Structural Features of Alkaline Dioxane Lignin and Residual Lignin from Eucalyptus grandis × E. urophylla.

In the present study, lignin from eucalyptus was extracted with 80% alkaline dioxane (0.05 M NaOH) from ball-milled wood and subsequently fractionated by gradient acid precipitation from the filtrate. Meanwhile, the residual lignin was prepared by a double enzymatic hydrolysis process. The yield of the lignin extracted by alkaline dioxane (LA-2) was 29.5%. The carbohydrate contents and molecular weights of the gradient acid precipitated lignin fractions gradually decreased from 4.90 to 1.36% and from 7770 to 5510 g/mol, respectively, with the decline of the pH value from 6 to 2. Results from two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance (NMR) and 31P NMR spectroscopy showed an evident reduction of ß- O-4 ' linkages with the pH value decrease, while the contents of aliphatic -OH, phenolic -OH, and carboxylic groups displayed an increasing trend. Moreover, the residual lignin exhibited the highest molecular weight (11690 g/mol), the most abundant ß- O-4 ' linkages (71.1%), and the highest S/G ratio (4.68).

Hydrothermal conversion of bamboo: identification and distribution of the components in solid residue, water-soluble and acetone-soluble fractions.

Hydrothermal conversion is an important thermochemical process to upgrade low-cost lignocellulose into valuable chemicals or fuels. Studies on hydrothermal products compositions and their distributions are of great significance in lignocellulose upgradation. In this work, the major products of bamboo hydrothermally treated at 180-240 °C for 3-60 min and their distributions were comparatively studied. According to the hydrothermal conditions, the hydrothermal products were composed of 37.11-89.98% of solid residues, 4.51-20.41% of water-soluble fractions (WS), and 4.23-16.17% of acetone-soluble fractions (AS). The products in WS fractions mainly consisted of furfural (FF), 5-hydroxymethylfurfural (HMF), and phenolic compounds, while the products in AS fractions were mainly 4-hydroxy-4-methyl-2-pentanone and complex aromatic compounds with multibenzene rings. Additionally, the highest yields of FF (33.4%) and HMF (15.6%) were observed at 200 °C for 60 min and 240 °C for 60 min, respectively.

Structural features and antioxidant activities of lignins from steam-exploded bamboo (Phyllostachys pubescens).

An environmentally friendly steam explosion process of bamboo, followed by alkali and alkaline ethanol delignification, was developed to fractionate lignins. Results showed that after steam explosion the lignins isolated showed relatively low carbohydrate contents (0.55-1.76%) and molecular weights (780-1050 g/mol). For each steam-exploded sample, alkali-extracted lignins presented higher phenolic OH values (1.41-1.82 mmol/g), p-coumaric acid to ferulic acid ratios (pCA/FA ratios 4.5-14.1), and syringyl to guaiacyl ratios (S/G ratios 5.0-8.5) than those from alkaline ethanol-extracted lignins (phenolic OH 0.85-1.35 mmol/g, pCA/FA ratios 1.6-5.2, and S/G ratios 3.5-4.8). The lignins obtained consisted mainly of ß-O-4' linkages combined with small amounts of ß-ß', ß-5', and α-O-4/ß-O-4 linkages. Antioxidant activities of the lignins obtained were tested by the 2,2-diphenyl-1-picrylhydrazyl, 2,2'-azobis(3-ethylbenzothiazoline-6-sulfonic acid), and ferric reducing activity power methods. It was found that alkali-extracted lignins obtained during the initial extraction process had higher antioxidant activities than alkaline ethanol-extracted lignins obtained during the second extraction process.

"Green" films from renewable resources: properties of epoxidized soybean oil plasticized ethyl cellulose films.

Epoxidized soybean oil (ESO), which is a biomass-derived resource, was first used as a novel plasticizer for ethyl cellulose (EC) film preparation. Surface morphologies, mechanical performances, thermal properties, oxygen and water vapor permeabilities of plasticized EC films were detected in detail to evaluate the plasticizing effect of ESO and explore the plastication mechanisms. Results showed that ESO was an effective plasticizer that outstripped conventional plasticizers, i.e. dibutyl phthalate (DBP) and triethyl citrate (TEC) in producing high-quality films. Especially, at plasticizer concentrations of 15-25%, ESO-EC films had preferable mechanical properties and better thermal stability, as well as non-flammability. In addition, the water vapor permeability of ESO-EC films was lower than that of traditional plasticized films. Their oxygen permeability was also remained in a low level. These outstanding performances were related to the relatively high molecular weight, hydrophobicity, chemical structure of ESO, and the intermolecular interactions between ESO and EC chains.

Discovery and preclinical evaluation of a novel class of cytotoxic propynoic acid carbamoyl methyl amides (PACMAs).

Herein, we discovered a series of propynoic acid carbamoyl methyl-amides (PACMAs) with potent cytotoxicity against a panel of cancer cell lines. These compounds interrupted cell cycle progression at low micromolar concentrations and induced early and late stage apoptosis. A representative compound suppressed tumor growth without apparent toxicity in an MDA-MB-435 mouse xenograft model. We used a Kinexus 628-antibody microarray and the Ingenuity Pathway Analysis (IPA) bioinformatics tools to better understand their mechanisms. The IPA analysis revealed the initiation of Nrf2-mediated oxidative stress through modulating the expression of SOD1 and STIP1 by compound 1. The involvement of the oxidative stress pathway was further validated by measuring the levels of the PACMA-induced mitochondrial superoxide species. To our knowledge, this is the first report on the discovery and biological evaluations of PACMAs as anticancer agents. Their broad-spectrum in vitro cytotoxicity, possibly through an oxidative stress-mediated pathway, and in vivo efficacy warrant further preclinical investigations.

Microwave-induced synthesis of carboxymethyl hemicelluloses and their rheological properties.

In this article, a facile, rapid, and efficient method was developed for the preparation of carboxymethyl hemicelluloses using microwave-induced organic reaction enhancement chemistry. The influences of the factors including reaction time, temperature, and the amount of sodium monochloroacetate and sodium hydroxide on the degree of substitution (DS) of the products were investigated. The rheological properties and the chemical structure of the resulting polymers were also studied. It was found that microwave irradiation could significantly promote the chemical reaction efficiency and accelerate the carboxymethylation of hemicelluloses with sodium monochloroacetate. Therefore, carboxymethyl hemicelluloses with higher DS of 1.02 could be obtained in much shorter time scales as compared to the conventional heating method. Results from rheological analysis indicated that carboxymethyl hemicellulose solutions exhibited shear-thinning behavior in the range of shear rates tested and showed lower viscosity and modulus in comparison with those of the native hemicelluloses due to lower molecular weight and the role of carboxymethyl groups in reducing the entanglements between hemicelluloses chains.

Synthesis and biological evaluation of novel hydrazide based cytotoxic agents.

Recently, we designed and synthesized a series of pyrroloquinoxaline compounds with hydrazine moiety linking a nitrogen-containing polycyclic group to a heteroaroyl system. Several derivatives, with attractive drug-like properties, were identified as promising cytotoxic agents, showing excellent potency in a panel of cancer cell lines. In the current study, we synthesized a further 19 new analogues to optimize their physicochemical properties and assess a coherent mechanism of action. Several chemical modifications were made to the reference compounds by varying the fused-ring system and/or the heteroacyl moiety. To evaluate their in vitro activity, we tested these compounds in six human cancer cell lines derived from different origins. Among them, two compounds ( 9 and 12 ) showed similar potency as the reference compounds with IC(50) values in the sub-micromolar range in all cell lines tested. Furthermore, compound 12 showed excellent in vivo efficacy in our preliminary human ovarian cancer mouse xenograft studies. Flow cytometric studies indicated that both derivatives interrupted cell cycle progression in colorectal cancer HCT116 cell lines and ovarian cancer SKOV-3 cells. Further mechanistic studies revealed that 9 and 12 were able to induce reactive oxygen species in SKOV-3 cells with apparently different kinetic patterns. Considering their cytotoxicity profiles in a variety of in vitro and in vivo cancer models, these hydrazide based compounds seem to have considerable potentials as novel chemotherapeutics.