Abstract
Trigonelline contents in many kinds of food samples were determined and extremely high contents (up to 1%) in coffee beans and very high contents in marine shellifishes were observed. Trigonelline-synthesizing enzyme nicotinate methyltransferase activity was found in marine shellfishes and plants. No activity of this enzyme was detected in land animals and microorganisms. Fundamental properties of the enzyme in coffee plant leaf and marine clam were revealed. Trigonelline was thermally decomposed and a part of it was turned into nicotinic acid at over 180℃. Indeed, trigonelline contents were decreasing and nicotinic acid contents were increasing during roasting coffee beans. The bioavailability of nicotinic acid in coffee beans was confirmed with young rats. Thus, coffee was proved to be an important drink for nicotinic acid intake. Moreover, trigonelline demethylating enzyme activity was found in animals, plants and microorganisms for the first time. Fundamental properties of the enzyme in hog liver were revealed. The effect of trigonelline on young rats was investigated with large amount of oral dose. As the results, trigonelline was rapidly excreted in urine and no special effect was observed in growth, NAD(P) content in blood and liver, and excretion pattern of niacin metabolites in urine. The effect of trigonelline on higher plants was investigated with duckweed and potent growth promoting effect was observed. After all, it is proved that trigonelline is not a dead-end metabolite of nicotinic acid but an important bioactive compound as a reusable stored form of nicotinic acid.
