3 and 4, respectively). The iodine-promoted addition of thiophenol or alpha-toluenethiol to 1 gave (2S)-2-phenylthio-2H-pyran-3(6H)-one (5) or its 2-benzylthio analogue 6, but these products showed low enantiomeric excesses (ee approximately 40-60%). However, dihydropyranone 5 with high optical purity (ee>94%) was successfully obtained by treatment of 4 with iodine in acetonitrile. On the other hand, it was established that the benzylthio group of 5 exerts high stereocontrol in reduction and cycloaddition reactions performed on the alpha,beta-unsaturated carbonyl system.