Bioavailability, metabolism, and excretion of a complex Alternaria culture extract versus altertoxin II: a comparative study in rats

Abstract

Despite the frequent infection of agricultural crops by Alternaria spp., their toxic secondary metabolites and potential food contaminants lack comprehensive metabolic characterization. In this study, we investigated their bioavailability, metabolism, and excretion in vivo. A complex Alternaria culture extract (50 mg/kg body weight) containing 11 known toxins and the isolated lead toxin altertoxin II (0.7 mg/kg body weight) were administered per gavage to groups of 14 Sprague Dawley rats each. After 3 h and 24 h, plasma, urine and feces were collected to determine toxin recoveries. For reliable quantitation, an LC-MS/MS method for the simultaneous detection of 20 Alternaria toxins and metabolites was developed and optimized for either biological matrix. The obtained results demonstrated efficient excretion of alternariol (AOH) and its monomethyl ether (AME) via feces (> 89%) and urine (> 2.6%) after 24 h, while the majority of tenuazonic acid was recovered in urine (20 and 87% after 3 and 24 h, respectively). Moreover, modified forms of AOH and AME were identified in urine and fecal samples confirming both, mammalian phase-I (4-hydroxy-AOH) and phase-II (sulfates) biotransformation in vivo. Despite the comparably high doses, perylene quinones were recovered only at very low levels (altertoxin I, alterperylenol, < 0.06% in urine and plasma, < 5% in feces) or not at all (highly genotoxic, epoxide-holding altertoxin II, stemphyltoxin III). Interestingly, altertoxin I was detected in all matrices of rats receiving altertoxin II and suggests enzymatic de-epoxidation in vivo. In conclusion, the present study contributes valuable information to advance our understanding of the emerging Alternaria mycotoxins and their relevance on food safety.

Alternaria alternata Toxins Synergistically Activate the Aryl Hydrocarbon Receptor Pathway In Vitro

“…Moreover, ATX-I is described as a secondary metabolite of Alternaria spp. itself, but was further suggested to be a metabolite of ATX-II in vivo , in vitro and in planta [ 30 , 64 , 74 ]. Therefore, the role of ATX-II and ATX-I in the context of combinatory bioactive mechanisms within the plethora of Alternaria toxins should not be underestimated.…”

“…Both ATX-I and ATX-II were reported to possess mutagenic activity in S. typhimurium , with a substantially lower potency for ATX-I [ 5 ], while the nitrosylation of ATX-I in turn was found to increase mutagenicity against two strains of Salmonella [ 29 ]. Considering a previous report of ATX-II to be de-epoxidized yielding ATX-I in vivo [ 30 ], both substances should be implemented in toxicological investigations for a proper risk assessment.…”

Gut microbiota and undigested food constituents modify toxin composition and suppress the genotoxicity of a naturally occurring mixture of Alternaria toxins in vitro

“…Reference materials of Alternaria toxins were obtained from several suppliers or were kindly provided by other researchers. For details, the interested reader may refer to Puntscher et al ( 2019a ).…”

Microfiltration results in the loss of analytes and affects the in vitro genotoxicity of a complex mixture of Alternaria toxins

“…FPG was bought from New England Biolabs (Frankfurt, Germany). A complete extract (CE) originating from rice infected with the Alternaria alternata strain DSM 62010 was acquired as stated in Puntscher et al ( 2019c ) and Puntscher et al ( 2019a ).…”

“…(For the detailed gradient, as well as mass transitions, please see Puntscher et al ( 2018 ).) The mass transitions of AST can be found at Puntscher et al ( 2019a ).…”