Summary: A modified basal medium was employed for the assay of nicotinic acid contained in various biological materials. Of the various possible comparisons of test material with standard nicotinic acid in the assay, the ‘internal standard’ method is preferable; by assaying the standard nicotinic acid in the presence of the test material, any discrepancies due to substances stimulating or inhibiting the nicotinic acid effect are minimized.

Of the different extraction procedures tested, treatment of samples with -NaOH and -HSO gave the most satisfactory results; both -NaOH and -HSO appeared to convert a ‘precursor’ in potato and bran, into nicotinic acid. 2-HCl extracts yielded lower values, but the conversion of the precursor was less effective with potato than with bran, suggesting different precursors in the two vegetable substances.

The results of microbiological and chemical assay were in good agreement. The coefficient of variation of the microbiological results was of the order of 9%.


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