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The present study was undertaken to evaluate the role of individual flavanols in the antimutagenic potential of green tea. Aqueous extracts of green tea were fractionated into four fractions, each of which was fully defined with respect to its content of (-)-epigallocatechin gallate, (-)-epicatechin gallate, (-)-epigallocatechin, (-)-epicatechin and gallic acid. The ability of each fraction to antagonize the mutagenicity of four model mutagens, namely N-nitrosopyrrolidine, benzo(a)pyrene, 2-aminoanthracene and Glu-P-1 (2-amino-6-methyldipyrido[1,2-a: 3,2-d]imidazole), was investigated in the Ames test. No correlation could be established between any of the flavanols and antimutagenic potential. Similarly, no correlation was evident between the flavanol content of each fraction and its ability to inhibit CYP1A, as exemplified by the O-dealkylations of methoxy- and ethoxy-resorufin. Furthermore, no relationship could be established between CYP2B activity, as exemplified by the O-depentylation of pentoxyresorufin and the antimutagenic potential of green tea. Using a modified Ames test procedure, the ability of each tea fraction to scavenge the metabolically generated reactive intermediates of the model mutagens was investigated, this being an additional mechanism of the antimutagenic potential of green tea. Generally, fractions with high flavanol content were more effective scavengers. It is concluded that the contribution of flavanols to the antimutagenic activity of green tea is, at best, limited. ©1997 SCI

The mutagenicity of the basic fractions of fried beef patties, grilled hamburgers and grilled sausages was determined in the Ames test using activation systems (S9-mix) derived from untreated and Aroclor-pretreated rats and hamsters, and from rats pretreated with 3-methylcholanthrene or phenobarbitone. In order to indicate whether the mutagenic activity was due to the presence of thermally generated amino imidazo aza-arenes of the type previously identified in heated meat products (i.e. 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,4-dimethylimidazo-[4,5-f]quinoline (MeIQ) and 2-amino-3,8-dimethylimidazo[4,5-f]quin-oxaline), these compounds were assayed under the same conditions. The mutagenicity of the basic fractions of the cooked foods and of the three aza-arenes varied with the activation system used. The activation patterns of the basic fractions from fried beef and grilled sausages resembled that of IQ, whereas that of grilled hamburgers was more similar to that of MeIQ. Interestingly the total mutagenic activity of fried beef patties was greater than that of grilled hamburgers.

The results are reported of single-blind, medically supervised studies in volunteers of the association between the histamine content of mackerel and the incidence of scombrotoxicosis. Volunteers consumed 25 or 50 g of fresh or spoiled mackerel containing varying quantities of endogenous or added histamine. In one study the ability of HI and H2 histamine antagonists to modify symptoms was investigated. Objective parameters (pulse rate, skin temperature and peak expiratory flow rate) were recorded for 6 h, and subjective parameters (headache, flushing, oral tingling, visual disturbances, abdominal pain, nausea, palpitations, wheeziness, diarrhoea, flatulence, shivering and miscellaneous) for 24 h. No significant effects were observed, even with portions of spoiled mackerel containing 300 mg histamine, or mackerel from a batch which was reported to have been associated with an incident diagnosed as scombrotoxicosis. It is concluded that the precise combination of circumstances required to cause a scombrotoxic event were not reproduced in these studies, but it is tentatively concluded that histamine alone is unlikely to be the causative agent.

A review of the occurrence of nitrate in unprocessed foods showed that high concentrations are frequently found in vegetables. Spinach and lettuce commonly exceed 1000 parts/106 nitrate while, of the root vegetables, beets, turnips and radishes are similarly rich in nitrate. In general, the pulses contain less nitrate than leaf and root vegetables, and most fruits contain little nitrate. Fresh dairy produce is usually low in nitrate. Well waters in some agricultural areas may contain nitrate concentrations so high as to represent a hazard if used as the sole water source for infants, but municipal supplies in the UK rarely exceed 45 parts/106 although they frequently approach this. It is concluded that vegetables and water supplies make a greater contribution to the mean weekly nitrate intake than do cured meats. Nitrite concentrations are usually very low in fresh, undamaged fruits, vegetables and drinking water but adverse storage conditions can lead to (mainly microbial) reduction of nitrate. In these circumstances vegetables naturally rich in nitrate may accumulate nitrite at concentrations which can be toxic to infants.

In addition to the gastrointestinal effects described by El-Harith et al.,1 raw potato starch caused serious impairment of the net protein utilisation and the food efficiency values when fed to growing rats. The gross caecal hypertrophy accompanied by occurrence of mortality, caused by synthetic diets containing 71% raw potato starch, was not encountered when using any of the cereal starches—maize, wheat, sorghum, rice—or the tuber Cassava.