J. Le Bars

Characterization of monascidin A from Monascus as citrinin

Following our investigations on red pigments and monascidin co-production by Monascus species, the antibiotic called monascidin A was characterized as citrinin. Evidence was given by qualitative methods, mass spectra and NMR. Citrinin, a nephrotoxic agent was produced both by Monascus purpureus and Monascus ruber, either in submerged culture of concentrations of 270 and 340 mg/l, respectively, or in solid state culture of concentration of 100 and 300 mg/kg dried matter, respectively. Since citrinin is a toxic product, it is essential that the production of red pigments as food additives from Monascus spp. avoid the occurrence of citrinin.

In vitro effect of diacetoxyscirpenol and deoxynivalenol on microbicidal activity of murine peritoneal macrophages

Diacetoxyscirpenol and deoxynivalenol, two trichothecene mycotoxins shown previously to exert immunosuppressive effects on the immune system were examined for their in vitro effects on some functions of murine peritoneal macrophages. The cells were pre-incubated for 4 hr with the mycotoxin concentrations of 0.1 ng/ml–1 μg/ml. At concentrations that did not affect the cell viability (Specific Lactate Dehydrogenase test), diacetoxyscirpenol and deoxynivalenol suppress microbicidal activity of phagocytic cells. The diacetoxyscirpenol concentrations, which reduce phagocytosis (2ng/ml), microbicidal activity (1 ng/ml), superoxide anion production (1 ng/ml) and phagosome-lysosome fusion (0.1 ng/ml), indicate that the inhibition of killing mechanism arise from both oxidative and non-oxidative pathways. Phagocytosis, microbicidal activity and superoxide anion production are inhibited by deoxynivalenol at 1 ng/ml whereas phagosome-lysosome fusion is reduce above 100 ng/ml. These results suggest that microbicidal activity inhibition by deoxynivalenol did not depend on non-oxidative pathway (phagosome-lysosome fusion) impairment.

Evaluation of a fluorodensitometric method for analysis of ergosterol as a fungal marker in compound feeds

Ergosterol is the principal sterol of fungi and plays an essential role as a component of the cell membrane and other cell constituents. This molecule is considered a good marker of fungal contamination in foods and feeds. This paper reports a rapid and sensitive method to test ergosterol content in compound feeds based on fluorodensitometry after thin-layer chromatography (TLC) separation. This method involves a thermal treatment of TLC plates that leads to the formation of a highly fluorescent ergosterol derivative. Such a dosage allows ergosterol testing in any naturally contaminated samples (limit of detection: 1 ppm of ergosterol) and gives results in close agreement with high-pressure liquid chromatography determination. Moreover, values obtained on mixed feeds for animals at different steps of fungal contamination are linked to quantitative development of storage fungi, evaluated by mycological technique, reinforcing the interest of a rapid method for measuring this fungal marker.

Production of aflatoxin B1 by Aspergillus ruber THOM and CHURCH.

Production of aflatoxins by Aspergillus ruber THOM and CHURCH was first reported by KULIK and HOLADAY (1967), although these results have lacked confirmation. In this paper we provide evidence that this fungal strain produces aflatoxins. This finding has implications for food hygiene, especially in countries where such moulds are used in the preparation of foodstuffs.

Comparative incidence of oral ochratoxicosis and aflatoxicosis on the activity of drug-metabolizing enzymes in rat liver

Mycotoxicosis has been produced in the rat by daily oral administrations of ochratoxin A (1.5 mg/kg/day) or aflatoxin B1 (1 mg/kg/day). Hepatic microsomal cytochrome P-450 and b5 contents and many phase I and II biotransformation systems have been measured in the course of ochratoxicosis (4 to 15 dosings) and aflatoxicosis (1 to 8 dosings). In case of ochratoxicosis, decreases in cytochrome P-450 level, aminopyrine demethylase and aniline hydroxylase activities were observed in rats receiving 15 administrations of the toxin. Aflatoxicosis induced more severe decreases in cytochrome P-450, aminopyrine demethylase and ethoxycoumarin deethylase following 8 daily gavages. In the two studies, there was no significant change in activities of liver phase II biotransformation enzymes.

Mycotoxigenesis in Grains Application to Mycotoxic Prevention in Coffee

Numerous fungal species may develop all along the food chain, from the plant in the fields during processing steps and storage down to consumer’s plate or cup. Fungal development in alimentary substrates can lead to several detrimental effects: (i) alterations of aspect and technological properties, (ii) modification of nutritive value, (iii) impairment of organoleptic features, (iv) production of toxic compounds. In this regard, it would be important to understand the general mechanisms and conditions conducive to mycotoxic contamination in foods in order to contribute to a logical prevention.

Correlation of desensitisation of platelet activating factor (PAF) receptors with intensity of inflammation and intestinal PAF content during experimental ileitis in guinea pig

Aim—To determine the kinetics of platelet activating factor (PAF) and prostaglandin E2 (PGE2) receptor desensitisation during intestinal inflammation induced by trinitrobenzenesulphonic acid (TNB) instillation and to study the relation between receptor regulation, inflammatory lesions, and PAF content of the gut wall. Methods—Receptor desensitisation was assessed on isolated smooth muscle cells from the circular layer. PAF content of the intestinal wall was determined by thin layer chromatography and radioimmunoassay. Results—After an acute inflammatory phase on day 1, subacute changes appeared in TNB instilled ileum, with a maximal intensity on day 6. In control animals, PAF 10 nM and PGE2 10 nM provoked a maximal contraction in the range of 24% of cell shortening. On days 1 and 3 after intestinal instillation of TNB, PAF induced contraction was not altered whereas the effect of PGE2 was progressively desensitised (2 logM rightward shift of its concentration-response curve: Cmax = 1 μM; p<0.01). Between days 4 and 6, the concentration-response curve of PGE2 shifted by only 1 logM (p<0.05) whereas the curve of PAF induced contraction shifted by 2 logM (Cmax = 1 μM; p<0.01). The PAF content of the ileal wall was maximal between days 3 and 5 (300 ng/mg tissue). On days 10 and 15, PAF and PGE2 induced contractions were similar to those observed on day 1, and PAF content returned to basal. Conclusion—Inflammation induced by TNB instillation triggers PAF and PGE2 receptor desensitisation; this is dependent on the duration of inflammation and correlates with PAF content in the ileum. This receptor desensitisation may play a protective role by preventing overstimulation of intestinal smooth muscle cells.

Ecotoxinogenesis of Pithomyces chartarum

Facial eczema is a hepatogenous photosensitivity mycotoxicosis resulting from sporidesmin ingestion. The morphological characters of toxigenic strains of P. chartarum are reported and the effect of temperature on growth and mycotoxin production are studied. The temperature range for which there is an actual risk of toxin accumulation (20-25 degrees C) is much narrower than for an appreciable growth (5-30 degrees C).