Lactoferrin-loaded contact lenses counteract cytotoxicity caused in vitro by keratoconic tears

Lactoferrin (LF), an iron-binding protein with antioxidant activity, is significantly reduced in the lacrimal film of patients affected by keratoconus (KC) compared to healthy subjects, and this is supposed to be the cause for tear iron increase and consequent iron deposition and oxygen free radical accumulation in the cornea. We decided to study if LF-loaded contact lenses (LF-CLs) could exert antioxidant activity on epithelial cells incubated in tears collected from two patients affected by keratoconus (KC1 and KC2). Moreover through this model we indirectly estimated iron concentration in the tears of healthy and KC subjects.Reflex tears were collected during the first 2 min of light or onion-induced lacrimation and stored at −20 °C. After incubation in tears for 18 h, mortality of epithelial cells was investigated by trypan blue exclusion test. Successively, LF-CLs were deposed on cells incubated in KC1 tears. For the indirect determination of iron content, cells were incubated with LF 1.2 mg/mL and different FeSO₄ concentrations, and for the estimation of iron from the patient’s tears, cells were incubated with free serum medium and healthy tears (1:1) and different FeSO₄ concentrations.Epithelial cells incubated with reflex tears of KC patients showed increased mortality (27.7 ± 3.9%, p = 0.0003, for KC1 and 17.6 ± 0.95%, p = 0.014, for KC2) compared to epithelial cells maintained in control healthy tears (8.6 ± 1.2%). This difference in mortality was correlated with tear iron concentration, which was estimated at 4.58 μg/mL for the healthy subjects, at 56.28 μg/mL for KC1, and at 8.7 μg/mL for KC2 patient. Application of LF-CLs counteracted KC tear cytotoxicity restoring viability obtained in the presence of control tears.Therapeutic contact lenses obtained by LF loading can reduce oxidative stress induced by patients’ tears and might represent an efficient device to arrest the progression of keratoconus.     

Catalysts of lipid oxidation in meat products

In emulsions consisting of refined lard, egg white and corn starch haemoglobin, initially a mixture of the oxy and met forms, at levels similar to the haemoprotein contents found in fresh meat, was a far more powerful catalyst of lipid oxidation, as measured by TBA number, than inorganic iron compounds at levels appropriate to those found in meat. This was true over the pH range 4·5 to 7·5. When added and evenly distributed to exhaustively washed muscle fibres (WF), at levels appropriate to those found in meat, haemoglobin was again a powerful catalyst, but all forms of inorganic iron appeared to have little prooxidant activity. The rate of oxidation of the lipid was very dependent on the haemoprotein concentration, being maximal in the range 10(-4) to 10(-5) M. This equates to an approximate unsaturated lipid to haem molar ratio of several hundred to one, similar to the values reported for model linoleate haem systems. In heated systems the haemoprotein again appeared to be a more effective catalyst than inorganic iron at levels appropriate to those found in meat. It is concluded that the conflicting results as to the roles of haem pigments and inorganic iron in lipid oxidation found in the literature are due, at least in part, to the difficulty of evenly dispersing the catalysts in the washed fibres, especially if heat or freezing leads to subsequent phase separation, and that H(2)O(2), formed by autoxidation of the oxypigments, may be necessary for ferric haem pigments to be effective catalysts.     

Analysis of radiolytic products of lipid in irradiated dried squids (Todarodes pacificus)

The lipid portion of dried squids (Todarodes pacificus) was extracted, and its hydrocarbons and 2-alkylcyclobutanones were separated using a florisil column. Both compounds were identified by gas chromatography and mass spectrometry and used to investigate the production of radiation-induced hydrocarbons and 2-alkylcyclobutanones. Concentrations of the hydrocarbons and 2-alkylcyclobutanones increased linearly with the radiation dosage. The major hydrocarbons in the irradiated dried squids were pentadecane and 1-tetradecene, which originated from palmitic acid. The amount of pentadecane was the highest among the radiation-induced hydrocarbons in the dried squids. The major 2-alkylcyclobutanone in the irradiated dried squids was 2-dodecylcyclobutanone, which was formed from the large amount of palmitic acid. 2-Tetradecylcyclobutanone, which may be produced from stearic acid in sample lipids, was also detected. Radiation-induced hydrocarbons and 2-alkylcyclobutanones were detected at > or = 0.5 kGy. These compounds were not detected in dried squids that were not irradiated. Radiation-induced hydrocarbons can be used as a detection marker for irradiated dried squids; however, the amount of 2-alkylcyclobutanones produced was not enough to be used as a marker. Radiolytic products of lipids, such as hydrocarbons or 2-alkylcyclobutanones. can be used to monitor food safety for consumers, ensuring proper irradiation labeling in foods and quarantine treatment in international trade.     

Histamine determination in tears as an index of safety in use of cosmetic products

To assess ocular irritancy caused by chemical and cosmetic products a reliable method based on evaluation of histamine (Hm) in tears is presented. Hm is measured at picomole levels by HPLC and fluorimetric detection after fluorescamine-HM derivatization. In order to avoid any uncontrolled irritation and stimulation of the conjunctiva during sample collection, a procedure of conjunctiva lavage was developed. A balanced salt solution (50 μl) containing a known amount of Hm-fluorophore as reference standard is instilled in the conjunctiva fornix. After a few seconds 20 μl of tear fluid is collected: 10 μl are immediately analysed and 10 μl after derivatization reaction. In this way it is possible to evaluate tear dilution and to assess Hm content in less than 10 minutes.
In a group of 20 normal subjects Hm has been determined in comparison with that of two volunteers after topical application of 50 μ of 0.2% and 0.4% sodium lauryl sulphate solution. A contact of 30 seconds of the cosmetic ingredient caused an immediate dose-dependent Hm release through a direct cytotoxic damage of cell membranes due to the surfactant action.
Évaluation de l'irritation occulaire due aux cosmétiques par la détermination de l'histamine lacrimale     

Formation and characterisation of melanoidin-like polycondensation products from amino acids and lipid oxidation products

Various coloured water-soluble high molecular weight and water-nonsoluble reaction products were isolated from model reactions of an amino acid (glycine or lysine) and a lipid oxidation product (hexanal, (2E)-hexenal, (2E, 4E)-decadienal) with or without glucose. They were characterised by UV–visible absorbance measurements, elementary analysis, and thermal degradation followed by SPME–GC–MS analysis. The UV–visible absorbance spectra before and after dialysis indicated that the most important contributors to the formation of water-soluble coloured material were constituents of the low molecular fraction. Elementary analysis data indicated that a higher amount of nitrogen was incorporated in the high molecular weight fractions as compared to the water-nonsoluble fractions, except for the water-nonsoluble reaction products from amino acid/(2E, 4E)-decadienal interactions, which showed the lowest C/N ratio found. Volatile carbonyl compounds, furans, aliphatic compounds, pyridines, pyrroles and benzene derivatives were the main groups identified in the thermal degradation profile of each fraction tested. Especially pyridines seem typical indicators of amino acid–lipid oxidation product interactions.     

The role of multi-purpose solutions in prevention and removal of lipid depositions on contact lenses

The sorption and desorption of radiolabeled dipalmitoylphosphatidylcholine (DPPC) and cholesterol (CH) were measured on 5 types of commercial contact lenses. The lenses were soaked in vitro in an artificial tear fluid for 16 h. The effects of borate buffered saline and two commercial multi-purpose lens-care solutions (MPSs) on reducing the lipid (DPPC and CH) sorption and increasing the lipid removal were examined. The results showed that silicone hydrogel (SiHy) lenses accumulated the most lipids, sorbing over an order of magnitude more than polymacon, a conventional hydrogel lens. Pre-soaking the SiHy lenses for 16 h in MPSs reduced the DPPC sorption by up to 13% and the CH sorption by up to 11%, compared to controls that were not pre-soaked. However neither these reductions nor those on polymacon were statistically significant (p > 0.05). In sorption experiments without presoaking, subsequent exposure to the MPSs removed some DPPC from the lenses (0–3.1% for SiHy lenses and 14–55% for polymacon), but CH removal was 0.0–0.8% for SiHy lenses and 0.6–28% for polymacon lenses. Some of these removals were statistically significant (p < 0.05).     

肉和肉制品中脂质氧化的研究进展

肉和肉制品在加工、贮藏和运输的过程中容易发生脂质氧化,影响肉制品的品质。脂质适度氧化可以促进肉制品的风味,但是脂质过度氧化还可能产生有毒有害物质,增加食用风险。脂质氧化反应产生的初级产物及次级产物化学性质不稳定,容易与肉中的其他成分(蛋白质、血红素、抗氧化添加剂等)发生反应从而影响肉制品的品质。因此,调控脂质氧化对肉及肉制品来说非常重要。本文主要综述了脂质的酶促氧化、自动氧化、脂质氧化与蛋白质氧化之间的关系。大量研究表明,脂质氧化过程复杂且受诸多因素和条件的影响,研究氧化过程及氧化机制对调控脂质氧化和提高食品品质的稳定性具有重要意义。     

An update on products and mechanisms of lipid peroxidation

The free radical reaction of polyunsaturated fatty acids with molecular oxygen leads to hydroperoxides as the first stable products. From linoleic acid the two conjugated diene hydroperoxides at carbons 9 and 13 were considered the only primary products until the recent discovery of the bis‐allylic 11‐hydroperoxide. The 11‐carbon is the site of the initial hydrogen abstraction, and the 11‐hydroperoxide is formed without isomerization of the 9,10 and 12,13 cis double bonds. In the autoxidation reaction, bis‐allylic hydroperoxides are obtained only in the presence of an efficient antioxidant, for example, α‐tocopherol. The antioxidant functions as a hydrogen atom donor, necessary to trap the fleeting bis‐allylic peroxyl radical intermediate as the hydroperoxide. Understanding of the mechanism of formation of bis‐allylic hydroperoxides has led to increased appreciation of the central role of the intermediate peroxyl radical in determining the outcome of lipid peroxidation.     

肉制品中脂肪氧化与蛋白质氧化及相互影响

近年来,食品中脂肪氧化与蛋白质氧化之间的联系在国内外引起了广泛关注。肉制品中脂肪及蛋白质的氧化能产生特征风味,但更多的是引起风味的劣化和颜色的褪变,且脂肪氧化和蛋白氧化之间是相互关联的,彼此相互促进。针对由脂肪氧化和蛋白质氧化影响肉制品品质的问题,就脂肪氧化与蛋白质氧化机理、肉制品中脂肪与蛋白质氧化的相互影响关系及控制措施进行综述。     

Cholesterol content and lipid composition of low fat dairy products

The lipid composition of different products obtained from the same raw milk was investigated. The cholesterol content of skim milk (0.05% total fat) and butter milk (0.57% total fat) lipids was 4.20% and 1.31%, respectively, while raw milk lipids and butter fat contained 0.34% or 0.30%, respectively. As the cholesterol content of these low fat milk products increases with decreasing fat content, equations were derived to estimate the fat-related cholesterol content from the value analysed in butter fat. In contrast to the fat-related cholesterol content, the product-related content is still relatively small in skim and butter milk. Their fat-related cholesterol content was found to be influenced by drying. The high content of phospholipids in skim and butter milk led to considerable changes in the fatty acid composition and affected the detection of foreign fat by butyric acid as well as by triglycerides. Skim and butter milk lipids contained only 2.41% or 2.33% butyric acid, respectively, instead of 3.36% found in raw milk lipids. Further, the overlap of phospholipids as well as cholesterol with the gas chromatographic triglyceride pattern resulted in calculated foreign fat contents of more than 20%.     

Comparison of different methods for total lipid quantification in meat and meat products

This study was aimed to evaluate the efficiency of six extraction methods for the quantification of total lipid content in meat and meat products: standard Soxhlet method (with and without previous acid hydrolysis), continuous Soxhlet method (with and without previous acid hydrolysis), and those methods based in the use of a mixture of chloroform and methanol, and described by Folch, Less, and Sloane (1957) and Bligh and Dyer (1959). Lipid content was determined in nine different meat products with different fat contents and physico-chemical features: cooked turkey breast, fresh pork loin, cooked ham, dry-cured ham, mortadella, beef burger, fresh sausage, dry-cured sausage and salami. The most effective methods for determining fat content in the studied meat products were the method described by Folch et al. (1957) and the Soxhlet with previous acid hydrolysis method. The Soxhlet method without previous acid hydrolysis adequately extracted lipids only in those meat products with very high fat content. The use of the method described by Bligh and Dyer (1959) gave rise to the lowest lipid contents in all the studied meat products.     

Preliminary study on health-related lipid components of bakery products

The purpose of this study was to evaluate the presence of health-related lipid components, in particular trans fatty acids and sterol oxidation products, in four bakery products. Both types of components are known for their adverse biological effects, especially the increase of atherogenic risk, and therefore it is advisable to monitor their presence in food products. Trans fatty acids were determined by silver-ion thin-layer chromatography-gas chromatography, whereas sterol oxidation was assessed by gas chromatography and gas chromatography-mass spectrometry determination of 7-keto derivatives (tracers of sterol oxidation). The amount of trans fatty acids (0.02 to 3.13 g/100 g of product), sterols (34.9 to 128.3 mg/100 g of product), and 7-keto derivatives of sterols (1.88 to 3.14 mg/kg of product) varied considerably among samples. The supply of phytosterols (22.5 to 64.0 mg/100 g of product) was not significant, and the extent of oxidation of most phytosterols to its corresponding 7-keto derivative was low (0.29 to 0.84%), except for that of brassicasterol (2.01 to 3.11%). The quality of ingredients and raw materials seems to have greatly influenced the fatty acid profile, stability, safety, and quality of the final product; these ingredients should be chosen with extreme care to decrease their potential negative health effects and to increase safety of these products.     

大豆皂醇抗脂质过氧化作用的研究

将大豆皂甙水解成大豆皂醇,研究大豆皂醇的体外抗脂质过氧化作用.用T-AOC方法测定化学模拟体系中的总抗氧化能力,用八木变法测定过氧化脂质(LOOH)含量,用硫代巴比妥酸(TBA)法测定丙二醛(MDA)含量,用分光光度法测定兔红细胞溶血和肝线粒体膨胀程度.结果表明,大豆皂醇的体外总抗氧化能力较强,可抑制血浆及肝组织脂质过氧化,减少红细胞溶血和减轻肝线粒体膨胀程度,说明大豆皂醇具有体外抗脂质过氧化作用.     

影响熟肉制品辐照所致脂肪氧化因素分析

就辐照诱导熟肉制品脂肪氧化机理进行了阐述,并分析不同因素(如脂肪含量、辐照剂量、包装形式、贮藏温度、添加剂、贮藏时间等)对辐照熟肉制品脂肪氧化的影响。     

顶空-气相色谱-质谱法测定婴幼儿米粉中的脂类降解产物

目的建立婴幼儿米粉中13种脂类降解产物的顶空-气相色谱-质谱测定方法。方法样品经水溶解分散后,选择顶空平衡温度和时间分别为80℃和25 min,经DB-624毛细管色谱柱分离,采用气相色谱-质谱仪进行分析,以保留时间对化合物离子定性,以内标法定量。结果 13种目标化合物在浓度范围2.0~2000μg内线性关系良好,相关系数(r~2)均大于0.999。13种脂类降解产物平均加标回收率为82.4%~114.7%,相对标准偏差在3.65%~8.66%之间。方法的检出限为0.001~0.10 mg/kg。结论该方法准确灵敏、简单快速,可适用于婴幼儿米粉中脂类降解产物的检测。     

Analysis of polyphenols in apple products

 Polyphenols of low molecular mass in apple samples were extracted by a C₁₈ solid-phase column, and analysed by HPLC. This extraction method had, in general, a greater extraction ability compared with liquid–liquid extraction using the ethyl acetate method. Received: 11 March 1996     

Characterization of lipid oxidation products in quinoa (Chenopodium quinoa)

The oxidative stability of lipids in processed quinoa was investigated in this study. Ground quinoa was subjected to accelerated aging for 30 days at 25, 35, 45, and 55 °C. Three samples were removed from each temperature treatment every 3 days. Free fatty acids, conjugated diene hydroperoxides, and hexanal were used as indicators of lipid oxidation. Storage time and temperature had significant effects (p ? 0.05) on all three parameters, while the interaction between storage time and temperature was not significant for conjugated diene hydroperoxides produced. The results from these tests suggest that quinoa lipids are stable for the period of time studied. With vitamin E as a naturally antioxidant occurring abundantly in quinoa, the potential for quinoa to be a new oilseed could be enhanced. This study provided some preliminary information on the oxidative stability of quinoa.