Melatonin acts as a crucial signaling and antioxidant molecule with multiple physiological functions in organisms. To explore effects of exogenous melatonin on postharvest browning and its possible ...mechanisms in litchi fruit, ‘Ziniangxi’ litchi fruits were treated with an aqueous solution of melatonin at 0.4 mM and then stored at 25 °C for 8 days. The results revealed that melatonin strongly suppressed pericarp browning and delayed discoloration during storage. Melatonin treatment reduced relative membrane-leakage rate and inhibited the generation of superoxide radicals (O2 –·), hydrogen peroxide (H2O2), and malondialdehyde (MDA). Melatonin treatment markedly promoted the accumulation of endogenous melatonin; delayed loss of total phenolics, flavonoids, and anthocyanins; and enhanced the activities of antioxidant enzymes, including superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), ascorbate peroxidase (APX, EC 1.11.1.11), and glutathione reductase (GR, EC 1.6.4.2). By contrast, the activities of browning-related enzymes including polyphenoloxidase (PPO, EC 1.10.3.1) and peroxidase (POD, EC 1.11.1.7) were reduced. In addition, melatonin treatment up-regulated the expression of four genes encoding enzymes for repair of oxidized proteins, including LcMsrA1, LcMsrA2, LcMsrB1, and LcMsB2. These findings indicate that the delay of pericarp browning and senescence by melatonin in harvested litchi fruit could be attributed to the maintenance of redox homeostasis by the improvement of the antioxidant capacity and modulation of the repair of oxidatively damaged proteins.
•Hydrogen water (HW) treatment significantly delayed pericarp browning of litchi.•HW treatment maintained fruit quality of litchi during postharvest storage.•GSH and secondary metabolites played ...vital role in HW-delaying pericarp browning of litchi.•H2O2 might play a positive role in HW-delaying pericarp browning of litchi.
Litchi fruit were exposed to 0.7 PPM hydrogen water (HW) before storage at 25 ± 1 ℃. HW treatment delayed the pericarp browning and maintained the total soluble solids (TSS) of litchi fruit. Then, a total of 25 antioxidant system-related characters were determined to evaluate the effects of HW on antioxidant system during pericarp browning. Compared with control pericarp, the pericarp of HW-treated litchi fruit exhibited higher levels of superoxide radical (O2−·) scavenging activity, glutathione (GSH), monodehydroascorbate reductase (MDHAR), polyphenol oxidase (PPO) and total flavonoids during whole storage, higher levels of hydrogen peroxide (H2O2), catalase (CAT), glutathione disulfide (GSSG), ascorbate oxidase (AAO) and total phenols only on day 1, and higher levels of ascorbate peroxidase (APX), total anthocyanin, glutathione reductase (GR) and glutathione peroxidases (GPX) at later stage of storage. Those HW-induced antioxidant system-related characters might directly or indirectly enhanced the antioxidant capacity and delayed the pericarp browning of litchi.
•Apple polyphenols (APP) delayed browning and loss of red colour in litchi pericarp.•Delayed browning by APP was associated with suppressed anthocyanins degradation.•Effect of APP involved reduced ...oxidative stress and enhanced antioxidant activities.•APP treatment may be a promising strategy for controlling browning of litchi fruit.
‘Guiwei’ litchi fruit were treated with 5ga.i.L−1 apple polyphenols (APP) and then stored at 25°C to investigate the effects on pericarp browning. APP treatment effectively reduced pericarp browning and retarded the loss of red colour. APP-treated fruit exhibited higher levels of anthocyanins and cyanidin-3-rutinoside, which correlated with suppressed anthocyanase activity. APP treatment also maintained membrane integrity and reduced oxidative damage, as indicated by a lower relative leakage rate, malondialdehyde content, and reactive oxygen species (ROS) generation. The data suggest that decompartmentalisation of peroxidase and polyphenoloxidase and respective browning substrates was reduced. In addition, APP treatment enhanced the activities of antioxidant enzymes (superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase), as well as non-enzymatic antioxidant capacity (DPPH radical-scavenging activity and reducing power), which might be beneficial in scavenging ROS. We propose that APP treatment is a promising safe strategy for controlling postharvest browning of litchi fruit.
► Avocado ripening is delayed in response to increasing doses of 1-methylcyclopropene. ► Ripening is accompanied by increases in antioxidant chemicals and enzymes. ► 1-MCP treatment results in ...delayed accumulation of antioxidant chemicals and enzymes. ► 1-MCP delays but induces no unique responses of antioxidant features in avocado. ► Antioxidant systems of fruits show variable responses to ethylene-action suppression.
Preclimacteric avocado (Persea americana Mill. cv. Booth 7) fruit were treated with aqueous 1-methylcyclopropene (1-MCP) at 0.93 and 9.3mmolm−3 and then stored at 20°C to investigate the effect of 1-MCP on antioxidant systems of mesocarp tissue during ripening. Exposure to 1-MCP concentrations significantly delayed softening and peak ethylene production. 1-MCP significantly delayed accumulation of total soluble phenolics, flavonoids, and total antioxidant capacity although levels eventually reached control fruit maxima. The influence of 1-MCP was more pronounced at the higher concentration. Activities of peroxidase POD (EC 1.11.1.7), superoxide dismutase SOD (EC 1.15.1.1), catalase CAT (1.11.1.6) and l-ascorbate peroxidase APX (EC 1.11.1.11) increased during early ripening of control fruit followed by slight (CAT) or significant (POD, APX) declines with further ripening. Increases in activities of all enzymes were delayed in proportion to 1-MCP concentration, and maximum activities attained during ripening were largely unaffected by 1-MCP. Postclimacteric declines in POD and APX were not observed at the higher 1-MCP concentration, possibly reflecting incomplete ripening. The results indicate that changes in antioxidant parameters of avocado fruit are not markedly influenced by 1-MCP but are delayed or altered in proportion to the general suppression of ripening as indicated by ethylene production and fruit softening trends. Together with previously published reports, the data also indicate that the effects of ethylene-action suppression on antioxidant parameters during ripening vary considerably among different fruits. Relationships between antioxidant systems, ethylene and ripening are discussed.
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•Two polysaccharide components including PLP1 and PLP2 were purified from pepper leaves by HSCCC.•The separation process was completed using the polymer two-phase aqueous system.•The ...purified PLP2 exhibited good scavenging abilities on DPPH and ATBS radicals.•The purified PLP2 possessed notable hypoglycemic effect in diabetic mice.
In the present study, polysaccharides with antioxidant and hypoglycemic activities were isolated from the crude extract of pepper leaves by high-speed countercurrent chromatography in one step for the first time. An aqueous polymer two-phase system comprising PEG1000-K2HPO4-KH2PO4-H2O (0.8:1.25:1.25:6.5, w/w) was used for separation. During each separation, 2.0 g of the crude sample yielded two homogeneous components of polysaccharides PLP1 (226 mg) and PLP2 (273 mg). The molecular weights of PLP1 and PLP2 were 123 kDa and 243 kDa, respectively. PLP1 primarily consisted of mannose and glucose at a molar ratio of 1:2.4, whereas PLP2 was mainly composed of galactose, glucose, and rhamnose at a molar ratio of 2.6:1:2.2 with 10.3% (w/w) sulphates. Biological activity showed that sulfated PLP2 exhibited stronger antioxidant activity in vitro and hypoglycemic activity in diabetic mice than PLP1. The results demonstrated that sulfated PLP2 possessed potential as natural hypoglycemic agents or antioxidants in food or pharmaceuticals.
Abstract
Fresh fruits have good flavor and high nutritional value, but in the postharvest stage they will age and decay rapidly, so we need to find green postharvest fruit preservatives. And natural ...organic acids are promising natural fruit preservatives due to their safety and effectiveness. The present work reviews recent applications of natural organic acids in postharvest fruit quality management and discussed its potential biochemical mechanisms. This work indicates that numerous natural organic acids are effective postharvest fruit preservatives, such as oxalic acid, salicylic acid, citric acid, ascorbic acid, phenolic acid and terpenic acid. Natural organic acid treatments can improve postharvest fruit quality, as reflected by delaying senescence, alleviating chilling injury, controlling disease, and inhibiting browning. And natural organic acid can have multiple benefits on postharvest fruit. Natural organic acids also play a variety of roles in postharvest fruit disease control. In addition, chemical modification and cotreatment of natural organic acids can be performed to improve the efficiency of postharvest fruit preservation applications. The work provides an important reference for postharvest fruit quality management and the development of natural OAs fruit preservatives.
Melatonin (MLT) is a vital signaling molecule that regulates multiple physiological processes in higher plants. In the current study, the role of MLT in regulating chilling tolerance and its possible ...mechanisms in litchi fruit during storage at ambient temperatures after its removal from refrigeration was investigated. The results show that the application of MLT (400 μM, dipping for 20 min) to 'Baitangying' litchi fruit effectively delayed the development of chilling injury (CI) while inhibiting pericarp discoloration, as indicated by higher chromacity values (
,
,
) and anthocyanin levels. MLT treatment suppressed the enhancements of the relative electrical conductivity (REC) and malondialdehyde (MDA) content, which might contribute to the maintenance of membrane integrity in litchi fruit. MLT treatment slowed the decline in cellular energy level, as evidenced by higher adenosine triphosphate (ATP) content and a higher energy charge (EC), which might be ascribed to the increased activities of enzymes associated with energy metabolism including H
-ATPase, Ca
-ATPase, succinate dehydrogenase (SDH), and cytochrome C oxidase (CCO). In addition, MLT treatment resulted in enhanced proline accumulation, which was likely a consequence of the increased activities of ornithine-δ-aminotransferase (OAT) and Δ
-pyrroline-5-carboxylate synthase (P5CS) and the suppressed activity of proline dehydrogenase (PDH). These results suggest that the enhanced chilling tolerance of litchi fruit after MLT treatment might involve the regulation of energy and proline metabolism.
•Tea seed oil delays the browning and loss of red color of litchi pericarp.•Tea seed oil maintains membrane integrity and thereby delays fruit senescence.•Delayed browning by tea seed oil is linked ...with enhanced energy status.•Effect of tea seed oil involves the regulation of energy-relative genes expression.•Tea seed oil treatment is a promising strategy to control browning of litchi fruit.
‘Dadingxiang’ litchi fruit were treated with 0.1% tea seed oil (TSO) and then stored at 25°C for up to 8days to investigate the effects of TSO and possible mechanisms on pericarp browning. The results showed that TSO effectively delayed the development of pericarp browning and the loss of red color in litchi fruit. TSO treatment markedly maintained membrane integrity as indicated by a lower relative electrical conductivity, which might contribute to delayed fruit senescence. In addition, TSO treatment enhanced the ATP level, energy charge and activities of H+-ATPase and Ca2+-ATPase and regulated the expression of four genes related to energy metabolism, including LcAtpB, LcAAC1, LcAOX1 and LcSnRK2. These results indicate that the process of browning and senescence in litchi fruit may be closely associated with energy status via the regulation of energy metabolism-related enzymes and genes. We suggest that TSO treatment is a convenient and safe approach for reducing browning of harvested litchi fruit.
•Nitric oxide (NO) inhibited anthracnose, Colletotrichum gloeosporioides, in mango fruit.•NO did not exert direct antifungal activity against C. gloeosporioides in vitro.•NO induced defense-related ...enzymes and inhibited ripening in mango fruit.•NO treatment could be a promising strategy for controlling mango anthracnose.
Nitric oxide (NO) acts as an important signal molecule with diverse physiological functions in plants. In this study we investigated the effects and possible mechanisms of exogenous NO on anthracnose caused by Colletotrichum gloeosporioides in mango fruit. ‘Guifei’ mango fruit were treated with NO donor (sodium nitroprusside of 0.1mM) at 25°C for 5min, inoculated with spore suspension of C. gloeosporioides after 24h of NO treatment, and stored at ambient temperature (25°C). NO treatment effectively suppressed lesion development on mango fruit inoculated with C. gloeosporioides, and lesion diameters at 2 through 8d in NO-treated fruit averaged 30% lower than those in control fruit. Additionally, NO treatment reduced natural anthracnose incidence and severity of mango fruit ripened at ambient temperature, and the values of both parameters from 4 to 10d of storage in NO-treated fruit averaged 40 and 45% lower, respectively, than those for control fruit. NO did not exhibit in vitro antifungal activity against C. gloeosporioides. NO treatment enhanced the activities of defense-related enzymes including phenylalanine ammonia-lyase (PAL), cinnamate-hydroxylase (C4H), 4-coumarate: CoA ligase (4CL), peroxidase (POD), β-1,3-glucanase (GLU) and chitinase (CHT). NO treatment also promoted the accumulation of total phenolics, flavonoids and lignin that might contribute to inhibition of the pathogen. In addition to antifungal efficacy, NO treatment delayed flesh softening, yellowing, and changes in soluble solids content (SSC) and titratable acidity (TA), and peaks of respiration rate and ethylene production during ripening. These results suggest that the resistance of NO-treated mango to anthracnose may be attributed to activation of defense responses as well as delay of ripening.
Postharvest abnormal chilling injury (CI) behavior in papaya (Carica papaya L.) fruit is a rare phenomenon that may be associated with respiratory metabolism. This study thus aimed to investigate the ...impacts of storage temperatures (1 and 6 °C) on the respiratory metabolism of postharvest papaya and its impact on CI development. Results demonstrated that 1 °C storage reduced the activities of hexokinase (HK), phosphofructokinase (PFK), pyruvate kinase (PK), citrate synthase (CS), and α-ketoglutarate dehydrogenase (α-KGDH) and regulated the expression of corresponding enzymes in the Embden–Meyerhof–Parnas (EMP) pathway and tricarboxylic acid (TCA) cycle compared with 6 °C storage, resulting in a lower respiration rate of the EMP-TCA pathway and mitigating the development of CI. Meanwhile, lower contents of nicotinamide adenine dinucleotide (hydrogen) (NAD(H)) were observed in papaya fruit stored at 1 °C. Notably, papaya fruit stored at 1 °C maintained higher activity and transcriptional levels of SDH and IDH during the whole storage period. These findings suggest that 1 °C storage reduced the respiration rate of the EMP-TCA pathway by reducing the expression level and activity of related enzymes, which is conducive to the reduction of respiration substrate consumption and finally alleviating the occurrence of CI.
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