Non-destructive and direct determination of the degree of substitution of carboxymethyl cellulose by HR-MAS 13C NMR spectroscopy.

We report on the direct assessment of the degree of substitution (DS) of carboxymethyl cellulose (CMC) by High Resolution Magic Angle Spinning (HR-MAS) 13C NMR spectroscopy. The method is applied to industrial CMCs with low and high viscosity and nominal DS, purified and technical samples, and from cellulose linters or wood. The preparation of a set of purified CMC working standards with accurate DS values for the method validation is also described. The DS values determined via HR-MAS 13C NMR on the industrial samples are critically compared to the corresponding values achieved through the USP 37 〈281〉 method (ASH method) and the HPLC method, and the advantages and limitations of the HR-MAS NMR method highlighted. Finally, the HR-MAS NMR approach allowed the accurate DS assessment in CMC with low DS, characterized by a non-negligible fraction of non-functionalized cellulose. The proposed "effective DS" accounts for the DS of the solvent-exposed CMC.

Carcinogenicity tests of fecapentaene-12 in mice and rats.

Fecapentaenes, a class of direct-acting bacterial mutagens, have been isolated from the feces and intestinal tract of humans on a Western meat-containing diet. Two bioassays to test pure fecapentaene-12 (FP-12) for carcinogenicity were performed. FP-12 in dimethylsulfoxide (DMSO) solution was injected i.p. into newborn ICR/MA mice on days 1, 3, 7, 10, 14 and 21. The mice killed after 21 months had neoplasms in liver, lung, glandular stomach and subcutaneous fibrosarcoma. Intrarectal (i.r.) infusion of FP-12 in an aqueous vehicle into male F344 rats for 71 weeks, and killing the rats after 21 weeks more, displayed no evidence of neoplasia associated with FP-12 exposure. The positive control, N-nitrosomethylurea (NMU), given i.r. as 4 2-mg doses in 2 weeks, as expected, yielded multiple colonic neoplasms in less than 11 months. Fecapentaene may exert its effect in bacteria and in newborn mice through the generation of hydroxy radicals. However, adult rodent and human colon may have adequate biochemical defense mechanisms against low level, even continuous exposures to chemicals like FP-12, and thus be at low risk of neoplasia, as was found.

Synthesis and biological activity of analogs of fecapentaene-12.

Analogs of the potent fecal mutagen fecapentaene-12 have been prepared and tested both for mutagenicity and for their ability to serve as biological precursors of 1. It was found that mutagenicity in three different Salmonella tester strains TA96, TA100, and TA104, decreased rapidly as the number of conjugated double bonds was reduced. The aldehyde 8, analogous to the hydrolysis product of 1, showed only low mutagenicity, even in the aldehyde-sensitive strain TA104. None of the polyenes prepared was able to function as a direct biological precursor of 1 under the conditions employed.

Synthesis, physical properties and microbiological activities of more water soluble silver sulfadiazine derivatives.

In this study the preparation of five hydrophilic derivatives of sulfadiazine is reported. The common structural element in the compounds is the 2-sulfonamidopyrimidine moiety. Three of these compounds are suitable for the preparation of a photostable I: I silver compound. These silver compounds are five to ten times more water soluble than silver sulfadiazine. The IR, 1H- and 13C-NMR data point to a similar co-ordination of silver in these compounds as with silver sulfadiazine. The microbiological activity of these silver compounds against St. aureus is slightly lower.