Aspergillus section Flavi and aflatoxins in Algerian wheat and derived products

Wheat and its derivatives are a very important staple food for North African populations. The aim of this study was to analyze populations of Aspergillus section Flavi from local wheat based on aflatoxins (AFs), cyclopiazonic acid (CPA) and sclerotia production, and also to evaluate AFs-contaminated wheat collected from two different climatic regions in Algeria. A total of 108 samples of wheat were collected during the following phases: pre-harvest, storage in silos and after processing. The results revealed that among the Aspergillus species isolated, those belonging to section Flavi were predominant. Of the 150 strains of Aspergillus section Flavi isolated, 144 were identified as Aspergillus flavus and 6 as Aspergillus tamarii. We showed that 72% and 10% of the A. flavus strains produced AFs and CPA, respectively. Among the 150 strains tested, 60 produced amounts of AFB1 ranging from 12.1 to 234.6 μg/g of CYA medium. Also, we showed that most strains produced large sclerotia. AFB1was detected by HPLC in 56.6% of the wheat samples and derived products (flour, semolina and bran) with contamination levels ranging from 0.13 to 37.42 μg/kg.     

Impacts of Climate Change Interacting Abiotic Factors on Growth,aflD and aflR Gene Expression and Aflatoxin B1 Production by Aspergillus flavus Strains In Vitro and on Pistachio Nuts

Pistachio nuts are an important economic tree nut crop which is used directly or processed for many food-related activities. They can become colonized by mycotoxigenic spoilage fungi, especially Aspergillus flavus, mainly resulting in contamination with aflatoxins (AFs), especially aflatoxin B₁ (AFB₁). The prevailing climate in which these crops are grown changes as temperature and atmospheric CO₂ levels increase, and episodes of extreme wet/dry cycles occur due to human industrial activity. The objectives of this study were to evaluate the effect of interacting Climate Change (CC)-related abiotic factors of temperature (35 vs. 37 °C), CO₂ (400 vs. 1000 ppm), and water stress (0.98–0.93 water activity, a_w) on (a) growth (b) aflD and aflR biosynthetic gene expression and (c) AFB₁ production by two strains A. flavus (AB3, AB10) in vitro on milled pistachio-based media and when colonizing layers of shelled raw pistachio nuts. The A. flavus strains were resilient in terms of growth on pistachio-based media and the colonisation of pistachio nuts with no significant difference when exposed to the interacting three-way climate-related abiotic factors. However, in vitro studies showed that AFB₁ production was significantly stimulated (p < 0.05), especially when exposed to 1000 ppm CO₂ at 0.98–0.95 a_w and 35 °C, and sometimes in the 37 °C treatment group at 0.98 a_w. The relative expression of the structural aflD gene involved in AFB₁ biosynthesis was decreased or only slightly increased, relative to the control conditions at elevated CO, regardless of the a_w level examined. For the regulatory aflR gene expression, there was a significant (p < 0.05) increase in 1000 ppm CO₂ and 37 °C for both strains, especially at 0.95 a_w. The in situ colonization of pistachio nuts resulted in a significant (p < 0.05) stimulation of AFB₁ production at 35 °C and 1000 ppm CO₂ for both strains, especially at 0.98 a_w. At 37 °C, AFB₁ production was either decreased, in strain AB3, or remained similar, as in strain AB10, when exposed to 1000 ppm CO₂. This suggests that CC factors may have a differential effect, depending on the interacting conditions of temperature, exposure to CO₂ and the level of water stress on AFB₁ production.     

Characterization of 260 Isolates of Aspergillus Section Flavi Obtained from Sesame Seeds in Punjab,Pakistan

Sesame Sesamum indicum L. is a major oil-based seed crop that has been widely cultivated and consumed in Pakistan. Unfortunately, sesame is highly prone to Aspergillus fungal growth in the field, and under inappropriate storage conditions can become contaminated with aflatoxins, the most potent carcinogen found in nature. Here, we have isolated a high number of Aspergillus isolates from sesame seeds in fresh and stored conditions obtained from rainfed and irrigated zones of Punjab, Pakistan, and characterized them for aflatoxigenic potentials. Using morphological identification techniques, 260 isolates were grouped as potential Aspergillus section Flavi, with 126 and 134 originating from the rainfed and irrigated zones, respectively. Out of 260 in total, 188 isolates were confirmed to produce aflatoxins. There were no significant differences in potential aflatoxigenic isolates with respect to the rainfed and irrigated zones. However, the number of potential aflatoxigenic isolates was significantly higher (p < 0.05) in stored samples than that of those from fresh sesame seeds in the rainfed and irrigated zone. Whole genome sequencing and comparative analyses of 12 select isolates have revealed that one of the A. flavus isolates, which produced very low aflatoxins (AFP10), has an elevated missense variant rate, numerous high impact mutations, and a 600 base pair deletion in the norB gene. In summary, our study provides insights into aflatoxigenic potential and the associated genetic diversity of indigenous Aspergillus section Flavi isolates and potential management strategies for reducing aflatoxin contamination levels in a major crop consumed in Punjab, Pakistan.     

银杏叶提取物对AFB1致HepG2细胞毒性保护作用的观察

目的:研究银杏叶提取物(EGb761)对AFB1致HepG2细胞毒性的保护作用。方法:以MTT实验检测AFB1对HepG2细胞的生长抑制率,再以MTT、FCM等实验,观察EGb761预处理后对AFB1诱导HepG2细胞存活率的影响,然后通过硫代巴比妥酸(TBA)法及二氛荧光素双乙酸(DCFH-DA)法检测细胞内脂质过氧化产物丙二醛(MDA)及氧化代谢产物活性氧簇(ROS)水平,以观察EGb761对AFB1毒性引起的HepG2细胞活性保护作用及对脂质过氧化的抑制作用。结果:AFB1显著降低HepG2细胞活力,IC50为15μg/mL。EGb761能显著增加AFB1处理后的细胞活力,以219μg/mLEGb761预处理在24、48和72h均提高了AFB1(15μg/mL)处理的细胞存活率,分别提高了28%、47%及47%,P值均<0.01;在3个时间点都明显抑制了AFB1诱导的MDA的形成及ROS的水平,P值均<0.01。结论:EGb761对AFB1致HepG2细胞损伤具有保护作用,其机制可能与清除氧自由基、对抗脂质过氧化有关。     

AFLATOXINS AND KWASHIORKOR

Aflatoxin was found more frequently in the serum of children with kwashiorkor than in normal and marasmic controls. They also demonstrated different handling of the toxin.     

Association of aflatoxin exposure and height-for-age among young children in Guatemala

Aflatoxin exposure has been proposed to affect child height-for-age. The following hypothesized associations were tested in Guatemala: (1) aflatoxin (B₁, B₂, G₁, G₂) exposure and environmental enteric dysfunction (EED) and child height-for-age z-score; and (2) aflatoxin exposures and subsequent symptoms of aflatoxins. Maize consumption data, health data, and samples of maize from households were collected from mothers and their children – under five – in October 2016 (n = 320) and February 2017 (n = 120). Maize samples were tested for aflatoxin levels and maize consumption data were used to compute an aflatoxin exposure level. Results suggest that there was a significant negative correlation between the putative aflatoxin exposure level and child height-for-age z-score (?0.073, p = 0.030), but not for EED. Furthermore, aflatoxin exposure was significantly correlated with aflatoxin symptoms only at the same time point (0.123, p = 0.026). These results support the potential need for engineered solutions to household aflatoxin transmission problems in rural communities of Guatemala.     

亚硒酸钠等五种化合物对黄曲霉毒素B_1诱变效应的拮抗

应用 Ames 试验对亚硒酸钠(Na_2SeO_3)、茶多酚(GTP)、维生素E(VE)、L—色氨酸和叶酸等五种化合物进行黄曲霉毒素B_1(AFB_1)诱导鼠伤寒沙门氏菌TA98、TA100突变株回复突变作用实验.当五种化合物加入培养基时,有Na_2SeO_3、GPT和VE等三种化合物对AFB_1诱导TA98、TA100引起的回变菌落数明显减少.结果表明这三种化合物对AFB_1的诱变效应有明显的拮抗作用,且显示良好的剂量效应关系.提示对预防肝癌可能有意义.     

Impact of nanoencapsulated natural bioactive phenolic metabolites on chitosan nanoparticles as aflatoxins inhibitor

Aflatoxins are part of fungal secondary metabolites which become serious health, environmental, and economic problems and can cause corruption of many crops and agricultural grains that used as food and feed for human and animal. Aflatoxins mainly produce by Aspergillus spp. especially Aspergillus flavus and Aspergillus parasiticus. The present work aimed to study the effect of nanoencapsulation of chitosan (CS) nanoparticles with two phenolic compounds 1‐(2‐ethyl,6‐heptyl)phenol (EHP) extracted from Cuminum cyminum and 5‐ethyl‐2‐(methoxymethyl)phenol (EMMP) extracted from black pepper on growth and aflatoxins production of A. flavus and A. parasiticus. A. flavus growth was completely inhibited by 0.6 mg/ml of EHP and EMMP as well as A. parasiticus which showed the same minimal inhibition concentration with the first compound and 0.8 mg/ml with the second one. CS nanoparticles inhibited the growth of the tested organisms more than CS especially with A. parasiticus and this potency became much better when nanoencapsulated with the two extracted phenolic compounds. In inhibition of aflatoxins production, EHP reduced the production of aflatoxin B1 and B2 of A. flavus by 68.6% and 69.7%, respectively. In the same manner EMMP reduce the production of the two toxins by 87.3% and 82.6%, respectively. The reduction effect of CS nanoparticles is much more than that of CS as it record in most cases about twofold increase. Nanoencapsulation of CS nanoparticles by the extracted phenolic compounds is much more effective with complete inhibition of aflatoxin B1 of both fungi and aflatoxin G1 of A. parasiticus.     

淡豆豉炮制过程中黄曲霉毒素含量的动态变化规律分析

目的: 检测淡豆豉炮制过程中不同时间点样本的黄曲霉毒素(AFTs)含量,明确AFTs的动态变化规律及其产生的关键时间点。方法: 按实验室前期已建立的规范炮制工艺制备淡豆豉,获取淡豆豉炮制过程中不同时间点的样本;采用超高效液相色谱-串联质谱法(UPLC-MS/MS)检测各样本中4种AFTs [黄曲霉毒素B₁(AFB₁),AFB₂,AFG₁,AFG₂]含量。结果: 4种黄曲霉毒素在选定的质量浓度范围内与峰面积线性关系良好(R²均大于0.99),重复性相对标准偏差(RSD)0.4%~0.9%,精密度RSD 0.7%~2.6%,稳定性RSD 0.8%~1.74%,加样回收率介于95.09%~107.20%(RSD 3.14%~12.71%);AFB₁含量在淡豆豉整个炮制过程中呈先上升后下降的趋势,在"再闷"第6天时达最高值6.95 μg·kg^-1,再闷第12天后各样本均未检测出AFTs。结论: 本研究建立了简单、快速、灵敏度高且适用于淡豆豉中4种AFTs检测的UPLC-MS/MS法;淡豆豉炮制过程中AFTs含量呈动态变化,表明淡豆豉炮制中生物拮抗作用自然存在,从安全性角度证实淡豆豉炮制中"再闷"环节的重要性和"再闷"时间的合理性。     

2010年某地粮食类食品安全风险监测结果分析

目的了解某地粮食类食品铅、镉、汞和黄曲霉毒素污染状况,为食品安全监管提供依据。方法 2010年对694份粮食类食品标本的铅、镉、汞和黄曲霉毒素污染状况进行监测,并将监测结果与国家相关标准进行对照。结果该地粮食类食品总体合格率为97.41%。大米中铅超标率为9.17%,镉超标率为4.95%,汞超标率为0.92%;镉在大米、小麦粉、玉米面中均被检出,超标率分别为4.95%、4.55%、4.35%;黄曲霉毒素B1检出率为4.17%。不同采集地食品合格率比较,超市高于农贸市场。结论该地粮食类食品污染状况需要引起关注,监管部门今后应加强对各类粮食类食品的监测及安全监管,并科学发布预警信息引导公众正确消费。