Commercially available rice grains in Thailand were examined to isolate the monoverticillate Penicillium species responsible for toxic yellowed rice. Penicillium species were obtained from seven out of 10 rice samples tested. Among them, one Penicillium citreonigrum isolate and six Penicillium brocae isolates were morphologically identified. The P. citreonigrum isolate produced the mycotoxin citreoviridin on a yeast extract sucrose broth medium. Mycotoxin surveys showed that citreoviridin was not detected in any samples, but one out of 10 rice samples tested was positive for aflatoxin B1 at a level of 5.9 μg/kg. An Ames test revealed that methanol extracts from rice grains inoculated with selected P. brocae isolates were positive for strains TA100 and YG7108 of Salmonella typhimurium, suggesting the presence of base-pair substitution and DNA alkylation mutagens. Our data obtained here demonstrated that aflatoxin B1 and toxic P. citreonigrum were present on domestic rice grains in Thailand, although limited samples were tested. Penicillium brocae, which may produce mutagenic metabolites, was isolated for the first time from the surface of Thai rice grains.

Citreoviridin (CTVD), a mycotoxin called yellow rice toxin, is reported to be related to acute cardiac beriberi; however, its toxicokinetics remain unclear. The present study elucidated the toxicokinetics through in vivo experiments in swine and predicted the human toxicokinetics by comparing the findings to those from in vitro experiments. In vivo experiments revealed the high bioavailability of CTVD (116.4%) in swine. An intestinal permeability study using Caco-2 cells to estimate the toxicokinetics in humans showed that CTVD has a high permeability coefficient. When CTVD was incubated with hepatic S9 fraction from swine and humans, hydroxylation and methylation, desaturation, and dihydroxylation derivatives were produced as the predominant metabolites. The levels of these products produced using human S9 were higher than those obtained swine S9, while CTVD glucuronide was produced slowly in human S9 in comparison to swine S9. Furthermore, the elimination of CTVD by human S9 was significantly more rapid in comparison to that by swine S9. These results suggest that CTVD is easily absorbed in swine and that it remains in the body where it is slowly metabolized. In contrast, the absorption of CTVD in humans would be the same as that in swine, although its elimination would be faster.

27Citreoviridin (CIT) produced by Penicillium citreonigrum as a secondary metabolite is a 28 yellow rice toxin that has been reported to be related to acute cardiac beriberi; however, its 29 toxicokinetics remain unclear. The present study elucidated the toxicokinetics through swine 30 in vivo experiments and predicted the human toxicokinetics by a comparison with findings 31 from in vitro experiments. Swine in vivo experiments revealed that CIT had a high 32 bioavailability of more than 90%. In addition, it showed a large volume of distribution (1.005 33 ± 0.195 L/kg) and long elimination half-life (17.7 ± 3.3 h) in intravenous. These results 34suggested the possibility of a slow metabolism of CIT. An intestinal permeability study using 35 the human cell line Caco-2 showed that CIT had a high permeability coefficient, suggesting it 36 would be easily absorbed in human intestine, similar to its absorption in swine. The 37 metabolite profiles were investigated by incubating CIT with S9 obtained from swine and 38 humans. Hydroxylation, methylation, desaturation and dihydroxylation derivatives were 39 detected as the predominant metabolites, and CIT glucuronide was produced slowly 40 compared with above metabolites. A comparison of the peak area ratios obtained using 41 quadrupole time-of-flight mass spectrometer showed that the rates of all of the main 42 metabolites except for glucuronide produced using human S9 were three-fold higher than 3 43 those obtained using swine S9. Furthermore, the elimination of CIT using human S9 was 44 more rapid than when using swine S9, indicating that CIT would be metabolized faster in 45 humans than in swine. These in vivo results suggested that CIT is easily absorbed in swine 46 and persists in the body for a long duration. Furthermore, the CIT metabolism appeared to be 47 faster in human liver than in swine liver in vitro, although the bioavailability of CIT was 48 predicted to be similarly high in humans as in swine. 49 4 50 Introduction 51 Citreoviridin (CIT) is a mycotoxin produced by Penicillium citreonigrum, Aspergillus terreus 52 and Eupenicillium ochrosalmoneum as a secondary metabolite [1]. Because CIT is mainly 53 found as a contaminant in rice, it is a serious problem in countries where people consume rice 54 as a staple food. 55 In 2006, an outbreak of beriberi occurred in Brazil, with a reported 40 of 1207 cases 56 dying [2]. Since P. citreonigrum and CIT were detected in rice samples, it was suspected that 57 rice was the causative food of beriberi in the area [3]. CIT contaminating yellow rice has 58 been reported to be related to acute cardiac beriberi (so-called "Shoshin-kakke") [4]. 59 Uraguchi et al. discovered that an ethanol extract from rice infected with P. citreo-viride 60 Biourge (current P. citreonigrum) caused symptoms in mice similar to acute cardiac beriberi 61 in humans. In addition, Ueno et al. reported that the isolate from P. citreo-viride BIourge 62 which was isolated by Sakabe et al. was chemically identical with CIT [4][5]. Although 63 "Shoshin...