In Situ Copolymerization Studies of Lignin, Acrylamide, and Diallyldimethylammonium Chloride: Mechanism, Kinetics, and Rheology

In this work, free-radical polymerization of kraft lignin, acrylamide (AM), and diallyldimethylammonium chloride (DADMAC) was studied in detail. In situ nuclear magnetic resonance (NMR), rheological analysis, and particle size techniques were conducted to understand the physicochemical characteristics of this copolymerization system. The copolymerization of lignin-AM and lignin-DADMAC had activation energies of 65.7 and 69.3 kJ/mol, respectively, and followed the first-order kinetic model, which was monitored by in situ H1 NMR results. The highest conversions of AM and DADMAC were 96 and 68%, respectively, in the copolymerization of lignin, AM, and DADMAC at the molar ratio of 5.5:2.4:1, pH 2 and 85 °C. The results illustrated that the participation of AM in the reaction was essential for polymerizing DADMAC to lignin due to less steric hindrance of AM than DADMAC facilitating its bridging performance. The monomer conversion ratio and dynamic rheology of the reaction system indicated that lignin acted as an inhibitor in the copolymerization reaction. The particle size analysis of the reaction mixtures reflected the alteration in the size of particles from coarse particles (>300 μm) to fine particles (<10 and 10-50 μm) and suspension to colloidal systems when the reaction progressed. The oscillation study of the reaction media confirmed the gradual increase in the viscosity of the reaction media, illustrating the crosslinking of lignin, AM, and DADMAC.

Lead optimization of novel quinolone chalcone compounds by a structure-activity relationship (SAR) study to increase efficacy and metabolic stability

Many agents targeting the colchicine binding site in tubulin have been developed as potential anticancer agents. However, none has successfully made it to the clinic, due mainly to dose limiting toxicities and the emergence of multi-drug resistance. Chalcones targeting tubulin have been proposed as a safe and effective alternative. We have shown previously that quinolone chalcones target tubulin and maintain potent anti-proliferative activity vis-à-vis colchicine, while also having high tolerability and low toxicity in mouse models of cancer and refractivity to multi-drug resistance mechanisms. To identify the most effective anticancer chalcone compound, we synthesized 17 quinolone-chalcone derivatives based on our previously published CTR-17 and CTR-20, and then carried out a structure-activity relationship study. We identified two compounds, CTR-21 [((E)-8-Methoxy-3-(3-(2-methoxyphenyl)-3-oxoprop-1-enyl) quinolin-2(1H)-one)] and CTR-32 [((E)-3-(3-(2-ethoxyphenyl)-3-oxoprop-1-enyl) quinolin-2(1H)-one)] as potential leads, which contain independent moieties that play a significant role in their enhanced activities. At the nM range, CTR-21 and CTR-32 effectively kill a panel of different cancer cells originated from a variety of different tissues including breast and skin. Both compounds also effectively kill multi-drug resistant cancer cells. Most importantly, CTR-21 and CTR-32 show a high degree of selectivity against cancer cells. In silico, both of them dock near the colchicine-binding site with similar energies. Whereas both CTR-21 and CTR-32 effectively prevents tubulin polymerization, leading to the cell cycle arrest at G2/M, CTR-21 has more favorable metabolic properties. Perhaps not surprisingly, the combination of CTR-21 and ABT-737, a Bcl-2 inhibitor, showed synergistic effect in killing cancer cells, since we previously found the "parental" CTR-20 also exhibited synergism. Taken together, CTR-21 can potentially be a highly effective and relatively safe anticancer drug.

Lignin-carbohydrate complexes: properties, applications, analyses, and methods of extraction: a review

The complexity of lignin and hemicellulose segmentation has been known since the middle of the ninetieth century. Studies confirmed that all lignin units in coniferous species and 47-66% of lignin moieties in deciduous species are bound to hemicelluloses or cellulose molecules in lignin-carbohydrate complexes (LCC). Different types and proportions of lignin and polysaccharides present in biomass lead to the formation of LCC with a great variety of compositions and structures. The nature and amount of LCC linkages and lignin substructures affect the efficiency of pulping, hydrolysis, and digestibility of biomass. This review paper discusses the structures, compositions, and properties of LCC present in biomass and in the products obtained via pretreating biomass. Methods for extracting, fractionating, and analyzing LCC of biomass, pulp, and spent pulping liquors are critically reviewed. The main perspectives and challenges associated with these technologies are extensively discussed. LCC could be extracted from biomass following varied methods, among which dimethyl sulfoxide or dioxane (Björkman's) and acetic acid (LCC-AcOH) processes are the most widely applied. The oxidation and methylation treatments of LCC materials elucidate the locations and frequency of binding sites of hemicelluloses to lignin. The two-dimensional nuclear magnetic resonance analysis allows the identification of the structure and the quantity of lignin-carbohydrate bonds involved in LCC. LCC application seems promising in medicine due to its high anti-HIV, anti-herpes, and anti-microbial activity. In addition, LCC was successfully employed as a precursor for the preparation of spherical biocarriers.