Metabolism and Degradation of Nicotinic Acid in Parsley (Petroselinum hortense) Cell Suspension Cultures and Seedlings

Application of [6- C]-or [7- C]nicotinic acid to parsley cell suspension cultures led to the accumulation of labelled nicotinamide mononucleotide, nicotinamide adenine dinucleotide, nicotinamide N-riboside, nicotinamide and nicotinic acid, indicating the operation of the pyridine nucleotide cycle in these cells. As main conjugates, nicotinic acid N-glucoside and nicotinic acid glucose ester were found. For nicotinic acid degradation the following sequence is suggested: nicotinic acid → 6-hydroxynicotinic acid → 2,5-dihydroxypyridine → a C /C unit of unknown structure → CO . In aseptically grown parsley seedlings nicotinic acid is also degraded to CO