Combination of heat treatment and chitosan coating to improve postharvest quality of wolfberry (Lycium barbarum)

The synergistic application of hot water dip at 42 °C for 30 min and 1% chitosan coating on differentiation in postharvest quality traits, microstructure as well as microbiological evolution of wolfberry fruits was investigated. Fresh wolfberry fruits were stored at 2 ± 0.5 °C and 90% relative humidity (RH) for 28 days. Results indicated the combination of prestorage heat treatment and chitosan coating maintained higher levels of ascorbic acid, total phenolic contents and antioxidant capacity as well as lower decay, compared with untreated wolfberry fruits. The possible mechanism was that the heat treatment almost sealed open stomata to limit the sites of pathogen penetration into fruits independently, followed by the biofilm formed by chitosan which controlled secondary infections as well as slowed changes in fruit respiration and metabolic activity in wolfberries. The synergistically treated fruit also exhibited a higher acceptability obtained by sensory analysis after cold storage. In this sense, the integrated application of heat treatment and chitosan coating could be regarded as an effective strategy to extend storage life and maintain the postharvest quality of wolfberry fruits.     

Moderate antioxidative efficiencies of flavonoids during peroxidation of methyl linoleate in homogeneous and micellar solutions

The relative reactivities as well as the stoichiometric coefficients for a number of flavonoids, catechols, and—for comparison—standard phenolic antioxidants were determined by analyzing the kinetics of oxygen consumption in organic and micellar systems, with peroxidation initiated by lipid- and water-soluble azo initiators. The results demonstrated that the flavonoids did not behave as classic phenolic antioxidants such as α-tocopherol, but showed only moderate chain-breaking activities. The results were in line with other structure-activity relationship studies on the importance of the B-ring catechol structure, the 2,3-double bond, and the 3,5-hydroxy groups. The data are discussed in view of possible explanations of the deviations flavonoids reveal in their behavior compared with regular phenolic antioxidants.     

Biflavonoid-Induced Disruption of Hydrogen Bonds Leads to Amyloid-β Disaggregation

Deposition of amyloid β (Aβ) fibrils in the brain is a key pathologic hallmark of Alzheimer’s disease. A class of polyphenolic biflavonoids is known to have anti-amyloidogenic effects by inhibiting aggregation of Aβ and promoting disaggregation of Aβ fibrils. In the present study, we further sought to investigate the structural basis of the Aβ disaggregating activity of biflavonoids and their interactions at the atomic level. A thioflavin T (ThT) fluorescence assay revealed that amentoflavone-type biflavonoids promote disaggregation of Aβ fibrils with varying potency due to specific structural differences. The computational analysis herein provides the first atomistic details for the mechanism of Aβ disaggregation by biflavonoids. Molecular docking analysis showed that biflavonoids preferentially bind to the aromatic-rich, partially ordered N-termini of Aβ fibril via the π–π interactions. Moreover, docking scores correlate well with the ThT EC₅₀ values. Molecular dynamic simulations revealed that biflavonoids decrease the content of β-sheet in Aβ fibril in a structure-dependent manner. Hydrogen bond analysis further supported that the substitution of hydroxyl groups capable of hydrogen bond formation at two positions on the biflavonoid scaffold leads to significantly disaggregation of Aβ fibrils. Taken together, our data indicate that biflavonoids promote disaggregation of Aβ fibrils due to their ability to disrupt the fibril structure, suggesting biflavonoids as a lead class of compounds to develop a therapeutic agent for Alzheimer’s disease.     

蝗虫中黄酮的含量及提取工艺研究

蝗虫含有丰富的黄酮，不同品种之间和同一品种不同地域之间有很大差异。稻蝗的黄酮含量最高，为2014.9mg／100g,内蒙黄胫小车蝗的含量最低。为293．2mg／100g。采用有机溶剂提取法对内蒙黄胫小车蝗所含黄酮提取工艺进行了研究，结果表明，甲醇具有很好的提取效果，其最佳提取工艺条件为：提取时间24h。料液比1：30，黄酮的提取量为293．2mg／100g。     

银杏叶中有效成分的提取及其应用

研究了银杏叶中黄酮类抗氧化成分的提取工艺，并对黄酮类物质清除自由基和抗氧化性能进行了探讨。结果表明：用质量分数70％乙醇回流提取银杏叶，65℃时黄酮的质量浓度高达0．0625μg/mL。黄酮类物质有很强的清除自由基能力和抗氧化能力，随着黄酮浓度的增加，溶液的吸光度逐渐减小，即对．OH的清除率逐渐增大，抗氧化能力逐渐增大。且对人体无毒害作用，可考虑代替合成的抗氧化剂。     

高纯竹叶碳苷黄酮复合纳米生物材料的制备及其结构表征（急）

采用离子交联法，以高纯竹叶碳苷黄酮制剂（碳苷总质量分数﹥90%，记为H-BLF）和芫根阴离子多糖（TP）为原料，通过ε-聚赖氨酸（ε-PL）的阳离子桥键合而成竹叶碳苷黄酮纳米混悬液（H-BLFnd），进一步在混悬液中添加8%（w/v）的γ-环糊精、经真空冷冻干燥得到纳米冻干粉（H-BLFnp），采用粒径分析、TEM、UV、FTIR、TG和DSC对其外观、性能、结构进行表征。结果表明： H-BLFnp外观为白色粉状，表面光洁平整，色泽均匀，平均粒径为（679±10.2）nm，分散系数为（0.349±0.004），包埋率为（92.39±0.34）%。     

Flavonoids released by carrot (Daucus carota) seedlings stimulate hyphal development of vesicular-arbuscular mycorrhizal fungi in the presence of optimal CO2 enrichment

Carbon dioxide has been previously identified as a critical volatile factor that stimulates hyphal growth ofGigaspora margarita, a vesiculararbuscular mycorrhizal fungus, and we determined the optimal concentration at 2.0%. The beneficial effect of CO₂ on fungal development is also visible in the presence of stimulatory (quercetin, myricetin) or inhibitory (naringenin) flavonoids. Sterile root exudates from carrot seedlings stimulate the hyphal development ofG. margarita in the presence of optimal CO₂ enrichment. Three flavonols (quercetin, kaempferol, rutin or quercetin 3-rutinoside) and two flavones (apigenin, luteolin) were identified in carrot root exudates by means of HPLC retention time. Flavonols like quercetin and kaempferol are known to have stimulatory effects on hyphal growth ofG. margarita.     

Flavonoid pigments in chalkhill blue (Lysandra coridon Poda) and other lycaenid butterflies

Nine flavonoids, namely, kaempferol, kaempferol 7-rharanoside, kaempferol 3-rhamnoside, kaempferol 3-glucoside, kaempferol 3-glucoside, 7-rhamnoside, quercetin 3-glucoside, quercetin 3,7-diglucoside, isorhamnetin 3-glucoside, and isorhamnetin 3,7-diglucoside, have been identified in the body and wings of the chalkhill blue butterflyLysandra coridon Poda. Flavonoids have also been found in 15 of a further 17 lycaenid species examined. Analysis of the two-dimensional paper chromatographic flavonoid patterns and aglycone results has shown that the flavonoid content ofL. coridon and the other lycaenids is dependent on the flavonoid content of the larval diet. Differences in the flavonoid patterns ofL. coridon and its leguminous larval food plantsHippocrepis comosa, Anthyllis vulneraria, andLotus corniculatus, indicate that the ingested flavonoids are metabolized byL. coridon or its gut flora before sequestration. Despite the presence of fiavones, glycoflavones, and isoflavones in the larval food plant species, only flavonols are sequestered by the lycaenid species examined. The relationship between lycaenid butterflies and their larval food plants, and the possible role(s) of flavonoids in lycaenids has been discussed. Interactions between ants, plants, flavonoids, and myrmecophilous lycaenids have also been considered.     

温差-超声波复合破壁法对花粉破壁率和黄酮得率的影响

采用温差破壁结合超声波辅助的复合花粉破壁法对花粉进行破壁,考察了不同的温差破壁因素对花粉破壁率和黄酮得率的影响,并以黄酮得率为指标进行正交试验L9（3^3）优化因素,得到温差破壁的最佳工艺条件为：温差100℃、料液比1：15、冷冻时间24h,此条件下花粉破壁率为61．61％,黄酮得率为3．166％．进一步用超声辅助对花粉进行破壁,使其破壁率达到85％～90％,黄酮得率提高到3．310％．同时,通过试验分析阐述了破壁率和黄酮得率两者的联系．