312

Mutagens in water: importance of moderately hydrophilic compounds in relation to water-treatment processes

All samples of organic compounds isolated in 1981 from water of the rivers Rhine and Meuse and lake IJssel were found to be mutagenic in the Ames test with strain TA98. The organics were isolated by adsorption on XAD-4, subsequently at pH 7 (lipophilic compounds) and at pH 2 (moderately hydrophilic compounds). In order to achieve optimal adsorption in particular of moderately hydrophilic compounds, the ratio between sample size and XAD bed volume must not exceed 10 3 and the flow must be one bed volume/min. The number of revertants in TA98 induced by XAD samples of Rhine water was about 1.5 times higher in neutral than in acid fractions. In samples from Meuse and lake IJssel the mutagenic effect was higher in acid than in neutral fractions. Promutagens were always present in the neutral fraction, but only incidentally in the acid fraction.

Treatment processes for drinking water preparation seem to be more successful in removing lipophilic than hydrophilic mutagens. In contrast to surface water, samples of treated water always displayed a higher mutagenic effect in acid than in neutral fractions. The mutagenic effect in the moderately hydrophilic fraction was partly associated with contaminations of surface water which were not removed by treatment, partly with newly formed mutagens related to ozonisation and chlorina- tion.

151

Van der Hoeven, J.C.M., F.M.H. Debets 1, I.M. Bruggeman, I.H.M. Van Erp. M. Rutgers and J.H. Koeman, Department of Toxicology, Agricultural University, De Dreijen 12, 6703 BC Wageningen, and 1 Notox Pathobiology Research, Haringvliet 100, 3011 TH Rotterdam (The Netherlands)

Evaluation of the genotoxicity of some mutagenic compounds of plant origin in in vitro mammalian test systems

Quercetin, emodin, safrole and heliotrine, 4 mutagens of plant origin, are known from the literature to give contradictory results in short-term genotoxicity assays. 2 of these compounds, safrole and heliotrine, are hepatocarcinogens. The data con- cerning the carcinogenicity of quercetin are conflicting. Emodin has not been tested for carcinogenicity, although it shows structural similarity with the carcinogens daunamycin and luteoskyrin. Both emodin and quercetin respond clearly positive in the Salmonella/microsome assay, whereas safrole and heliotrine do not. In this study we have investigated the genotoxicity of these compounds in V79 Chinese hamster cells (SCEs and HGPRT locus) and L5178Y mouse lymphoma cells (HGPRT and TK loci). With V79 cells 2 metabolic activation systems were used: liver homogenate and intact chick-embryo hepatocytes. In the presence and absence of liver homogenate all compounds responded negative. Only quercetin induced a

313

dose-related increase of TK-deficient mutants. Addition of liver homogenate abolished this effect. In a co-cultivation system of chick-embryo hepatocytes and V79 cells heliotrine responded positive. It induced a marked increase in the SCE frequency, whereas it was a weak inducer of forward mutations at the H G P RT locus. In conclusion positive results obtained in the Salmonella/microsome assay with emodin and quercetin do not correspond with the results obtained in this study with mammalian cell systems. The carcinogenicity of safrole seems not to be accompanied by a genotoxic effect in mammalian cells.

152

Van der Hoeven, J.C.M., W.J. Lagerweij, C.A.J.M. Meeuwissen, P.C.M. Hauwert, A.G.J. Voragen i and J.H. Koeman, Department of Toxicology and l Department of Food Science and Technology, Agricultural University, De Dreijen 12, 6703 BC Wageningen (The Netherlands)

Mutagens in food products of plant origin

To investigate the occurrence of natural mutagens in processed and unprocessed food, extracts of various food products of plant origin were tested in the Salmonella/microsome assay. In addition to liver homogenate also gut flora extracts were applied as a metabolising system. Freeze-dried products were extracted subse- quently with light petroleum, chloroform, methanol and water. Bracken fern, 3 types of bread and various cultivars of lettuce, rhubarb, spinach, paprika and string beans were studied.

The methanol extract of bracken responded positively after treatment at alkaline conditions (NaOH; pH > 5). This extract contains at least 2 different mutagens of unknown structure (no flavonoids). We have isolated one of these mutagens by means of HPLC. Identification procedures are now carried out.

All types of bread investigated contained mutagens, that could be recovered in acidic fractions. This in contrast to mutagens found in bread that, according to the literature, are recovered in basic fractions. In the present study a significantly increased number of revertants were induced by extracts from 74 mg bread crusts.

All vegetables tested, except spinach, did show mutagenic activities in the presence of gut flora extracts. Extracts of rhubarb also responded positive in the presence of liver homogenate. The mutagenic activity did show a marked inter- cultivar variation.

153

Van Kreijl, C.F., M. de Vries, H.J. van Kranen, H.J. Kool and E. de Greef, National Institute for Water Supply (NIWS), Postbox 150, 2260 AD Leidschendam (The Netherlands)