Computational Antioxidant Capacity Simulation (CAOCS) Assay of Catechol, Resorcinol and Hydroquinone
Pages 143-156
Sunday Olakunle Idowu and Morenikeji Ayodele Adeyemo

DOI: http://dx.doi.org/10.6000/1929-5030.2016.05.03.5

Published: 17 October 2016

Abstract: There is an urgent need for a biorelevant antioxidant capacity assay, which is crucial to quality-assured polyphenol dietary supplements. We hypothesize that the 'position', more than the 'number' of phenolic groups, is critical to the antioxidant capacity of polyphenols. Computational Antioxidant Capacity Simulation (CAOCS) assay was implemented to test the hypothesis, while refinement of existing assay protocol was aimed at reducing the cost of analysis. The antioxidant capacities of resorcinol, catechol and hydroquinone (3 diphenol positional isomers) were determined by CAOCS assay. Photometric titration experiments and associated informatics that constitute CAOCS assay were evaluated through the use of small increments (< 1 mL) of antioxidant solution. Antioxidant capacity ranking of the positional isomers was found to be; hydroquinone > catechol > resorcinol, (60/g, 46/g and 28/g respectively). The relative bond strength of the phenolic groups, which governs the ranking, was accounted for by structural theory. Optimal 250 µL increment of antioxidant solution afforded a 75% reduction of the amount of antioxidant required in the original assay protocol, where a 1 mL increment was used. CAOCS values vary widely for the positional isomers. The unique structure-antioxidant capacity-correlation (SACC) which confirmed our hypothesis is a signature of biorelevance. Significantly, microliter increments reduced the amount of active material required and hence, the cost of analysis. The methodology is thus attractive for profiling exotic and more expensive polyphenols. CAOCS assay holds a great promise of enabling quality-by-design (QbD) of polyphenol dietary supplements.

New General Models for Evaluating Interactions in Non-Regular Solutions and Adsorption Energies Based on Both Hansen’s and Drago’s Parameters
Pages 57-70
Michel Buchmann, Nam-Tran Ho, Roger Lamartine and Isabelle Bonnamour

DOI: http://dx.doi.org/10.6000/1929-5030.2016.05.02.1

Published: 30 May 2016

Abstract: This study aims at providing a model for the internalmixing energy of two liquids. The concerned variables are the solute molar volume V (cm³/mol.), the cohesion parameters and the Drago's parameters. The model is based on the following fundamental novelties:

The fragmentation of molar cohesive energy ΔE_coh (kJ/mol) into two distinct categories. Indeed, the dispersive and polar cohesion energies are magnetic and electrical in nature, and the cohesive energy of the chemical bonds (Hydrogen Bond) is due to charge transfer and orbital overlap. The origins of these two categories of energy are different, requiring two different treatments in use.

For the first time, a relationship has been established between the cohesive energy from chemical bonds ΔE_h (kJ/mol) and Drago's parameters E_a, E_b, C_a, and C_b (KJ^{1/ 2}mol^-1/2).

A simple equation has been proposed for the salvation energy of a gaseous solute in a liquid solvent. This equation contains a term for the perturbation energy of the solvent in the presence of the solute, namely the cavity formation energy, and different types of interaction energies between the solvent and the solute at infinite dilution.

Based on calorimetric data published, the proposed model is compared with the classic model in terms of the mixing energy. The result shows a clear advantage of the new model over the old or conventional one.

Clearly, this new model should provide a new method to determine the interaction parameters or interaction capacities of complex pharmaceutical molecules using a series of simple and well-chosen solvents.