Biodegradation of Amphipathic Fluorinated Peptides Reveals a New Bacterial Defluorinating Activity and a New Source of Natural Organofluorine Compounds.

Three peptides comprising mono-, di-, and tri-fluoroethylglycine (MfeGly, DfeGly, and TfeGly) residues alternating with lysine were digested by readily available proteases (elastase, bromelain, trypsin, and proteinase K). The degree of degradation depended on the enzyme employed and the extent of fluorination. Incubation of the peptides with a microbial consortium from garden soil resulted in degradation, yielding fluoride ions. Further biodegradation studies conducted with the individual fluorinated amino acids demonstrated that the degree of defluorination followed the sequence MfeGly > DfeGly > TfeGly. Enrichment of the soil bacteria employing MfeGly as a sole carbon and energy source resulted in the isolation of a bacterium, which was identified as Serratia liquefaciens. Cell-free extracts of this bacterium enzymatically defluorinated MfeGly, yielding fluoride ion and homoserine. In silico analysis of the genome revealed the presence of a gene that putatively codes for a dehalogenase. However, the low overall homology to known enzymes suggests a potentially new hydrolase that can degrade monofluorinated compounds. 19F NMR analysis of aqueous soil extracts revealed the unexpected presence of trifluoroacetate, fluoride ion, and fluoroacetate. Growth of the soil consortium in tryptone soya broth supplemented with fluoride ions resulted in fluoroacetate production; thus, bacteria in the soil produce and degrade organofluorine compounds.

Unusual amino acids and monofluoroacetate from Dichapetalum michelsonii (Umutambasha), a toxic plant from Rwanda.

In the course of our investigations on Umutambasha in order to identify its convulsant principles, small quantities of monofluoroacetate were observed in stem bark, leaves, and fruits of this plant newly identified as Dichapetalum michelsonii Hauman. Conclusive evidence for a monofluoroacetate presence came from its isolation from the freeze-dried extract of stem bark. Three free unusual amino acids, named N-methyl-α-alanine, N-methyl-ß-alanine, and 2,7-diaminooctan-1,8-dioic acid, described for the first time in a plant, and known trigonelline were also isolated from the stem bark of D. michelsonii. Structure elucidations were mainly achieved by spectroscopic methods (1H-NMR, 2D-NMR, MS) and by comparison with authentic references. These unusual amino acids were detected by a fast, reliable TLC analysis in all our batches of Umutambasha, suggesting that they could be used for identification purposes in case of human or livestock intoxications. Finally, EEG recordings and behavioural observations performed in mice suggested that the convulsive patterns produced by Umutambasha are the consequence of monofluoroacetate presence in D. michelsonii.

Qualitative and quantitative determination of fluoroacetic acid in Arrabidea bilabiata and Palicourea marcgravii by 19F-NMR spectroscopy.

Qualitative and quantitative examination of Arrabidea bilabiata and Palicourea marcgravii by 19F-NMR spectroscopy has shown the presence of fluoroacetic acid. By acid-base enrichment it is possible to detect amounts of fluoroacetic acid which otherwise are below detection rate. The detection limit (without enrichment) is estimated to be about 4 micrograms/g. Disturbing metal ions of higher oxidation states are also removed by this way. Arrabidea bilabiata contains 64.1 micrograms/g (seeds) and 3.0 micrograms/g (leaves), and Palicourea marcgravii contains 5.4 micrograms/g (leaves).

Is monofluoracetic acid the active neurotoxic principle in Palicourea marcgravii (St. Hill) leaves?

Acute intoxication of rats with the crude extract of Palicourea marcgravii (PM) and with monofluoracetic acid (MFA) solutions was compared since it has been reported that PM leaves contain monofluoracetates (455 micrograms/g air-dried material). The neurotoxic signs produced by oral administration of PM and MFA were similar and included tonic-clonic seizures. The dose-response curves constructed for the convulsant effects of PM and MFA were parallel and the CD50s were 630 mg/kg (508-781) and 0.90 mg/kg (0.76-1.06), respectively. These data suggest that the neurotoxic signs produced by PM are the consequence of MFA present in the plant leaves.

Acute toxicity of the leaves and extracts of Dichapetalum barteri (Engl.) in mice, rabbits and goats.

Acute toxicity of the leaves and extracts of Dichapetalum barteri for mice, rabbits and goats was investigated. Consumption of 0.5 g/kg and 2.2 g/kg body weight of dried leaves was lethal to rabbits and goats, respectively, within 4 h. Plants collected in the dry season were more toxic than those collected during the wet season. Clinical signs observed were initial depression followed by restlessness, convulsions, and death. The main lesions observed were acute vasculitis and congestion of the liver, lung, kidney, spleen as well as extensive oedema and congestion of the myocardium. The water extract of the leaves was lethal to mice at 2.0 g/kg, to rabbits at 0.1 g/kg and toxic to isolated rabbit heart at 2 mg/ml of Locke's solution. Monofluoroacetate was detected in the plant material and is probably the toxic principle of D. barteri.