Ultra-microindentation at the surface of silk membranes

Ultra-microindentation was used to measure the microhardness and modulus of silk (Bombyx mori) membranes, cast from 20 to 80 °C. The microhardness and modulus were determined from the loading/unloading curves. The membranes exhibit microhardness of about 400 MPa which is larger than the values for most common synthetic polymers (50-300 MPa) implying a greater scratch resistance. The moduli are of the order of those measured by the other means for B. mori silk membranes (5 GPa), and fibers (7-11 GPa). There is some correlation between microhardness and the dimensions of the grains/nanofibrils, but none with surface roughness. The results extend the range of an empirical correlation between microhardness and modulus. The present data together with previous data from other polymers fit the equation, H=0.55E0.74, with a correlation coefficient of 0.94. Finally, it is shown that elastic recovery of the silk membranes is an increasing function of the maximum load applied.     

Regeneration of Bombyx mori silk by electrospinning—part 1: processing parameters and geometric properties

We studied the effect of electrospinning parameters on the morphology and fiber diameter of regenerated silk from Bombyx mori. Effects of electric field and tip-to-collection plate distances of various silk concentrations in formic acid on fiber uniformity, morphology and diameter were measured. Statistical analysis showed that the silk concentration was the most important parameter in producing uniform cylindrical fibers less than 100 nm in diameter.     

Free radical scavenging capacity as related to antioxidant activity and ginsenoside composition of Asian and North American ginseng extracts

Different Panax species derived from Asia (Panax ginseng C.A. Meyer) and North America (Panax quinquefolium L.) were extracted by methanol and evaluated for relative ginsenoside composition and antioxidant activities. Ginseng root contained a greater proportion of total ginsenoside compared to ginseng hair analyzed by high-performance liquid chromatography. North American ginseng root was characterized with undetectable ginsenoside Rf and greater Rb₁/Rb₂ than Asian ginseng root. Panax quinquefolium exhibited a relatively higher (P<0.05) affinity to scavenge free radical than panax ginseng using the 2,2-azobis (3-ethylbenzothine-6-thine-6-surfonic acid) radical model. In a bilayer lamella suspension oxidation model induced by peroxyl radicals, ginseng samples exhibited notable antioxidant activity. Specifically, however, the P. quinquefolium extracts delayed lipid peroxidation longer (P<0.05) than the P. ginseng extracts. Ginseng extracts from both Panax species protected human low-density lipoprotein against cupric ion-mediated oxidation. Similar protection was observed against peroxyl radical-induced supercoiled DNA breakage. A pure ginsenoside standard (e.g., Rb₁) produced similar results. The antioxidant activities of different ginseng species and specific plant parts include free radical scavenging and may be related to ginsenoside Rb₁/Rb₂ content.     

Antitermitic activity ofLonchocarpus castilloi flavonoids and heartwood extracts

The heartwood of the tropical treeLonchocarpus castilloi Standley (Leguminosae) is highly resistant to attack by the drywood termitesCryptotermes brevis (Walker); nevertheless successive extraction with hexane, diethyl ether, acetone, methanol, and water reduced its resistance to these organisms. Antitermitic properties of the extracts were bioassayed using impregnated filter paper disks. Although the five extracts reduced both feeding and survival ofC. brevis, no significant differences among them were detected. Choice feeding tests showed that termites avoided eating the paper treated with the extracts. Two flavonoid compounds isolated from the heartwood, castillen D and castillen E, impregnated into filter paper showed concentration-dependent feeding deterrent activity, but were not toxic toC. brevis.     

Enzyme and high pressure assisted extraction of carotenoids from tomato waste

Enzyme (EA) and high pressure (HP) assisted extraction of carotenoids, especially lycopene, from tomato waste using various organic solvents was examined. Total carotenoid and lycopene extraction yields were increased by the use of pectinase and cellulase enzymes, when compared to the non enzyme treated solvent extraction process. The increase of extraction yield depended on the solvent. Maximum total carotenoid (127 mg/kg d.w.) and lycopene (89.4 mg/kg d.w.) extraction yields were obtained in enzyme treated samples extracted with ethyl lactate (solvent:solid = 10:1 mL:g), corresponding to almost 6-fold and 10-fold increase, respectively, with respect to non enzyme treated samples. HP assisted extraction led to higher extraction yields (from 2 to 64% increase depending on the solvent used) compared to conventional solvent extraction process performed at ambient pressure for 30 min. HP assisted solvent extraction was successfully performed at 700 MPa by using significantly (P < 0.05) lower ratios of solvent:solid (6:1 and 4:1 mL:g) and reduced processing time (10 min), compared to solvent extraction performed at ambient pressure, solvent:solid ratio 10:1 mL:g and 30 min extraction time.     

Antioxidant activity of flavonoids isolated from Scutellaria rehderiana

The present study examined the antioxidant activity in heated canola oil of hexane, acetone, and methanol extracts of dry roots of gansu huangqin (Scutellaria rehderiana) as well as six flavonoids isolated from the acetone and methanol extracts. The oxidation was conducted at 95°C by monitoring oxygen consumption and decreases in both linoleic and α-linolenic acids. The acetone extract was most effective in inhibiting oxidation of canola oil, followed by the methanol extract. The antioxidant activity of gansu huangqin acetone extract was dose-dependent. Among the six flavonoids, baicalein and ganhuangenin were more effective than butylated hydroxytoluene (BHT) in protecting canola oil from oxidation. The present results suggest that the acetone extract of this root may be a potential source of natural antioxidants for use in processed foods.     

Structure and morphology of electrospun silk nanofibers

Nanoscale fibers of natural silks of Bombyx mori and Nephila clavipes were produced from solutions in hexafluoro-2-propanol. The electrospun fibers were observed by optical, scanning electron, and transmission electron microscopy. These nanofibers showed optical retardation, appeared to have a circular cross-section, and were thermally stable under nitrogen to 280 °C (N. clavipes) and to 245 °C (B. mori). The diameter of the fibers ranged from approximately 6.5-200 nm making them orders of magnitudes smaller than the natural silks spun by most silkworms and spiders. The smallest fiber diameters correspond to 200 molecules in the cross section of the N. clavipes fibers and 150 in B. mori. Electron diffraction patterns of annealed electrospun fibers of B. mori and N. clavipes exhibit diffraction peaks demonstrating orientational and crystalline order comparable to that of naturally spun silks.     

Supercritical fluids extraction and anti-solvent purification of carotenoids from microalgae and associated bioactivity

This study investigated co-solvent modified supercritical carbon dioxide extraction of lipids and carotenoids from the microalgal species of Nannochloropsis oculata. Supercritical carbon dioxide (SCCO₂) anti-solvent precipitation of carotenoids from the extracts following purification of Zeaxanthin was also examined. Continuous modification by ethanol of supercritical carbon dioxide extractions showed that the addition ratio was important for extraction efficiency of lipids and carotenoids. SCCO₂ extraction at 350 bar, 323 K and 16.7 wt% of ethanol addition yielded 239.7 mg of triglycerides and 7.61 mg of carotenoids per gram extract with a total yield of 15.5%. SCCO₂ anti-solvent experiments showed that the content of Zeaxanthin in the precipitate was greater than that in the fraction of normal phase column chromatography. The purest Zeaxanthin (93.8%) was then successfully isolated from the purified fraction by using a reverse-phase HPLC column chromatography. Rat macrophages treated by ultra-sonicated water extracts of the SCCO₂ defatted algae showed a positive phagocytotic activity.     

The crystal modulus of silk (Bombyx mori)

It is shown that experimentally determined values of the crystal modulus of Bombyx mori silk agree reasonably well with the computationally determined values, if account is taken of the stress relaxation, which occurs during the experimental measurements. The experimental are 16-22 GPa depending on the sample and the computational are 13 or 16 GPa depending on the method of analysis.     

Isolation of polyphenols from the extracts of olive leaves (Olea europaea L.) by adsorption on silk fibroin

General objective of the present work was to assess the isolation of polyphenols from olive leaves. The effects of extraction conditions on the total phenol content and antioxidant activity of olive leaf extract (OLE) were investigated. An extract with good antioxidant activity (7.52 mmol of Trolox equivalent antioxidant capacity (TEAC)/g olive leaf extract), and a high content of oleuropein (13.4%) and rutin (0.18%) could be obtained using 70% ethanol as extraction solvent. There was a good correlation between the antioxidant activity and the total phenol content. Furthermore, silk fibroin was used as a novel adsorbent to recover the polyphenols from the olive leaf extracts. The adsorbed amounts of rutin and oleuropein were 15 mg rutin/g silk fibroin and 96 mg oleuropein/g silk fibroin. Fraction consisting of mainly oleuropein and fraction rich in rutin, luteolin-7-glucoside, verbascoside, apigenin-7-glucoside were obtained by using silk fibroin filled column. Silk fibroin was found to be a promising adsorbent for the purification of oleuropein and rutin from olive leaf extracts.     

弯萼金丝桃总黄酮提取及抗氧化、降糖活性

摘要：为获得弯萼金丝桃总黄酮（TF）最佳提取工艺及抗氧化活性、降糖活性,探究5种提取工艺(超声辅助提取、酸解提取、酶解提取、热水提取、热醇提取) 对TF提取量的影响,通过单因素和响应面实验优化提取工艺。采用高效液相色谱(HPLC)测定并分析7种主要黄酮苷元的分布及含量,并进一步研究TF与体外抗氧化活性（DPPH?清除能力、ABTS自由基清除能力、羟基自由基清除能力、还原能力）的相关性及对α-葡萄糖苷酶的体外降糖能力。结果表明,超声辅助提取TF提取量最高。响应面优化最佳提取工艺为：温度68 ℃,时间23 min、乙醇体积分数24 %、液料比63:1 mL/g,在该条件下,TF提取量为34.85 mg RT/g（以每克弯萼金丝桃中黄酮类化合物相当于芦丁RT质量表示）;高效液相色谱法分别鉴定出TF中7种主要黄酮类化合物,其中TF中含量最高的黄酮化合物为槲皮素-3-O-洋槐糖-7-0-鼠李糖苷、槲皮素,分别为3.897 mg/g、2.874 mg/g;TF质量浓度与DPPH?清除能力、ABTS自由基清除能力、羟基自由基清除能力、还原能力呈显著正相关,对α-葡萄糖苷酶的降糖能力可达到92.6 %。     

Clinoptilolite-rich mineral as a novel carrier for the active constituents present in Ginkgo biloba leaf extract

The possible use of clinoptilolite-rich mineral as a novel carrier for the active constituents present in Ginkgo biloba leaf extract solutions was investigated. The flavonoid aglycone constituents were found to be selectively adsorbed on the clinoptilolite surface. The antioxidant activity determinations of the extract solutions were performed by the Trolox Equivalent Antioxidant Capacity (TEAC) assay. The antioxidant activity measurements performed for the Ginkgo leaf extract solutions showed decreasing antioxidant activities due to adsorption. The decrease in antioxidant activity was attributed to the adsorption of phenolic constituents on the clinoptilolite surface.     

Regeneration of Bombyx mori silk by electrospinning. Part 3: characterization of electrospun nonwoven mat

Regenerated Bombyx mori silk fibroin in formic acid was electrospun and the morphological, chemical and mechanical properties of these nanofibers were examined by field emission environmental scanning electron microscopy (FESEM), Raman spectroscopy (RS), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and tensile testing. FESEM indicated that the average fiber diameter was less than 100 nm and circular in cross section. This paper maps the silk fibroin molecular conformations of each step of the sample preparation and the electrospinning process. The secondary structural compositions (random and β-sheet) of the fibroin were determined by FTIR and RS. The crystallinity index of the electrospun fiber, calculated as the intensity ratio of 1624 (β-sheet) and 1663 (random) cm⁻¹ FTIR bands was higher than that of the pristine fiber. Raman spectra of the amide I (1665 cm⁻¹, random) to amide III (1228 cm⁻¹, β-sheet) ratio of the electrospun fiber was less than that of the pristine fiber indicative of higher β-sheet content. The fiber crystallinity, determined by XRD, showed a lower value for the electrospun fiber. The electrospun fiber shows small but significant increases in the β-sheet content in comparison with the pristine fiber. Dissolution of fibroin in formic acid enhances β-sheet crystallization and may facilitate β-sheet formation in electrospun fiber. The electrospun random silk mat had a Young's modulus, ultimate tensile strength and strain of 515 MPa, 7.25 MPa and 3.2%, respectively.     

Effects of rosemary extracts and major constituents on lipid oxidation and soybean lipoxygenase activity

Rosemary (Rosemarinus officinalis L.) leaves were extracted with three different solvents, namely hexane, acetone and methanol. A reverse-phase high-performance liquid chromatography system in combination with a mass detector was used to quantitate the content of carnosol, carnosic acid and ursolic acid in the rosemary extracts. All rosemary extracts showed strong inhibitory effects on lipid oxidation and soybean lipoxygenase activity.     

蒙山莴苣总黄酮的纯化及体外抗氧化活性研究

研究了蒙山莴苣总黄酮的纯化条件和体外抗氧化能力。结果表明,最佳的聚酰胺柱层析纯化条件为:用p H 5～6,质量浓度5. 21 mg/m L的上样液1. 5 BV,按1. 5 m L/min上样,用4 BV水淋洗,4. 5 BV 80%乙醇溶液(V/V)按1. 5 m L/min解吸,聚酰胺每使用5次可以进行一次再生。以VC为对照,蒙山莴苣总黄酮对DPPH自由基、·O-2和·OH都有一定的清除能力,对Fe3+有一定的还原能力,但效果均弱于VC。     

Radical-scavenging activity of extracts from Cordia verbenacea DC obtained by different methods

The possibility of using the leaves of Cordia verbenacea as a new source of natural antioxidant compounds was investigated. In the present work, extracts from C. verbenacea were obtained using different extraction methods: supercritical fluid extraction (SFE), Soxhlet (SE), hydrodistillation and maceration, with the objective to evaluate the methods in terms of yield and antioxidant potential. The high-pressure technique was applied using pure CO₂ and CO₂ with co-solvent at different temperatures and pressures (30, 40 and 50 °C and 100, 200, and 300 bar). Organic solvents with different polarities were used to obtain extracts by low-pressure extraction processes. The extracts were evaluated according to their antioxidant activity using total phenolic content, scavenging abilities on DPPH radical, total antioxidant activities (ABTS^•+), superoxide anion radical-scavenging (O₂^•) and protection against lipid peroxidation in vitro (LPO). Ethyl acetate fraction obtained by maceration and extract isolated by SE using 25% aqueous mixture of ethanol possessed the highest scavenger activity against DPPH radical (IC₅₀ = 9.2 ± 0.4 μg/ml, IC₅₀ = 27.4 ± 0.1 μg/ml, respectively). The SFE with 8% ethanol as a co-solvent produced extracts with distinguished increase in the antioxidant activity. The Soxhlet extract with ethyl acetate exhibited a strong reduction of lipid peroxidation (IC₅₀ = 209 ± 3 μg/ml) value comparable to the standard rutin (IC₅₀ = 203 ± 2 μg/ml). The results indicate that extracts of C. verbenacea have important potential as a source of bioactive compounds with antioxidant activity.     

柠檬香茅精油的提取及抗氧化活性研究

文中采用水蒸汽蒸馏法对海南产柠檬香茅进行精油提取,研究了提取时间、料液比、香茅粗细、香茅部位、提取液成分等因素对精油收率及主要成分存在影响,精油提取率为0.09-1.06%,50g 长2cm的干柠檬香茅在1400mL含8 g NaCl的水溶液,提取时间180min时精油出油率最高,为1.06%;随提取条件不同,精油成分有所变化,但主要成分无明显差异,主要为芳樟醇、橙花醛、香叶醛、香叶醇和香叶酸,此五种主要成分的含量约占精油总量的86-96%。电子自旋共振法（ESR）测试结果表明1%香茅精油乙醇溶液对羟基自由基具有一定清除活性,清除率32%。     

Phenolic compounds and antioxidant activity of extracts of Ginkgo leaves

The aim of the present study was to determine the flavonol contents of crude extracts from Ginkgo (Ginkgo biloba L.) leaves, their antioxidant properties in model system studies, and their inhibitory action of linoleic acid oxidation in an emulsion system and of triacylglycerols (TAG) in rapeseed oil. Extracts were prepared from both green and yellow leaves of Ginkgo trees using water, aqueous acetone, and ethanol. Extracts were analyzed by HPLC for their presence and content of selected flavonols; these included myricetin, quercetin, kaempferol, isorhamnetin, and morin. The highest level of flavonols, especially quercetin, myricetin and kaempferol, were found in the aqueous acetonic extracts. Crude extracts from yellow Ginkgo leaves contained greater amounts of flavonols. The best DPPH radical‐scavenging activity amongst the Ginkgo extracts examined was determined for aqueous acetonic extracts, while the lowest was noted for the ethanolic extract of green leaves. Water infusion extracts exhibited the highest iron(II) chelating activity. The reducing power of extracts from yellow leaves was 2 higher than that of crude extracts from green leaves. Nevertheless, extracts from green Ginkgo leaves imparted a greater protection factor against TAG oxidation, as assessed by the Rancimat method. Crude extracts from yellow Ginkgo leaves were more efficacious than green ones at inhibiting oxidation of the linoleic acid emulsion.     

黑苦荞麦黄酮的提取及体外抗氧化活性研究

采用超声辅助溶剂浸提法提取黑苦荞麦黄酮,研究黑苦荞麦黄酮的体外抗氧化活性。研究表明,黑苦荞麦黄酮提取的最适条件为:乙醇浓度70%(V/V),液料比50∶1 mL/g,超声功率200 W,超声时间10 min,水浴温度50℃,水浴时间40 min,此时得率为19.31 mg/g干重。黑苦荞麦黄酮具有较好的体外抗氧化能力,对·OH具有很强的清除能力,效果好于V_C;对DPPH、·O^(2-)具有一定的清除效果和还原能力,但是效果均稍差于V_C。     

Extraction of phenolic compounds from fresh leaves: A comparison of methods

The conventional sonicator/shaker bath method for phenolic extraction was compared with a less traditional one using a homogenizer. The homogenizer proved to be both more efficient and consistent in extracting phenolics from tender, as well as tough, leaves. We propose that adoption of the homogenizer technique will increase phenolic yield and efficiency.