Fluoorasetaat-, aminosuur- en organiese suurmetabolisme van gifblaar (Dichapetalum cymosum Engl.)

Abstract

It has been shown by means of respiration stu,dies that Gifblaar is capable of metabolizing FAc. A method was worked out for the synthesis of

FAc-2- 14C from MeBrAc-2- 14C w1tp. a yield of 65%. When FAc-2- 14C was applied to Gifblaar leaves it was found that one of the first radioactive components was an unknown carbohydrate. Indications were found that Grysappel (Parinarium capense), a control plant, also metabolizes FAc-2-14c to a small extent. The application of fluorocitrate ( FC) was shown to inhibit the respiration of Gifblaar and lead to an accumulation of citrate. This indicates that FAc is not metabolized via FC and that Gifblaar contains an active Krebs cycle. The latter was confirmed in experiments with radioactive pyruvate, citrate, acetate, alanine, serine and glycine. It was found that Gifblaar has a relatively high free amino acid concentration and that the two amino acids present in the highest concentration are not commonly encountered in other organisms. These two amino acids represented more than 30% of the total nitrogen present in the tip of the rhizome. The two amino acids were isolated and with the aid of elementary analysis, mass spectrometry, nuclear magnetic resonance spectrometry and infrared spectroscopy they were characterized as N-methyl-L-alanine (NMA) and N-methyl-L-serine (NMS) respectively. These amino acids have not yet been encountered in other plants, as far as is known. It was found that a high NMA and NMS concentration Usually went hand in hand with a high FAc concentration. Furthermore these amino acids were not poisonous to mice and it was established that they are formed in vivo by methylation of alanine and serine.