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65 Years On from Aflatoxin Discovery—a Themed Issue in Honor...
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65 Years On from Aflatoxin Discovery—a Themed Issue in Honor of Professor John D. Groopman

A special issue of Toxins (ISSN 2072-6651). This special issue belongs to the section "Mycotoxins".

Deadline for manuscript submissions: 31 October 2025 | Viewed by 4513

Special Issue Editors

Prof. Dr. David L. Eaton

E-Mail Website
Guest Editor
Professor Emeritus, Department Environmental Occupational Health Sciences, School of Public Health, University of Washington, Seattle, WA 98195, USA
Interests: biochemical toxicology; aflatoxin carcinogenesis; glutathione-mediated biotransformation of toxic chemicals.
Prof. Dr. Thomas W. Kensler

E-Mail Website
Guest Editor
Professor Emeritus, Department of Environmental Health and Engineering, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205，USA
Interests: chemical carcinogenesis; aflatoxin; chemoprevention; hepatocarcinogenesis; reactive oxygen; Keap1; Nrf2; sulforaphane; triterpenoids; biomarkers; clinical trials

Special Issue Information

Dear Colleagues,

Aflatoxins are a group of fungal metabolites produced primarily by certain strains of the common mold, Aspergillus; these include, in particular, A. flavus and A. parasiticus. Aflatoxins were discovered in the 1960s following the outbreak of liver toxicity in turkeys (so-called ‘Turkey X disease) and a nearly simultaneous outbreak of normally rare hepatocellular tumors in hatchery-reared rainbow trout, where the diets of both species were contaminated with Aspergillus. One specific form, Aflatoxin B1 (AFB1), is now widely recognized throughout the world to be one of the most potent known human liver carcinogens. In addition to cancer, hepatotoxicity, immune suppression, stunting, and delayed development have been reported to be aflatoxin-associated outcomes in humans and animals. Aflatoxin is certainly the most researched of the mycotoxins. Current inquiries seek to better understand the mechanistic underpinnings of these toxicities in human and veterinary settings, the factors leading to the elaboration of aflatoxins in foods and feeds, along with the likely impact of climate change on these processes and their distribution across the globe. Collectively, this knowledge will better inform risk analyses that aim to guide regulatory and interventional strategies to mitigate exposures and their sequalae. The development of biomarkers of internal dose (urinary metabolites and aflatoxin–albumin adducts) and early biological effects (aflatoxin-DNA adducts in urine and tissue), pioneered by Professor John D. Groopman, has contributed greatly to our understanding of the global public health consequences of aflatoxin contamination. This Special Issue of Toxins welcomes contributions that further refine our understanding across all aspects of aflatoxin toxicology.

Prof. Dr. David L. Eaton
Prof. Dr. Thomas W. Kensler
Guest Editors

Manuscript Submission Information

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Keywords

  • epidemiology
  • risk assessment
  • mechanisms
  • chemical carcinogenesis
  • hepatotoxicity
  • dietary exposure
  • biomarkers

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Published Papers (4 papers)

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Research

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23 pages, 6311 KiB  
Article
Green-Engineered Montmorillonite Clays for the Adsorption, Detoxification, and Mitigation of Aflatoxin B1 Toxicity
by Johnson O. Oladele, Xenophon Xenophontos, Gustavo M. Elizondo III, Yash Daasari, Meichen Wang, Phanourios Tamamis, Natalie M. Johnson and Timothy D. Phillips
Toxins 2025, 17(3), 131; https://doi.org/10.3390/toxins17030131 - 11 Mar 2025
Viewed by 563
Abstract
Dietary and environmental exposure to aflatoxins via contaminated food items can pose major health challenges to both humans and animals. Studies have reported the coexistence of aflatoxins and other environmental toxins. This emphasizes the urgent need for efficient and effective mitigation strategies for [...] Read more.
Dietary and environmental exposure to aflatoxins via contaminated food items can pose major health challenges to both humans and animals. Studies have reported the coexistence of aflatoxins and other environmental toxins. This emphasizes the urgent need for efficient and effective mitigation strategies for aflatoxins. Previous reports from our laboratory have demonstrated the potency of the green-engineered clays (GECs) on ochratoxin and other toxic chemicals. Therefore, this study sought to investigate the binding and detoxification potential of chlorophyll (CMCH and SMCH) and chlorophyllin (CMCHin and SMCHin)-amended montmorillonite clays for aflatoxin B1 (AFB1). In addition to analyzing binding metrics including affinity, capacity, free energy, and enthalpy, the sorption mechanisms of AFB1 onto the surfaces of engineered clays were also investigated. Computational and experimental studies were performed to validate the efficacy and safety of the clays. CMCH showed the highest binding capacity (Qmax) of 0.43 mol/kg compared to the parent clays CM (0.34 mol/kg) and SM (0.32 mol/kg). Interestingly, there were no significant changes in the binding capacity of the clays at pH2 and pH6, suggesting that the clays can bind to AFB1 throughout the gastrointestinal track. In silico investigations employing molecular dynamics simulations also demonstrated that CMCH enhanced AFB1 binding as compared to parent clay and predicted hydrophobic interactions as the main mode of interaction between the AFB1 and CMCH. This was corroborated by the kinetic results which indicated that the interaction was best defined by chemosorption with favorable thermodynamics and Gibbs free energy (∆G) being negative. In vitro experiments in Hep G2 cells showed that clay treatment mitigated AFB1-induced cytotoxicity, with the exception of 0.5% (w/v) SMCH. Finally, the in vivo results validated the protection of all the clays against AFB1-induced toxicities in Hydra vulgaris. This study showed that these clays significantly detoxified AFB1 (86% to 100%) and provided complete protection at levels as low as 0.1%, suggesting that they may be used as AFB1 binders in feed and food. Full article
(This article belongs to the Special Issue 65 Years On from Aflatoxin Discovery—a Themed Issue in Honor of Professor John D. Groopman)
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18 pages, 3357 KiB  
Article
Structurally Similar Mycotoxins Aflatoxin B1 and Sterigmatocystin Trigger Different and Distinctive High-Resolution Mutational Spectra in Mammalian Cells
by Pennapa Thongararm, Marisa Chancharoen, Nutchapong Suwanwong, Somsak Ruchirawat, Mathuros Ruchirawat, Bogdan I. Fedeles, Robert G. Croy and John M. Essigmann
Toxins 2025, 17(3), 112; https://doi.org/10.3390/toxins17030112 - 27 Feb 2025
Viewed by 573
Abstract
Aflatoxin B1 (AFB1) and sterigmatocystin (ST) are mycotoxins that pose significant threats to human and animal health owing to their mutagenic, carcinogenic, and toxic properties. They are structurally similar and widely believed to exert their biological effects via the generation [...] Read more.
Aflatoxin B1 (AFB1) and sterigmatocystin (ST) are mycotoxins that pose significant threats to human and animal health owing to their mutagenic, carcinogenic, and toxic properties. They are structurally similar and widely believed to exert their biological effects via the generation of DNA-damaging epoxides at their respective terminal furan rings. Despite structural identity in the warhead portion of each toxin, this work shows that distal parts of each molecule are responsible for the distinctive mutational fingerprints seen in gptΔ C57BL/6J mouse embryo fibroblasts (MEFs). The two toxins differ structurally in the puckered cyclopentenone ring of AFB1 and in the planar xanthone functionality of ST. While both toxins mainly induce GC→TA mutations, the aforementioned differences in structure apparently trigger unique patterns of mutations, as revealed by high-resolution duplex sequencing of MEF genomes. AFB1 is more mutagenic than ST and displays its transversion mutations in a pattern with primary and secondary hotspots (underscored) in 5′-CGC-3′ and 5′-CGG-3′ contexts, respectively. ST displays a modest 5′-CGG-3′ hotspot while its other GC→TA transversions are more uniformly distributed in a pattern resembling established oxidative stress mutational spectra. This research delineates the mutational spectra of AFB1 and ST, establishing these patterns as possible early-onset biomarkers of exposure. Full article
(This article belongs to the Special Issue 65 Years On from Aflatoxin Discovery—a Themed Issue in Honor of Professor John D. Groopman)
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Review

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44 pages, 3456 KiB  
Review
Species Differences in the Biotransformation of Aflatoxin B1: Primary Determinants of Relative Carcinogenic Potency in Different Animal Species
by David L. Eaton, David E. Williams and Roger A. Coulombe
Toxins 2025, 17(1), 30; https://doi.org/10.3390/toxins17010030 - 9 Jan 2025
Cited by 4 | Viewed by 1345
Abstract
It has been known since the early days of the discovery of aflatoxin B1 (AFB1) that there were large species differences in susceptibility to AFB1. It was also evident early on that AFB1 itself was not toxic but required bioactivation to a reactive [...] Read more.
It has been known since the early days of the discovery of aflatoxin B1 (AFB1) that there were large species differences in susceptibility to AFB1. It was also evident early on that AFB1 itself was not toxic but required bioactivation to a reactive form. Over the past 60 years there have been thousands of studies to delineate the role of ~10 specific biotransformation pathways of AFB1, both phase I (oxidation, reduction) and phase II (hydrolysis, conjugation, secondary oxidations, and reductions of phase I metabolites). This review provides a historical context and substantive analysis of each of these pathways as contributors to species differences in AFB1 hepatoxicity and carcinogenicity. Since the discovery of AFB1 as the toxic contaminant in groundnut meal that led to Turkey X diseases in 1960, there have been over 15,000 publications related to aflatoxins, of which nearly 8000 have addressed the significance of biotransformation (metabolism, in the older literature) of AFB1. While it is impossible to give justice to all of these studies, this review provides a historical perspective on the major discoveries related to species differences in the biotransformation of AFB1 and sets the stage for discussion of other papers in this Special Issue of the important role that AFB1 metabolites have played as biomarkers of exposure and effect in thousands of human studies on the toxic effects of aflatoxins. Dr. John Groopman has played a leading role in every step of the way—from initial laboratory studies on specific AFB1 metabolites to the application of molecular biomarkers in epidemiological studies associating dietary AFB1 exposure with liver cancer, and the design and conduct of chemoprevention clinical trials to reduce cancer risk from unavoidable aflatoxin exposures by alteration of specific AFB1 biotransformation pathways. This article is written in honor of Dr. Groopman’s many contributions in this area. Full article
(This article belongs to the Special Issue 65 Years On from Aflatoxin Discovery—a Themed Issue in Honor of Professor John D. Groopman)
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14 pages, 2094 KiB  
Review
65 Years on—Aflatoxin Biomarkers Blossoming: Whither Next?
by Thomas W. Kensler and David L. Eaton
Toxins 2024, 16(11), 496; https://doi.org/10.3390/toxins16110496 - 18 Nov 2024
Cited by 4 | Viewed by 1344
Abstract
Aflatoxins are mycotoxins produced by Aspergillus flavus and several other related organisms and are common contaminants of numerous grains and nuts, especially maize (corn) and peanuts. Although, undoubtedly, aflatoxins have been present in the food of humans for millennia, their toxic effects were [...] Read more.
Aflatoxins are mycotoxins produced by Aspergillus flavus and several other related organisms and are common contaminants of numerous grains and nuts, especially maize (corn) and peanuts. Although, undoubtedly, aflatoxins have been present in the food of humans for millennia, their toxic effects were not discovered until 1960, first becoming evident as a non-infectious outbreak of poisoning of turkeys (Turkey X disease) arising from contaminated groundnut meal. The elucidation of specific chemical structures in 1963 led to the rapid characterization of aflatoxins as among the most potent chemical carcinogens of natural origin ever discovered. As a frontispiece to the Special Issue “65 Years on from Aflatoxin Discovery—A Themed Issue in Honor of Professor John D. Groopman”, we highlight many of Professor Groopman’s important contributions utilizing urinary (aflatoxin–N7–guanine) and, especially, serum (aflatoxin–albumin adducts) biomarkers; this work focused on over 40+ years of the development of analytical methods to measure biomarkers of aflatoxin exposure and their application in experimental and clinical studies. Collectively, this work serves as a template for using chemical-specific biomarkers as key tools to probe ‘exposure–disease relationships’—in this instance, dietary aflatoxins and liver cancer. New approaches to measuring carcinogen biomarkers will build upon this ‘aflatoxin paradigm’ to inform the public health implications of diverse exposures around the world. Full article
(This article belongs to the Special Issue 65 Years On from Aflatoxin Discovery—a Themed Issue in Honor of Professor John D. Groopman)
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