Patricia Mollinedo

Potato starch (Solanum spp.) undergoes structural and functional modifications during traditional Andean chuño production; however, the integrated effects of processing history, cultivar-associated characteristics, and field-based environmental conditions remain insufficiently characterised. This study investigated the effects of chuño processing on the compositional, pasting, morphological, molecular, and crystalline properties of starches isolated from three potato cultivars (Condor Imilla, Luk’i Turno, and Dutch Désirée). Native and chuño starches were characterised by amylose quantification, viscoamylography, scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD), together with severe thermal treatment to evaluate structural stability. Chuño processing was associated with a reduction in amylose content across all cultivars (6.9–23.4%) and an increase in gelatinisation onset temperature of approximately 21.5% (from ~65 °C to ~79 °C). Peak viscosity decreased substantially after processing (457.5–1110 BU to 194.5–442.5 BU), while breakdown values remained close to zero, indicating increased resistance to viscosity loss during heating. SEM analysis revealed changes in granule morphology and size distribution associated with chuño processing and subsequent thermal treatment, with more pronounced reductions in granule size observed in Condor Imilla and Luk’i Turno than in Dutch Désirée. FT-IR analysis demonstrated modifications in short-range molecular organisation without the appearance of new functional groups, indicating structural reorganisation rather than chemical transformation. XRD analysis confirmed that all starches retained the native B-type crystalline polymorph after chuño processing, although reductions in diffraction intensity and peak definition indicated decreased long-range structural order. Severe thermal treatment eliminated detectable crystalline order in all samples, producing predominantly amorphous diffraction profiles. Overall, chuño processing was associated with reduced swelling capacity, lower paste viscosity, enhanced thermal stability, and multiscale structural reorganisation while preserving the fundamental B-type polymorph. Given that the plant material originated from distinct agroecological environments and that traditional chuño production involved a variable number of processing cycles, the observed differences should be interpreted as integrated responses of starch systems to processing history and material characteristics rather than strictly genotype-driven effects. These findings highlight the potential of chuño as a naturally modified starch system with distinctive technological properties.

The antioxidant activity of natural and semi-synthetic depsides and benzofurans—including R-(+)-usnic acid (1), dibenzoyl usnic acid (2), atranorin (3), 2,4-bis(benzoyloxy)atranorin (4), 4-O-methyl atranorin (5), decarboxythamnolic acid (6), thamnolic acid (7), and perlatolic acid (8)—was evaluated in this study. Natural compounds were isolated from selected lichen species, whilst semi-synthetic derivatives were prepared to investigate the influence of esterification and methylation on electronic properties and radical-scavenging capacity. Structural elucidation was performed using NMR spectroscopy and mass spectrometry (MS). Electronic and thermodynamic descriptors, including the bond dissociation energy (BDE) of the most reactive O–H group, HOMO and LUMO_r energies, the HOMO–HOMO-1 energy gap (ΔH(H-1)), polarisability, and logP, were calculated and correlated with experimentally determined antioxidant capacity using the TEAC assay. Multivariate partial least squares (PLS-1) analysis identified ΔH(H-1) and LUMO_r as the primary determinants of antioxidant activity, with BDE and ΔHf providing complementary contributions. Perlatolic acid (8) exhibited the highest radical-scavenging capacity (TEAC = 2.7), whereas R-(+)-usnic acid (1) and dibenzoyl usnic acid (2) were the least active compounds (TEAC ≈ 0.1). Antioxidant activity was found not to correlate with the number of hydroxyl groups, but rather to be governed by electronic redistribution, conjugation effects, and substituent modulation. Exclusion of the outlier decarboxythamnolic acid (6) improved model performance, explaining 79.8% of the variance in TEAC values (R²Y), with strong predictive ability (Q² = 0.724) using a single latent variable. Overall, these findings provide a robust basis for the prediction and rational design of new antioxidant compounds, highlighting the relevance of lichen-derived metabolites as structurally stable scaffolds with potential applications in pharmaceutical and nutraceutical development.