Silicon-Doped Carbon Nanotubes: Promising CO₂/N₂ Selective Agents for Sequestering Carbon Dioxide

The potential ability of single-walled silicon–carbon nanotubes (SWSiCNTs) as CO₂ scavengers was investigated using density functional theory calculations and (5,5) SWSiCNT models with 2%, 33%, and 50% Si. It was found that while the reactions between CO₂ and pristine C tubes are endergonic, Si-doped materials have exergonic adsorption routes. It was also found that 50–50 Si–C composition is not required for the SWSiCNTs to be able to sequester CO₂, which seems to be relevant because this is the maximum Si–C proportion allowed to maintain the SWSiCNT stability. The modeled SWSiCNTs are predicted to be selective to CO₂ over N₂, which is a critical feature for materials with potential applications for CO₂ capture. The rate constants for the SWSiCNT reactions with CO₂ were found to be around 10⁵ M^–1 s^–1, which suggests that they are fast enough to ensure efficient CO₂ capture at room temperature. In addition, for the SWSiCNT with 33% Si, the possibility of multiple CO₂ adsorption was also investigated (up to seven CO₂ molecules). It was found that all the consecutive reactions are significantly exergonic, which indicates that one SWSiCNT is able to sequester several CO₂ equivalents. These findings suggest that SWSiCNT-based materials are promising candidates for selectively, and efficiently, sequestering CO₂ molecules, in particular, SWSiCNTs with intermediate (2–33%) Si amounts

Ellagic Acid: An Unusually Versatile Protector against Oxidative Stress

Several aspects related to the antioxidant activity of ellagic acid were investigated using the density functional theory. It was found that this compound is unusually versatile for protecting against the toxic effects caused by oxidative stress. Ellagic acid, in aqueous solution at physiological pH, is able of deactivating a wide variety of free radicals, which is a desirable capability since in biological systems, these species are diverse. Under such conditions, the ellagic acid anion is proposed as the key species for its protective effects. It is predicted to be efficiently and continuously regenerated after scavenging two free radicals per cycle. This is an advantageous and unusual behavior that contributes to increase its antioxidant activity at low concentrations. In addition, the ellagic acid metabolites are also capable of efficiently scavenging a wide variety of free radicals. Accordingly, it is proposed that the ellagic acid efficiency for that purpose is not reduced after being metabolized. On the contrary, it provides continuous protection against oxidative stress through a free radical scavenging cascade. This is an uncommon and beneficial behavior, which makes ellagic acid particularly valuable to that purpose. After deprotonation, ellagic acid is also capable of chelating copper, in a concentration dependent way, decreasing the free radical production. In summary, ellagic acid is proposed to be an efficient multiple-function protector against oxidative stress

CADMA-Chem: A Computational Protocol Based on Chemical Properties Aimed to Design Multifunctional Antioxidants

A computational protocol aimed to design new antioxidants with versatile behavior is presented. It is called Computer-Assisted Design of Multifunctional Antioxidants and is based on chemical properties (CADMA-Chem). The desired multi-functionality consists of in different methods of antioxidant protection combined with neuroprotection, although the protocol can also be used to pursue other health benefits. The dM38 melatonin derivative is used as a study case to illustrate the protocol in detail. This was found to be a highly promising candidate for the treatment of neurodegeneration, in particular Parkinson’s and Alzheimer’s diseases. This also has the desired properties of an oral-drug, which is significantly better than Trolox for scavenging free radicals, and has chelates redox metals, prevents the ●OH production, via Fenton-like reactions, repairs oxidative damage in biomolecules (lipids, proteins, and DNA), and acts as a polygenic neuroprotector by inhibiting catechol-O-methyl transferase (COMT), acetylcholinesterase (AChE) and monoamine oxidase B (MAOB). To the best of our best knowledge, CADMA-Chem is currently the only protocol that simultaneously involves the analyses of drug-like behavior, toxicity, manufacturability, versatile antioxidant protection, and receptor–ligand binding affinities. It is expected to provide a starting point that helps to accelerate the discovery of oral drugs with the potential to prevent, or slow down, multifactorial human health disorders