Mycotoxins Aspergillus Toxins Lecture 11 PDF

Made with Xodo PDF Reader and Editor Mycotoxins Aspergillus toxins Lecture 11 Mohamed Nasr El-Deen Gomaa Professor of Marine Toxicology  Made with Xodo PDF Reader and Editor Aspergillus toxins 1. Aflatoxins  Made with Xodo PDF Reader and Editor 1. Aflatoxins ...

Made with Xodo PDF Reader and Editor Mycotoxins Aspergillus toxins Lecture 11 Mohamed Nasr El-Deen Gomaa Professor of Marine Toxicology  Made with Xodo PDF Reader and Editor Aspergillus toxins 1. Aflatoxins  Made with Xodo PDF Reader and Editor 1. Aflatoxins  Made with Xodo PDF Reader and Editor What is Aflatoxins Producing organisms and Discovery Fungal secondary metabolites (naturally occurring) Produced by strains of Aspergillus flavus and Aspergillus parasiticus. The term "aflatoxin" is derived from the name of the species Aspergillus flavus, in which some of the compounds first were discovered. First isolated and identified in England 1960 after its discovery as the source of “Turkey X disease” where 100,000 turkeys died by Brazilian peanut meal  Made with Xodo PDF Reader and Editor What is Aflatoxins Producing organisms Aspergillus flavus is a saprotrophic and pathogenic The organism is a broom like shape Consist of Hypha, conidia, and sclerotia Hyphal growth usually occurs by thread-like branching and produces mycelia. They also have both sexual and asexual forms of reproduction. Asexual reproduction produces conidia spore and sclerotia While sexual reproduction produces sclerotia. The conidia is responsible of the colony color from yellow green (young colony) to dark green (old colony)  Made with Xodo PDF Reader and Editor What is Aflatoxins Producing organisms and contamination Domain: Eukaryota Kingdom: Fungi Division: Ascomycota Class: Eurotiomycetes Hypha broom like Contamination Aspergillus flavus cycle  Made with Xodo PDF Reader and Editor What is Aflatoxins Various exposure methods Through consumption of contaminated food. Aflatoxins are common contaminant in a variety of foods including peanuts, cottonseed meal, corn, and other grains. Contamination occurs pre-harvest and post-harvest. Through contaminated animal feed that affect animals and affect humans after consumption of contaminated animal products) Direct contact with fungus  Made with Xodo PDF Reader and Editor What is Aflatoxins chemical structure Highly stable compounds, withstand normal food/feed processing procedures. Low MW compounds (312Da) Composed of three parts Coumarin nucleus Lactone ring Furan ring (a key active site for its toxic and carcinogenic activities)  Made with Xodo PDF Reader and Editor What is Aflatoxins Major types and their metabolites 4 major types Aflatoxin B1 and B2 (AFB), as they have Blue fluorescence under UV on TLC. AFB produced by A.flavus and A.parasiticus. Aflatoxin G1 and G2 (AFG), as they have Green fluorescence under UV on TLC. TLC Thin Layer Chromatography AFG produced by some Goup II A.flavus and A.parasiticus  Made with Xodo PDF Reader and Editor What is Aflatoxins Major types and their metabolites Aflatoxin B1 is considered the most toxic compound B1, G1 has a double bond in the Furan ring where B2, G2 hasn’t. B1, B2 has a five membered ring in the Coumarin nucleus where G1, G2 has a sex membered ring. TLC Thin Layer Chromatography  Made with Xodo PDF Reader and Editor What is Aflatoxins Major types and their metabolites Other aflatoxins metabolites Aflatoxin M2 (AFM): metabolite of aflatoxin B2 in milk of cattle fed on contaminated foods Aflatoxicol (AFL): metabolite produced by breaking down the lactone ring Aflatoxin Q1 (AFQ1): major metabolite of AFB1 in in-vitro liver preparations of other higher vertebrates AFM, AFQ, and AFL retain the possibility to become an epoxide. Nevertheless, they appear much less capable of causing mutagenesis than the unmetabolized toxin.  Made with Xodo PDF Reader and Editor What is Aflatoxins Toxicity Exert toxic effects on animals and human beings. Aflatoxins is a very potent carcinogen with a TD50 3.2 μg/kg/day in rats. TD50 is the threshold dose or median toxic dose of a substance in which toxicity occurs in 50% of a species. It is, therefore a measure of carcinogenic potency. This carcinogenic potency varies across species. Rats and monkeys are much more susceptible than others. LD50 range 0.5 - 10 mg/kg body weight rat.  Made with Xodo PDF Reader and Editor What is Aflatoxins Toxicity The diseases caused by the consumption of aflatoxins are known as aflatoxicoses. Liver is the primary target organ Causing DNA damage and gene mutation 20 ppb max. safe level for human consumption Chronic aflatoxicosis leads to cancer, immune suppression and other slow pathological conditions. Acute aflatoxicosis leads to death. Aflatoxin B1 is classified as group I carcinogen by WHO.  Made with Xodo PDF Reader and Editor What is Aflatoxins Symptoms Aiding factors High fever, Wrong crop production practices Progressive Jaundice, Inadequate harvesting Weakness, Wrong drying and storage practices Tachycardia, Suitable climatic conditions Edema Absence of policy and institutional capacity Nausea, Lack of awareness Headache, Disease is more sever in Rash Patients with Hepatitis B Ascites Persons with Malnutrition  Made with Xodo PDF Reader and Editor What is Aflatoxins Geographic correlation  Made with Xodo PDF Reader and Editor What is Aflatoxins Impact on Public Health Health complications Fatal at high concentrations outbreaks in East Africa where hundreds of persons died due to aflatoxin poisoning (Probst et al., 2007) Major source for liver cancer (WHO, 1988; 2002) children slow growth and underweight Suppression of human immune system 4.5 billion people chronically exposed (WHO, 2004)  Made with Xodo PDF Reader and Editor What is Aflatoxins Impact on Economy Health care and treatment cost for 4.5 billion people that chronically exposed Around 25 % of global grown cereals per year become contaminated by aflatoxins Loss in animal wealth. Economy disturbance during outbreaks High cost for monitoring programs and management strategies.  Made with Xodo PDF Reader and Editor What is Aflatoxins Metabolism and Toxicity Mechanisms As the liver is a lipophilic organ, it stores and concentrates all compounds carried by blood stream (i.e. mycotoxins) in the hepatocytes With a long exposure time, may transform themselves into a cancer cell line. Aflatoxin (the parent compound) is not metabolic bioactive compound by itself Toxicity occurred inside the target organism after the bioactivation of the parent compound. Bioactivation occurred by the conversion of the bio-inactive Aflatoxins to the reactive 8,9-epoxide form (also known as aflatoxin-2,3 epoxide).  Made with Xodo PDF Reader and Editor What is Aflatoxins Metabolism and Toxicity Mechanisms Epoxide form binds to both DNA and protein by cytochrome P450 enzymes to form adducts. Aflatoxin B1-DNA adducts can result in GC to TA transversions. Transversion is the point of mutation in DNA in which (two ring) purine (A or G) is changed for a (one ring) pyrimidine (T or C), or vice versa. Consequently, loss of cellular control occurred. The Enzyme system of Glutathione S-transferase can Neutralizes the active epoxide form.  Made with Xodo PDF Reader and Editor What is Aflatoxins Metabolism and Toxicity Mechanisms A reactive glutathione S- transferase system in the cytosol and microsomes catalyzes the conjugation of activated aflatoxins with reduced glutathione leading to the excretion of aflatoxins  Made with Xodo PDF Reader and Editor What is Aflatoxins Protection strategies Three main strategies to counteract aflatoxins hazards Preharvest Prevention strategy Postharvest Prevention strategy Decontamination and Detoxification  Made with Xodo PDF Reader and Editor What is Aflatoxins Prevention of Aflatoxin Formation Pre-harvest Resistant varieties (if practicable) Improve farming practices (crop rotation, irrigation) Insect management Harvest ripe crops quickly Minimize kernel damage during harvesting  Made with Xodo PDF Reader and Editor What is Aflatoxins Prevention of Aflatoxin Formation Post-harvest Clean and dry corn to lt15 moisture Proper crop/food storage Store facility with temperature-moisture control Do not mix animal feed Insect and pest management  Made with Xodo PDF Reader and Editor What is Aflatoxins Decontamination and Detoxification Strategies Physical separation Food/Feed processing Fermentation Thermal processing over 100ºC in wet condition and over 360ºC in dry condition Diverting contaminated grain to industrial uses with high precautions and control and monitoring processes. Chemical inactivation Ammonia Sodium bisulfite  Made with Xodo PDF Reader and Editor What is Aflatoxins Regulations USFDA Regulatory Levels for Total Aflatoxins (ppb or µg/Kg) All products for humans, except milk 20 Milk (Aflatoxin M1) 0.5 Corn for immature animals and dairy cattle 20 Corn for breeding beef cattle, mature poultry 100 Corn for finishing beef cattle 300 Cottonseed meal (as feed ingredient) 300 All other feedstuffs 20 Saudi-FDA is following the USFDA as it is the most reasonable conservative regulations  Made with Xodo PDF Reader and Editor Thank you