Effects of Planting and Processing Modes on the Degradation of Dithianon and Pyraclostrobin in Chinese Yam (Dioscorea spp.)

A Frontier Review of Nutraceutical Chinese Yam

Yams are the edible subterranean rhizomes, or tubers, of plants from the genus Dioscorea. There are approximately 600 species of yam plants in the world, with more than 90 of these growing in East Asia. One particular species, Dioscorea opposita Thunb., is highly praised as "the Chinese yam". This distinction arises from millennia of storied history, both as a nutritional food source and as a principal ingredient in traditional Chinese medicine. Among the many cultivars of Dioscorea opposita Thunb., Huai Shanyao has been widely regarded as the best. This review surveyed the historical background, physiochemical composition, applications as food and medicine, and research prospects for the Chinese yam. Modern science is finally beginning to confirm the remarkable health benefits of this yam plant, long-known to the Chinese people. Chinese yam promises anti-diabetic, anti-oxidative, anti-inflammatory, immunomodulatory, anti-hyperlipidemic, anti-hypertensive, anti-cancer, and combination treatment applications, both as a functional food and as medicine.

Bimetallic AuNR@AgNCs for ultrasensitive surface-enhanced Raman scattering sensing of dithianon in apple juice

In this study, a bimetallic surfaced-enhanced Raman spectroscopy (SERS)-active substrate consisting of AuNR@AgNCs was proposed for the rapid detection of dithianon. Due to the significant synergistic enhancement of the core-shell nanocuboids, the obtained AuNR@AgNC substrate exhibited excellent SERS performance. The simulation findings supported the practical SERS results and demonstrated that interactions were mainly maintained by the nitrile functional group. The AuNR@AgNCs could be used to detect dithianon with an LOD value of 20 nM. Moreover, dithianon in river water and apple juice could be detected with recovery in the satisfactory ranges of 97.41%-98.35% and 97.77%-98.70%, respectively, by using this substrate under optimal conditions, indicating that the AuNR@AgNC substrate could serve as an excellent SERS detection platform for pesticide residues in fruit.

Photochemical advanced oxidative process treatment effect on the pesticide residues reduction and quality changes in dried red peppers

Pesticide residues in crops are widely monitored, and the residue reduction techniques at the post-harvest stage are important to maintain food safety. In dried crops, pesticide residues can be concentrated after dehydration, which increases concerns regarding residue risk. Therefore, the residue reduction effects of ultraviolet (UV), ozone, and photochemical advanced oxidative process (pAOP) were investigated for dried peppers at the post-harvest stage. UV₂₅₄ treatment reduced 59.7% of the residue concentration on average, while UV₃₆₀ showed a reduction of only 13.3% under 9.6 W m^-2 of UV exposure for 24 h. Gaseous ozone treatments reduced the residue concentrations up to 57.9% on average. In contrast, the pAOP treatment reduced the concentration up to 97% and was superior to UV or ozone treatment alone. Increased drying temperature under pAOP condition resulted in higher reduction ratios at 40-80 °C. The pAOP conditions with 12 and 24 µmol/mol of ozone and UV₂₅₄ irradiation for 24-48 h reduced the residue concentrations to 39-67%. Particularly, difenoconazole, fludioxonil, imidacloprid, and thiamethoxam residue concentrations were drastically reduced by over 50% under 12 µmol/mol ozone of the pAOP condition, while carbendazim, fluquinconazole, and pyrimethanil were relatively stable and their concentrations reduced below 50% under 24 µmol/mol ozone of the pAOP treatment. Various drying-related quality parameters of drying peppers such as water-soluble color, capsanthin, capsaicinoids, acid value, peroxide value, and thiobarbituric acid value were slightly altered, but not significantly, under 12 µmol/mol ozone of the pAOP condition, while the peroxide value was significantly altered under the higher ozone conditions. Therefore, pAOP treatment combined with gaseous ozone can be used for reducing residual pesticides in peppers without greatly reducing quality.

Transfer Behaviors of 30 Pesticide Residues during the Common Processing of Ginseng

To reduce safety issues of ginseng products caused by excessive pesticide levels, this paper systematically elucidates the transfer rules of pesticides during processing by calculating the transfer rates and processing factors (PFs). The common methods of ginseng processing (water extraction, alcohol extraction, concentration, water extraction and alcohol precipitation, vacuum drying, freeze drying, spray drying) and 30 pesticides frequently occurring in ginseng were used as research objects. The results indicate that the pesticide residues in alcohol extract are much higher than those in water extract. During water extraction and alcohol precipitation, 93.2% of pesticides are transferred to the upper ethanol solution. Besides, drying could reduce the total amount but increase the concentration of pesticide residues. Water extraction-concentration-spray drying (PF ranges from 0.01 to 0.36) and alcohol extraction-concentration-vacuum drying (PF ranges from 1.10 to 3.70) are the processing methods with the lowest and highest pesticide processing factors, respectively.

A field trials-based authentication study of conventionally and organically grown Chinese yams using light stable isotopes and multi-elemental analysis combined with machine learning algorithms

In this study, stable isotopes and multi-element signatures combined with chemometrics were used to distinguish conventional and organic Chinese yams based on field trials. Four light stable isotopes δD, δ¹³C, δ¹⁵N, δ¹⁸O, and 20 elements (e.g. Li, Na, Mn) were determined, then evaluated using significance analysis and correlation analysis, and modeling of various chemometrics methods. Consequently, the RandomForest model showed the best performance with AUC value of 0.972 and predictive accuracy of 97.3%, and Mn, Cr, Se, Na, δD, As, and δ¹⁵N were screened as significant variables. Moreover, many chemical components and antioxidant activity of yam samples were determined spectrophotometrically. The results indicated that organic yams had advantages in secondary metabolites such as polyphenol, flavonoid and saponin; conversely, conventional samples had more primary metabolites like protein and amino acids. Above all, this work provides a beneficial case in the authentication and quality evaluation of conventional and organic yams.

Enhanced photodegradation of applied dithianon fungicides on plant leaves by dissolved substances in atmosphere under simulated sunlight

Photolysis of pesticides has been widely investigated for evaluating their environmental behavior and agricultural effectiveness after crop spraying. However, little information about the effects of the water-soluble substances in atmosphere on photodegradation of pesticides is available. In current study, we found that photolysis of applied dithianon fungicides on real plant leaves was much faster than that in sealed stock aqueous suspensions under simulated sunlight. To simulate the natural conditions, for the first time, photodegradation of dithianon in air-saturated solutions containing typical dissolved atmospheric substances (DAS) including CO₂ (HCO₃^-/CO₃^2-), NO₂ (NO₃^-), Fe³⁺ (Fe³⁺-complexes), and humic-like substances (HULIS) exposed to simulated solar irradiations were carried out in lab-scale. Fulvic acid (FA) was used as a surrogate for atmospheric HULIS in this study. The dithianon photodegradation was significantly enhanced in the presence of DAS and the photo-generated reactive species such as ·OH, ¹O₂, CO₃·- and ³FA∗ play important roles according to the results of reactive species quenching, electron spin resonance spectroscopy, and laser flash photolysis experiments. Moreover, the photodegraded intermediates and final products of dithianon on plant leaves have been identified by HPLC-MS analysis, and its possible photodegradation pathways were proposed. This work indicated that, except for direct photolysis, indirect photosensitive degradation induced by the dissolved photo-active substances in atmosphere should be considered for evaluating the degradation of the applied pesticides on crops.

Effect of Application Rate and Timing on Residual Efficacy of Pyraclostrobin in the Control of Pepper Anthracnose

Anthracnose is a devastating disease that seriously affects pepper production worldwide. Anthracnose management is currently a major problem because of the widespread and long period of infection of this disease. Therefore, determination of the optimal fungicide application timing is important for controlling anthracnose in a timely manner . In vitro sensitivity tests showed no significant difference in the pyraclostrobin sensitivity of Colletotrichum scovillei collected from 2016 and 2017, with mean half maximal effective concentration values of 0.349 to 0.542 and 0.0475 to 0.0639 mg/liter for the inhibition of mycelial growth and spore germination, respectively. Fungicide application initiated at the full-bloom stage could significantly delay anthracnose disease onset, decrease anthracnose incidence and development (23.67 to 89.80%), and increase pepper yield by 10.7 to 29.2%. In addition, the application dosage was decreased by >50%. BF-500-3, the main metabolite of pyraclostrobin, was detected in pepper fruit and exhibited high inhibitory activity against C. scovillei. The final residues of all fungicides at different application timing were below maximum residue limits. Moreover, structural equation modeling indicated that application timing plays the most important role in anthracnose disease inhibition. The tank mixtures of pyraclostrobin with tebuconazole and fludioxonil showed more satisfactory efficacy (69.87 to 78.36%) against anthracnose than did pyraclostrobin alone under field conditions. This study is the first to determine the best fungicide application timing for anthracnose management. These results establish the basis for sustainable development of the pepper industry.

Dissipation Behavior of Three Fungicides during the Industrial Processing of Paeoniae Radix Alba and Associated Processing Factors

Before being administered as medicinal products, Chinese herbal medicines (CHMs) must be processed and decocted for human consumption. While the presence of pesticide residues in CHMs is a major concern, pesticide dissipation behavior during CHM processing has rarely been reported. In this study, the dissipation of three pesticide residues in the CHM Paeoniae Radix Alba (PRA) was investigated during each step of industrial processing. The boiling process was found to significantly reduce pesticide residues (61–89%), and the peeling process also contributed to pesticide degradation (29–68%). The high temperature (60 °C) during the drying process led to further pesticide degradation. The processing factors of all three pesticides after each processing step were less than one, and the processing factors for the overall process were lower than 0.027, indicating that industrial processing clearly reduced the amount of pesticide residues (97.3–99.4%). The findings provide guidance for the safe use of fungicides in CHMs and can help establish maximum residue limits for PRA to reduce human exposure to pesticides.

Facile synthesis of magnetic zinc metal-organic framework for extraction of nitrogen-containing heterocyclic fungicides from lettuce vegetable samples

We present a simple method for the fabrication of a magnetic amino-functionalized zinc metal-organic framework based on a magnetic graphene oxide composite. The resultant framework exhibited a porous 3D structure, high surface area and good adsorption properties for nitrogen-containing heterocyclic fungicides. The adsorption process and capacity indicated that the primary adsorption mechanism might be hydrogen bonding and π-π conjugation. In addition, an optimized protocol for magnetic solid phase extraction was developed (such as adsorbent content, pH, and desorption solvent), and utilized for the extraction of nitrogen-containing heterocyclic fungicides from vegetable samples. Quantitation by high performance liquid chromatography coupled with tandem mass spectrometry offered a detection limit of 0.21-1.0 μg/L (S/N = 3) with correlation coefficients larger than 0.9975. These results demonstrate that magnetic amino-functionalized zinc metal-organic framewor is a promising adsorbent for the extraction and quantitation of nitrogen-containing heterocyclic fungicides.