Determination of combined benzidine in FD&C Yellow No. 6 (Sunset Yellow FCF).

Samples from 67 manufactured lots of FD&C Yellow No. 6 (Sunset Yellow FCF; Colour Index No. 15985) were analysed for combined benzidine. These samples were selected from those submitted to the US Food and Drug Administration for certification between October 1991 and December 1992 by 13 dye distributors. Dithionite was used to reduce any combined benzidine present in the form of azo or disazo dyes to free benzidine. This reduction was followed by extraction, diazotization and coupling with 2-naphthol-3,6-disulfonic acid disodium salt (R salt). The total benzidine was quantified as benzidine-R salt disazo dye by HPLC with detection at 540 nm and a quantification limit of 10 ng benzidine/g FD&C Yellow No. 6. Of the 67 samples analysed, 34 were found to contain more than 10 ng combined benzidine/g. Of these, 30 samples were from one manufacturing company, including three of its subsidaries. The level of combined benzidine found ranged from 11 to 104 ng/g, except for one sample containing 941 ng/g.

Determination of combined benzidine in FD & C yellow no. 5 (tartrazine), using a highly sensitive analytical method.

53 samples of FD & C Yellow No. 5 (tartrazine; Colour Index No. 19140) were examined for combined benzidine. These samples, which represent separate lots from 12 dye distributors, were submitted to the US FDA for certification between 28 February 1990 and 27 June 1991. A method was developed to reduce the dye matrix with dithionite so that combined benzidine present in the form of azo or disazo dyes would be converted to free benzidine. Reduction was followed by extraction, diazotization and coupling with pyrazolone T, and the total benzidine present was quantitated as benzidine-pyrazolone T disazo dye (BZPT) by HPLC with detection at 500 nm. The limit of quantitation for benzidine in FD & C Yellow No. 5 by this method is 5 ng/g. 25 samples of FD & C Yellow No. 5 were found to contain 7-83 ng/g of combined benzidine that was released by dithionite reduction. 23 of these samples were from the same manufacturer. The identify of the BZPT from two FD & C Yellow No. 5 samples was confirmed by spectral analysis using HPLC with a photodiode array detector.

Evaluation of azo food dyes for mutagenicity and inhibition of mutagenicity by methods using Salmonella typhimurium.

The mutagenicity of 4 azo dyes (FD&C Yellow No. 5, FD&C Yellow No. 6, FD&C Red No. 40 and amaranth) that are widely used to color food has been evaluated. 4 different methods were used: (1) the standard Ames plate-incorporation assay performed directly on the dyes in the absence of S9 and in the presence of rat- or hamster-liver S9; (2) application of the standard plate assay to ether extracts of aqueous solutions of the dyes; (3) a variant of the standard assay, using hamster liver S9, preincubation, flavin mononucleotide (FMN) and other modifications designed to facilitate azo reduction; and (4) reduction of the dyes with sodium dithionite, followed by ether extraction and the standard plate assay. Assays that include chemical reduction (methods 3 and 4) were included because azo compounds ingested orally are reduced in the intestine with the release of free aromatic amines. No mutagenic activity was seen for any of the azo dyes tested by using the standard Ames plate assay (method 1). Ether extracts of some samples of FD&C Yellow No. 6, FD&C Red No. 40 and amaranth were active (method 2), but only at high doses, generally 250 mg-equivalents or more per plate. These results indicate the presence of low levels of ether-extractable mutagenic impurities. The FMN preincubation assay (method 3) gave negative results for all dye samples tested. Most batches of FD&C Red No. 40 tested had mutagenic activity that was detectable when the ether extract of less than 1 mg of dithionite-reduced dye was plated in the presence of S9 (method 4). This finding implies that an impurity in these samples of FD&C Red No. 40 can be reduced to yield an ether-extractable mutagen. Dithionite-reduced samples of FD&C Yellow No. 6 and amaranth showed ether-extractable mutagenic activity only at much higher doses than those at which activity was seen with most dithionite-reduced samples of FD&C Red No. 40 (method 4). FD&C Yellow No. 5 showed no mutagenic activity with this method. Mutagenic activity was not detected when FD&C Red No. 40 was tested by using the azo reduction preincubation assay with FMN (method 3).(ABSTRACT TRUNCATED AT 400 WORDS)

Chromatographic and catalytic properties of multiple forms of rabbit pulmonary cytochromes P-450.

Rabbit pulmonary cytochrome P-450 forms 2, 5, and 6 were resolved using anion-exchange high-performance liquid chromatography (HPLC) and their properties compared with rabbit liver cytochrome P-450 isozymes LM2 and LM6. Although rabbit pulmonary form 2 and liver LM2 had similar electrophoretic mobilities and similar substrate specificities in reconstitution experiments, they differed in their HPLC elution profiles. High-performance liquid chromatography of pulmonary microsomes from rabbits treated with 3-methylcholanthrene (3-MC) revealed the induction of form 6 isozyme, which had a retention time, electrophoretic mobility, and substrate specificity similar to those of rabbit liver LM6. In reconstitution experiments, forms 2 and 6 showed the highest substrate specificities toward benzphetamine and 7-ethoxyresorufin, respectively. Rabbit lung cytochrome P-450 form 5 was relatively inactive toward all substrates tested.

Mutagenicity of benzidine and benzidine-congener dyes and selected monoazo dyes in a modified Salmonella assay.

We have evaluated the mutagenic activity of a series of diazo compounds derived from benzidine and its congeners o-tolidine, o-dianisidine and 3,3'-dichlorobenzidine as well as several monoazo compounds. The test system used was a modification of the standard Ames Salmonella assay in which FMN, hamster liver S9 and a preincubation step are used to facilitate azo reduction and detection of the resulting mutagenic aromatic amines. All of the benzidine and o-tolidine dyes tested were clearly mutagenic. The o-dianisidine dyes except for Direct Blue 218 were also mutagenic. Direct Blue 218 is a copper complex of the mutagenic o-dianisidine dye Direct Blue 15. Pigment Yellow 12, which is derived from 3,3'-dichlorobenzidine, could not be detected as mutagenic, presumably because of its lack of solubility in the test reaction mixture. Of the monoazo dyes tested, methyl orange was clearly mutagenic, while C.I. Acid Red 26 and Acid Dye (C.I. 16155; often referred to as Ponceau 3R) had marginal to weak mutagenic activity. Several commercial dye samples had greater mutagenic activity with the modified test protocol than did equimolar quantities of their mutagenic aromatic amine reduction products. Investigation of this phenomenon for Direct Black 38 and trypan blue showed that it was due to the presence of mutagenic impurities in these samples. The modified method used appears to be suitable for testing the mutagenicity of azo dyes, and it may also be useful for monitoring the presence of mutagenic or potentially carcinogenic impurities in otherwise nonmutagenic azo dyes.