Julio Santiago

Polymeric Schiff bases derived from aromatic diamines have attracted significant interest due to their potential applications as fluorescent chemosensors. In this study, polymeric Schiff bases were synthesized from oxidized alginates (oxidation degrees of 20%, 40%, and 60%) and o-phenylenediamine. ¹ H-NMR and FT-IR confirmed the chemical changes produced in all synthesized polymers. Rheological analysis revealed that the oxidized alginates exhibited Newtonian behavior, with a marked reduction of their thixotropy. In contrast, the synthesized Schiff bases exhibited a slight recovery in viscosity and thixotropic behavior, along with viscoelastic characteristics. All Schiff bases presented a fluorescence emission at nearly 370 nm in aqueous solution, and their fluorescence quenching responses toward Zn ²⁺ , Co ²⁺ , Ni ²⁺ and Cu ²⁺ ions were evaluated. OSA 20%-OPD exhibited the strongest response to Cu ²⁺ ; this Schiff base reached a limit of detection of 22.1 μM and a limit of quantification of 73.8 μM, while the Stern-Volmer analysis indicated a static-dynamic fluorescence quenching mechanism between the polymer and Cu ^2+. This study offers valuable results of a new water-soluble fluorescent chemosensor for the detection of Cu ²⁺ .

Betalains and anthocyanins are natural pigments valued for their color and bioactivity, but their interactions are not well understood. This study examines their copigmentation and the development of encapsulated formulations with improved stability. Fluorescence spectroscopy indicated the formation of 1:2 complexes via static quenching. Molecular dynamics simulations confirmed stable sandwich-type complexes between betanin and cyanidin-3-glucoside, mainly stabilized by π–π stacking and hydrogen bonding. Thermal degradation studies (50–70 °C) showed that a 1:5 ratio significantly improved color stability, achieving up to a 2.7-fold increase. Encapsulation produced nanoparticles (~520 nm) with enhanced physicochemical properties. The encapsulated complex also exhibited greater antioxidant activity (IC₅₀ = 306.73 μg/mL), improved protection against oxidative stress (17.48 nmol/g), and notable acetylcholinesterase inhibition (42.08%). Overall, betalain–anthocyanin copigmentation yields stable, functional complexes, highlighting their potential as thermally stable, bioactive food colorants.

5-Phenyl-1H-tetrazole (5-PHTA) and its derivatives exhibit relevant properties in pharmacology, corrosion, and coordination chemistry. In this work, a new methodology was proposed to obtain 5-PHTA under hydrothermal conditions using the [3 + 2] cycloaddition reaction between C₆H₅CN and NaN₃, with Co­(CH₃COO)₂·4H₂O as the catalyst and water as the solvent. This new method is an ecological and economical alternative that utilizes water instead of traditional organic solvents, such as DMSO, DMF, ethyl acetate, and n-hexane, for the synthesis and purification of 5-PHTA, reducing the E-factor and carbon footprint. The yield of the reaction was optimized by applying the statistical technique RSM on variables A (molar ratio C₆H₅CN/NaN₃), B (molar ratio Co²⁺/NaN₃), and C (reaction time), where the coordinates A = 2.09, B = 0.48, and C = 6.29 h produced a maximum yield of 81%. 5-PHTA structure was confirmed by single-crystal X-ray diffraction, ¹H-NMR, elemental analysis, FT-IR, and UV–vis. DFT calculations (B3LYP/def2-TZVP) were performed at 433.150 K and 1.45 atm, using water as the reaction solvent. The results demonstrate the crucial role of Co­(II) as a catalyst, via the formation of intermediates that are both kinetically and thermodynamically favored relative to the tested free-catalyst systems.

Alzheimer’s disease (AD) involves oxidative stress in brain tissue, creating a need for stable neuroprotective agents. Anthocyanins are potent antioxidants, but they are highly susceptible to degradation. This study evaluated anthocyanins from purple corn (PCA) and camu-camu (CCA) and the copigmentation effects of the phenolic acids cinnamic (C), ferulic acid (F), resveratrol (R) and polyaspartic acid (P) on the stability and neuroprotective capacity of these anthocyanins. HPLC-MS analysis identified twelve anthocyanins in PCA, including a new one (petunidin sophoroside). Copigmentation was assessed via UV-Vis spectroscopy, FTIR, TG, and stability tests at pH 7.4. The TBARS assay evaluated protection against oxidative stress in brain tissue. Copigment R provided the strongest hyperchromic effect for PCA, while P was most effective for CCA. TG analysis showed that copigmentation with R significantly improved the thermal and pH stability of both anthocyanin sources. All single copigmented samples showed improved stability of anthocyanins in physiological conditions. Furthermore, R-copigmented anthocyanins exhibited the most potent neuroprotective effects, significantly inhibiting lipid peroxidation. Thus, copigmentation, particularly with R, is a highly effective strategy for stabilizing anthocyanins and enhancing their potential as neuroprotective agents against oxidative stress.

Alzheimer's disease involves oxidative stress in brain tissue, creating a need for stable neuroprotective agents. Anthocyanins are potent antioxidants, but they are highly susceptible to degradation. This study evaluated anthocyanins from purple corn (PCA) and camu-camu (CCA) and the copigmentation effects of the phenolic acids cinnamic (C), ferulic acid (F), resveratrol (R) and polyaspartic acid (P) on the stability and neuroprotective capacity of these anthocyanins. HPLC-MS analysis identified twelve anthocyanins in PCA, including two novel compounds. Copigmentation was assessed via UV-Vis spectroscopy, FTIR, TG, and stability tests at pH 7.4. The TBARS assay evaluated protection against oxidative stress in brain tissue. Copigment R provided the strongest hyperchromic effect for PCA, while P was most effective for CCA. TG analysis showed that copigmentation with R significantly improved the thermal and pH stability of both anthocyanin sources. All single copigmented systems showed improved stability of anthocyanins in physiological conditions. Furthermore, R-copigmented anthocyanins exhibited the most potent neuroprotective effects, significantly inhibiting lipid peroxidation. Thus, copigmentation, particularly with R, is a highly effective strategy for stabilizing anthocyanins and enhancing their potential as neuroprotective agents against oxidative stress.

The enzyme acetylcholinesterase (AChE) plays a crucial role in the termination of nerve impulses by hydrolyzing the neurotransmitter acetylcholine (ACh). The inhibition of AChE has emerged as a promising therapeutic approach for the management of neurological disorders such as Lewy body dementia and Alzheimer’s disease. The potential of various compounds as AChE inhibitors was investigated. In this study, we evaluated the impact of natural compounds of interest on the intrinsic deformability of human AChE using computational biophysical analysis. Our approach incorporates classical dynamics, elastic networks (ENM and NMA), statistical potentials (CUPSAT and SWOTein), energy frustration (Frustratometer), and volumetric cavity analyses (MOLE and PockDrug). The results revealed that cyanidin induced significant changes in the flexibility and rigidity of AChE, especially in the distribution and volume of internal cavities, compared to model inhibitors such as TZ2PA6, and through a distinct biophysical-molecular mechanism from the other inhibitors considered. These findings suggest that cyanidin could offer potential mechanistic pathways for future research and applications in the development of new treatments for neurodegenerative diseases.

The enzyme acetylcholinesterase (AChE) plays a crucial role in the termination of nerve impulses by hydrolyzing the neurotransmitter acetylcholine (ACh). The inhibition of AChE has emerged as a promising therapeutic approach for the management of neurological disorders such as Lewy body dementia and Alzheimer's disease. The potential of various compounds as AChE inhibitors has been investigated. In this study, we evaluated the impact of natural compounds of interest on the intrinsic deformability of human AChE using computational biophysical analysis. Our approach incorporates classical dynamics, elastic networks, statistical potentials, energy frustration, and volumetric cavity analyses. The results revealed that cyanidin induced significant changes in the flexibility and rigidity of AChE, especially in the distribution and volume of internal cavities, compared to model inhibitors such as TZ2PA6, and through a distinct biophysical-molecular mechanism from the other inhibitors considered. These findings suggest that cyanidin could offer potential mechanistic pathways for future research and applications in the development of new treatments for neurodegenerative diseases.

Anthocyanins are colored water-soluble plant pigments. Upon consumption, anthocyanins are quickly absorbed and can penetrate the blood–brain barrier (BBB). Research based on population studies suggests that including anthocyanin-rich sources in the diet lowers the risk of neurodegenerative diseases. The copigmentation caused by copigments is considered an effective way to stabilize anthocyanins against adverse environmental conditions. This is attributed to the covalent and noncovalent interactions between colored forms of anthocyanins (flavylium ions and quinoidal bases) and colorless or pale-yellow organic molecules (copigments). The present work carried out a theoretical study of the copigmentation process between cyanidin and resveratrol (CINRES). We used three levels of density functional theory: M06-2x/6-31g+(d,p) (d3bj); ωB97X-D/6-31+(d,p); APFD/6-31+(d,p), implemented in the Gaussian16W package. In a vacuum, the CINRES was found at a copigmentation distance of 3.54 Å between cyanidin and resveratrol. In water, a binding free energy ∆G was calculated, rendering −3.31, −1.68, and −6.91 kcal/mol, at M06-2x/6-31g+(d,p) (d3bj), ωB97X-D/6-31+(d,p), and APFD/6-31+(d,p) levels of theory, respectively. A time-dependent density functional theory (TD-DFT) was used to calculate the UV spectra of the complexes and then compared to its parent molecules, resulting in a lower energy gap at forming complexes. Excited states’ properties were analyzed with the ωB97X-D functional. Finally, Shannon aromaticity indices were calculated and isosurfaces of non-covalent interactions were evaluated.

The incorporation of the drug Isoniazid (an anti-tuberculosis drug) into nanoparticles of polyelectrolyte chitosan-poly(aspartic acid) complexes was carried out by the ionotropic gelation technique, adding a sodium polyaspartate solution containing the drug to a chitosan solution in different proportions in a mass ratio (mg/mg) Isoniazid/Chitosan. This was confirmed by MALDI-TOF/MS, ESI/MS, FTIR, and UV-Vis. The lowest average particle diameter (PD), estimated by DSL, was 148.5 ± 1 nm corresponding to an Isoniazid/chitosan ratio (mg/mg) of 0.5:1. FE-SEM showed nanoparticles in the order of 100–300 nm; whereas AFM showed semi-spherical particle morphology. Graphical Abstract