Carvacrol delays Phomopsis stem-end rot development in pummelo fruit in relation to maintaining energy status and antioxidant system

DNP and ATP modulate the pulp softening and breakdown in fresh longan by acting on the antioxidant system and the metabolisms of membrane lipids and cell wall polysaccharides

Compared to the control longan, DNP treatment elevated pulp breakdown index, reduced the values of pulp firmness, CSP, ISP, cellulose, and hemicellulose by enhancing the activities of PE, PG, Cx, XET, and β-Gal. Additionally, DNP treatment increased the levels of PLD, lipase, LOX, PA, and SFA, and decreased the values of PC, PI, USFA, U/S, and IUFA, displaying higher cell membrane permeability and more severe cell membrane damage in longan pulp. Furthermore, DNP treatment weakened the levels of SOD, CAT, APX, AsA, GSH, TP, and TF, thereby exacerbating ROS outbreak and MDA production. These results indicate that DNP treatment destroyed the antioxidant system to cause ROS eruption. This disruption further disturbed the metabolisms of membrane lipids and cell wall polysaccharides, leading to the breakdown of cell membrane and cell wall, and eventually aggravated longan pulp softening and breakdown. However, ATP treatment exhibited the opposite effects of DNP treatment.

Carvacrol enhances antioxidant activity and slows down cell wall metabolism by maintaining the energy level of 'Guifei' mango

BACKGROUND

Postharvest mango fruit are highly susceptible to rapid ripening, softening and senescence, greatly limiting their distribution. In this study, we evaluated the potential effects of carvacrol (0.06 g L-1) on mango (25 ± 1 °C) and the mechanisms by which it regulates antioxidant activity, energy and cell wall metabolism.

RESULTS

The results showed that carvacrol treatment delayed the 'Guifei' mango color transformation (from green to yellow) and the decrease in firmness, titratable acidity, weight loss and soluble solids content, and suppressed the increase in relative conductivity, malondialdehyde content and reactive oxygen species (H2O2 and O2 ·-) as well as enhancing antioxidant activity. In addition, carvacrol treatment increased ascorbic acid and reduced glutathione levels, ascorbate peroxidase, glutathione reductase, monodehydroascorbate reductase and dehydroascorbate reductase activities in mango. Meanwhile, energy level (adenosine triphosphate, adenosine diphosphate, adenosine monophosphate and energy charge) content and energy metabolizing enzyme activities (H+-ATPase, Ca2+-ATPase, succinate dehydrogenasepears and cytochrome C oxidase) were increased on carvacrol treatment, which resulted in the maintenance of higher energy levels. Finally, the application of carvacrol was effective in maintaining firmness and cell wall components by inhibiting the activities of polygalacturonase, cellulase, pectin methyl esterase and β-galactosidase.

CONCLUSION

The current study demonstrates that carvacrol effectively delays the ripening and softening of mangoes by modulating energy metabolism and cell wall dynamics through the attenuation of oxidative stress. © 2024 Society of Chemical Industry.

Antifungal Activity of Phloroglucinol Derivatives against Botrytis cinerea and Monilinia fructicola

Naturally derived compounds show promise as treatments for microbial infections. Polyphenols, abundantly found in various plants, fruits, and vegetables, are noted for their physiological benefits including antimicrobial effects. This study introduced a new set of acylated phloroglucinol derivatives, synthesized and tested for their antifungal activity in vitro against seven different pathogenic fungi. The standout compound, 3-methyl-1-(2,4,6-trihydroxyphenyl) butan-1-one (2b), exhibited remarkable fungicidal strength, with EC50 values of 1.39 μg/mL against Botrytis cinerea and 1.18 μg/mL against Monilinia fructicola, outperforming previously screened phenolic compounds. When tested in vivo, 2b demonstrated effective antifungal properties, with cure rates of 76.26% for brown rot and 83.35% for gray mold at a concentration of 200 μg/mL, rivaling the commercial fungicide Pyrimethanil in its efficacy against B. cinerea. Preliminary research suggests that 2b's antifungal mechanism may involve the disruption of spore germination, damage to the fungal cell membrane, and leakage of cellular contents. These results indicate that compound 2b has excellent fungicidal properties against B. cinerea and holds potential as a treatment for gray mold.

Biocontrol Mechanisms of Three Plant Essential Oils Against Phytophthora infestans Causing Potato Late Blight

Late blight, caused by the notorious pathogen Phytophthora infestans, poses a significant threat to potato (Solanum tuberosum) crops worldwide, impacting their quality as well as yield. Here, we aimed to investigate the potential use of cinnamaldehyde, carvacrol, and eugenol as control agents against P. infestans and to elucidate their underlying mechanisms of action. To determine the pathogen-inhibiting concentrations of these three plant essential oils (PEOs), a comprehensive evaluation of their effects using gradient dilution, mycelial growth rate, and spore germination methods was carried out. Cinnamaldehyde, carvacrol, and eugenol were capable of significantly inhibiting P. infestans by hindering its mycelial radial growth, zoospore release, and sporangium germination; the median effective inhibitory concentration of the three PEOs was 23.87, 8.66, and 89.65 μl/liter, respectively. Scanning electron microscopy revealed that PEOs caused the irreversible deformation of P. infestans, resulting in hyphal shrinkage, distortion, and breakage. Moreover, propidium iodide staining and extracellular conductivity measurements demonstrated that all three PEOs significantly impaired the integrity and permeability of the pathogen's cell membrane in a time- and dose-dependent manner. In vivo experiments confirmed the dose-dependent efficacy of PEOs in reducing the lesion diameter of potato late blight. Altogether, these findings provide valuable insight into the antifungal mechanisms of PEOs vis-à-vis late blight-causing P. infestans. By utilizing the inherent capabilities of these natural compounds, we could effectively limit the harmful impacts of late blight on potato crops, thereby enhancing agricultural practices and ensuring the resilience of global potato food production.

Robust construction of konjac glucomannan/polylactic acid nanofibrous films incorporated with carvacrol via microfluidic blow spinning for food packaging

In recent years, the application of biopolymer-based nanofibers prepared via microfluidic blow spinning (MBS) for food packaging has continuously increased due to their advantages of biocompatibility, biodegradability, and safety. However, the poor spinnability, undesirable water barrier capacity, and loss of antibacterial and antioxidant properties of biopolymer-based nanofibers strictly restrict their real-world applications. In this work, carvacrol (CV) incorporated konjac glucomannan (KGM)/polylactic acid (PLA) nanofibrous films (KP-CV) were produced by MBS. The FTIR spectra and XRD analysis revealed the hydrogen bonding interactions among CV, PLA, and KGM, thus significantly improving the TS of KP-CV nanofibrous films from 0.23 to 1.27 MPa with increased content of CV from 0 % to 5 %. Besides, KP-CV nanofibrous films showed improved thermal stability, excellent hydrophobicity (WCA: 128.19°, WVP: 1.02 g mm/m2 h kPa), and sustained release of CV combined with good antioxidant activities (DPPH radical scavenging activity: 77.51 ± 1.57 %), and antibacterial properties against S. aureus (inhibition zone: 26.33 mm) and E. coli (inhibition zone: 22.67 mm). Therefore, as prepared KP-CV nanofibrous films can be potentially applied as packaging materials for the extended shelf life of cherry tomatoes.

Apple polyphenols delay postharvest senescence and quality deterioration of 'Jinshayou' pummelo fruit during storage

INTRODUCTION

Apple polyphenols (AP), derived from the peel of mature-green apples, are widely used as natural plant-derived preservatives in the postharvest preservation of numerous horticultural products.

METHODS

The goal of this research was to investigate how AP (at 0.5% and 1.0%) influences senescence-related physiological parameters and antioxidant capacity of 'Jinshayou' pummelo fruits stored at 20°C for 90 d.

RESULTS

The treating pummelo fruit with AP could effectively retard the loss of green color and internal nutritional quality, resulting in higher levels of total soluble solid (TSS) content, titratable acidity (TA) content and pericarp firmness, thus maintaining the overall quality. Concurrently, AP treatment promoted the increases in ascorbic acid, reduced glutathione, total phenols (TP) and total flavonoids (TF) contents, increased the scavenging rates of 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) and hydroxyl radical (•OH), and enhanced the activities of superoxide dismutase (SOD), catalase, peroxidase, ascorbate peroxidase (APX), and glutathione reductase (GR) as well as their encoding genes expression (CmSOD, CmCAT, CmPOD, CmAPX, and CmGR), reducing the increases in electrolyte leakage, malondialdehyde content and hydrogen peroxide level, resulting in lower fruit decay rate and weight loss rate. The storage quality of 'Jinshayou' pummelo fruit was found to be maintained best with a 1.0% AP concentration.

CONCLUSION

AP treatment can be regarded as a promising and effective preservative of delaying quality deterioration and improving antioxidant capacity of 'Jinshayou' pummelo fruit during storage at room temperature.

Thymol Edible Coating Controls Postharvest Anthracnose by Regulating the Synthesis Pathway of Okra Lignin

Okra has received extensive attention due to its high nutritional value and remarkable functional characteristics, but postharvest diseases have severely limited its application. It is important to further explore the methods and potential methods to control the postharvest diseases of okra. In this study, Colletotrichum fioriniae is the major pathogen that causes okra anthracnose, which can be isolated from naturally decaying okra. The pathogenicity of C. fioriniae against okra was preliminarily verified, and the related biological characteristics were explored. At the same time, an observational study was conducted to investigate the in vitro antifungal effect of thymol edible coating (TKL) on C. fioriniae. After culturing at 28 °C for 5 days, it was found that TKL showed an obvious growth inhibition effect on C. fioriniae. The concentration for 50% of the maximal effect was 95.10 mg/L, and the minimum inhibitory concentration was 1000 mg/L. In addition, it was found that thymol edible coating with a thymol concentration of 100 mg/L (TKL100) may cause different degrees of damage to the cell membrane, cell wall, and metabolism of C. fioriniae, thereby inhibiting the growth of hyphae and causing hyphal rupture. Refer to the results of the in vitro bacteriostatic experiment. Furthermore, the okra was sprayed with TKL100. It was found that the TKL100 coating could significantly inhibit the infection of C. fioriniae to okra, reduce the rate of brown spots and fold on the okra surface, and inhibit mycelium growth. In addition, the contents of total phenols and flavonoids of okra treated with TKL100 were higher than those of the control group. Meanwhile, the activities of phenylalaninammo-nialyase, cinnamic acid-4-hydroxylase, and 4-coumarate-CoA ligase in the lignin synthesis pathway were generally increased, especially after 6 days in a 28 °C incubator. The lignin content of TKL-W was the highest, reaching 65.62 ± 0.68 mg/g, which was 2.24 times of that of CK-W. Therefore, TKL may promote the synthesis of total phenols and flavonoids in okra, then stimulate the activity of key enzymes in the lignin synthesis pathway, and finally regulate the synthesis of lignin in okra. Thus, TKL could have a certain controlling effect on okra anthracnose.

Maintenance of postharvest storability and overall quality of 'Jinshayou' pummelo fruit by salicylic acid treatment

INTRODUCTION

The loss of postharvest storability of pummelo fruit reduces its commodity value for long run. To maintain its storability, the effects of postharvest dipping treatment by salicylic acid (SA) with different concentrations (0, 0.1, 0.2, or 0.3%) were investigated on pummelo fruit (Citrus maxima Merr. cv. Jinshayou) during the room temperature storage at 20 ± 2°C for 90 d.

RESULTS AND DISCUSSION

Among all treatments, pre-storage SA treatment at 0.3% demonstrated the most significant ability to reduce fruit decay incidence, decrease weight loss, delay peel color-turned process, and inhibit the declines in total soluble solids (TSS) as well as titratable acid (TA) content. The increases in electrolyte leakage, hydrogen peroxide (H₂O₂), and malondialdehyde (MDA) content of the 0.3% SA-treated pummelo fruit were reduced compared to the control (dipped in distilled water). Pummelo fruit treated with 0.3% SA exhibited the most outstanding ability to excess reactive oxygen species (ROS) accumulation, as evidenced by promoted the increases in glutathione (GSH), total phenolics and flavonoids contents, delayed the AsA decline, and enhanced the activities of antioxidant enzymes and their encoding genes expression.

CONCLUSION

Pre-storage treatment dipped with SA, particularly at 0.3%, can be used as a useful and safe preservation method to maintain higher postharvest storability and better overall quality of 'Jinshayou' pummelo fruit, and thus delaying postharvest senescence and extend the storage life up to 90 d at room temperature.

Fucoidan treatment alleviates chilling injury in cucumber by regulating ROS homeostasis and energy metabolism

INTRODUCTION

Chilling injury is a major hindrance to cucumber fruit quality during cold storage.

METHODS AND RESULTS

In this study, we evaluated the effects of fucoidan on fruit quality, reactive oxygen species homeostasis, and energy metabolism in cucumbers during cold storage. The results showed that, compared with the control cucumber fruit, fucoidan-treated cucumber fruit exhibited a lower chilling injury index and less weight loss, as well as reduced electrolyte leakage and malondialdehyde content. The most pronounced effects were observed following treatment with fucoidan at 15 g/L, which resulted in increased 1,1-diphenyl-2-picrylhydrazyl and hydroxyl radical scavenging rates and reduced superoxide anion production rate and hydrogen peroxide content. The expression and activity levels of peroxidase, catalase, and superoxide dismutase were enhanced by fucoidan treatment. Further, fucoidan treatment maintained high levels of ascorbic acid and glutathione, and high ratios of ascorbic acid/dehydroascorbate and glutathione/oxidized glutathione. Moreover, fucoidan treatment increased the activities of ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, and glutathione reductase and their gene expression. Fucoidan treatment significantly delayed the decrease in ATP and ADP, while preventing an increase in AMP content. Finally, fucoidan treatment delayed the decrease of energy charge and the activities and gene expression of H⁺-ATPase, Ca²⁺-ATPase, cytochrome c oxidase, and succinate dehydrogenase in cucumber fruits.

CONCLUSION

Altogether, our findings indicate that fucoidan can effectively enhance antioxidant capacity and maintain energy metabolism, thereby improving cucumber cold resistance during cold storage.

Lignin Biosynthesis Pathway and Redox Balance Act Synergistically in Conferring Resistance against Penicillium italicum Infection in 7-Demethoxytylophorine-Treated Navel Orange

7-Demethoxytylophorine (DEM), a natural water-soluble phenanthroindolizidine alkaloid, has a great potential for in vitro suppression of Penicillium italicum growth. In the present study, we investigated the ability of DEM to confer resistance against P. italicum in harvested "Newhall" navel orange and the underlying mechanism. Results from the in vivo experiment showed that DEM treatment delayed blue mold development. The water-soaked lesion diameter in 40 mg L^-1 DEM-treated fruit was 35.2% lower than that in the control after 96 h. Moreover, the decrease in peel firmness loss and increase in electrolyte leakage, superoxide anion (O₂^•-) production, and malondialdehyde (MDA) content were significantly inhibited by DEM treatment. Hydrogen peroxide (H₂O₂) burst in DEM-treated fruit at the early stage of P. italicum infection contributed to the conferred resistance by increasing the activities of lignin biosynthesis-related enzymes, along with the expressions of their encoding genes, resulting in lignin accumulation. The DEM-treated fruit maintained an elevated antioxidant capacity, as evidenced by high levels of ascorbic acid and glutathione content, and enhanced or upregulated the activities and gene expression levels of APX, GR, MDHAR, DHAR, GPX, and GST, thereby maintaining ROS homeostasis and reducing postharvest blue mold. Collectively, the results in the present study revealed a control mechanism in which DEM treatment conferred the resistance against P. italicum infection in harvested "Newhall" navel orange fruit by activating lignin biosynthesis and maintaining the redox balance.

Efficacy and Mechanism of Thymol/KGM/LG Edible Coating Solution on Inhibition of Mucor circinelloides Isolated From Okra

With the increasing demand and quality requirement for the natural nutritious food in modern society, okra has attracted much attention because of its high nutritional value and remarkable functionality. However, the occurrence of postharvest diseases of fresh okra severely limited the application and the value of okra. Therefore, in this study, the dominant pathogens causing postharvest diseases such as soft rot were isolated from naturally decaying okra. It was identified as Mucor circinelloides by its morphological characteristics and standard internal transcribed spacer ribosomal DNA sequence. Furthermore, the biological characteristics of M. circinelloides were studied, and the inhibitory effect of thymol/KGM/LG (TKL) edible coating solution on M. circinelloides and its possible mechanism was discussed. In addition, TKL edible coating solution had a dose-dependent inhibitory effect on M. circinelloides, with a 50% inhibitory concentration (EC50) of 113.55 mg/L. The TKL edible coating solution at 960 mg/L of thymol completely inhibited mycelial growth and spore germination of M. circinelloides. The results showed that the best carbon source of M. circinelloides was maltose, the best nitrogen source was beef extract and potassium nitrate, the best pH was 6, the best temperature was 28°C, the best NaCl concentration was 0.5%, and the light was conducive to the growth of M. circinelloides. It was also observed by scanning electron microscope (SEM) that TKL was more likely to destroy the cell wall integrity of M. circinelloides, inhibit spore morphology and change mycelium structure. Meanwhile, the activity of chitinase (CHI), an enzyme related to cell wall synthesis of M. circinelloides, was significantly decreased after being treated by TKL with thymol at 100 mg/L (TKL100). The content of Malondialdehyde (MDA) in M. circinelloides decreased significantly from 12 h to 48 h, which may cause oxidative damage to the cell membrane. The activity polygalacturonase (PG), pectin methylgalacturonase (PMG), and cellulase (Cx) of M. circinelloides decreased significantly. Therefore, the results showed that TKL had a good bacteriostatic effect on okra soft rot pathogen, and the main bacteriostatic mechanism might be the damage of cell membrane, degradation of the cell wall, inhibition of metabolic activities, and reduction of metabolites, which is helpful to further understand the inhibitory effect of TKL on okra soft rot pathogen and its mechanism.

Trehalose Regulates Starch, Sorbitol, and Energy Metabolism to Enhance Tolerance to Blue Mold of "Golden Delicious" Apple Fruit

The efficacy of trehalose on the lesion diameter of apples (cv. Golden Delicious) inoculated with Penicillium expansum was evaluated to screen the optimal concentration. The changes in gene expression and activity of the enzyme in starch, sorbitol, and energy metabolism were also investigated in apples after trehalose treatment. The results revealed that trehalose dipping reduced the lesion diameter of apples inoculated with P. expansum. Trehalose suppressed the activities and gene expressions of β-amylase, NAD-sorbitol dehydrogenase, and NADP-sorbitol dehydrogenase, whereas it decreased the sorbitol 6-phosphate dehydrogenase gene expression and amylose, amylopectin, total starch, and reducing sugar contents. Additionally, trehalose improved the gene expressions and activities of α-amylase, starch-branching enzymes, total amylase, H⁺-ATPase, and Ca²⁺-ATPase, as well as soluble sugar, adenosine triphosphate, and adenosine diphosphate contents and energy charge in apples. These findings imply that trehalose could induce tolerance to the blue mold of apple fruit by regulating starch, sorbitol, and energy metabolism.

Antofine Triggers the Resistance Against Penicillium italicum in Ponkan Fruit by Driving AsA-GSH Cycle and ROS-Scavenging System

Postharvest fungal infection can accelerate the quality deterioration of Ponkan fruit and reduce its commodity value. Penicillium italicum is the causal pathogen of blue mold in harvested citrus fruits, not only causing huge fungal decay but also leading to quality deterioration. In our preliminary study, antofine (ATF) was found to have a great potential for significant in vitro suppression of P. italicum growth. However, the regulatory mechanism underpinning ATF-triggered resistance against P. italicum in citrus fruit remains unclear. Here, the protective effects of ATF treatment on blue mold development in harvested Ponkan fruit involving the enhancement of ROS-scavenging system were investigated. Results showed that ATF treatment delayed blue mold development and peel firmness loss. Moreover, the increase of electrolyte leakage, O2 •- production, and malonyldialdehyde accumulation was significantly inhibited by ATF treatment. The ATF-treated Ponkan fruit maintained an elevated antioxidant capacity, as evidenced by inducted the increase in glutathione (GSH) content, delayed the declines of ascorbic acid (AsA) content and GSH/oxidized GSH ratio, and enhanced the activities of superoxide dismutase, catalase, peroxidase, and six key AsA-GSH cycle-related enzymes, along with their encoding gene expressions, thereby maintaining ROS homeostasis and reducing postharvest blue mold in harvested Ponkan fruit. Collectively, the current study revealed a control mechanism based on ATF-triggered resistance and maintenance of a higher redox state by driving AsA-GSH cycle and ROS-scavenging system in P. italicum-infected Ponkan fruit.