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Proteases such as trypsins in the gut of Spodoptera frugiperda are responsible for breaking down dietary proteins into amino acids necessary for insect growth and development. In this study, we characterized the insecticidal potential of dioscorin, the storage protein of yam (Dioscorea alata), using molecular docking and molecular dynamics simulations to determine the interactions between trypsin enzymes and the protein inhibitor dioscorin. To achieve this, we used the three-dimensional structures of the trypsin-like digestive enzymes of S. frugiperda, a pest of corn and cotton, as receptors or target molecules. We performed protein-protein docking using Cluspro software, estimation of the binding free energy, and information on the dynamic and time-dependent behavior of dioscorin-trypsin complexes using the NAMD package. Our computational analysis showed that dioscorin can bind to the digestive trypsins of S. frugiperda, as confirmed by the affinity energy values (-1022.4 to -1236.9), stability of the complexes during the simulation trajectory, and binding free energy values between -57.3 and -66.9 kcal/mol. Additionally, dioscorin uses two reactive sites to bind trypsin, but the largest contribution to the interaction energy is made by amino acid residues between amino acid backbone positions 8-14 by hydrogen bonds, hydrophobic, and Van der Waals (VdW) interactions. VdW is the energy that makes the greatest contribution to the binding energy. Collectively, our findings demonstrate, for the first time, the binding capacity of the yam protein dioscorin to the digestive trypsin of S. frugiperda. These promising results suggest a possible bioinsecticide action of dioscorin.

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BACKGROUND: The present study investigated the sensory acceptance, oxidative damage and protection, and possible anatomical-structural damage of cells from the surface of shapes of minimally processed yam. The tubers were minimally processed into the peeled rondelle, dice and 'chateau cut' (chateau) shapes, the latter of which was obtained after performing the abrasion technique. Control treatment corresponded to the rondelle shape with the periderm. The pieces were kept packed at 5 ± 2 °C for 14 days. RESULTS: Peeled rondelle and chateau were sensorially the most well-accepted yam shapes and achieved the highest purchase intention. The enzymes were partially modulated by the detected H2 O2 levels. Oxidative burst lasted longer in the minimally processed tissues than in the control. Polyphenol oxidase activity showed a clear difference in behavior between the minimally processed pieces and the control. Minimal processing induced transient increases in phenolic compounds, for which the expression was lowest in the abraded pieces. On the other hand, these pieces exhibited greater cell collapse on the surface of the amyliferous parenchyma. CONCLUSION: Based on the results of the trained panel, the abrasion technique is an alternative to provide shapes that are better accepted and marketable, more resistant to browning, and can be stored for up to 12 days. Resistance to browning may be related to a more efficient modulation of enzymatic antioxidant systems and intense deposition of cell debris on the surface of the amyliferous parenchyma. © 2021 Society of Chemical Industry.

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This study optimizes the pyrodextrinization of yam (Dioscorea sp.) starch isolated from tubers grown in Brazil to produce a yellow pyrodextrin with the lowest enzymatically available starch (AS) content and color difference (ΔE) index. At 140 °C (fixed heating temperature), the effects of acid concentration (0.65 - 2.99 g of HCl/kg of starch) and incubation time (53 - 307 min) on the response variables were evaluated using a response surface methodology. Some physicochemical characteristics were also determined on pyrodextrins. Both factors negatively affected the AS content, although positively influenced the ΔE (P < 0.05). The yellow pyrodextrin produced with 1.82 g/kg and heating for 307 min, presented physicochemical properties similar to the commercial pyrodextrins from potato starch, with 46.6 % of AS, 24.5 of ΔE, high solubility and very low viscosity. The pyrodextrinization caused a decrease of 30 - 54 % in AS content (P < 0.05), making these yam pyrodextrins a promising material for water-soluble and very low viscous dietary fiber.

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The use of lactic bacteria in the development of functional foods has increased in recent years. In addition to their probiotic characteristics, they can ferment a variety of substrates, such as cereals, roots, and tubers. Phytase producer lactic acid bacteria strains and their behavior during the fermentation process of yam-based food were studied. Leuconostoc lactis CCMA 0415, Lactobacillus plantarum CCMA 0744, and Lactobacillus fermentum CCMA 0745 were selected due to phytase production, pH reduction, and growth during 24 h of fermentation. Oxalate activity was not detected in all assays, suggesting its concentration was reduced due to the bleaching process. Among the selected strains, L. lactis CCMA 0415 appeared to be a promising strain in yam-based fermentations because it maintained a cell viability above 8 log CFU/mL and did not reduce diosgenin concentrations (around 8.0 µg/mL) after fermentation for 24 h, thereby, generating a potentially functional yam food. Furthermore, this strain promoted the decrease of pH value from 6.1 to 3.8 and produced 8.1 g/L lactic acid, at 6 h of fermentation. The L. lactis CCMA 0415 was reported as a starter culture in fermented products based on cereals, roots, and tubers.

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BACKGROUND: This study investigated how the activities of the enzymes and metabolites of oxidative metabolism are affected in different regions of cut tissue, associating these changes with the evolution of browning in fresh-cut yam. Samples were collected from yam at 0-5 and 5-10 mm from the cut site. Fresh-cut yams were stored at 5 or 26 °C for days or hours respectively, simulating commercialization, with or without packaging. RESULTS: The results demonstrated that the injury to the yam was a physical inducer of changes in the levels of lipid peroxidation and phenolic compounds and in the activities of superoxide dismutase, catalase, ascorbate peroxidase, polyphenol oxidase and peroxidase. These responses were significant in the tissue closest to the wound but also observed, although less intense, in the more distant tissue. The combined effects of wounding and dehydration during storage intensified the above responses. Conversely, refrigeration attenuated the transmission of the wounding response through the adjacent tissue. CONCLUSION: The results of this work provide the first evidence in cut yam roots that the membrane degradation products, enzymes involved in oxidative protection and enzymes that modulate the oxidation of phenolic compounds are intertwined mechanisms that cause tissue darkening. © 2018 Society of Chemical Industry.

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Background: The perennial medicinal herb Dioscorea zingiberensis is a very important plant used for steroid drug manufacturing for its high level of diosgenin in rhizome. Although the stimulation of diosgenin accumulation by ethylene has been reported in a few of plant species, its regulation is not yet characterized at the molecular level, the underlying molecular mechanism remains elusive. Results: In this study, the effects of ethylene on diosgenin biosynthesis in in vitro cultures of D. zingiberensis were described. The results showed that, in samples treated with ethylene at concentration E3 (10(4) dilution of 40% ethephon), the diosgenin biosynthesis was significantly promoted in comparison with the control samples. Treatment with high concentrations of ethylene had inhibitory effect, whereas with low concentration of the gas elicitor brought about no detectable deleterious effect on the growth rate and diosgenin content of the cultures. The considerable increase of diosgenin level in in vitro cultured Dioscorea zingiberensis by ethylene application is accompanied by the concomitant increase of soluble proteins and chlorophyll content. The gene expressions of cycloartenol synthase and 3-hydroxy-3-methylglutaryl-CoA reductase but not of squalene synthase or farnesyl pyrophosphate synthase were up-regulated by applied ethylene. Conclusions: Our results suggest that ethylene treatment enhanced diosgenin accumulation via up-regulation of the gene expressions of cycloartenol synthase and 3-hydroxy-3-methylglutaryl-CoA reductase.

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This work aimed to characterize the molecular structure and functional properties of starches isolated from wild Dioscorea yams grown at the Amazons, using conventional and up-to-date methodologies. Among the high purity starches isolated (≥99%), the chain lengths were similar, whereas variations in gelatinization profile were observed. Starches have shown varied-shaped granules with monomodal distribution, and B-type crystallinity. Variations in amylose contents found by three analyses were hypothesized being related to intermediate material. Linear chain lengths were similar, and their amylopectins showed a dense, spherical conformation and similar molecular characteristics. The average molar mass and the radius of gyration of the chromatograms of the yam amylopectin, M¯W and R¯G were ranging between 174×10(6) g mol(-1) and 237×10(6) g mol(-1), and 201 nm and 233 nm, respectively. The white yams starches were more sensible to enzymes than the other two. All starches have shown a wide range of functional and nutritional properties.

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"Mapuey" tubers in Venezuela are staple food for indigenous peoples from the Caribbean coast and Amazon regions. Noticeable differences between genotypes of yam starches were observed. Granules were large, triangular, or shell-shaped with monomodal particle size distribution between 24.5 and 35.5 µm. Differential scanning calorimetry (DSC) analyses revealed onset gelatinization temperatures from 69.1 to 73.4 °C with high gelatinization enthalpy changes from 22.4 to 25.3 J g(-1). All X-ray diffractograms of starches exhibit B-type crystallinity. Crystallinity degrees varied from 24% to 40%. The highest crystallinity was found for the genotype having the highest amylose content. Iodo-colorimetric, amperometric, and DSC amylose determinations varied from 1.4 to 8.7%, 2.2 to 5.9%, and 1.4 to 3.5% for Amazonian genotypes, in comparison with commercial Mapuey starches: 12.0, 9.5, and 8.7%, respectively. Solubility and swelling power at 90 °C varied from 2.1 to 4.4% and 20.5 to 37.0%, respectively. Gel clarity fluctuated from 22.4 to 79.2%, and high rapid visco analyzer (RVA) viscosity was developed at 5% starch suspension (between 1430 and 2250 cP). Amylopectin weight average molar mass M(w), radius of gyration R(G), hydrodynamic coefficient ν(G), and apparent molecular density d(Gapp) were determined using high-performance size exclusion chromatography (HPSEC) and asymmetrical flow field flow fractionation (A4F) techniques coupled with multiangle laser light scattering (MALLS) on the Dioscorea trifida genotypes exhibiting the lowest and highest amylose contents. Amylopectins showed very similar molecular conformations. M(w) values were 1.15 × 10(8) and 9.06 × 10(7) g mol(-1) using HPSEC and A4F, respectively, thus, 3-5 times lower than those reported with the same techniques for other yam species, and very close to those of potato and cassava amylopectins. This discovery of a new natural amylose-free starch in the neglected yam "Mapuey" could present some potential for the food industry.

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Los microtubérculos en algunas especies de plantas constituyen una importante alternativa como material vegetal de plantación. Se definió como objetivo de trabajo evaluar en campo la respuesta morfoagronómica de las plantas obtenidas de los microtubérculos de ñame formados en Sistema de Inmersión Temporal (SIT). Como variantes experimentales se plantaron tres categorías de microtubérculos, clasificados según su masa fresca (I. de 0,5 a 0,9 g; II. de 1,0 a 2,9 g; III. igual o mayor de 3,0 g), plantas in vitro previamente aclimatadas y corona de tubérculo. Se evaluó el efecto de la masa fresca de los microtubérculos sobre su brote, supervivencia y posterior desarrollo de las plantas derivadas de ellos en campo. Con los microtubérculos de ñame, con una masa fresca igual o superior a 3,0 g, se alcanzó el más alto porcentaje de brotación (91,30%) y supervivencia de las plantas (96,50%), así como las mejores respuestas en los caracteres cuantitativos que se evaluaron en campo. Estos resultados confirmaron la importancia de la masa fresca de los microtubérculos para ser empleados como material vegetal de plantación directo en campo.

Microtubers in some plant species represent an important alternative crop-planting material. The presentwork involved field work for evaluating the morphoagronomic response of plants obtained from yam microtubersproduced in a temporary immersion system (TIS). Three categories of microtuber were planted asexperimental variants; they were classified by fresh mass (1 - 0.5 to 0.9 g, 2 - from 1.0 to 2.9 g and 3 - equal to or greater than 3.0 g), previously in vitro-acclimated plants and tuber crowns. The effect of microtuber freshweight on their sprouting, survival and later development of the plants derived from them in the field were evaluated. The highest sprouting (91.30%) and plant survival percentages (96.50%) and the best response in quantitative traits evaluated in the field were obtained with yam microtubers having a fresh mass equal to or greater than 3.0 g. These results confirmed the importance of microtubers’ fresh weight for using them as plant material in direct planting in the field.

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The levels of three essential minerals Ca, Fe and Mg and the extent of their availability were assessed in four commonly eaten Caribbean tuber crops [dasheen (Xanthosoma spp.), Irish potato (Solanum tuberosum), sweet potato (Ipomoea batatas) and yellow yam (Dioscorea cayenensis)] in their processed and unprocessed states. Calcium was highest in cooked dasheen (5150+/-50 mg/kg) while Magnesium was highest in uncooked Irish potato (3600+/-200 mg/kg). There was no significant loss of calcium from the food samples upon cooking. All the uncooked food samples displayed higher levels minerals assessed compared to the cooked samples except for cooked Irish potato that recorded the level of iron (182.25+/-8.75 mg/kg). Availability of these minerals in the cooked and uncooked tubers crops upon digestion also showed a similar pattern. In conclusion, the consumption of these tuber crops in the Caribbean may not be responsible for the reported cases of iron deficiency in the region. However, the availability of minerals from these tuber crops when consumed with other foods (the usual practice in the Caribbean) needs further investigation.

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