Polycyclic Aromatic Hydrocarbons (PAHs) and their Bioaccessibility in Meat: a Tool for Assessing Human Cancer Risk

Polycyclic aromatic hydrocarbons (PAHs) are primarily formed as a result of thermal treatment of food, especially barbecuing or grilling. Contamination by PAHs is due to generation by direct pyrolysis of food nutrients and deposition from smoke produced through incomplete combustion of thermal agents. PAHs are ubiquitous compounds, well-known to be carcinogenic, which can reach the food in different ways. As an important human exposure pathway of contaminants, dietary intake of PAHs is of increasing concern for assessing cancer risk in the human body. In addition, the risks associated with consumption of barbecued meat may increase if consumers use cooking practices that enhance the concentrations of contaminants and their bioaccessibility. Since total PAHs always overestimate the actual amount that is available for absorption by the body, bioaccessibility of PAHs is to be preferred. Bioaccessibility of PAHs in food is the fraction of PAHs mobilized from food matrices during gastrointestinal digestion. An in vitro human digestion model was chosen for assessing the bioaccessibility of PAHs in food as it offers a simple, rapid, low cost alternative to human and animal studies; providing insights which may not be achievable in in vivo studies. Thus, this review aimed not only to provide an overview of general aspects of PAHs such as the formation, carcinogenicity, sources, occurrence, and factors affecting PAH concentrations, but also to enhance understanding of bioaccessibility assessment using an in vitro digestion model.     

脱氧雪腐镰刀菌烯醇生物可及性体外消化模型的构建及验证

目的构建脱氧雪腐镰刀菌烯醇(DON)生物可及性体外消化模型并验证,并对影响模型的主要因素进行优化。方法模拟胃肠道生理消化过程,研究消化时间、禁食和进食状态、消化液体积、消化液pH值、同时进食的多种食物成分等对DON在口腔、胃和小肠中生物可及性的影响,确定DON生物可及性体外消化模型最优技术参数,并对模型进行验证。结果经过优化,食品中DON释放到唾液、胃液、十二指肠液和胆汁中浓度达最高的最佳条件为:口腔、胃和十二指肠中的消化时间分别为6min、1.5h和1.5h;消化液pH分别为6.5、0.9、7.5和8.0;消化液体积分别为6、13、11ml和6ml;禁食和进食等各种状态下DON生物可及性范围为81.28%～99.58%,DON的生物可及性随胃内容物的增加而降低;食品基质类别(玉米和小麦粉)对DON生物可及性无影响;同时进食的其他食物成分可降低谷物中DON的生物可及性。结论构建的DON体外消化模型稳定性高、重复性好,完全可以满足对食品中DON生物可及性的研究。     

β-carotene and α-tocopherol coencapsulated in nanostructured lipid carriers of murumuru (Astrocaryum murumuru) butter produced by phase inversion temperature method: characterisation,dynamic in vitro digestion and cell viability study

Hydrophobic bioactives can be more easily incorporated into food and have their bioavailability enhanced if nanostructured lipid carriers (NLC) are used as carriers. In the present study, beta-carotene-loaded NLC were produced by low emulsification using murumuru butter and a mixture of Span 80 and Cremophor RH40 as surfactants. Their average diameter was 35?nm and alpha-tocopherol was required to protect the encapsulated β-carotene. Besides the evaluation of their physicochemical stability, NLC were submitted to dynamic in vitro digestion and cell viability assays with Caco-2 and HEPG cells. The bioaccessibility of beta-carotene in the dynamic system was about 42%. Regarding cell viability, results indicated NLC were toxic to the cell cultures tested. Such high toxicity is probably related to the type of surfactant used and to the extremely reduced particle size, which may have led to an intense and fast permeation of the NLC through the cells.     

Release of 5-aminosalicylate from an MMX mesalamine tablet during transit through a simulated gastrointestinal tract system

5-Aminosalicylate (5-ASA; mesalamine) is the current first-line treatment for mild to moderate ulcerative colitis, a chronic inflammatory condition that most commonly affects the distal part of the colon. MMX™ mesalamine (Lialda™ [US]; Mezavant™ XL [UK and Ireland]; Mezavant™ [elsewhere]; Shire Pharmaceuticals Inc., Wayne, Pa, under license from Giuliani SpA, Milan, Italy) was created to be a novel, once-daily 5-ASA formulation. MMX mesalamine in tablet form has a pH-dependent, gastroresistant coating and is designed to delay the release of 5-ASA during transit through the upper gastrointestinal tract; it consists of hydrophilic and lipophilic excipients that are designed to prolong the release of 5-ASA throughout the colon. The release kinetics of 5-ASA from an MMX mesalamine tablet were assessed with the use of a dynamic in vitro gastrointestinal tract system (TNO GastroIntestinalModel) that simulates physiologic conditions in the adult human gastrointestinal tract under standardized fed and fasted conditions. This system incorporates removal of released drug via dialysis and automated sampling taken at various sections of the system. Less than 1 % of 5-ASA was found to be released from the tablet in the simulated stomach and small intestine (before introduction into the simulated colon). Most of the 5-ASA within each tablet was released in the simulated colon (fasted state conditions: 78.0%; fed state conditions: 68.5%). Substantial quantities were released during the 8-to 18-hour sampling period (49.6 mg/h [fasted] and 40.7 mg/h [fed]). In conclusion, with the use of an in vitro system, the investigators showed that 5-ASA release from an MMX mesalamine tablet was delayed until the tablet reached the simulated colon. Throughout the simulated colon, release of 5-ASA from an MMX mesalamine tablet was prolonged     

An investigation into the bioaccessibility of potassium in unprocessed fruits and vegetables

Epidemiological studies and clinical trials have consistently shown an inverse association between potassium intake and blood pressure. As a means of raising potassium intake within the UK population, an increase in the consumption of fruits and vegetables is strongly advocated. The aim of this study was to determine the bioaccessibility of potassium in these foods. A 10-day crossover feeding trial was performed on 11 healthy volunteers. For 5 days a diet providing most of the potassium in the form of unprocessed fruits and vegetables was followed by a diet in which the potassium was believed to be almost wholly bioaccessible, being derived from animal foods and fruit juices. The potassium and sodium of the diets and the urine were determined by chemical analysis: 96.3% of the potassium in the ‘high bioaccessible diet’ was recovered in the urine, compared with 76.8% from the diet rich in fruits and vegetables. This difference is attributed to the cellular structure of plant foods. The relatively poor bioaccessibility of potassium diminishes the perceived nutritive value of these foods with regard to potassium intake.     

砷的体外生物利用度研究进展

为了正确评估砷的人体吸收量,以及对人体的毒害程度,同时解决体内生物利用度实验的高费用、难重现、操作复杂等问题,建立了在体外模拟人体内胃肠道消化过程的生物利用度实验。本文对砷的体外生物利用度的概念、模型原理、各种实验方法和影响因素作了简要介绍,综述了近年来用于砷的体外生物利用度检测的最新研究成果。     

Orange juice is a good folate source in respect to folate content and stability during storage and simulated digestion

Background Estimated average folate intake in Sweden is less than 55% of the recommended daily intake (RDI) for women of childbearing age (Becker and Pearson in Riksmaten 1997–1998 Kostvanor och n?ringsintag i Sverige. National Food Administration, Uppsala, pp 34, 44, 121, 2002). Because a good folate status reduces the risk of neural tube defects, mandatory folic acid fortification is discussed in some European countries. This however, could lead to exposure to unintentionally high amounts of folic acid for some population groups, therefore targeted folic acid fortification could be an alternative. Aims To (1) determine natural folate content in three popular brands of orange juice sold in Sweden, (2) determine stability of natural folate and folic acid fortificant during shelf life in a folic acid/iron fortified orange juice, (3) determine folate stability in four juices during simulated household consumption for one week and (4) determine the in vitro bioaccessibility of natural folate in one brand of orange juice using the TNO gastroIntestinal Model (TIM). Methods Natural folate content in juices was determined using RP-HPLC-FL. To determine folic acid content and confirm RP-HPLC-FL values LCMS was used. Stability during shelf life was determined in unopened bottles of a folic acid/iron fortified juice and for one week in four popular juices under household consumption conditions with reopening of bottles daily. For an in vitro folate bioaccessibility experiment in orange juice the TNO TIM Model was used. Results 5-CH₃-H₄folate was the dominant natural folate form in the juices with contents ranging from 16–30 μg/100 g. Shelf life losses of folic acid fortificant were 1–4%. During one week simulated household consumption 5-CH₃-H₄folate content decreased by up to 7% (n.s). Bioaccessibility of natural folate in orange juice was almost 100%. Most folate was released for absorption in jejunum between 60–120 min after trial start. Conclusion Orange juice may be considered a good source of natural folate in respect to content and stability during storage and simulated digestion. Moreover, added folic acid fortificant in a folic acid/iron fortified orange juice was stable during shelf life.     

Comparison of different digestive tract models for estimating bioaccessibility of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) from red slag 'Kieselrot'

'Kieselrot' (red slag), a highly PCDD/F-contaminated leaching residue from a copper production process, has been used as surface layer for more than 1,000 sports fields, playgrounds and pavements in Germany and neighbouring countries. Children can ingest this material directly by hand-to-mouth activities or soil-pica behaviour. Furthermore secondary contamination of farm land or kitchen gardens by drift of red slag dust may lead to an enrichment of PCDD/F within the food-chain. PCDD/F can be mobilized from contaminated materials by digestive juices and thus become bioaccessible for intestinal absorption. Two different digestive tract models were used to estimate the bioaccessibility of PCDD/F from red slag and to study the influence of food material on the mobilization of the contaminants. The bioaccessibility of PCDD/F from red slag depends on the charge of red slag material used, the bile content of the intestinal juice and on the presence of lipophilic foodstuffs. A low bioaccessibility of less than 5% was found when using a digestive tract model with a low bile content and in absence of food material. The bioaccessibility was estimated to be more than 60% when using a model with a higher bile content and in the presence of whole milk powder. A low bioaccessibility of PCDD/F from red slag in general--as assumed until now and mentioned in legal provision--was not confirmed by our study. Considering observations for the different homologue groups it is obvious that bioaccessibility is the first of several important steps to estimate human health risks arising from contaminated materials. In case red slag contaminated with PCDD/F their absorption rate in the digestive tract and/or metabolism might be at least just like important.     

Vegetable relishes,high in β-carotene,increase the iron,zinc and β-carotene nutritive values from cereal porridges

Iron, zinc and vitamin A deficiencies are serious public health problems in sub-Saharan Africa, which can be alleviated by dietary diversification. The effects of adding cowpea leaf (CL) and orange-fleshed sweet potato (OFSP) relishes to sorghum and maize porridges on iron, zinc and β-carotene contents and bioaccessibilities were determined. Despite the high iron content of the CL relish (14.59?mg/100?g), the vegetable relishes had little effect on the iron bioaccessibility from the cereal porridges. Importantly, the addition of the CL relish increased the percentage and amount of bioaccessible zinc 2- and 3-fold, respectively. Addition of CL and OFSP relishes resulted in β-carotene contents of 10–13?mg/100?g. The β-carotene from the OFSP relish meals was double as bioaccessible than that from the CL relish meals. Addition of the vegetable relishes has real potential to improve especially the vitamin A and zinc nutritive value of cereal diets.     

Inter-laboratory validation of bioaccessibility testing for metals

Bioelution assays are fast, simple alternatives to in vivo testing. In this study, the intra- and inter-laboratory variability in bioaccessibility data generated by bioelution tests were evaluated in synthetic fluids relevant to oral, inhalation, and dermal exposure. Using one defined protocol, five laboratories measured metal release from cobalt oxide, cobalt powder, copper concentrate, Inconel alloy, leaded brass alloy, and nickel sulfate hexahydrate. Standard deviations of repeatability (s_r) and reproducibility (s_R) were used to evaluate the intra- and inter-laboratory variability, respectively. Examination of the s_R:s_r ratios demonstrated that, while gastric and lysosomal fluids had reasonably good reproducibility, other fluids did not show as good concordance between laboratories. Relative standard deviation (RSD) analysis showed more favorable reproducibility outcomes for some data sets; overall results varied more between- than within-laboratories. RSD analysis of s_r showed good within-laboratory variability for all conditions except some metals in interstitial fluid. In general, these findings indicate that absolute bioaccessibility results in some biological fluids may vary between different laboratories. However, for most applications, measures of relative bioaccessibility are needed, diminishing the requirement for high inter-laboratory reproducibility in absolute metal releases. The inter-laboratory exercise suggests that the degrees of freedom within the protocol need to be addressed.