不同荔枝品种采后果皮褐变与多酚氧化酶关系的研究

以无核荔枝、妃子笑、紫娘喜3个荔枝品种为试材,研究了不同耐贮性荔枝品种果实采后果皮多酚氧化酶活性与果皮褐变之间的关系,结果表明,在相同贮藏阶段,3个荔枝品种中无核荔枝褐变指数最高,妃子笑次之,紫娘喜最低。不同处理条件下妃子笑、紫娘喜果皮PPO酶活性均呈先上升后下降的趋势,常温贮藏时无核荔枝果皮PPO活性逐渐下降,低温贮藏则先下降后上升再下降。果实贮藏前期,PPO结合酶、游离酶与总酶活性以无核荔枝最高,妃子笑次之,紫娘喜最低。新采收果实中,紫娘喜果皮PPO同工酶仅2条带,妃子笑3条,而无核荔枝有4条。不同处理对同工酶带数无影响,但低温减少了无核荔枝某些阶段果皮PPO同工酶带数。不同品种荔枝果皮褐变进程差异与果实贮藏前期果皮PPO酶活性差异及同工酶带数有关。     

Characterization of polyphenol oxidase activity in a range of forage ecotypes with different phenol substrates. A new insight for PPO and protein‐bound phenol evaluation

Plant phenols can influence utilization of forages by ruminants through binding with proteins either by complexing with oxidized phenols (products of polyphenol oxidase activity or formed in oxidizing conditions) or by hydrogen binding with tannins. These protein‐bound phenols (PBPs) affect rumen metabolism by inhibition of both proteolysis and lipolysis. The aim of this work was to assess the level of polyphenol oxidase (PPO) activity (determined with a range of diphenolic substrates), PBP content, and to identify the main source of variation in different forage ecotypes harvested at different phenological stages. PPO activity was strongly influenced by substrate type with a significant effect of forage ecotype. Forage ecotype and phenological stage also influenced PPO and PBP content. PPO showed a strong relationship with dry matter and phenol content of plants.     

Chemical evaluation of some important varieties of onion (Allium cepa L.)

Five white and seven red varieties of onion were analysed for dry matter, carbohydrates, total phenols, coloring matter, lachrymatory factor and pyruvic acid content. Percent dry matter varied from 10.66 to 14.80. Total water soluble sugars, reducing sugars and total phenols ranged from 41.50 to 74.00, 12.00 to 22.25, and 1.75 to 2.95 percent (on a dry wt basis), respectively. The lachrymatory factor and pyruvic acid content ranged from 8.00 to 27.25 mg/100g and 6.18 to 13.27 micro moles/g respectively on a fresh wt basis. Red varieties contained a higher phenolic content than white ones. Varieties with higher phenolic content also had a greater amount of coloring matter in the dehydrated onions. The variety Punjab-48 was considered to be most suitable for dehydration purposes.     

Molecular and physico-chemical evaluation of enzymatic browning of whole meal and dough in a collection of tetraploid wheats

Many studies have demonstrated the role of polyphenol oxidase (PPO; E.C. 1.14.18.1) in darkening of wheat products. Even slight browning of pasta is a major hindrance to consumer acceptance. The aim of this research was to evaluate the variability of PPO activity, browning level, and protein content in a collection of more than 100 genotypes of tetraploid wheat, including cultivars and landraces. A molecular approach was followed to evaluate the efficiency of marker PPO18, discovered and used in common wheat, in detecting tetraploid wheat genotypes with low browning level. The data showed a significant genotype influence on the activity of the PPO enzyme, which was correlated with brown index of whole meal and dough, and with protein content. On the whole, the cultivars showed lower PPO activity, brown index, and protein content than landraces, but wide variability was present. Marker PPO18 detected four different alleles for Ppo-A1. The allele Ppo-A1f identified genotypes with high PPO activity and brown index, while the Ppo-A1b and null alleles were associated with the opposite characteristics. Hence, this marker can be used to select new tetraploid wheat cultivars with low browning level.     

Composition of Antioxidants and Amino Acids in Stevia Leaf Infusions

Stevia, a non-caloric natural sweetener with beneficial properties and considerable antioxidants and amino acids, is increasingly consumed as an infusion. This work evaluates the influence of the conditions (temperature: 50, 70 or 90 °C and time: 1, 5, 20 or 40 min) applied to obtain Stevia infusions, on antioxidants (total phenols, flavonoids and antioxidant activity) and amino acids. The total concentration of the eleven amino acids found was 11.70 mg/g in dried leaves and from 6.84 to 9.11 mg/g per gram of Stevia in infusions. However, infusions showed higher levels of certain amino acids (alanine, asparagine, leucine and proline), and greater values of the three antioxidant parameters in comparison with dry leaves. Temperature had more influence (minimum values at 50 °C and maximum at 90 °C) than time in the case of antioxidants. At 90 °C there were no important increases in the extraction of antioxidant compounds after 5 min; each gram of Stevia had 117 mg trolox (total antioxidant activity), 90 mg gallic acid (total phenols) and 56 mg catechin equivalents (flavonoids). Varying the temperature and time conditions no notable differences were observed in the concentrations of the majority of amino acids. However, the infusion treatment at 90 °C for 5 min was the best, as it gave the highest yield of 8 of the 11 amino acids. Therefore, with respect to the compounds analyzed in this study, the best way to obtain Stevia leaf infusions is the same as the domestic process, almost boiling water for a short time.     

Effects on milk production of feeding silage and three levels of sugar-beet pulp either as a mixed ration or as an ensiled blend

Twenty-one British Friesian dairy cows, in mid-lactation, were used in a seven-treatment, partially balanced change-over design experiment consisting of three periods each of 4 weeks' duration. Treatments involved offering grass silage either without a sugar-beet pulp (beet pulp) supplement (US) or supplemented with beet pulp at silage/beet pulp dry matter ratios of 80:20 (C40), 65:35 (C80) and 55:45 (C120), and offered in the form of a mixed ration. A further three treatments consisted of offering ensiled blends of silage and beet pulp, produced by mixing 40 (E40), 80 (E80) and 120 (E120)kg beet pulp t^?1 of grass at ensiling. Silage was offered ad libitum on all treatments, with cows receiving 1kg d^?1 of a concentrate supplement containing 470 g crude protein kg^?1 fresh weight. Dry matter intakes increased with increasing level of beet pulp inclusion in the diet, irrespective of method of beet pulp inclusion in the diet. Similarly, milk fat + protein yields increased with increasing level of beet pulp offered. However, when comparisons were made between the two methods of beet pulp inclusion in the diet with beet pulp requirements equivalent to those obtained in treatments C40, C80 and C120, namely 2·28, 4·53 and 6·21 kg d^?1, offering beet pulp as a supplement to an untreated silage resulted in fat + protein yields of 32 (s.e.d. 9·8), 53 (s.e.d. 19·5) and 81 (s.e.d. 21·3)gd^?1 greater than would have been achieved had equivalent quantities of beet pulp been included at ensiling as part of an ensiled blend. This effect can be attributed to the higher metabolizable energy intakes with the control silage supplemented with beet pulp at feeding, a consequence of the loss of nutrients from the beet pulp fraction during ensiling, in the case of treatments E40, E80 and E120. However, when account is taken of differences in the efficiency of recovery of edible silage dry matter between ensilage systems and differences in forage dry-matter intake between treatments, overall efficiency of feed use was not significantly different between the two systems of beet pulp inclusion in the diet.     

不同土壤水分条件下吲哚丁酸钾对大豆根系形态建成及生理代谢的影响

为了研究吲哚丁酸钾（IBA-K）在减轻干旱对大豆根系的伤害中的作用,以垦丰16（干旱敏感型）和合丰50（耐旱型）为材料,采用盆栽法研究IBA-K拌种对两个品种大豆在正常供水、干旱和复水条件下根系形态建成及生理代谢的影响。结果表明,与正常供水相比,干旱胁迫抑制了大豆根系的生长发育,而IBA-K处理后,大豆根系干物质积累量、形态建成、抗氧化酶活性和渗透调节物质含量在不同土壤水分条件下均高于其干旱对照,膜受损程度减轻。IBA-K处理下,大豆根系SOD活性、POD活性、可溶性糖和脯氨酸含量在干旱条件下均显著高于其干旱对照;MDA含量、相对电导率显著低于其干旱对照。IBA-K处理下的两个品种大豆根表面积、根平均直径、根体积、POD活性和CAT活性在复水条件下分别高于其干旱对照,均未达到显著性差异。复水后,IBA-K处理下的垦丰16根干重和总根长分别较其干旱对照显著增加了3.13%和24.51%,合丰50根干重和总根长较其干旱对照未达到显著性差异。IBA-K处理下的合丰50相对电导率和MDA含量分别较其干旱对照显著降低11.80%和15.09%,SOD活性和可溶性糖含量分别较其干旱对照显著增加14.90%和3.94%,垦丰16相对电导率、MDA含量、SOD活性和可溶性糖含量较其干旱对照未达到显著性差异。IBA-K处理下的两个品种大豆根系脯氨酸含量分别较其干旱对照显著增加了10.62%和10.70%。IBA-K处理和不同土壤水分处理对两个品种大豆根系形态和生理指标存在显著或极显著影响,二者间的交互作用无明显调控作用。综上,IBA-K通过提高根系干物质积累量、抗氧化酶活性和渗透调节物质含量,降低MDA含量和相对电导率,减轻干旱胁迫对苗期大豆根系的伤害。     

不同耕作和施氮模式对淮北地区小麦干物质积累、产量及水分利用效率的影响

为明确不同耕作和施氮模式对淮北砂姜黑土地区小麦产量及水分利用效率的影响，以烟农19为试验材料，设置旋耕+氮肥基施（RW）、旋耕+氮肥后移（RA）、翻耕+氮肥基施（DW）和翻耕+氮肥后移（DA）共4个处理，开展了大田小区试验，考察不同处理下小麦花后光合特性、干物质积累、根系分布、水分利用效率（WUE）及产量的差异。结果表明，相同施氮模式下，翻耕较旋耕显著提升了小麦产量，增产的原因是穗数、穗粒数和粒重的显著增加；相同耕作模式下，氮肥后移（RA和DA）的产量较氮肥基施（RW和DW）分别提高了25.54%和17.94%。翻耕和氮肥后移均增强了花后旗叶抗氧化酶活性，降低了丙二醛含量，显著提高了旗叶叶绿素含量和净光合速率以及花后光合同化物积累对籽粒产量的贡献率和总干物质积累量。RA、DW、DA处理较RW处理均显著提高了开花期0~60 cm土层的根长密度、根干重密度及WUE，其中WUE增幅分别为21.35%、12.71%和31.21%。综合来看，在淮北砂姜黑土地区采用翻耕结合氮肥后移的种植模式能延缓小麦花后旗叶衰老，维持叶片光合能力，增加群体干物质积累量，促进根系生长，实现产量和WUE的协同提升。     

金花葵的营养价值与抗氧化活性

本研究以广东地区引种种植的金花葵为试材,检测了其花朵和嫩果荚中氨基酸、矿质元素、总黄酮、总酚和多糖等营养成分含量,并评估了其抗氧化能力。结果表明,金花葵的花朵和嫩果荚中均检测到16种氨基酸（含7种必需氨基酸）,氨基酸总量分别占干重的13.01%和12.56%,氨基酸比值系数分（SRC）分别为70.49和67.83。花朵中总黄酮、总酚、铁和钾含量显著高于嫩果荚,而嫩果荚中多糖、钙和镁含量则显著高于花朵。对DPPH和ABTS自由基的清除试验表明,花朵的抗氧化能力要优于嫩果荚。综合来看,金花葵的花朵和嫩果荚都具有食用和药用价值,且适合在广东地区种植。     

常温下荔枝贮藏保鲜的研究

测定了不同保贮条件下荔枝褐变相关生理指标：多酚氧化酶（ＰＰＯ）、过氧化物酶（ＰＯＤ）、透性和呼吸强度的变化，同时，也测定了保贮期相应的营养成分：可溶性固形物、维生素Ｃ、类胡萝卜素、水溶性蛋白、游离氨基酸、糖等的变化。结果表明：乙烯吸收剂＋ＳＳＣ（１％ＮａＣｌ＋２％Ｎａ２Ｓｏ３＋５％柠檬酸的溶液）浸果贮藏，糯米糍品种荔枝在常温条件下，可延长贮藏７－１ｄ，保持色香味不变。     

Oxidation of ortho‐diphenols in red clover with and without polyphenol oxidase (PPO) activity and their role in PPO activation and inactivation

Oxidation of phenol to quinone with its subsequent binding and complexing with protein in red clover (Trifolium pratense L.) when fed to ruminant livestock has been shown to improve nitrogen‐use efficiency and the deposition of polyunsaturated fats into animal products. This oxidation has, almost exclusively, been attributed to the activity of the enzyme group polyphenol oxidases (PPOs) and, specifically, catecholase during conservation. However, during conservation, temporal inactivation of PPO occurs and oxidation of phenolic substrate may occur through other mechanisms not associated with PPO. T₁ progeny of a cross between a red clover clone having normal levels of foliar PPO activity and a transgenic PPO‐silenced red clover plant with undetectable levels of PPO activity were divided into two populations based on the presence of the silencing transgene and lack of measurable PPO activity (PPO?) or the absence of the silencing transgene and normal levels of PPO activity (PPO+). This material was subsequently used to determine the relevant extent of phenolic oxidation in the presence and absence of PPO activity under two damage regimes (heavy and light). PPO+ and PPO? material was passed through a garden shredder as the light‐damaged regime, or frozen at ?20°C as the heavy damaged regime. Material was left at room temperature and sampled at regular intervals for the determination of PPO enzyme activity (active and total), PPO activation (conversion from latent to active forms) and formation of protein‐bound phenol (PBP) as a measure of oxidation. Experiments with red clover leaf extracts were carried out to determine the mechanism for the temporal activation and inactivation (loss of enzymatic activity) of PPO during wilting. PBP formation was evident in both PPO? and PPO+ treatments with the response further catalysed during the first 2 h by extent of damage that increased the activation of PPO, but which also resulted in a more rapid temporal inactivation of PPO. PBP formation, PPO activation and PPO inactivation were all shown to be mediated predominantly by quinone binding. A role of non‐PPO oxidation in PBP formation in wilted red clover is reported, showing the importance of o‐diphenolic substrate concentration and not just PPO activity to increase nitrogen use efficiency and the deposition of polyunsaturated fats into animal products.     

红树林植物海莲不同部位提取物抗氧化活性研究

植物抗氧化研究对寻找高效率、低毒性天然抗氧化剂具有重要的指导意义。以在海南分布较广的红树林植物海莲进行抗氧化活性研究,以期对海莲开发利用的可能性提供理论依据。采用清除DPPH自由基和清除ABTS自由基对海莲不同部位———根、茎、叶、花的乙酸乙酯提取物进行抗氧化能力评价,采用比色法和福林酚法测定总黄酮和总酚含量。结果显示,海莲茎的提取物在4个部位中抗氧化活性最好,清除二者的IC50分别为(0.234±0.053)mg/m L和(0.196±0.080)mg/m L,海莲中酚类物质含量较大,4个部位中茎的总酚含量最多,含量为13.2 mg。说明海莲各部位均显示出了较好的抗氧化能力,具有较好的开发潜力。     

Effect of soil salinity on internal browning of potato tuber tissue in two soil types

A study was carried out with potato (Solanum tuberosum; cv. Atlantic) during 2001 and 2002 to determine the effect of soil salinity on internal tuber browning. The effect of varying levels of soil salinity on proline content, polyphenol oxidase enzyme activity, and chlorogenic acid content in potato leaves and tubers was examined. NaCl treatments (2.1, 4.25, 6.38, 8.5 g NaCl L^?1) were applied to the pots, the first 46 days after planting, and four additional treatments were applied, each about 7 days apart. Increasing NaCl concentrations resulted in an increase in browning of tuber tissue and proline content in the tubers. Chlorogenic acid content in the leaves increased up to 6.4 g NaCl L^?1, but then decreased at 8.5 g NaCl L^?1 and in tubers tended to be maximal at the highest saline concentration tested (8.5 g NaCl L^?1). Increasing NaCl concentration resulted in a reduction in yield per plant and average tuber weight, and also increased tuber number. There were major differences in the impact of salinity over the 2-year period, which was probably due to the impact of the growing media; a low organic matter (about 1% OM) silty loam soil and a high organic content (about 90% OM) Muck soil were used in 2001 and 2002, respectively. Tuber browning increased linearly with salinity in 2002, but only markedly increased at 8.5 g NaCl L^?1 in 2001. Sodium and chloride ion concentration was always greater (about two times) at equivalent application rates in the 2002 trial. The high organic matter content soil retained sodium and chloride ions more effectively than the silty loam soil and enhanced the impact of increased salinity concentration on physiological properties of potato plants and particularly on tuber tissue browning and proline accumulation.     

Change in Colour and Antioxidant Content of Tomato Cultivars Following Forced-Air Drying

Three New Zealand grown tomato (Lycopersicon esculentum L.) cultivars, Aranka, Encore, and Flavourine, were analysed for colour (CIELAB L^∗ a^∗ b^∗ values), ascorbic acid, total phenolics, lycopene, and total antioxidant activity (ABTS assay). Colour analyses of the air-dried tomatoes showed that the colour degradation as measured by the L^∗ a^∗ b^∗ values was minimal, and the colour was not significantly different (p < 0.05) between each of the dried cultivars. In general, there was no significant difference (p < 0.01) between the fresh cultivars in terms of antioxidant components or total antioxidant activity. The average values obtained for antioxidant components in the three fresh cultivars were: ascorbic acid, 276 mg/100 g DM, total phenolics, 613 mg gallic acid equivalents (GAE)/100 g dry matter (DM) and lycopene 38 mg/100 g DM. Total antioxidant activity of the fresh cultivars was 2917 μmole Trolox equivalent antioxidant capacity (TEAC)/100 g DM. Following forced air-drying treatment at 42 ^∘C for 48 hr, all cultivars showed significant decreases in ascorbic acid, total phenolics and total antioxidant activity, and increases in extractable lycopene contents. This study was undertaken to identify cultivars that would provide the best colour and nutrient contents after commercial air drying.     

Polyphenol oxidase and peroxidase activities of apricots (Prunus armeniaca L.) as affected by cultivar,location, and year of harvest

A total of 22 samples of apricots belonging to ten cultivars from two locations and picked in the years 1975–78 were assayed for polyphenol oxidase (PPO) and partly for peroxidase (POD) activities, heat resistance of these enzymes,o-dihydroxy phenol (ODP) content, and initial rate of enzymatic browning (BA). Of these characteristics, ODP content showed the greatest and BA the least variation. PPO activity relative to fresh weight was found to depend on the year of harvest rather than on the cultivar, while POD activity relative to fresh weight was cultivar dependent. The values of BA and ODP content were markedly influenced by both cultivar and year. For a given cultivar, PPO and POD activities relative to fresh weight as well as BA were higher in the samples picked in 1976 at one location than in those picked in the other years at the other location.The initial rate of browning of apricots was primarily dependent on the ODP content as shown by linear regression analysis with two independent variables. The relative influence of ODP content as compared with that of PPO activity related to fresh weight was the stronger the higher the value of the ratio of PPO-ODP, i.e. the smaller the values of the endogenous substrate available to the enzyme in the tissues. This suggests substrate depletion to be the limiting factor in the enzymatic browning of apricots.Heat inactivation of PPO was found to be a simple exponential process, while that of POD a biphasic one. PPO was less heat resistant than POD: total inactivation occurred after 10-min heat treatment at 75°C and 85°C, respectively.     

Antioxidant properties of wheat and rye bran extracts obtained by pressurized liquid extraction with different solvents

Rye and wheat brans are valuable sources of bioactive compounds, which could be used for the development and commercialization of high added value functional ingredients such as dietary antioxidants. The aim of this study was to evaluate antioxidant potential of rye and wheat bran using different polarity solvents. Cereal brans were ground to four different particle size fractions and extracted at 10.3 MPa pressure and 80 °C temperature by consecutive application of hexane, acetone and methanol:water (80:20%). The highest extract yield was obtained from rye bran using methanol-water; particle size in most cases had a significant effect. Antioxidant potential of extracts was assessed by ABTS^+•, DPPH^• scavenging, ORAC and total phenols content (TPC) assays. Extraction solvent had a major influence on TPC and antioxidant activity of the extracts. The most active extracts were obtained using methanol:water; rye bran extracts, in general, were stronger antioxidants than wheat bran extracts. For the majority of assays, reduction of particle size resulted in higher antioxidant activity values. However, ABTS^+• scavenging was found to decrease by decreasing particle size of rye bran used for extraction.     

微波真空干燥对铁皮石斛品质特性影响的研究

本研究以新鲜铁皮石斛为原料,采用微波真空干燥方法干燥,通过测定铁皮石斛的多糖含量、色泽、多酚氧化酶（PPO）、水分分布状态、组成氨基酸以及多酚的DPPH?和?OH清除率,研究微波真空干燥对铁皮石斛品质特性的影响。结果表明：相比于新鲜样品,当微波强度为9 W/g,干燥后样品的多糖含量最高可达52.21%;氨基酸分析仪分析结果表明,微波真空干燥后铁皮石斛的总游离氨基酸和风味氨基酸含量显著提高。在微波强度9 、12 、15 W/g下,微波真空干燥的铁皮石斛的PPO活性分别在干燥16、12、6 min后不再存在,表明微波真空干燥能够在较短时间内钝化铁皮石斛的PPO活性,且微波强度越大时间越短。干燥过程的非酶促褐变主要由Maillard反应引起。低场核磁共振结果表明,自由水驰豫时间T₂₃和A₂₃均显著降低。自由基清除能力研究结果表明,铁皮石斛多酚仍具有较强的羟基自由基清除能力。通过观察干燥后样品的微观结构发现,随着微波功率密度的增大,样品孔状结构受到更严重破坏,微波强度越大,铁皮石斛的复水特性越好。     

Digestion of rice straw and oil palm fronds by microflora from rumen and termite bacteria, in vitro

The digestion and Volatile Fatty Acid (VFA) production from rice straw and oil palm fronds by cellulolytic bacteria isolated from the termite Coptotermes curvignathus were investigated. The bacteria were Acinetobacter strain Raminalimon, Enterobacter aerogenes strain Razmin C, Enterobacter cloacae strain Razmin B, Bacillus cereus strain Razmin A and Chryseobacterium kwangyangense strain Cb. Acinetobacter strain Raminalimon is an aerobic bacterium, while the other species are facultative anaerobes. There were significant differences (p<0.05) among the bacteria for Dry Matter (DM) lost and acetic acid production from rice straw and Acinetobacter strain Raminalimon showed the highest activity. The facultative bacteria C. kwangyangense strain Cb (cfu mL(-1) 231 x 10(-6), OD: 0.5), E. cloacae (cfu mL(-1) 68 x 10(-7), OD: 0.5) and E. aerogenes (cfu mL(-1) 33 x 10(-7), OD: 0.5) were used for digestion study with the rumen fluid microflora. The in vitro gas production technique was applied for the comparative study and the parameters measured were pH, gas (volume), dry matter lost, acetic acid, propionic acid and butyric acid concentrations. pH was not significantly (p<0.05) different among the five treatments. The bacterium C. kwangyangense strain Cb showed the highest activity (p<0.05) for DM lost, acetic acid, propionic acid and butyric acid production from rice straw when compared to the other bacterial activities. There was no significance (p<0.05) difference between the three bacteria for the dry matter lost of oil palm fronds but the production of Volatile Fatty Acids (VFA) was significantly (p<0.05) high in the treatment which was inoculated with C. kwangyangense strain Cb. The Gen Bank NCBI/EMBL accession numbers for the bacterial strains are EU332791, EU305608, EU305609, EU294508 and EU169201.     

Antioxidant Activity and Chemical Characterization of Essential Oil of <Emphasis Type="Italic">Bunium persicum</Emphasis>

The search for natural antioxidants, especially of plant origin, has notably increased in recent years. Bunium persicum Boiss. is an economically important medicinal plant growing wild in the dry temperature regions in Iran. In this study, chemical constituents of the essential oil of the seed from Bunium persicum Boiss. have been studied by GC/MS technique. The major components were caryophyllene (27.81%), gamma-terpinene (15.19%), cuminyl acetate (14.67%). Individual antioxidant assays such as, DPPH* scavenging activity and beta-carotene bleaching have been carried out. In DPPH* system, the EC(50) value of essential oil was determined as 0.88 mg/mL. In beta-carotene bleaching antioxidant activity of essential oil (0.45%) was almost equal to BHT at 0.01%. In addition, the antioxidant activity of the essential oil was evaluated in crude soybean oil by monitoring peroxide and thiobarbituric acid values of the oil substrate. The results showed that the Bunium persicum essential oil (BPEO) was able to reduce the oxidation rate of the soybean oil in the accelerated condition at 60 degrees C (oven test). The essential oil at 0.06% showed the same effect of BHA at 0.02%. Hence, BPEO could be used as an additive in food after screening.     

千层金叶片醇提物抗氧化活性的研究

为了探究千层金叶片醇提物的抗氧化活性,本文研究了千层金叶片醇提物及其不同极性部位的抗氧化活性和总多酚含量。研究结果表明：千层金叶片醇提物正丁醇相的总多酚含量最高,为(453.75±0.75) mg/g;75%甲醇粗提物及其正丁醇相对ABTS ⁺自由基的清除能力较抗坏血酸（VC）强;各组分还原力强弱顺序为VC>正丁醇相>75%甲醇粗提物>水相>乙酸乙酯相>BHT>石油醚相;正丁醇相和乙酸乙酯相对DPPH自由基的清除能力较醇提物和水相强,石油醚相最弱;千层金叶片醇提物及其不同极性部位清除ABTS ⁺自由基清除能力、DPPH自由基清除能力及还原力均与其总多酚含量呈正相关。除石油醚相外,千层金叶片醇提物及其不同极性部位均有较强的抗氧化活性,可作为一种良好天然抗氧化剂的物质来源。