Enzymatic extraction procedure for the liquid chromatographic determination of niacin in foodstuffs

An enzymatic extraction procedure for the determination of the niacin present in foodstuffs by means of a NAD glycohydrolase (or NADase) has been proposed as a replacement for the hydrochloric acid hydrolysis usually used. The determination of nicotinic acid and nicotinamide by HPLC/fluorimetry [according to Lahély et al. (Food Chemistry, 1999, 65, 129)] has made it possible to show that the acid treatment very definitely led to the release of forms of nicotinic acid not bioavailable in some foodstuffs (wheat flour, wheat germ, peanuts), unlike hydrolysis with NADase from Neurospora crassa [37 °C, 18 h, pH 4.5, 24 μg g−1 of sample (0.013 U g−1)] which led to both an accurate determination of the respective contents of nicotinic acid and nicotinamide and a reliable estimation of the bioavailable niacin in the different foodstuffs analysed. The combined addition of a protease and an amylase to the NADase, sometimes recommended when acid hydrolysis was used, proved to be superfluous.