Interactions in plasticizer mixtures used for sugar replacement

In our quest for novel ingredients to be used in sugar replacement strategies, we have investigated the thermodynamics of polycarboxylic acids, such as citric acid. We have demonstrated the applicability of the Flory-Huggins (FH) theory to describe the thermodynamics of polycarboxylic acids solutions. Moreover, for citric acid we can describe the complete phase diagram with the theory. It shows that polycarboxylic acids have similar plasticizing and hygroscopic properties as sugars and polyols. Regarding mixtures of polycarboxylic acids and carbohydrates, the FH theory is able to describe a) the water activity of the mixtures, b) the solubility of ternary mixtures of acids and sugars, c) the lowering of the deliquescence point for binary mixtures of crystals, and d) the melting point depression in eutectic mixtures. Unexpectingly, our investigations show there is a strong non-zero FH interaction parameter between carboxylic acids and carbohydrates. In our prior sugar replacement strategy we have assumed zero interactions between plasticizers. Here, we will readdress this assumption. Carefull investigations of solid-liquid equilibrium of eutectic mixtures involving polycarboxylic acids and/or carbohydrates, shows nearly zero interaction in eutectic mixtures consisting only of two carbohydrates or two polycarboxylic acids. We now hold the hypothesis that there is strong non-zero interaction if the mixture contains plasticizers strongly differing in the amount of hydrogen bonding groups. This strong interaction explains why these mixtures, like polycarboxylic acids and carbohydrates, are excellent candidates as deep eutectic solvents. Furthermore, we conclude that polycarboxylic acids are useful additions to the toolbox of sugar replacers, albeit that there are some limitations to their amounts used.

Assessment of antitumor activity of BP-C1, a platinum-based anticancer agent with a lignin-derived polymeric ligand, in autochthonous induced and spontaneous carcinogenesis rodent models

BACKGROUND

A standard approach to study the anticancer activity of novel drugs is their testing in animals with inoculated tumors, which has some limitations. An alternative is the use of spontaneous or carcinogen-induced tumor models as they have better translation potential. The carcinogen-induced and transgenic tumor models were used to assess the antitumor activity of BP-C1, a platinum-containing drug with lignin-derived polymeric ligand.

METHODS

We used female Swiss-H-derived mice and Wistar female rats to induce autochthonous tumors via exposure to benzo[a]pyrene and 1,2-dimethylhydrazine, respectively. Additionally, transgenic HER-2/neu FVB/N female mice, prone to the development of spontaneous mammary carcinomas, were used.

RESULTS

Antitumor activity of BP-C1 was observed in soft tissue sarcomas, induced by benzo[a]pyrene. The animals treated with BP-C1 exhibited more stabilizations and therapy responses compared to placebo controls. The efficacy of BP-C1 was somewhat reduced compared to cyclophosphamide; however, their combination resulted in an enhanced antitumor effect. For the 1,2-dimethylhydrazine-induced rat colon cancer model, BP-C1 reduced tumor multiplicity by 21-41 %. For mammary adenocarcinomas in HER-2/neu FVB/N mice, short-termed complete responses were observed in the BP-C1 groups with a frequency of 12-13 %, while complete responses were absent in the placebo group.

CONCLUSION

The results acquired indicated a wide spectrum of antitumor activity of BP-C1.

Sustainable panels based on starch bioadhesives: An insight into structural and tribological performance

This work was focused on evaluating the effects of polycarboxylic acid addition and retrogradation phenomenon on tribological performance, thermal, and mechanical properties of both, bioadhesives and sustainable panels. The rheological behavior of adhesives was affected by retrogradation, exhibiting formulations containing CA higher elastic modulus than those with BTCA, regardless of the acid concentration. With regard to tribomechanical properties, panels formulated with CA20 and BTCA80 adhesives presented the lower friction coefficient and wear degree. Thermocompression process induced a crosslinking reaction between wood fibers and starch-based adhesives, leading to more hydrophobic and thermally stable matrices in the presence of BTCA. The selection of the adhesive formulation depends on the moment of its use, since retrogradation limits its performance and that of the derived sustainable panels, being the adhesive CA20 more appropriate in freshly prepared formulations. Meanwhile, when the storage of the adhesive prepared in batch is required, the BTCA80 formulation would be more suitable. Thus, bioinspired materials can provide a valuable insight towards incorporating starch-based adhesives for wood applications.

Hydrolysis and interactions of d-cellobiose with polycarboxylic acids

The hydrolysis of cellulose model compound d-cellobiose was studied with a series of eight common polycarboxylic acids and two monocarboxylic acids in aqueous medium using 0.500 mmol -COOH/L at 170 °C. The maleic acid showed the highest catalytic activity with turnover frequency (TOF) of 29.5 h^-1. The interaction of carboxylic acids with d-cellobiose in DMSO‑d₆ was studied by determination of the pseudo first-order rate constant k_H of anomeric -OH exchange rate in cellobiose using ¹H NMR spectroscopy. The maleic, oxalic and citric acids showed infinitely large k_H values indicating very strong interactions with d-cellobiose. The next highest interactions were found with phthalic acid (k_H = 248.8 Hz). The FT-IR studies showed significant carboxylic acid C=O stretching frequency shifts (Δν_C=O) of 12, 13 and 10 cm^-1 for maleic, oxalic and acetic acids respectively in mixtures with d-cellobiose.