2 — nicotinic acid

Nicotinic acid was first identified as an essential dietary supplement in 1937. It can be found in an active form as either free nicotinic acid, the amide derivative or bound to the pyridine-containing nucleotides (nicotinamide adenine dinucleotide (NAD) and the corresponding phosphate ester (NADP)). 

Nicotinic acid and its derivatives are stable to oxidation by heat, light, acid or alkali and this means that extraction into solvent systems compatible with HPLC is relatively easy by comparison with other vitamins. Biological extracts are readily prepared by deproteini-sation with acetone followed by extraction with dilute hydrochloric acid alternatively, ethyl acetate in combination with hydrochloric acid may be used to extract samples. The most popular HPLC mode for the separation of nicotinic acid is reversed phase ion-pair chromatography. For example, using a fiBondapak Cjg column with a mobile phase of water-methanol (9 1) plus 0.05 M tetrabutylam-monium phosphate as the ion-pair reagent, nicotinamide-A-oxide, 2-hydroxypyridine-5-carboxylic acid, nicotinamide, nicotinic acid and nicotinuric acid were consecutively eluted (Hengen et al., 1978). 

Several methods of pre-column derivatisation have been investigated to improve sensitivity of detection and early reports suggested that the use of cyanogen bromide coupled with -aminoacetophenone provided a sensitive fluorescence detection system (excitation at 435 nm and emission at 500 nm). However, a recent report presents a simple alternative using derivatisation with lV,Af -dicyclohexyl-0-(7-methoxycoumarin-4-yl) melhylisouiea in which nicotinic acid concentrations as low as 0.2 nmol/ml were detectable in serum samples of only 100 jal (Tsuruta et al., 1984). The nicotinic acid derivatives 

HPLC determination of nicotinic acid in (a) normal serum and (b) serum fortified with nicotinic acid (50 nmol/ml). Chromatographic conditions stationary phase, Lichrosorb RP-18 (Merck) (5 jam) (150x4 mm I.D.) mobile phase, acetonitrile-water (4 6 v/v) containing 5 mM sodium 1-hexane sulphonate flow rate, 1.3 ml/min temperature, ambient detection, pre-column derivatisation, excitation at 325 and 335 nm and emission at 395 and 390 nm, respectively. 1, nicotinic acid 2, 2-chloronicotinic acid. Reproduced from Tsuruta et al. (1984), with permission. 

Both analytical and preparative separations have been carried out using normal phase conditions on a pelUcular silica support (Snyder and Kirkland, 1979). Most analyses are currently performed using 

Nicotinic acid is prepared in good yield by the oxidation of p picoline with potassium permanganate  

Studies of the mode of action of nicotinic acid revealed the interesting fact that the hypo-cholesterolemic action is restricted to pure nicotinic acid and its salts (sodium and aluminium nicotinate) and that nicotinamide, part of the molecule of the codehydrogenases DPN and TPN, does not show any cholesterol-lowering effect. The relevant literature on these drugs has been summarized by Sanwald (1966). 

Liquid skim milk Fish, fowl, liver or cottage cheese Lean meat — beef, lamb or veal Safflower oil, corn, cotton or soy Nuts — 50% walnuts (100% in lower cal. diets) 

Whole grain cereal (cooked) or Dry or prepared Fruits 20% or 10% 

Approximate protein Approximate fat Approximate CHO Approx, linoleic acid (see note) 

Linoleic acid is calculated as if cotton, com or soy oil is used (approximately 50% linoleic acid) and that 100% walnuts (62% linoleic acid) are used on all diets up to 1600 calorie. For 2000 calorie diets and above, walnuts should supply 50% of nuts. 

The hypocholesterolemic effect of nicotinic acid was first reported by 

Altschul et al. (2) in 1955 and has since been confirmed by a number of investigators. The mechanism of action of nicotinic acid has been studied in a number of laboratories from various points of departure. Two recent reviews of the possible mechanisms of action of this compound are available (3,4). One suggestion has been that nicotinic acid accelerates bile acid excretion, affects bile acid conjugation, or does both. 

Miller et al. (7) reported that nicotinic acid did not increase bile acid excretion in man. Miettinen (8), in a sterol balance study of five hypercho- 

TABLE I. Influence of Nicotinic Acid on Lipids and Bile Acid Metabolism in Six Hypercholesterolemic Patients  

In another study, Wollenweber et al. (9) determined half-life, pool size, and turnover of cholic and chenodeoxycholic acids in six hypercholesterol-emic patients. Their findings are summarized in Table I. It is apparent that turnover of neither cholic nor chenodeoxycholic acid was affected significantly by administration of nicotinic acid. Failey et al (10) found that the ratio of glycocholamic/taurocholanic acid in seven patients treated with nicotinic acid (2 g/day) fell from 4.0 to 1.7. These authors also reported that subjects given 8 g/day of either benzoic or / -aminobenzoic acid showed changes in these ratios of 1.9 to 3.0 and 2.4 to 0.9, respectively. The available data show that nicotinic acid does not affect bile acid metabolism. 

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Commercially, pyridine is manufactured from ethyne and ammonia. It is used as a solvent, particularly in the plastics industry, in the manufacture of nicotinic acid, various drugs and rubber chemicals. 

Method 1. Reflux a mixture of pure nicotinic acid (Section V,22), 84 g. (105 ml.) of absolute ethanol and 90 g. (50 ml.) of concentrated sulphuric acid in a flask for 4 hours on a steam bath. Cool the solution and pour it slowly and with stirring on to 200 g. of crushed ice. Add sufficient ammonia solution to render the resulting solution strongly alkaline generally, some ester separates as an oil but most of it remains dissolved in the alkaline solution. Extract the solution with five 25 ml. portions of ether, dry the combined ethereal extracts with anhydrous magnesium sulphate, remove the ether and distil under reduced pressure. The ethyl nicotinate passes over at 117-118°/ 6 mm. the yield is 34 g. The b.p. under normal pressure is 222-224°. 

XXU XXII, 1st 1935 3242-3457 One Cyclic Nitrogen (continued). Carboxylic acids Nicotinic acid, 38. 

Ionization can be improved in many cases by placing the sample in a matrix formed from sinapic acid, nicotinic acid, or other materials. This variant of laser desorption is known as matrix-assisted laser desorption ionization (MALDI). The vaporized acids transfer protons to sample molecules (M) to produce protonated ions [M + H]+. 

VITAT S - NIACINE,NICOTINAMIDEAND NICOTINIC ACID] (Vol25)... 

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