By Sheila Mulhern

XENOBIOTICS: AFLATOXINS

Aflatoxins• A naturally occurring mycotoxin which is toxic and among most known carcinogenic substances

•Mycotoxin: toxic secondary metabolite produced by fungi organisms • Produced by fungi that readily colonize crops; can produce many similar species of mycotoxins

• Products from four types of mold with two main types being : Aspergillus flavus and Aspergillus parasiticus

How Aflatoxins Cause Damage•Mutagenic and carcinogenic effects•Metabolites can intercalate (adds molecule or group between molecules) into DNA and alkylates bases (transfer alkyl group to other molecules) through its epoxide moiety (functional group)•Thought to cause gene mutation (p53 gene) needed to prevent cell cycle progression for DNA mutations (also called signaling apoptosis – programmed cell death)•Certain codons of p53 more susceptible to aflatoxin-mediated mutations

Aflatoxins• Common, found widespread in nature• Corn, cottonseed and peanuts are the crops most at risk. • Also commonly grows on beans, rice, tree nuts and wheat. It grows less often on other grains and nuts.

•Most often found when certain grains are grown under stressful conditions (drought)

• If animals are given feed contaminated with aflatoxins then aflatoxin mycotoxins can end up in milk, eggs and meat.

• Aflatoxin M1 and M, which are often found in cow's milk, are metabolites produced by animals which have eaten aflatoxins.

Types of Aflatoxins•Three main types

• Aflatoxins B: This group includes aflatoxin B1 and B2. Aflatoxin B1 is the most common aflatoxin, as well as the most toxic and carcinogenic.

• Aflatoxins G: This group includes aflatoxin G1 and aflatoxin G2

• Aflatoxins M: This group includes aflatoxins M1 and M2. These aflatoxins are metabolic products which are found in the urine and milk produced by animals which have been given feed with aflatoxins in it.

Aflatoxins•United States limits the level of aflatoxins to under 20 parts per billion in food and specifies that the aflatoxins must be below 0.5 parts per billion in milk.

• Chemical processes are used to remove aflatoxins in foods such as nuts, corn, grains and milk but most foods do still contain very small amounts of aflatoxins 

• LD50 rate (the dosage level that causes 50% of a group to die) for animals is between 0.5 and 10 mg/kg of weight

Aflatoxins• In the recent news:•Aug, 2012: Corn Belt Drought threatens crops and aflatoxins found but too soon to tell extent of damage•Dec, 2011: Dog food recalls from FDA: Iams, Arrow Brand

•How to treat•Recent Exposure: • Urine test for AFB1-guanine adduct• Short half-life for metabolite so only used for possible exposure in past 24 hours

•Prolonged or past exposure• Measure AFB1-albumin adduct level in blood serum

Past Research•Aflatoxins were confirmed 20 years ago as potent liver carcinogenics

•Use aflatoxin exposure biomarkers in new research for growth faltering and immune suppression

•Studies in underdeveloped areas

•Also used to assess the effectiveness of intervention strategies

Case Study: Introduction• Inhibitory effect of the essential oil of Curcuma longa L. and curcumin on aflatoxin production by Aspergillus flavus Link• Turmeric,Curcuma longa L., is a native plant of Southeast Asia

and has antimicrobial, antioxidant and antifungal properties • Tested various concentrations (from 0.01% to 5.0% ) with

mycotoxin production• To analyze aflatoxin levels used thin layer chromatography

(TLC), ran tests 4 times

Case Study: Analysis• Fig. 1. Thin layer chromatography of aflatoxin production by Aspergillus flavus L. isolates that were cultured with theessentialoil of Curcuma longa L. (0.01%, 0.1%, 0.5% and 1.0%) and AFB1, AFB2, AFG1 and AFG2 standards (P)

Case Study: Results• Both essential oil and curcumin inhibited production of aflatoxins• The 0.5% level had a greater than 96% inhibitory effect • Levels of aflatoxin B1 (AFB1) production were 1.0 and 42.7 μg/mL, respectively, for the samples treated with the essentialoil of C. longa L. and curcumin at a concentration of 0.5%. • Inhibitory effect of essential oil: • Decrease damaging effect by inhibiting binding effect to DNA• Protect cells from aflatoxins reactive oxygen• Conclusion:  Study demonstrated that 0.5% of the essentialoil of C. longa inhibited 99.9% and 99.6% AFB1 and AFB2production by A. flavus. Additional research is needed to determine its potential usefulness in fungal control programs.

References• The role of biomarkers in evaluating human health concerns from fungal contaminants in food. Turner, Flannery, et al. Nutrition Research Reviews. Maryland Institute for Applied Environmental Health, School of Public Health, University of Maryland, College Park. 2012, http://www.ncbi.nlm.nih.gov/pubmed/22651937• http://www.medterms.com/script/main/art.asp?articlekey=10796• http://articles.chicagotribune.com/2012-08-29/business/chi-latest-thr

eat-to-droughtstricken-corn-aflatoxin-20120829_1_aflatoxin-contamination-corn-harvest-corn-samples • http://www.foodsafetynews.com/2011/12/more-aflatoxin-related-dog-

food-recalls-revealed/ • Case study:

http://www.sciencedirect.com/science/article/pii/S0308814612012770