青橄榄浸膏的提取及其抗氧化活性研究

为优化青橄榄浸膏提取工艺,并探讨其抗氧化性。以茂名盛产的青橄榄为原料,采用超声波辅助乙醇提取法,以总黄酮和总多酚得率为评价指标,考察各因素对青橄榄浸膏提取效果的影响。采用邻苯三酚自氧化法、结晶紫法和DPPH清除能力评价青橄榄浸膏的抗氧化活性。结果显示,浸膏的最佳提取工艺为:乙醇体积分数70%,料液比1∶18 (g∶mL),超声提取温度50℃,时间6 min(超声提取阶段);单纯有机溶剂提取温度60℃,时间45 min(有机溶剂浸提阶段);此条件下总黄酮得率为1. 76%,总多酚得率为15. 53%。终产物浸膏在0. 3 mg/mL浓度下对超氧阴离子自由基抑制率为22. 74%,相当于同等质量浓度的抗坏血酸抑制效果的23. 47%;在0. 02 mg/mL浓度下对羟基自由基的清除率为67. 32%,相当于同等质量浓度的抗坏血酸清除效果的112. 58%;在0. 2 mmol/mL的DPPH溶液体系中,0. 15 mg/mL的浸膏对DPPH的清除率为95. 40%,相当于同等质量浓度的抗坏血酸清除效果的140. 83%;总体来讲,浸膏具有良好的抗氧化能力,虽然对超氧阴离子自由基抑制率弱于抗坏血酸,但羟基自由基的清除率及DPPH清除率均优于抗坏血酸。     

沙棘果渣总黄酮提取工艺优化及抗氧化活性研究

利用果胶酶协同超声波法,对沙棘果渣有效成分总黄酮的提取工艺及其抗氧化活性进行了研究。以提取率为指标,通过酶用量、液料比、乙醇浓度、提取时间、提取温度、超声功率等单因素分析,选定酶用量、液料比、超声提取时间3个因素进行响应面试验,确定提取优化工艺条件为:果胶酶用量5.1%,液料比41∶1,超声提取时间81 min,此条件下,沙棘果渣总黄酮提取率达到8.91 mg/g;以BHT为阳性对照,进行了抗氧化活性研究,得出沙棘果渣总黄酮提取液浓度为0.14 mg/mL时,对DPPH自由基的清除率达到了94.42%;提取液浓度为1.2 mg/mL时,对羟自由基和超氧阴离子的清除率分别为83.10%和43.41%。整体来看,沙棘果渣总黄酮具有较强的抗氧化能力。     

响应面法优化金莲花总酚酸的提取工艺及其美白活性研究CSCD

采用响应面分析法中Box-Behnken设计实验优化乙醇回流提取金莲花总酚酸的工艺条件,同时研究了金莲花总酚酸对DPPH自由基、羟基自由基的清除能力、还原能力及其对酪氨酸酶的抑制作用。结果表明,金莲花总酚酸的最佳提取工艺为乙醇浓度60%,回流时间90 min,回流温度60℃,液料比40∶1(mL/g);在此条件下金莲花总酚酸得率为92.245 mg/g。此外,其对DPPH自由基、羟基自由基具有一定的清除能力和还原能力,并且能够显著性地抑制酪氨酸酶活性。本研究所得的提取工艺稳定可靠,金莲花总酚酸具有一定的体外抗氧化活性和酪氨酸酶抑制作用,为进一步科学合理开发利用金莲花奠定基础。     

广东石豆兰多糖的提取工艺及其抗氧化活性

为优化广东石豆兰多糖的提取工艺并评价其抗氧化活性。在单因素试验基础上,采用正交设计和方差分析,研究液料比、提取温度、时间及沉淀多糖的乙醇浓度对石豆兰多糖浸提量的影响并优化了工艺条件,确定最优条件为液料比50∶1 (mL/g),提取温度90℃,时间6 h,醇沉浓度为95%,此条件下多糖提取量为79.060 mg/g,RSD为0.132%。抗氧化结果表明广东石豆兰多糖的总还原力为L-抗坏血酸的3.46%;对DPPH、·OH、·O■自由基半清除浓度(EC₅₀)分别为2769.58、594.60、586.94μg/mL,其清除能力分别是L-抗坏血酸的0.68%、47.17%和29.00%;对Fe²⁺的半螯合浓度(EC₅₀)为160.83μg/mL,螯合能力是EDTA的2.12%。本研究结果为石豆兰多糖的提取及进一步开发利用提供参考依据。     

紫皮石斛总酚提取工艺优化及其抗氧化活性研究

目的：研究紫皮石斛总酚提取工艺及体外抗氧化活性。方法：在单因素试验的基础上，采用响应面法优化紫皮石斛总酚的超声波辅助提取工艺条件，通过测定紫皮石斛总酚对超氧阴离子、DPPH自由基及羟自由基的清除率，评价其抗氧化活性。结果：紫皮石斛总酚最优提取工艺条件为乙醇浓度69%，料液比1∶40 (g/mL)，提取时间31 min，在此条件下总酚提取量为1.56 mg/g，与理论值1.58 mg/g接近。紫皮石斛总酚对超氧阴离子、羟自由基及DPPH自由基的半数抑制浓度(IC₅₀)分别为19.40μg/mL、118.35μg/mL及30.75μg/mL。结论：优选的紫皮石斛总酚提取工艺合理可行，且其具有较强的体外抗氧化活性。     

纳豆多糖发酵工艺的优化及清除自由基研究

考察了纳豆菌接种量、料液比、发酵温度及发酵时间对纳豆菌发酵豆粕产生的纳豆多糖得率的影响,进行了响应面设计实验,得出最佳发酵工艺参数;探究了纳豆多糖的抗氧化活性,并与维生素C进行比较。实验结果表明:接种量为0. 6%,料液比为1∶3,发酵温度40℃,发酵时间48 h,在此工艺条件下水溶性纳豆多糖得率最高为4. 371%。纳豆多糖浓度为1. 5 mg/mL时,对羟基自由基的清除率是50. 07%,对超氧阴离子自由基的清除率达95. 79%,对DPPH自由基的清除率为16. 35%。     

新疆戈宝麻叶中芦丁的优化提取工艺

采用乙醇回流提取法提取戈宝麻叶中芦丁,高效液相层析法测定戈宝麻叶中芦丁含量,通过响应面法优化新疆戈宝麻叶中芦丁的提取工艺,提高芦丁得率。在提取温度、提取时间、提取次数、提取温度、料液比等单因素试验的基础上,采用响应面法建立芦丁得率的数学回归模型,分析了模型的有效性、单因素效应及各因素间的交互作用。响应面法优化后芦丁提取最佳工艺条件如下:提取时间为2.080 h、料液比为1∶14.866 (g∶mL)、提取3次、提取温度为60℃、乙醇浓度为86.189%,在此工艺条件下戈宝麻中芦丁理论得率为0.685%,实际结果得率为0.677%,与模型预测值吻合度高,说明该模型切实可靠,为戈宝麻叶中芦丁的加工利用提供了试验基础。     

莞香叶及成茶中黄酮类化合物的提取及其对亚硝酸盐的清除率研究

以莞香茶成茶和新鲜莞香叶为原料,乙醇超声辅助提取莞香茶中的黄酮类化合物,考察液料比、提取温度、提取时间、乙醇浓度等条件对黄酮类化合物得率的影响。结果表明,莞香茶黄酮类化合物的最优提取条件为:液料比为20∶1(mL∶g),提取温度为60℃,提取时间为3.5 h,乙醇浓度为60%。后采用紫外分光光度法测定莞香茶中黄酮类化合物在模拟胃液条件下对亚硝酸盐的清除率。试验结果表明,莞香茶中黄酮得率与新鲜莞香叶相比有上升也有下降,但下降幅度均不超过5%;3个品牌中黄酮对亚硝酸盐的清除能力也均有下降,但下降幅度不超过13%。     

黑小豆种皮花色苷的提取及体外抗氧化活性研究

为了探索新的花色苷资源,以黑小豆种皮为原料,对其花色苷类色素的提取工艺进行了研究。通过单因素和L_9(3~4)正交试验,考察了乙醇浓度、料液比、温度和p H对粗提液中花色苷含量的影响。结果表明,最佳提取条件为:乙醇浓度60%、料液比1∶20(g∶m L)、温度50℃、p H=2.0。此条件下,黑小豆种皮粗提液中花色苷的含量最大(5.912 mg/g);黑小豆种皮花色苷粗提物得率为19.1%,纯度为3.06%;粗提物具有一定的总抗氧化能力和清除O~(-·)_2、·OH和DPPH自由基的能力。黑小豆种皮可作为一种新型花色苷资源加以利用。     

超声辅助提取四齿四棱草中总黄酮及其抗氧化活性

本文采用正交实验优选超声辅助提取四齿四棱草中总黄酮的最佳工艺,测定其含量,并以Vc为对照,采用DPPH法、ABTS法和FRAP法对四齿四棱草总黄酮抗氧化活性进行综合评价。通过单因素实验和正交实验,研究乙醇浓度、超声时间、料液比、提取温度对四齿四棱草中总黄酮提取率的影响,优选出超声辅助提取四齿四棱草总黄酮的最佳工艺:乙醇浓度为70%,料液比为1∶30 g/m L,50℃超声提取两次,每次30 min,四齿四棱草总黄酮提取率为4.78%。四齿四棱草总黄酮对DPPH自由基(IC_(50)=42.91μg/m L,最大清除率为88.57%)、ABTS自由基(IC_(50)=44.61μg/m L,最大清除率为92.86%)的清除能力较好,对Fe~(3+)的还原能力(AEAC=5380μmol/g)亦较强,是一种天然的抗氧化剂。     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.     

Composition and diversity of bird communities in Swedish farmland–forest mosaic landscapes

CapsuleThe amount of forest (at local and landscape scales) and occurrence of residual habitats at the local scale are shown to be the major factors influencing bird community composition in farmland–forest landscapes in central Sweden.

Aims To investigate the importance of local habitat and landscape structure for breeding birds in farmland–forest landscapes in central Sweden.

Methods Breeding birds were censused at 292 points. A detailed habitat mapping was made within 300 m of the points. Within a 300–600 m radius only two major habitats (forests and arable fields) were identified.

Results Cluster analyses of bird communities identified three site types that also differed in habitat composition: (i) partially forested sites in forested landscapes; (ii) heterogeneous sites with residual habitats in mosaic landscapes; and (iii) field-dominated farmland sites in open landscapes. A total of 19 of 25 farmland bird species (restricted to farmland or using both farmland and forest) had the highest abundance in farmland sites with mosaics of forest and farmland, while only six farmland species had the highest abundance in field-dominated sites. The bird community changed from being dominated by farmland species to being dominated by forest species (common in forest landscapes without farmland) at small proportions (10–20%) of forest at the local scale. A major difference in habitat composition between heterogeneous and field-dominated sites was the occurrence of different residual habitats (e.g. shrubby areas and seminatural grasslands). These habitats seemed to influence bird community composition more than land-use, despite covering <10% of the area. Seminatural grasslands were important for bird community composition and species-richness, but grazing seemed to be less important. Among different land-use types, cereal crops were the least preferred fields. Set-asides with tall vegetation and short rotation coppices were positively associated with species-richness of farmland birds.

Conclusion In general, the composition of the landscape was important for bird community composition, although amount and distribution of forests, occurrence of residual habitats and land-use of fields at the local scale had the strongest influence on bird community composition. The possible implications of these patterns for managing farmland–forest landscapes are discussed.     

Chemical constituents from the fruits of Rhus typhina L. and their chemotaxonomic significance

This work describes the isolation and characterization of twenty-nine compounds from the fruits of Rhus typhina L., including eleven flavonoids (1–11), eleven phenols (12–22), two pentacyclic triterpenes (23–24), two organic acids (25–26), one lumichrome (27), one courmarin (28) and one pyrimidine (29) on the basis of their spectroscopic data. Compounds apigenin (1), daidzein (4), orobol (5), 3′, 5, 5′, 7-tetrahydroxyflavanone (6), naringenin (7), butein (8), (-)-catechin (9), quercetin-3-O-α-L-(3″-O-galloyl)-rhamnoside (11), 2-hydroxybenzoic acid (13), 4-hydroxybenzaldehyde (14), vanillin (15), methyl 3,4-dihydroxybenzoate (16), 3,5-dihydroxybenzamide (18), tyrosol (19), caffeic acid (20), 3-(2,4,6-trihydroxyphenyl)-1-(4-hydroxyphenyl)-propan-1-one (21), phlorizin (22), friedelin (23), oleanolic acid (24), 4,4-dimethyl-heptanedioic acid (25), anthranilic acid (26), lumichrome (27), scoparone (28) and uracil (29) have not been recorded before in this plant. This is the first report on the occurrence of compounds 4–7, 9, 11, 13–14, 16, 18–21, 25–29 from the genus Rhus. Moreover, the chemotaxonomic significance of these isolated compounds was also summarized.