In vitro and in vivo metabolism of ochratoxin A: a comparative study using ultra-performance liquid chromatography-quadrupole/time-of-flight hybrid mass spectrometry

Abstract

Ochratoxin A (OTA) is a mycotoxin that frequently contaminates a wide variety of food and feedstuffs. The metabolism of OTA greatly affects fate and toxicity in humans and animals, because of its possible carcinogenic character (International Agency for Research on Cancer (IARC), group 2B). To completely characterize the metabolites of OTA, the metabolism of OTA in liver microsomes of rats, chickens, swine, goats, cows, and humans was investigated using ultra-performance liquid chromatography-quadrupole/time-of-flight hybrid mass spectrometry (UPLC-Q/TOF-MS). In addition, an in vivo comparative metabolism study of OTA was performed among rats and chickens after oral administration of OTA. As a result, a clear metabolic profile of OTA in different species was proposed, and a total of eight metabolites were identified, of which three hydroxylated metabolites at the phenylalanine moiety were discovered for the first time (preliminarily identified as 9'-OH-OTA, 7'-OH-OTA, and 5'-OH-OTA). Considerable amounts of 7'-OH-OTA were detected in different species' liver microsomes, especially in chickens and humans. Moreover, the metabolism of OTA in chickens was elucidated for the first time in the present study. The 7'-OH-OTA proved to be the main metabolite in vitro and in vivo in chickens. Furthermore, the 4(S)-OH-OTA isomer was the major one, and 4(R)-OH-OTA the minor metabolite in chickens, which was different from others where 4R was the major. OTA undergoes metabolism via three different pathways, namely hydroxylation, dechlorination, and conjugation. The proposed metabolic pathways of OTA in various species provide the scientific community useful data for the toxicological safety evaluation of OTA among different species, and will further facilitate the food safety evaluation of OTA.

Risk assessment of ochratoxin A in food

“…Whether dechlorination of OTA leading to formation of OTB, OTHQ and OTQ and associated GSH‐conjugates can also occur under physiological conditions is of key interest as this may indicate formation of reactive metabolic intermediates and may thus have a bearing on the question of OTA genotoxicity. OTB has been repeatedly reported as a minor metabolite of OTA (usually in the range of 1% of OTA) in vitro (El Adlouni et al., ; Faucet‐Marquis et al., ; Yang et al., ) (see Appendix E, Table E.1) and in vivo (Mally et al., ; Yang et al., ) (see Appendix E, Table E.2). However, because the OTA used in metabolic studies is invariably of fungal origin and only very rarely analysed for OTB, it is difficult to discriminate the OTB introduced as contaminant of OTA from OTB potentially arising from the metabolism of OTA.…”

Mycotoxin Biomarkers of Exposure: A Comprehensive Review

“…However, the amount of produced metabolites was species‐dependent. Human liver microsomes had a more noticeable amount of metabolites (>30%) compared to other species for similar OTA exposure (Yang et al., ), suggesting a larger catabolic capability to metabolize OTA through the liver. In human liver microsomes, and also from rat, swine, and goat, the main OTA‐metabolite was (4R)‐hydroxyochratoxin A (4(R)‐OH‐OTA), while its isomer (4S)‐hydroxyochratoxin A (4(S)‐OH‐OTA) was the most common metabolite in cows.…”

“…In human liver microsomes, and also from rat, swine, and goat, the main OTA‐metabolite was (4R)‐hydroxyochratoxin A (4(R)‐OH‐OTA), while its isomer (4S)‐hydroxyochratoxin A (4(S)‐OH‐OTA) was the most common metabolite in cows. 7‐hydroxyochratoxin A (7’‐OH‐OTA) was the most prevalent OTA metabolite in chickens (Yang et al., ), while 10‐hydroxyochratoxin A (10‐OH‐OTA) was the most important metabolite in rabbits (Størmer, Støren, Hansen, Pedersen, & Aasen, ). Aside from the most common metabolites mentioned above, other compounds have been identified with different concentrations depending on animal species (Table ).…”

“…Aside from the most common metabolites mentioned above, other compounds have been identified with different concentrations depending on animal species (Table ). It is worth to mention that OTB was prevailing with a larger concentration (>50%) in human microsomes than in other species, pointing out that humans had a large dechlorination capacity (Yang et al., ). Rat liver microsomes did not provide satisfying information, as more than 85% of OTA remained unmetabolized, hinting that OTA was not primarily metabolized by the liver (Han et al., ).…”

Unraveling the in vitro and in vivo metabolism of diacetoxyscirpenol in various animal species and human using ultrahigh-performance liquid chromatography-quadrupole/time-of-flight hybrid mass spectrometry

“…Hepatic microsomes were prepared from the homogenized livers of untreated animals (rats, chickens, swine, goats, and cows) by differential centrifugation, according to the procedure reported by Yang et al [26][27][28][29]. Microsomes and cytosol were frozen in liquid nitrogen, then stored at −80°C until use.…”