Weibo Jiang

Antioxidant Properties of the Mung Bean Flavonoids on Alleviating Heat Stress

Background It is a widespread belief in Asian countries that mung bean soup (MBS) may afford a protective effect against heat stress. Lack of evidence supports MBS conferring a benefit in addition to water. Results Here we show that vitexin and isovitexin are the major antioxidant components in mungbean (more than 96% of them existing in the bean seed coat), and both of them could be absorbed via gavage into rat plasma. In the plasma of rats fed with mungbean coat extract before or after exposure to heat stress, the levels of malonaldehyde and activities of lactate dehydrogenase and nitric oxide synthase were remarkably reduced; the levels of total antioxidant capacity and glutathione (a quantitative assessment of oxidative stress) were significantly enhanced. Conclusions Our results demonstrate that MBS can play additional roles to prevent heat stress injury. Characterization of the mechanisms underlying mungbean beneficial effects should help in the design of diet therapy strategies to alleviate heat stress, as well as provide reference for searching natural medicines against oxidative stress induced diseases.

Regulation of 1-MCP-treated banana fruit quality by exogenous ethylene and temperature

Ripe green banana (Musa sp., AAA group, cv. Zhonggang) fruits treated with 1-methylcyclopropene (1-MCP) significantly delayed the peaks of respiration rate and ethylene production but did not reduce the peak height. Mature banana fruits were also treated with 1-MCP for 24 h at 20 C and then exposed to 50 mL/L ethylene or stored at different temperatures to analyse the effects of external added ethylene. Reductions in firmness, titratable acidity (TA) and starch content (SC) of banana fruits were remarkably delayed by 1-MCP treatment. 1-MCP treatment also delayed the increase of total soluble sugar (TSS) and soluble pectin (SP) contents. Soluble solids (SS) content in the 1-MCP-treated fruit remained almost unchanged during the first 10 days of storage at 20 C. No significant differences in TA, TSS, SP and SS levels were observed between the fruit treated with 1-MCP alone and the fruit treated with 1-MCP plus ethylene. The 1-MCP effects on all the parameters related to banana ripening were enhanced by low temperature storage and reduced by high temperature storage.

Identification of the flavonoids in mungbean (Phaseolus radiatus L.) soup and their antioxidant activities.

Mung bean soup (MBS) has been traditionally taken as a kind of health food in China. To learn the mechanisms underlying its health benefits, antioxidant capacities of the soup prepared with three cultivars of mung bean were measured. The highest DPPH radical scavenging or ferric reducing activity was observed in soup of mung bean cv. Huang. The MBS of cv. Huang and Mao exhibited higher ABTS(+) reducing activities than MBS of cv. Ming. The two major flavonoids in the MBS were purified and identified as vitexin and isovitexin, respectively. Modeling samples containing vitexin and isovitexin at the same levels as them in the MBS were prepared to assess their antioxidant contributions in the MBS. Our results showed that antioxidant capacities of the MBS mainly derived from vitexin and isovitexin, these flavonoids accounted for the most of total DPPH radicals scavenging, ferric reducing and ABTS(+) reducing scavenging activities in MBS of all the three cultivars.

Effects of reactive oxygen species on cellular wall disassembly of banana fruit during ripening.

Fruit softening is generally attributed to cell wall disassembly. Experiments were conducted to investigate effects of various reactive oxygen species (ROS) on in vitro cellular wall disassembly of harvested banana fruit. The alcohol-extracted insoluble residue (AEIR) was obtained from the pulp tissues of banana fruit at various ripening stages and then used to examine the disassembly of cellular wall polysaccharides in the presence of superoxide anion (O2(-)), hydrogen peroxide (H2O2) or hydroxyl radical (OH) and their scavengers. The presence of OH accelerated significantly disassembly of cellular wall polysaccharides in terms of the increase in contents of total sugars released and uronic acid, and the decrease in molecular mass of soluble polysaccharides, using gel permeation chromatography. However, the treatment with H2O2 or O2(-) showed no significant effect on the disassembly of cellular wall polysaccharides. Furthermore, the degradation of the de-esterified AEIR was more susceptible to OH attack than the esterified AEIR. In addition, the effect of OH could be inhibited in the presence of OH scavenger. This study suggests that disassembly of cellular wall polysaccharides could be initiated by OH as the solublisation of the polysaccharides increased, which, in turn, accelerated fruit softening.

Effects of postharvest salicylic acid dipping on Alternaria rot and disease resistance of jujube fruit during storage

BACKGROUND Considerable postharvest losses caused by Alternaria alternata often occur in Chinese jujube fruit, and synthetic fungicides have been widely used to protect the fruit from Alternaria rot. However, the potential harmfulness of fungicide residues to human health and the environment cannot be ignored. This study was conducted to develop an alternative approach for controlling postharvest disease by inducing fruit resistance with salicylic acid (SA) dipping. RESULTS Disease incidence and lesion area in the jujube fruit inoculated with A. alternata were significantly inhibited by 2 and 2.5 mmol L(-1) SA dipping. Naturally infected decay rate and index in jujubes were also significantly reduced by SA dipping during long-term storage at 0°C. SA enhanced activities of the main defense-related enzymes including phenylalanine ammonia-lyase, peroxidase, chitinase and β-1,3-glucanase in the fruit during storage. SA strongly decreased catalase activity but increased superoxide dismutase activity and ascorbic acid content in jujubes. CONCLUSION The beneficial effects of SA on fruit protection may be due to its ability to activate several highly coordinated defence-related systems in jujubes, instead of its fungicidal activity. The findings indicated that application of SA would offer an alternative approach that helps to control postharvest disease and maintain storage quality in fruits.

Preventing the wound-induced deterioration of Yali pears by chitosan coating treatments

Yali pears (Pyrus bretschneideri Rehd.) are susceptible to mechanical damage. In this study, the protective effects of chitosan treatments on the quality of bruised pears were evaluated. The fruit were treated with 1.5% chitosan before or after bruise damage, respectively. Then, the fruit were stored at 16 °C and 85–90% relative humidity. Postharvest quality parameters were analyzed during the storage. Bruise damage accelerated the decrease of firmness and the ratio of sugar to acid, while a delay of firmness and sugar-to-acid ratio in those pears treated with chitosan before or after was found. Meanwhile, chitosan treatments both before and after damage delayed the color changes caused by damage, inhibited disease incidence increase, and enhanced the bruise recovery during the storage. Our results suggested that chitosan treatment could be used to control the physiological responses induced by bruise damage.

Effect of yeast mannan treatments on ripening progress and modification of cell wall polysaccharides in tomato fruit

Yeast mannan treatments effectively delayed colour change and firmness decline and inhibited ethylene production in two cultivars of tomato fruit during storage. The yeast mannan treatment maintained the integrity of tomato pericarp cell wall architecture and suppressed the modification of water-soluble and insoluble pectic polysaccharides in the cell wall. A decrease in the neutral sugars, including d-galactose, l-arabinose and l-rhamnose, in water-insoluble pectin and an increase in these sugars in water-soluble pectin were inhibited by yeast mannan. The contents of d-xylose and d-mannose in the hemicellulose fraction were significantly higher in the yeast mannan-treated fruit after storage. The activities of several cell wall-modifying enzymes, including pectinmethylesterase, polygalacturonase and β-galactosidase, were suppressed in fruit treated with yeast mannan during storage. Overall, the yeast mannan-induced delay in the ripening progress of tomato fruit might occur via the strong suppression of ethylene synthesis, causing inhibition of solubilization and depolymerization of cell wall polysaccharides.

Partial properties of an aspartic protease in bitter gourd (Momordica charantia L.) fruit and its activation by heating

Bitter gourd (BG fruit) is usually heated in hot water to reduce bitterness and improve flavour before being served. Protein extract from BG was analyzed for protease activity by gelatin-gel electrophoresis. The study showed that the proteolytic activity in BG flesh was enhanced by heat-treatment at temperatures ranging from 50°C to 75°C. An aspartic protease (AP) was characterized by gel electrophoresis. The optimal AP activity was at pH 7; the pI of the AP was demonstrated to be 4.8; the protein molecular weight of the BG-AP was estimated to be 60KD by SDS-PAGE. The AP was implicated in the proteolysis of the photosynthetic enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase. The AP was further purified and submitted for analysis of peptide mass fingerprint (PMF). The Mascot peptide mass fingerprint of the AP protein hit no existing protein (score>60), and it proved to be a novel AP.

Effects of chlorogenic acid on capacity of free radicals scavenging and proteomic changes in postharvest fruit of nectarine

To study how chlorogenic acid affects changes of reactive oxygen species (ROS) and the proteins involved in ROS scavenging of nectarine during storage time, the fruits were treated with chlorogenic acid (CHA) then stored at 25°C for further studies. The CHA-treatment significantly reduced O2-· production rate, H2O2 content, and membrane permeability of nectarine fruit during storage. The key proteins related the nectarine fruit senescence during storage were identified by two-dimensional electrophoresis and MALDI-TOF/TOF. Level and enzymatic activity of peroxidase were reduced, while both the protein levels and the enzymatic activities of superoxide dismutase, glutathione reductase, glutathione-s-transferase and monodehydroascorbate reductase were enhanced in nectarine fruit treated with CHA. In addition, levels of several pathogen-related proteins were also enhanced by CHA-treatment. Taking together, the present study showed that CHA could influence changes in defense related proteins and reduced oxidative damage in nectarine fruit during postharvest ripening.

Polyphenol composition and antioxidant capacity in pulp and peel of apricot fruits of various varieties and maturity stages at harvest

Polyphenol composition and antioxidant capacities of peel and pulp tissues of six apricot varieties were determined. Variations in polyphenol and antioxidant capacity based on variety (early‐maturing varieties and late‐maturing varieties) and harvest maturity (green mature and full mature) were assessed. The results of principal component analysis revealed that (+)‐catechin made the most important contributions to the antioxidant capacities of the pulp. As the (+)‐catechin content in ‘Dajie’ apricot decreased by 36.8% from green mature to full mature, the antioxidant capacities determined by ABTS free radical scavenging assay, DPPH free radical scavenging assay and cupric ion reducing antioxidant capacity assay decreased by 50.0%, 45.2% and 45.8%, respectively. Levels of phenolic compounds in the apricot peels were approximately 2–4 times higher than those of the pulps. Quercetin‐3‐rutinoside may be substantially responsible for the antioxidant capacities of the peels. The late‐maturing varieties tended to have higher levels of phenolic compounds and higher antioxidant capacities than the early‐maturing varieties. The antioxidant capacities in green mature apricots were much higher than those of full mature apricots.