Low Aflatoxin B1 Research Articles

The protective effects of Lactobacillus SNK-6 on growth, organ health, and intestinal function in geese exposed to low concentration Aflatoxin B1

Aflatoxin B1 (AFB1) is a prevalent mycotoxin present in feed ingredients. In this study, we investigated the effects of Lactobacillus salivarius (L. salivarius) on the Landes geese exposed to AFB1. The 300 one-day-old Landes geese were randomly divided into five groups: The control group received a basic diet, while the other groups were fed a basic diet supplemented with 10 μg/kg AFB1, 10 μg/kg AFB1+ 4*108 cfu/g L. salivarius, 50 μg/kg AFB1, and 50 μg/kg AFB1 + 4*108 cfu/g L. salivarius for 63 d. Results showed that high level AFB1 exposure significantly decreased final BW and ADG, increased feed/gain ratio (F/G) and liver index (P < 0.05). L. salivarius improved levels of IL-1, IL-6, and IL-12 under low level of AFB1 exposure (P < 0.05), along with similar trends observed in serum IgA, IgG, IgM, T3, T4, TNF-ɑ, and EDT (P < 0.05). AFB1 exposure reduced jejunum villus high and villus high/crypt depth ratio, and suppressed expression of ZO-1, Occludin, and Claudin-1 mRNA, and significant improved with L. salivarius supplementation under low level AFB1 exposure (P < 0.05). AFB1 significantly increased expression levels of TLR3 and NF-kB1, with supplementation of L. salivarius showing significant improvement under low AFB1 exposure (P < 0.05). Cecal microbiota sequencing revealed that under low level AFB1 exposure, supplementation with L. salivarius increased the abundance of Bacteroidetes and Lactococcus. In summary, supplementation with 4*108 cfu/g L. salivarius under 10 μg/kg AFB1 exposure improved growth performance and immune capacity, enhanced jejunum morphology, reduced liver inflammation, altered the cecal microbial structure, and positively affected the growth and development of geese.

Neurobehavioral and biochemical responses to artemisinin-based drug and aflatoxin B1 co-exposure in rats.

Populations in malaria endemic areas are frequently exposed to mycotoxin-contaminated diets. The possible toxicological outcome of co-exposure to dietary aflatoxin B1 (AFB1) and artemisinin-based combination therapy warrants investigation to ascertain amplification or attenuation of cellular injury. Here, we investigated the neurobehavioral and biochemical responses associated with co-exposure to anti-malarial drug coartem, an artemether-lumefantrine combination (5mg/kg body weight, twice a day and 3days per week) and AFB1 (35 and 70µg/kg body weight) in rats. Motor deficits, locomotor incompetence, and anxiogenic-like behavior induced by low AFB1 dose were significantly (p < 0.05) assuaged by coartem but failed to rescue these behavioral abnormalities in high AFB1-dosed group. Coartem administration did not alter exploratory deficits typified by reduced track plot densities and greater heat map intensity in high AFB1-dosed animals. Furthermore, the reduction in cerebral and cerebellar acetylcholinesterase activity, anti-oxidant enzyme activities, and glutathione and thiol levels were markedly assuaged by coartem administration in low AFB1 group but not in high AFB1-dosed animals. The significant attenuation of cerebral and cerebellar oxidative stress indices namely reactive oxygen and nitrogen species, xanthine oxidase activity, and lipid peroxidation by coartem administration was evident in low AFB1 group but not high AFB1 dose. Although coartem administration abated nitric oxide level, activities of myeloperoxidase, caspase-9, and caspase-3 in animals exposed to both doses of AFB1, these indices were significantly higher than the control. Coartem administration ameliorated histopathological and mophometrical changes due to low AFB1 exposure but not in high AFB1 exposure. In conclusion, contrary to AFB1 alone, behavioral and biochemical responses were not altered in animals singly exposed to coartem. Co-exposure to coartem and AFB1 elicited no additional risk but partially lessened neurotoxicity associated with AFB1 exposure.

Growth and Aflatoxin B1 biosynthesis rate of model Aspergillus flavus NRRL 3357 exposed to selected infrared wavelengths

Aflatoxin B1 (AFB1) is a highly toxic substance produced mainly by Aspergillus spp., which are known to contaminate a wide variety of foods and feeds. The objective of this study was to understand the growth and AFB1 production rate of Aspergillus flavus NRRL 3357 and investigate the impact of different infrared (IR) heat intensities on the growth and aflatoxin-producing potential of A. flavus. Thirty healthy corn kernels were inoculated with 1 × 106 spores/mL of A. flavus spores and incubated at 25 °C. Then, A. flavus plate count, ergosterol, and AFB1 were measured every 24 h. In another experiment, inoculated corn incubated for 24 h was exposed to different IR heat intensities and heating durations. Afterward, the IR-exposed A. flavus were incubated for additional 3 and 6 days (4 and 7 days of incubation in total), and the ergosterol and AFB1 concentrations were measured. For non-IR exposed A. flavus, the highest AFB1 concentration (32.2 μg/g) was observed after 6 days of incubation. Treatment at high IR heat intensities and heating duration resulted in low AFB1 and ergosterol concentrations. However, IR heat treatment at low intensities (e.g., 1.86 kW/m2) for 20 s resulted in high AFB1 and ergosterol concentrations (97.83 and 34.84 μg/g, respectively). The sublethal IR heat intensity may have increased the potential of the exposed A. flavus NRRL 3357 to grow and produce AFB1. The outcome of this study will contribute to and enhance the continual efforts of mitigating AFB1 contamination of economically important grains.

Effects of Turmeric Powder on Aflatoxin M1 and Aflatoxicol Excretion in Milk from Dairy Cows Exposed to Aflatoxin B1 at the EU Maximum Tolerable Levels.

Due to the climatic change, an increase in aflatoxin B1 (AFB1) maize contamination has been reported in Europe. As an alternative to mineral binders, natural phytogenic compounds are increasingly used to counteract the negative effects of AFB1 in farm animals. In cows, even low dietary AFB1 concentrations may result in the milk excretion of the genotoxic carcinogen metabolite aflatoxin M1 (AFM1). In this study, we tested the ability of dietary turmeric powder (TP), an extract from Curcuma longa (CL) rich in curcumin and curcuminoids, in reducing AFM1 mammary excretion in Holstein–Friesian cows. Both active principles are reported to inhibit AFM1 hepatic synthesis and interact with drug transporters involved in AFB1 absorption and excretion. A crossover design was applied to two groups of cows (n = 4 each) with a 4-day washout. Animals received a diet contaminated with low AFB1 levels (5 ± 1 µg/kg) for 10 days ± TP supplementation (20 g/head/day). TP treatment had no impact on milk yield, milk composition or somatic cell count. Despite a tendency toward a lower average AFM1 milk content in the last four days of the treatment (below EU limits), no statistically significant differences with the AFB1 group occurred. Since the bioavailability of TP active principles may be a major issue, further investigations with different CL preparations are warranted.

The effects of natamycin and hexanoic acid on the bacterial community, mycotoxins concentrations, fermentation profiles, and aerobic stability of high moisture whole-crop corn silage

The objective of the study was to evaluate the effects of natamycin, hexanoic acid, and Lactobacillus plantarum on fermentation characteristics, aerobic stability, mycotoxins concentrations, and bacterial community in high moisture whole-crop corn silage. Whole-crop corn was harvested at 1/2 milk lines stage and ensiled without additive (CON), with L. plantarum (LP, 1 ×106 cfu/g FW), natamycin (NAT, 0.2 mg/kg FW), or hexanoic acid (HEX, 0.4 mg/kg FW). The addition of NAT and LP enhanced (P < 0.05) lactic acid (LA) production as compared to CON and HEX silage. HEX depressed LA accumulation leading to higher (P < 0.05) pH and water-soluble carbohydrates (WSC). The HEX and NAT silages had lower (P < 0.05) yeast count and ethanol concentration than CON and LP silages. NAT and LP decreased the concentration of ammonia N as compared to CON silage with the lowest value in LP silage. After 60 d of ensiling, LP silage spoiled within 22 h, NAT silage was stable for 41 h, which was slightly (P > 0.05) longer than CON silage (34 h). The HEX silage showed the longest aerobic stability (>144 h) among all silages. Ensiling decreased zearalenone (ZEN) and deoxynivalenol (DON) concentrations (P < 0.05). The LP and NAT silages had significantly (P < 0.05) lower aflatoxin B1(AFB1), ZEN, and DON concentrations than fresh corn, CON, and HEX silages. All additives depressed the growth of Lactococcus, but increased the relative abundance (RA) of Lactobacillus compared to CON. LP reduced the RA of Leuconostocs, while HEX showed stronger antibacterial abilities to Klebsiella than LP and NAT. In conclusion, HEX improved the aerobic stability, whereas NAT and LP improved fermentation quality by enhancing the proliferation of Lactobacillus during ensiling of high moisture whole-crop corn.

Probiotic gut-borneSaccharomyces cerevisiae reduces liver toxicity caused by aflatoxins in weanling piglets

The present study was conducted to investigate the aflatoxin B1 (AFB1) liver toxicity and gut histomorphometry after gut borne-Saccharomyces cerevisiae supplementation to AFB1-contaminated piglet diets. Thirty-two male mixed-breed piglets (weaned at 21 days old) were housed in individual pens and allowed to acclimate for 7 days. Animals were randomly assigned to four treatments of 22 days: T1 – low AFB1 levels diet (L, 31.6 μg/kg); T2 – L +S. cerevisiae 1 g/kg; T3 – high AFs levels diet (H, 495 μg/kg); T4 – H +S. cerevisiae 1 g/kg. The addition of probiotic yeast was able to reduce 72% of residual AFB1 present in the liver. The liver histopathology of piglets fed AFB1 showed a typical macroscopic and microscopic pattern of subclinical aflatoxicosis that was prevented by the yeast. Also, the addition of the yeast was able to decrease the alanine-aminotransferase (25.5±0.71 U) and aspartate-aminotransferase (26.5±6.10 U) even showing values lower than the control ones. The apparent absorption area showed the greater surface when the probiotic was present alone compared to the control (T1), whereas when present together with the toxin demonstrated a modulatory effect. The addition of probiotic gut-borneS. cerevisiae in the pig diets was effective in counteracting the toxic effects of harmful AFB1 in livers besides a tendency to improve the histomorphometric parameters and modulating the toxic effect of AFB1 on intestine. These results are promising for the production of feed additives that will be used in animal feed, since the probiotic action and the decontamination of mycotoxins in the same product are complemented.

Feasibility of L. plantarum and prebiotics on Aflatoxin B1 detoxification in cow milk

Abstract Milk is a key food worldwide prone to mycotoxins contamination. Lactobacillus plantarum and prebiotics detoxification ability was evaluated by a Plackett-Burman Design considering the reduction of aflatoxin B1 (AFB1) and its bioaccessibility in artificially contaminated ultra-high temperature cow milk. Six variables were evaluated: AFB1 concentration (from 5.0 to 10.0 μg L−1); incubation time (0 to 6 h); and inulin, oligofructose, β-glucan, and polydextrose concentrations (from 0.00 to 0.75%). The reduction in AFB1 ranged from 0% to 55.85% and in vitro bioaccessibility from 15.62% to 51.09%. The greatest reduction in AFB1 occurred by adding L. plantarum combined with inulin, oligofructose and β-glucan. The greatest reduction in bioaccessibility occurred by adding inulin or oligofructose and L. plantarum with a 10.0 μg L−1 AFB1 concentration. A sharp reduction in AFB1 was accompanied by higher bioaccessibility rates, and in this case, bioaccessibility is considered the main factor to ensure a low AFB1 absorption by the body. The best experimental condition was 10.0 µg L-1 AFB1, added of L. plantarum and inulin or oligofructose (0.75%), ensuring > 16% final bioaccessibility. Such results represent a safe AFB1 decontamination level for milk.

Changes in growth performance, aflatoxin B1 residues, immune response and antioxidant status of Litopenaeus vannamei fed with AFB1-contaminated diets and the regulating effect of dietary myo-inositol supplementation

This study aimed to investigate if myo-inositol (MI) supplementation could alleviate adverse effects caused by aflatoxin B1 (AFB1) with respect to growth performance, AFB1 residues, immune response and antioxidant status of Litopenaeus vannamei. 800 shrimp (initial weight: 1.1 g) were divided into five groups: MI0 (basal diet); MI0 + LA, MI0 + HA, MI200 + LA and MI200 + HA fed with AFB1-contaminated diets (LA, low concentration AFB1; HA, high concentration AFB1; MI200, adding 200 mg MI kg−1 diet). The results showed that HA significantly decreased growth performance, systemic inositol content and lipid content. AFB1 residues were detected in the hepatopancreas of shrimp, but not the muscle. Histological lesions were observed in MI0 + LA and MI0 + HA groups. HA supplementation raised malondialdehyde and protein carbonyl content and reduced some antioxidant enzyme activities and immune-related genes expression, which was slightly ameliorated by MI supplementation. Our results suggest that myo-inositol may slightly mitigate negative impacts caused by AFB1 in L. vannamei.

Discrimination of aflatoxin B1 contaminated pistachio kernels using laser induced fluorescence spectroscopy

Aflatoxin contamination of pistachio is one of the most significant issues related to its quality. The conventional ultraviolet (UV) induced fluorescence spectroscopy method of assessment is difficult to use for the screening of samples contaminated with low levels of aflatoxin due to its weak signal intensity and the interference of background constituents. Laser induced fluorescence spectroscopy (LIFS) technique is a highly sensitive and specific approach which has been successfully used to determine of the trace compounds in agricultural products. In this study, the feasibility of classifying aflatoxin B1 (AFB1) contamination in 250 kernels of two pistachio varieties (“Wanlong”, WL and “Hengkang”, HK) using LIFS was investigated. Four low concentration AFB1 solutions (5, 10, 20, and 50 ppb) were artificially applied on the surface of the kernels. The contaminated pistachios presented lower fluorescence intensity in the range 400 nm–610 nm when compared to uncontaminated control kernels. Principal component analysis (PCA) showed a pattern of separation between uncontaminated and contaminated kernels. Similar accuracy (92.3%–100%) was found in both varieties using a support vector machine (SVM) technique, indicating that changes in variety or kernel type are unlikely to have an influence on classification accuracy. Good discriminant ability (accuracy ≥ 98.4%) was achieved for AFB1 contamination of the pooled samples based on a combination of the standard normal variate (SNV) and the second derivative. Although these preliminarily results demonstrated that it is feasible to screen pistachios artificially contaminated with low concentration of AFB1 by LIFS, further work is necessary to test the performance of the LIFS method for detecting naturally contaminated samples.

Aflatoxin B1 adsorption/desorption dynamics in the presence of Lactobacillus rhamnosus RC007 in a gastrointestinal tract-simulated model.

(i) To determine the aflatoxin B1 (AFB1 ) adsorption and desorption dynamics in the presence of Lactobacillus rhamnosus RC007 under simulated transit of AFB1 at each gastrointestinal tract (GIT-saliva, stomach and intestine) stage consecutively and then, separately, (ii) to study the ability of L. rhamnosus RC007 to biotransform AFB1 as a strategy that complements the adsorption process. The AFB1 adsorption and desorption assay simulating the GIT passage of AFB1 (93·89ngg-1 ) in the presence of L. rhamnosus RC007 (108 CFU per ml) was conducted. Moreover, lactic acid production was determined. Results demonstrated that predominant environmental conditions in salivary solution induced a low AFB1 adsorption, while the transit through the gastric solution and intestinal solution allowed high percentages of adsorption and did not generate significant AFB1 desorption. The AFB1 adsorption and desorption dynamics in the presence of L. rhamnosus RC007 was favoured by gastric and intestinal environment. The knowledge of the adsorption dynamics of AFB1 with a micro-organism of interest will allow predicting its behaviour at each stage of the GIT.

The effects of low levels of aflatoxin B1 on health, growth performance and reproductivity in male rabbits

This study investigated the chronic effects of relatively low exposure to aflatoxin B1 (AFB1) on the growth performance, immune situation and reproduction in male rabbits. Bucks (n=32, 4.82±0.22 kg) were individually assigned to 4 treatments (8 replicates each) using a randomised complete block design. Four diets containing 0, 0.02, 0.05, and 0.1 mg AFB1/kg, were provided to bucks for 8 wk. Growth performance and semen quality were measured. Blood, organ and tissue samples were collected to measure haematological indices, liver function, organ weights and immune parameters. Compared to control, AFB1-contaminated diets reduced body weight and average daily gain (&lt;em&gt;P&lt;/em&gt;&amp;lt;0.05), altered certain haematological indices and liver function with decreased monocytes percentage and mean corpuscular haemoglobin concentration, and increased plateletcrit and albumin (&lt;em&gt;P&lt;/em&gt;&amp;lt;0.05), slightly impaired reproductive parameters with enhanced ratio of morphologically abnormal sperm cells at early stage and reduced post-stage acrosome integrity, testis weight and serum testosterone concentration (&lt;em&gt;P&lt;/em&gt;&amp;lt;0.05), decreased immune function with reduced relative liver weight (%) and tumour necrosis factor-α levels in serum and liver tissue, and increased serum 8-hydroxy-2’-deoxyguanosine levels (&lt;em&gt;P&lt;/em&gt;&amp;lt;0.05). Furthermore, bucks fed diets with relatively high AFB1 (0.05 and 0.1 mg AFB1/kg) had reduced red blood cell and haematocrit (&lt;em&gt;P&lt;/em&gt;&amp;lt;0.05) in contrast with the low AFB1 group (0.02 mg AFB1/kg). In conclusion, diets containing 0.05 and 0.1 mg AFB1/kg had negative effects on bucks’ growth performance, haematology, reproductivity and immune function, whereas diet containing 0.02 mg AFB1/kg had only minor effects on the parameters measured.

Assessment of intraspecies variability in fungal growth initiation of Aspergillus flavus and aflatoxin B1 production under static and changing temperature levels using different initial conidial inoculum levels

Intraspecies variability in fungal growth and mycotoxin production has important implications for food safety. Using the Bioscreen C we have examined spectrophotometrically intraspecies variability of A. flavus using 10 isolates under different environments, including temperature shifts, in terms of growth and aflatoxin B1 (AFB1) production. Five high and five low AFB1 producers were examined. The study was conducted at 5 isothermal conditions (from 15 to 37 °C) and 4 dynamic scenarios (between 15 and 30 °C). The experiments were carried out in a semisolid YES medium at 0.92 aw and two inoculum levels, 102 and 103 spores/mL. The Time to Detection (TTD) of growth initiation was determined and modelled as a function of temperature through a polynomial equation and the model was used to predict TTD under temperature upshifts conditions using a novel approach. The results obtained in this study have shown that a model can be developed to describe the effect of temperature upshifts on the TTD for all the studied isolates and inoculum levels. Isolate variability increased as the growth conditions became more stressful and with a lower inoculum level. Inoculum level affected the intraspecies variability but not the repeatability of the experiments. In dynamic conditions, isolate responses depended both on the temperature shift and, predominantly, the final temperature level. AFB1 production was highly variable among the isolates and greatly depended on temperature (optimum temperature at 30–35 °C) and inoculum levels, with often higher production with lower inoculum. This suggests that, from an ecological point of view, the potential isolate variability and interaction with dynamic conditions should be taken into account in developing strategies to control growth and predicting mycotoxin risks by mycotoxigenic fungi.

Potential for amelioration of aflatoxin B1-induced immunotoxic effects in progeny of white leghorn breeder hens co-exposed to vitamin E

This study was designed to evaluate the protective activity of Vitamin E (Vit E) on the immunotoxic effects induced by aflatoxin B1 (AFB1) in the progeny of breeder hens. For this purpose, 192 White Leghorn (WL) layer breeder hens were divided into 12 groups (A–L) and then fed test diets for either 1, 2 or 3 weeks. Group A was kept on basal feed (2900 Kcal/kg metabolizable energy) and served as control, while group B was offered a feed supplemented with Vit E at 100 mg/Kg. Groups C–G were offered feed containing 0.1, 0.5, 2.5, 5.0, and 10.0 mg/Kg AFB1, respectively, whereas groups H–L were offered the same dietary levels of AFB1 along with 100 mg/Kg Vit E supplementation. Hatching eggs were shifted to an incubator on a weekly basis to get progeny chicks. Hatched chicks in each group were maintained on basal ration and then subjected to different immunological assays. Lymphoproliferative responses (against PHA-P), antibody titers (against SRBC), oxidative damage to RBC, as well as phagocytic and nitrite production potential of the peritoneal macrophages from the chicks, were all adversely impacted by hen exposure to the higher doses of AFB1 or by increased intake (time) by the hens at a given dose of the toxin. No consistent ameliorative effects from Vit E were noted in these studies, i.e. effects seen against lower AFB1 doses were no longer apparent with the highest doses of AFB1. As such, for now it can be concluded that, with this particular single dose level of Vit E, AFB1-associated immunotoxic effects in progeny chicks can potentially be mitigated by dietary intake of Vit E by their hen dams. However, this is clearly an outcome that is driven by the level of the mycotoxin present in the feed. Future studies need to examine what impact higher Vit E doses than those employed herein might have in these ameliorative outcomes.

Association between aflatoxin exposure and health characteristics, liver function, hepatitis and malaria infections in Ghanaians

Purpose. We examined the relationship between various health parameters and aflatoxin B1 (AFB1) albumin adduct levels in plasma.Design. A cross‐sectional field study was conducted in four villages in the Ashanti region of Ghana.Methods. A survey on socio‐demographic and health characteristics was administered to 162 volunteers and blood (20 ml) was donated by 140 participants. AFB1 albumin adduct levels, liver function, hepatitis B and C viruses (HBV, HCV) and malaria infections were determined.Results. AFB1 levels ranged from 0.12 to 2.995 pmol mg−1 albumin (mean±standard deviation = 0.89±0.46) and was categorized based on the median as low (<0.80 pmol mg−1) or high (⩾0.80 pmol mg−1) and used in the analyses. By multivariate analysis, significantly higher levels of AFB1 were obtained for participants who reported symptoms of acute aflatoxicosis: history of yellow mouth (odds ratio = 5.5, confidence interval = 1.04–29.07, p = 0.04); history of sore swollen stomach (odds ratio = 4.54, confidence interval = 1.28–15.62, p = 0.01). A history of painful vomiting was marginally associated (p = 0.09) with high AFB1 levels. Between 30 and 40% of the study group had abnormal liver function and HBV/HCV infections. Total protein and alanine transaminase (ALT) were positively correlated to AFB1 levels (p<0.01 and p = 0.02, respectively). For every unit increase in AFB1, total protein increased by 0.27 units and ALT increased by 0.20 units. HBV was associated with high AFB1 levels (p = 0.055) and HCV was marginally associated with low AFB1 levels (p = 0.08). Approximately 20% of study participants were positive for malaria antigen in blood. A number of symptoms and disease markers were not significantly associated with AFB1.Conclusions. These results show high levels of AFB1 and symptoms of acute aflatoxicosis in a population that also has high levels of HBV/HCV infections and abnormal liver function. Thus, a high proportion of these study participants are at significant risk of developing hepatocellular carcinoma.

Moulds identification and detection of aflatoxin B1 on commercial codiments fermented of shrimp

Indonesian tropical climate have an opportunity for fungi growth as Aspergillus flavus Link which can produce aflatoxin within foodstuffs, include condiment of fermented shrimp. Aflatoxin B1 is the dangerous agent having roles as carcinogenic, mutagenic and teratogenic. The aims of this research were known kinds of moulds and detection of aflatoxin B1 on commercial condiments fermented of shrimp. Two brands of commercial condiments fermented of shrimp were taken from traditional markets and supermarkets in Surakarta. Isolation was done by made suspension of sample in aquadets. Suspension on appropriate dilutions was grown on CDA (Czapek’s Dox Agar) media withsurface spread. The grown colonies were separated and grown on PDA (Potato Dextrose Agar) slant media. Furthermore, isolates were cultured on CDA and MEA (Malt Extract Agar) media. The grown colonies were microscopes and microscopes examined and identified. Existence of aflatoxin B1 was known by Commercial RIDA Screen ELISA Kit that could detect qualitatively and quantitatively with detection sensitive &lt; 1.7 ppb. Moulds that could be isolated from condiments fermented of shrimp were: Aspergillus flavus Link, Aspergillus niger vanTieghem, Aspergillus wentii Wehmer, Aspergillus PU1 or Aspergillus PU2 and Penicillium citrinum Thom. There was aflatoxin B1 contaminated to 2 brands of commercial condiments fermented of shrimp that were examined. Traditional markets’ commercial condiments fermented of shrimp contained higher aflatoxin B1 than supermarkets’. The brands of commercial condiment of fermented shrimp which hadbetter inner package quality contained lower aflatoxin B1 than the worst inner package quality of commercial condiments of fermented of shrimp.© 2006 Jurusan Biologi FMIPA UNS SurakartaKeywords: commercial condiments fermented of shrimp, moulds, aflatoxin B1

Adsorption of mycotoxins by organozeolites

Adsorption of zearalenone (ZEN), ochratoxin A (OCHRA) and aflatoxin B1 (AFB1) on natural zeolite, clinoptilolite, modified with different amounts of octadecyldimethylbenzyl ammonium (ODMBA) ions was investigated. Results showed that adsorption of hydrophobic ionizable ZEN on unmodified zeolite tuff was very low and that adsorption on organozeolites increased with increasing hydrophobicity of the zeolitic surface. The adsorption was independent of the form of ZEN in solution and the solution pH, indicating that hydrophobic interactions with ODMBA are responsible for ZEN adsorption. Adsorption of low polar ionizable OCHRA on organozeolites also increased with increasing hydrophobicity of the zeolitic surface, however, OCHRA showed moderate adsorption on unmodified zeolitic tuff at pH 3. OCHRA adsorption on unmodified zeolite as well as on lower surface coverage of organozeolite was dependent on the form of OCHRA in solution; there was a decrease of adsorption at high pH, where OCHRA is in the anionic form. It indicated that at acidic pH, low surface coverage allows some combination of hydrophobic interaction with ODMBA and interactions with the surface of the zeolite. At higher surface coverage, the OCHRA adsorption was higher and practically independent of pH, indicating that the hydrophobic interactions of OCHRA with ODMBA are responsible for its adsorption. Nonionizable low polar AFB1 had a high affinity for the unmodified zeolitic tuff and the adsorption of AFB1 was greatly reduced for organozeolites, indicating that AFB1 does not have high tendency for hydrophobic interactions with ODMBA. pH dependence of AFB1 adsorption, while AFB1 has the same form at all pHs, demonstrated that the surface modification of the zeolite depends on pH and that these modifications have influence on its adsorption. The calculated dipole moments of neutral mycotoxin molecules: AFB1—9.5 D, OCHRA—6.9 D and ZEN—2.2 D are in qualitative agreement with adsorption experimental data.

Aflatoxin B1 albumin adduct levels and cellular immune status in Ghanaians

Although aflatoxins (AFs) have been shown to be immune-suppressive agents in animals, the potential role of AFs in modifying the distribution and function of leukocyte subsets in humans has never been assessed. We examined the cellular immune status of 64 Ghanaians in relation to levels of aflatoxin B1 (AFB1)-albumin adducts in plasma. The percentages of leukocyte immunophenotypes in peripheral blood, CD4+ T cell proliferative response, CD4+ T(h) and CD8+ T cell cytokine profiles and monocyte phagocytic activity were measured using flow cytometry. NK cell cytotoxic function was determined by perforin and tumor necrosis factor-alpha expression in CD3-CD56+ NK cells. AFB1-albumin adducts levels ranged from 0.3325 to 2.2703 (mean = 0.9972 +/- 0.40, median = 0.9068) pmol mg(-1) albumin. Study participants with high AFB1 levels had significantly lower percentages of CD3+ and CD19+ cells that showed the CD69+ activation marker (CD3+CD69+ and CD19+CD69+) than participants with low AFB1 levels (P = 0.002 for both). Also, the percentages of CD8+ T cells that contained perforin or both perforin and granzyme A were significantly lower in participants with high AFB1 levels compared with those with low AFB1 (P = 0.012 for both). Low levels of CD3+CD69+ (r = -0.32, P = 0.016) and CD19+CD69+ (r = -0.334, P = 0.010) cells were significantly associated with high AFB1 levels using correlation analysis. By multivariate analysis, there were strong negative correlations between the percentages of these cells (CD3+CD69+: b = -0.574, P = 0.001, and CD19+CD69+: b = -0.330, P = 0.032) and AFB1 levels. These alterations in immunological parameters in participants with high AFB1 levels could result in impairments in cellular immunity that could decrease host resistance to infections.

Bioactivation of aflatoxin B1 by lipoxygenases, prostaglandin H synthase and cytochrome P450 monooxygenase in guinea-pig tissues.

In the present investigation, we have examined the role of lipoxygenases in the bioactivation of aflatoxin B1 (AFB1) in hepatic and extrahepatic tissues. The enzyme activities were evaluated by determining [3H]AFB1-DNA adduct formation. The results demonstrated that both purified soybean lipoxygenase and guinea-pig tissue cytosolic lipoxygenases were able to activate AFB1 to form [3H]AFB1-DNA adduct(s). The reaction was completely inhibited by nordihydroguaiaretic acid (NDGA, 0.1 mM), a lipoxygenase inhibitor and an antioxidant, but not by indomethacin (0.1 mM), an inhibitor of prostaglandin H synthase (PHS), indicating that this reaction is associated with lipoxygenase activity, and/or is involved in a peroxyl radical process. While purified lipoxygenase showed arachidonic acid (AA)-dependent properties, the omission of AA did not diminish guinea-pig tissue cytosolic [3H]AFB1-DNA adduct formation, possibly because AA was released from lipid particles by AFB1. Within the range of hemoglobin (Hb) concentrations found in lung, kidney and liver cytosols (1.4-11.1 microM) and microsomes (0-0.5 microM), neither pure Hb, nor Hb of cytosols or microsomes from whole blood caused detectable AA-dependent AFB1-DNA binding. This indicates that Hb, as a contaminant with quasi-lipoxygenase activity, did not contribute to AFB1 activation attributed to guinea-pig tissue lipoxygenases. [3H]AFB1 concentrations at half-maximal DNA binding rate of pulmonary cytochrome P450 monooxygenases (P450) and lipoxygenases were similar, though P450 had a much higher maximum DNA binding rate. Pulmonary microsomal PHS activity for AFB1 activation was too low for its half-maximal binding concentrations of [3H]AFB1 and maximum rate to be accurately determined. In kidney, maximum rates for lipoxygenase, PHS and P450 were similar, whereas half-maximal binding concentrations for reactions by lipoxygenase and P450 were lower compared to that of PHS. The half-maximal binding concentration of hepatic lipoxygenase was significantly lower than those for PHS and P450. Hepatic half-maximal binding concentrations for PHS and P450 were similar, though P450 had a much higher maximum rate than PHS and lipoxygenases. These data suggest that lipoxygenase-catalyzed AFB1 activation can occur at low AFB1 concentrations. This may be important in view of human exposure to low AFB1 concentrations and predominant lipoxygenase activity in human airway epithelial cells. When expressed per gram of tissue, renal and hepatic PHS activities and renal lipoxygenase activities for AFB1 activation were similar, and higher than the activity of pulmonary PHS, while pulmonary PHS activity for the oxidation of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) was similar to that in liver and lower than that in kidney.(ABSTRACT TRUNCATED AT 400 WORDS)

Bioactivation of aflatoxin B 1 by human liver microsomes: Role of cytochrome P450 IIIA enzymes

Based on our previous observations (H. S. Ramsdell and D. L. Eaton, 1990, Cancer Res., 50, 615–620) that the proportion of aflatoxin B 1 (AFB 1) converted to the highly reactive AFB 1-8,9-epoxide in microsomal incubations varies with substrate concentration, we have examined the hypothesis of T. Shimada and F. P. Guengerich (1989, Proc. Natl. Acad. Sci. USA, 86, 462–465) that cytochrome P450 IIIA4 is principally responsible for the activation (epoxidation) of AFB 1 by human liver microsomes. The initial rates of formation of AFB 1-8,9-epoxide and hydroxylated AFB 1 metabolites were determined in microsomes prepared from livers of organ donors ( n = 14) at AFB 1 concentrations of 124 and 16 μ m. Microsomal oxidation of nifedipine, catalyzed primarily by P450 IIIA enzymes, was also determined by HPLC. Rates of formation of AFB 1 metabolites and nifedipine oxidation were poorly correlated at either AFB 1 concentration ( r 2 = 0.13–0.41). A somewhat better correlation between AFB 1 epoxidation and nifedipine oxidation was observed at 124 μ m AFB 1 ( r 2 = 0.41) than at 16 μ m AFB 1 ( r 2 = 0.26). Treatment of pooled microsomes with troleandomycin, an apparently specific inhibitor of P450 IIIA enzymes, resulted in 35% inhibition of AFB 1-8,9-epoxide formation at the high AFB 1 level but had little effect at 16 μ m AFB 1. An antibody against rat cytochrome P450 IIIA1 significantly inhibited AFB 1 epoxidation at high, but not low, AFB 1 concentrations, whereas AFQ 1 formation was strongly inhibited at all substrate levels examined. These results are consistent with the hypothesis that cytochrome P450 IIIA enzyme(s) can form AFB 1-8,9-epoxide, but are effective at only relatively high substrate concentrations. Another P450 enzyme(s) appears to be principally responsible for AFB 1-8,9-epoxide formation at the low AFB 1 levels that would be typical for dietary exposures.

Maize populations with resistance to field contamination by aflatoxin B1

AbstractMaize (Zea mays L) germplasm is needed with resistance to infection by Aspergillus flavus and/or subsequent contamination by aflatoxin B1 (AFB1). A select group of maize populations were evaluated for their resistance to AFB1 contamination at three locations. Four populations (Ibadan B and three others derived from crosses between Corn Belt inbreds and diploid perennial teosinte. Zea diploperennis) were compared with a susceptible hybrid check in a randomised complete block experiment with 10 replicates in Georgia, Missouri and South Carolina for two years. Ears were not inoculated, and naturally occurring concentrations of AFB1 in harvested grain were analysed for population differences. Ibadan B and Mo2 W × Z diploperennis had significantly lower average amounts of AFB1, 19 μg kg−1 and 18 μg kg−1, respectively, than other test entries. Backcrossing to susceptible Corn Belt inbreds produced populations as susceptible as the check when resistance was measured as the concentrations of AFB1 in the grain. The consistency and significance of low AFB1 concentrations for Ibadan B and Mo20W × Z diploperennis suggest that these may be useful sources of resistance.