The feasibility of antihypertensive oligopeptides encapsulated in liposomes prepared with phytosterols-β-sitosterol or stigmasterol

The feasibility of liposomes with cholesterol substituted by phytosterols and the effect of antihypertensive oligopeptides encapsulated in liposomes on blood pressure of spontaneously hypertensive rats (SHRs) were investigated. β-Sitosterol or stigmasterol was used as a substitute for cholesterol to prepare liposomes. OA3, angiotensin-I-converting enzyme (ACE) inhibitory oligopeptides derived from tuna cooking juice, was the agent used to lower the blood pressure in SHRs. Results indicated that sterol contained in liposomes showed better effect for OA3 encapsulation. The highest efficiency was observed when the molar ratio of lecithin/phytosterols was 1/0.5. Encapsulation efficiencies were 50% and 49% for β-sitosterol and stigmasterol, respectively. Furthermore, stabilities of storage, pH, oxidation and gastrointestinal enzyme exhibited no significant difference irrespective of sterol composition. Liposomes containing cholesterol or phytosterol all lowered blood pressure slowly as evaluated in vivo in SHRs. Therefore, replacing cholesterol with phytosterols in preparing liposomes is feasible and recommended.     

Sterol concentration and distribution in sunflower seeds (Helianthus annuus L.) during seed development

Sunflower seeds are currently used for edible oil production. Among oil minor compounds, phytosterols are of special interest due to their cholesterol reducing properties. This paper reports studies on their accumulation and distribution in the embryo and hull, and the effects of temperature on phytosterol contents in sunflower seed produced under both conventional and organic field conditions. An optimised method of sterol determination, adapted to studies on small samples of seed, is presented. Seventy-two percent of phytosterols were found in the embryo, 28% in the hull. The periods of phytosterols concentration varied according to sterol category and seed part. Application of these results to improve production of natural sterols for functional food use is discussed.     

Modification of the sterol profile in milk through feeding

The fortification of milk with phytosterols is an increasingly common practice to enhance the sterol profile and offer consumers potential health benefits. This study investigated whether cattle feed can influence the profile of phytosterols and cholesterol in the milk produced as an alternative to direct fortification of milk. Five experiments were performed using feeds commonly used by Australian dairy farmers and selected formulated rumen-protected feeds. Statistical significances were observed for some individual plant sterols and cholesterol in milk under these differing feeding regimens compared with the respective controls. In the case of the phytosterols, where the daily recommended consumption is typically 2 g per day, the total phytosterols were <0.12 mg/100 mL of milk. An experiment using a rumen-protected feed with high phytosterol levels suggested a decreased transfer of cholesterol to the milk by as much as 20%, although further work is required to confirm these preliminary results. Overall, the study suggests that different feeding practices have minimal effect on the resulting sterol profile of the milk.     

HPLC-UV法测定植物甾醇中3种甾醇单体的含量

本文建立了一种利用紫外高效液相法(HPLC-UV)测定植物甾醇中菜油甾醇、豆甾醇和β-谷甾醇的方法。采用 Waters Symmetry C₁₈柱(4.6 mm×250 mm,5 μm),以乙腈和水为流动相等度洗脱,柱温30 ℃,流速1.0 mL/min,紫外检测波长为208 nm。实验结果表明:菜油甾醇、豆甾醇和β-谷甾醇在38 min内均能实现基线分离,线性范围分别为2.52~50.30、5.08~101.60、5.10~102.00 μg/mL时,甾醇单体的线性关系良好,相关系数r分别为0.9971、0.9989、0.9991,检测限为2.5 μg/mL;日内精密度在0.06%~3.06%范围内,日间精密度介于1.56%~6.61%;加样回收率介于92.74%~106.25%之间。本方法能够准确测定4种植物甾醇中3种甾醇单体的含量,其中大豆甾醇和木甾醇中3种甾醇单体的含量组成差异较大,大豆甾醇中菜油甾醇和豆甾醇的含量分别为163.80~251.23 mg/g和134.89~235.04 mg/g,远高于木甾醇中的菜油甾醇和豆甾醇含量,而木甾醇中β-谷甾醇含量为(685.10±7.55) mg/g,则明显高于β-谷甾醇在大豆甾醇中的含量。相对现有的高效液相方法,本方法实现了对混合甾醇中菜油甾醇、豆甾醇和β-谷甾醇3种甾醇单体的精确定量分析。     

Phytosterol oxidation in oil-in-water emulsions and bulk oil

Dietary plants sterols (phytosterols) have been shown to lower plasma cholesterol level in humans. Since phytosterols may protect against coronary heart diseases, they are being incorporated into functional foods. However, phytosterols are susceptible to oxidative degradation. The purpose of this study was to evaluate the formation of phytosterols oxidation products (POPs) in oil-in-water emulsions and bulk corn oil. The extent of lipid oxidation was monitored by measuring the lipid hydroperoxides and hexanal, whereas 7-keto derivatives of phytosterols were determined by gas chromatography to follow sterol oxidation. A higher POPs level and formation rate was found in the oil-in-water (o/w) emulsion than in the bulk oil. Interfacial tension measurements showed that phytosterols had a high degree of surface activity, which would allow them to migrate to the oil–water interface of the emulsion droplets where oxidative stress is high.     

Dietary phytosterols modify the sterols and fatty acid profile in a tissue-specific pattern

Phytosterol consumption reduces the absorption of dietary cholesterol and can alter the tissue fatty acid composition. The effects of manipulating sterol and phospholipid fatty acid profile by increasing levels of phytosterols (1000 and 4000 mg/kg diet) have been investigated in young Sprague–Dawley rats. Cholesterol levels decreased significantly only in liver, heart and skin. Significant increased levels of phytosterols were detected in all ten tissues analysed, with levels of campesterol in general being greater than those of β-sitosterol. The level of phytosterol incorporation ranged widely in tissues, more than doubling in heart, lung, spleen and erythrocytes to no significant increases in brain. In heart, kidney, spleen and lung there were dose dependent increases in phytosterol levels. The phospholipid fatty acid profile showed some small, but significant changes, but these were not consistent between tissues or for fatty acid classes. Dietary phytosterols accumulated differently in tissues and affected cholesterol levels and phospholipid fatty acid composition in a tissue-specific manner.     

植物甾醇的提取、生理功能及在食品中的 应用综述

本文主要介绍了植物甾醇的相关性质、功能及在食品中的应用等。综述了在油脂加工副产物中甾醇的含量与提取：包括在副产物油脚中甾醇的含量与提取率;不同来源的副产物脱臭馏出物中甾醇的含量、主要甾醇成分及提取工艺等。介绍了植物甾醇的特殊功能（如降低胆固醇、减少冠心病发生、抗氧化等）及在食品中的广泛应用。天然植物甾醇常在食品体系中添加时出现结晶现象,且在水相和油相中溶解度低,为能在食品中广泛应用,常采用植物甾醇改性将其转变成甾醇酯的方式添加到食品中。文中介绍了植物甾醇改性的不同工艺并得到了较好的效果。在特殊的环境条件下,天然甾醇会发生氧化产生甾醇氧化产物。文中介绍了不同储藏条件甾醇氧化产物的含量及主要成分、甾醇氧化稳定性与结构的关系以及对主要慢性病的发生和发展的促进作用等。     

Determination of the contents of the main biochemical compounds of Adlay (Coxi lachrymal-jobi)

Adlay (Coxi lachrymal-jobi), an annual crop, has long been used in traditional Chinese medicine for its biological activity and as a nourishing food. Its phytochemical composition has been extensively studied; however, information on its policosanol (PC) and phytosterol content is scarce. The objective of this study was to examine and compare the PC, phytosterol and oleamide contents of different fractions of adlay collected from Laos, Thailand, Vietnam and Taiwan. Biochemical compositions of the samples were identified using a gas chromatograph coupled with a mass spectrometer (GC–MS). The adlay bran had higher contents of policosanols (246 mg/kg), phytosterols (4733 mg/kg) and oleamide (45.8 mg/kg) than had hulled and polished fractions. Although plant sterols reduce cholesterol absorption, policosanols may inhibit endogenous cholesterol synthesis. Although adlay contains beneficial phytochemicals that justify its use as a food ingredient or dietary supplement, research is still needed to confirm its traditional use in Asian medicine.     

Formulation of phytosterols in emulsions for increased dose response in functional foods

Phytosterols can significantly reduce cholesterol levels in humans. However, their dose response is strongly formulation dependent. Due to their insolubility in water and poor solubility in oil and their surface activity, the formulation in functional foods of unesterified non-crystalline phytosterols with an expected dose response even higher than the esterified phytosterols commonly applied today proved problematic. Supersaturating phytosterols with a crystallization inhibitor in the oil phase of an o/w emulsion in a special process combines high phytosterol concentrations with the potential of strongly increased dose response. In two formulations, no crystallization was observable in stability investigations over a period of 60 days.Industrial relevanceCompared to actual formulations as phytosterol fatty acid esters in fat-based foods, the method describe here for formulating free, solved and water-dispersible phytosterols allows for their incorporation into almost all kinds of foods as well as beverages. Additionally, the expected to dose–response to phytosterol formulated according to this method is expected to exceed by far that of phytosterol fatty acid esters. Combined with the comparably high concentration in the new, water-dispersible formulations, the method yields the opportunity of producing a wide variety of functional foods with phytosterols highly effective in lowering the risk for cardiovascular diseases.     

Sterols heating: degradation and formation of their ring-structure polar oxidation products

Cholesterol and phytosterols can be oxidised under heating conditions to give sterol oxidation products (SOPs), known by their toxic effects. This paper studied the degradation of cholesterol and three plant sterols during a 360 min heating treatment (180 °C). The formation and further degradation of SOPs was also analysed by GC-MS. Results revealed a sterol susceptibility to degradation according to the following decreasing order: campesterol≈β-sitosterol≥stigmasterol>cholesterol. The degradation curve fit (R(2)=0.907-0.979) a logarithmic model. SOPs increased their concentration during the first 5-10 min and thereafter, their degradation rate was higher than their formation rate, resulting in a decrease over time. Irrespective of the sterol from which they had derived, 7-keto derivatives presented the highest levels throughout the entire process, and also SOPs with the same type of oxidation followed a similar degradation pattern (R=0.90-0.99).     

The influence of phytosterols on the encapsulation efficiency of cholesterol liposomes

Lecithin vesicles, prepared by the dehydration‐rehydration (DR) method, were used to encapsulate bovine serum albumin (BSA). These were used to test the feasibility of making liposomes containing phytosterols, such as β‐sitosterol and stigmasterol, as a substitute for cholesterol. Their physicochemical properties such as encapsulation efficiency (EE), stabilities of storage, pH, and oxidization were investigated to assess substitutability. Liposomes prepared with phytosterols or cholesterol exhibited higher EE for BSA than those prepared without the addition of sterols. In addition, the EE of liposomes was increased with repeating a DR cycle five times. Liposomes at pH 6 or 7 were most stable, irrespective of phytosterols or cholesterol being added. Liposomes stored at 4 °C had a higher residual percentage than those stored at ?20 °C or room temperature. The addition of sterols to liposomes was effective in decreasing thiobarbituric acid‐reactive substances (TBARS) during storage periods; the antioxidation was more marked when α‐tocopherol was added to liposomes. The results indicate that replacing cholesterol with phytosterols in preparing liposomes is feasible and recommended.     

普通和乳化植物甾醇对育肥猪生长性能、血清生化指标和养分消化率的影响

本试验旨在研究普通和乳化植物甾醇对育肥猪生长性能、血清生化指标和养分消化率的影响。选用75头初始重为60 kg左右的杜长大育肥猪随机分为3组,其中对照组饲喂基础日粮,试验组在基础日粮中分别添加30 mg/kg普通植物甾醇(Ⅰ组)或乳化植物甾醇(Ⅱ组)。试验期为52 d。2种植物甾醇对育肥猪生产性能无显著影响,但显著降低血清总胆固醇(TC)、甘油三酯(TG)水平和白球比(A/G)(P0.05),显著提高血清总蛋白(TP)和球蛋白(GLO)水平(P0.05),Ⅰ组血清白蛋白(ALB)含量显著低于对照组(P0.05),而Ⅱ组无显著差异;显著提高育肥猪对干物质、有机物、粗蛋白的消化率(P0.05),Ⅱ组粗脂肪消化率亦显著高于对照组(P0.05)。结果显示,在育肥猪日粮中添加30 mg/kg 2种植物甾醇可改善养分消化率,调节血脂和蛋白质代谢,且从血清ALB和粗脂肪消化率数据来看,乳化植物甾醇的作用效果优于普通植物甾醇。     

Phytosterol Determination and Method Validation for Selected Nuts and Seeds

A method involving alkali and/or acid hydrolysis of phytosterols followed by trimethylsilyl ether derivatization coupled with GC-FID analysis was validated and applied in the analysis of major phytosterols (campesterol, stigmasterol, β-sitosterol, and Δ⁵-avenasterol) in nuts (n = 7), seeds (n = 9), legumes (n = 2), and grain (n = 1). The acid-labile Δ⁵-avenasterol was extracted with alkaline hydrolysis only before derivatization. Quantification of all phytosterols was done using the computed relative response factor of 5α-cholestane (internal standard). Analyses of internal and external phytosterol standards showed good linearity for all phytosterols (R ² of 0.999); LOD and LOQ of phytosterols were determined to be 0.01–0.12 and 0.04–0.40 mg/100 g, respectively. Repeatability and reproducibility precision analyses showed acceptable coefficient of variation of less than 3 and 4%, respectively, and satisfactory Horwitz ratio values of <1.0. Excellent accuracy was proved by the high recovery values of 91.4–106.0% for campesterol, β-sitosterol, and stigmasterol. Δ⁵-Avenasterol, the most oxidation-susceptible sterol, showed a recovery of about 60%. The total phytosterol (sum of major phytosterols quantified) contents in the 19 samples varied from 38.8 mg/100 g (white quinoa seed) to 246.2 mg/100 g (sunflower seed). β-Sitosterol was the predominant phytosterol (54–86.0% of total) among all samples except fennel seed in which stigmasterol was predominant. Analytical quality control chart maintained during the study period showed that assays were performed under control. Method validation indicated that the analytical method can be applied for accurate determination of campesterol, β-sitosterol, and stigmasterol in selected food samples.     

Rapid screening of phytosterols in orange juice by solid-phase microextraction on polyacrylate fibre derivatisation and gas chromatographic-mass spectrometric

The potential of solid-phase microextraction on polyacrylate coated fibre, with sequential or simultaneous trimethylsilyl derivatisation followed by gas chromatographic-mass spectrometric analysis, was evaluated for a rapid determination of the distribution of the phytosterols in aqueous food matrixes. Influences of different parameters (bis(trimethylsilyl)trifluoro-acetamide and sterol exposure time, sterol concentration and experimental protocol) on the recovery of sterols were investigated to determine optimum conditions which were tested for sterol extraction and analysis from orange juice. Best selectivity, sterol recovery and derivatisation yields were obtained by extraction and simultaneous derivatisation through immersion of the SPME-PA fibre in the orange juice (10 min, 65 °C) after headspace absorption of BSTFA (30 min, 65 °C) on the fibre. Nevertheless the method developed cannot be used for quantitative analysis. But the possibility to effect rapid screen of phytosterol containing in complex media have been shown.     

一种新型功能性食品——植物甾醇酯

植物甾醇是植物油中的一类天然组合,其降血胆固醇效果很早以来就为人所知,植物甾醇酯（PE）是它的酯化产物,具有比植物甾醇更优的脂溶和更佳的降血胆固醇效果。国外较多国家已开发出含PE的功能性食品（特别是人造黄油）,具有很好的市场前景。本文概述了植物甾醇的结构、制备方法、降血胆固醇效果以及其作用机制、国外对它的安全性最新评价等。     

Changes in Sterol Composition of Hazelnut During Fruit Development

Hazelnut is a valuable source of fat-soluble bioactive components. Among the fat-soluble bioactive components, phytosterols have gained much interest due to their cholesterol reducing properties. This study presents the evaluation of changes in the sterol composition of Turkish hazelnut cultivars (Tombul, Palaz, and Sivri) during fruit development. Three major sterols (β-sitosterol, campesterol, and Δ5-avenasterol), and five minor sterols (clerosterol, brassicasterol, stigmasterol, Δ7-stigmastenol, and Δ7-avenasterol) were detected in all hazelnut cultivars during all stages. The total sterol contents of Turkish hazelnut cultivars reached the maximum values at the early stage and a significant reduction in the total sterol content occurred at the harvest stage.     

Plant sterols in vegetables,fruits and berries

The plant sterol contents of the most important vegetables, fruits and berries available in Finland were determined by capillary gas chromatography. The sample preparation procedure included both acid and alkaline hydrolysis to liberate sterols from their conjugates. The plant sterol contents of fresh vegetables ranged from 51 to 370 mg kg^?1 fresh weight (fw) in samples obtained from retail sale. The highest contents (>300 mg kg^?1) were measured in broccoli, Brussels sprouts, cauliflower and dill and the lowest (51 mg kg^?1) in potato. The range of sterol contents on a dry weight (dw) basis was high, 246–4100 mg kg^?1 dw. Considerable variation was also observed when individual samples of some vegetables were compared. Sitosterol was the main sterol (proportion 43–86%) in all vegetables except cucumber and spinach, in which Δ⁷‐sterols dominated. The total sterol contents were in the range 116–228 mg kg^?1 fw in all fresh fruits except avocado, which contained more sterols, 752 mg kg^?1 fw. In fresh berries the corresponding range was 60–279 m kg^?1 fw. The wild berries lingonberry and blueberry were better plant sterol sources than the cultivated berries blackcurrant, redcurrant and strawberry. In fruits and berries the proportion of sitosterol ranged from 61–93% total sterols. On the basis of the results, the contribution of vegetables, fruits and berries to the total average daily plant sterol intake was estimated to be ca 60 mg. © 2003 Society of Chemical Industry     

Study on sterol fraction of commercial brands of milk,yoghurt and butter sold in Iranian market and chemometric data analysis

A gas chromatographic procedure for analysis of sterols was developed to detect possible addition of vegetable oils to milk, yoghurt and butter samples. The method involved fat extraction, saponification, hexane extraction, silylation of sterols and then analysis by gas chromatography. The sterol content of 102 samples of milk, yoghurt and butter was determined. Phytosterol content higher than 5% of total sterol was observed in four samples of milk and yoghurt. Principal component analysis showed that there was a direct relationship between the level of phytosterols and fat percentage in yoghurt samples. The described method is accurate and reliable enough to be employed regularly in food quality laboratories.     

Sterol Content of Fish,Crustacea and Mollusc: Effects of Cooking Methods

Sterol contents (desmosterol, cholesterol, stigmasterol, and sitosterol) of 36 fresh and cooked seafood and four freshwater fish species were investigated by high performance liquid chromatography (HPLC) method. Cholesterol and sitosterol were main sterols in seafood and freshwater fish species. Raw shellfish and molluscs contained cholesterol above 18.92 mg/100 g fish muscle, while the cholesterol content of marine fish ranged from 6.5 to 78.40 mg/100 g fish muscle. The cooking process resulted in significant effects on the sterol contents of seafood and freshwater species (p < 0.05). A remarkable increase in sitosterol (more than 3–4 fold compared to raw fish) was recorded for some fish species cooked in the oven. The highest desmosterol content was observed for fried fish, whereas the frying process resulted in a significant loss in cholesterol and sitosterol contents of marine fish (p < 0.05). The impacts of cooking methods on sterol content of seafood and their form varied depending on fish species and the cooking method used.     

植物甾醇的提取分离和分析检测方法研究进展

植物甾醇因其具有降低血清胆固醇等多种生物活性功能越来越受到人们的重视,并随着在医药等工业上进一步应用对其纯度也提出更高要求.因此如何从植物油脂中提取甾醇类物质以及进一步分离纯化和分析测定其含量和结构成为当前植物甾醇研究的重点.本文较全面地对传统和现代的植物甾醇的提取分离、纯化精制以及分析检测方法进行综述,希望对今后植物甾醇的研究会有所帮助.