pyrethrin-i and chrysanthemic-acid

Although natural insecticides pyrethrins produced by Tanacetum cinerariifolium are used worldwide to control insect pest species, little information is known of their biosynthesis. From the buds of T. cinerariifolium, we have purified a protein that is able to transfer the chrysanthemoyl group from the coenzyme A (CoA) thioester to pyrethrolone to produce pyrethrin I and have isolated cDNAs that encode the enzyme. To our surprise, the active principle was not a member of a known acyltransferase family but a member of the GDSL lipase family. The recombinant enzyme (TcGLIP) was expressed in Escherichia coli and displayed the acyltransferase reaction with high substrate specificity, recognized the absolute configurations of three asymmetric carbons and also showed esterase activity. A S40A mutation in the Block I domain reduced both acyltransferase and esterase activities, which suggested an important role of this serine residue in these two activities. The signal peptide directed the localization of TcGLIP::enhanced green fluorescent protein (EGFP) fusion, as well as EGFP, to the extracellular space. High TcGLIP gene expression was observed in the leaves of mature plants and seedlings as well as in buds and flowers, a finding that was consistent with the pyrethrin I content in these parts. Expression was enhanced in response to wounding, which suggested that the enzyme plays a key role in the defense mechanism of T. cinerariifolium.

Topics: Acyltransferases; Amino Acid Sequence; Amino Acid Substitution; Chrysanthemum cinerariifolium; Esterases; Esters; Flowers; Gene Expression; Insecticides; Kinetics; Lipase; Molecular Sequence Data; Mutagenesis, Site-Directed; Plant Leaves; Plant Roots; Plant Stems; Protein Sorting Signals; Protein Structure, Tertiary; Pyrethrins; Recombinant Fusion Proteins; Seedlings; Substrate Specificity

Pyrethrum as well as synthetic pyrethroids like allethrin, resmethrin, phenothrin, tetramethrin, cyfluthrin, cypermethrin, deltamethrin or permethrin are among the insecticides most often used worldwide. With a sensitive and valid gas-chromatographic-high resolution mass spectrometric method, it is possible to detect all pyrethrum and pyrethroid metabolites in one analytical run. Thus, for the first time a background level of trans-chrysanthemumdicarboxylic acid (CDCA) in urine (95th percentile: 0.15 microg/l) as a characteristic, e.g. for a pyrethrum exposure was found. Following a pyrethrum exposure lasting 1 day, CDCA was found in 27 out of 30 subjects with concentrations going up to 54 microg/l urine (mean: 1.1+/-4.4 microg/l). To obtain information about the elimination kinetics of pyrethrum in humans, urinary excretion of CDCA was investigated in three volunteers after oral intake of 0.3mg pyrethrin I. CDCA was detected during the first 36 h after intake with elimination being most rapid during the first 4h (mean elimination half-life: 4.2h).

Topics: Administration, Oral; Biomarkers; Chrysanthemum cinerariifolium; Environmental Monitoring; Humans; Insecticides; Male; Pyrethrins; Reference Values

Pilot exposure to pyrethrin was monitored after 2 aerial applications of a ultra-low-volume (ULV) pyrethrin insecticide for the control of adult mosquitoes. Pyrethrin exposure was estimated by measuring the excretion in urine of a common metabolite, trans-chrysanthemumdicarboxylic acid, of the natural pyrethrin mixture. Pyrethrin exposure estimated by total daily urine volume was well correlated (R2 = 0.8) with exposure estimated by the creatinine-adjusted volume of combined workday urine voids, indicating that a postapplication spot urine sample would be sufficient to measure pyrethrin exposure. Pilot exposure to pyrethrin was very low after both insecticide applications. The highest exposure was found on day 1, with a dose of 2.05 microg pyrethrin equivalents/day or a dosage of 0.03 microg pyrethrin equivalents/kg/day. These exposure rates represent approximately 1/2,800,000th of the low observed adverse effect level and 1/1,000th of the acceptable daily intake for pyrethrin. The aerial application of ULV pyrethrin insecticide for the control of adult mosquitoes does not result in undue exposure to a pilot who is trained and certified to conduct such control operations.

Topics: Aircraft; Animals; Humans; Male; Middle Aged; Mosquito Control; Occupational Exposure; Pyrethrins