Postharvest treatments with MnCl2 and ZnCl2 reduce enzymatic browning and enhance antioxidant accumulation in soya bean sprout.

Soya bean sprout is a nutrient-abundant vegetable. However, enzymatic browning of soya bean sprouts during storage remains a challenge. In this study, the effects of treatment with MnCl2 or ZnCl2 on the browning index, antioxidant nutrient accumulation, total antioxidant capacity and enzyme activities of phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO), peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) were investigated in soya bean sprouts after storage at 4 °C and 90% relative humidity for 0, 7, 14 and 21 days. The results showed that postharvest treatment with 1, 2 and 10 mM MnCl2 or ZnCl2 profoundly retarded enzymatic browning in soya bean sprouts to different extents. Compared with the control, the 10 mM MnCl2 and ZnCl2 treatments drastically enhanced ascorbic acid, total thiol and phenolic content, and enhanced FRAP (ferric-reducing ability of plasma) antioxidant capacity in stored soya bean sprouts. Moreover, the MnCl2 and ZnCl2 treatments enhanced SOD, CAT and PAL but decreased PPO and POD activities compared with the control. In addition, the Mn and Zn content in soya bean sprouts significantly increased, by approximately two- to threefold, compared with the control. This study provides a new method for improving the nutrient quality of soya bean sprouts based on postharvest Mn or Zn supplementation.

Melatonin improves nitrogen metabolism during grain filling under drought stress.

Drought affects the normal growth and development of soybeans. Melatonin reportedly alleviates drought stress-induced growth inhibition and plant injury, thus, its foliar application presumably has considerable potential in agriculture. However, few studies have investigated the mechanism responsible for its effects on soybean nitrogen metabolism. In this study, pot culture and plant physiological detection, qPCR, and other methods were used for analysis. The purpose of this study was to explore the effects of melatonin and melanin on glutathione metabolism. The results showed that drought stress led to an increase in soluble protein and proline content, concomitantly with a decrease in the activity of nitrogen metabolism-related key enzymes, an increase in inorganic nitrogen content, and a reduction in nitrogen accumulation and transport. Exogenous melatonin application under drought stress significantly increased the expression of key genes involved in nitrogen metabolism and the activity of key enzymes including, GOGAT, NR, Gs and GDH. Enhanced enzyme activity promotes the conversion of nitrate nitrogen in plants, increases proline, soluble protein, and ureide contents, and, consequently, nitrogen accumulation. Altogether, these changes were conducive to greater nitrogen assimilation and transport. Therefore, under drought stress, melatonin application upregulated key genes involved in nitrogen metabolism, thereby enhancing the activity of related enzymes and restoring growth, stable biomass production. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-022-01219-y.

Exogenous Melatonin Modulates Physiological Response to Nitrogen and Improves Yield in Nitrogen-Deficient Soybean (Glycine max L. Merr.).

Melatonin (MT) is a key plant growth regulator. To investigate its effect at different growth stages on the yield of soybean under nitrogen deficiency, 100 µM MT was applied to soybean supplemented with zero nitrogen (0N), low nitrogen (LN), and control nitrogen (CK) levels, during the plant vegetative growth (V3) and filling (R5) stages. This study revealed that the application of MT mainly enhanced the nitrogen fixation of plants by increasing the root nodule number and provided more substrates for glutamine synthetase (GS) under 0N supply. However, under the LN supply, more ammonium was assimilated through the direct promotion of nitrate reductase (NR) activity by MT. MT enhanced the activity of ammonium-assimilation-related enzymes, such as GOGAT and GDH, and the expression of their coding genes, promoted the synthesis of chlorophyll and amino acids, and increased the photosynthetic capacity under nitrogen deficiency. Exogenous MT directly upregulated the expression of genes involved in the photosynthetic system and stimulated dry-matter accumulation. Thus, MT alleviated the inhibitory effect of nitrogen deficiency on soybean yield. This mitigation effect was better when MT was applied at the V3 stage, and the seed weight per plant increased by 16.69 and 12.20% at 0N and LN levels, respectively. The results of this study provide a new theoretical basis to apply MT in agriculture to improve the resilience of soybean plants to low nitrogen availability.

In situ net fishing of α-glucosidase inhibitors from evening primrose (Oenothera biennis) defatted seeds by combination of LC-MS/MS, molecular networking, affinity-based ultrafiltration, and molecular docking.

Defatted seeds of evening primrose (DSEP), the by-product of evening primrose oil manufacture, exhibit potential α-glucosidase inhibitory activity; however, presently they are routinely discarded as waste. In this study, an in situ net fishing strategy was proposed for rapid recognition of α-glucosidase inhibitors from DSEP. Firstly, the DSEP extraction method was optimized employing a response surface methodology for the recovery of α-glucosidase inhibitors, just like "finding a good fishery before net fishing". Then, molecular networks of DSEP were generated by GNPS-based molecular networking after LC-MS/MS analysis, just like "casting tight nets in the fishery". Subsequently, affinity-based ultrafiltration was carried out for fishing the "hit" together with its structural analogues according to the molecular networks, just like "hauling the specific net fishing". Finally, molecular docking analysis was performed to rapidly verify α-glucosidase inhibitory activities of the potential bioactive components and predict their inhibition mechanisms. In the results, DSEP displayed significant inhibitory effects against yeast and rat intestinal α-glucosidase, and the results of an oral starch tolerance test suggested that DSEP showed postprandial blood-glucose-lowering activity. Moreover, 1-galloyl-glucose, gallic acid, methyl gallate, 1,6-digalloyl-ß-D-glucose, and 1,3,6-trigalloylglucose were rapidly identified as potential α-glucosidase inhibitors present in DSEP.

Effect of quercetin-3-O-sambubioside isolated from Eucommia ulmoides male flowers on spontaneous activity and convulsion rate in mice.

The purpose of this study was to evaluate the effects of quercetin-3-O-sambubioside on the neural system. Quercetin-3-O-sambubioside is a monomeric compound found in Eucommia ulmoides male flowers from which it was extracted using a system solvent method. In the experiments, spontaneous activity and convulsion rate in mice were recorded, and quercetin-3-O-sambubioside shows eminent effects similar to nikethamide on increasing spontaneous activity and stimulating the nerve center to enhance excitement. These findings are indicative of the powerful ability of quercetin-3-O-sambubioside to promote the stimulation of the nerve center.

Effects of amylose chain length and heat treatment on amylose-glycerol monocaprate complex formation.

Aqueous mixtures of amylose with different chain lengths (DP 23-849), which had been enzymatically synthesized or isolated from potato and maize starches, and glycerol monocaprate (GMC, 5:1 weight ratio) were analyzed by using a differential scanning calorimeter (DSC). The mixtures were thermally treated (first DSC scan: 20-140 °C, 5 °C/min and prolonged heat treatment: 100 °C for 24 h) and its effect on the amylose-GMC complex formation was analyzed by DSC and X-ray diffractometer. The amylose, especially short ones, readily associated in the dispersion forming the amylose-amylose crystals but the presence of GMC inhibited the crystal formation. The longer amylose had the greater possibility for the complex formation with GMC, and the prolonged heat treatment facilitated the amylose-GMC complex formation. Both type I and type II complexes were formed during quenching after the initial DSC heating. However, only the type II complexes were formed after the prolonged heat treatment with improved crystallinity and thermostability.