Quantitation of estragole by stable isotope dilution assays

Various calibration strategies for the quantitation of the phenylpropane estragole by gas chromatography-mass spectrometry were developed and compared. For application in stable isotope dilution assays, two deuterium labelled estragole isotopologues were synthesized. Of these, [3′,3′-²H₂]estragole was prepared by Wittig reaction of 4-methoxy-phenylacetaldehyde with [²H₃]methyl-triphenyl-phosphonium bromide, whereas [1″,1″,1″-²H₃]estragole was obtained by demethylation of estragole and deuteromethylation of the resulting 4-allylphenole.Besides estragole isotopologues, 1,2,4-trimethoxybenzene and 4-propylanisole were also tested as internal standards (I.S.) for the determination of estragole in fennel tea.[1″,1″,1″-²H₃]Estragole, 1,2,4-trimethoxybenzene, and 4-propylanisole revealed linear calibration functions and, therefore, were suitable for estragole quantitation. In contrast to this, [3′,3′-²H₂]estragole could only be applied as I.S. if it was added to the extracts in stoichiometric deficiency compared to unlabelled estragole. Moreover, due to its different chemical and physical properties, 1,2,4-trimethoxybenzene showed a recovery as low as 77%, whereas the other I.S. revealed recovery rates close to 100%. Considering the “real” values of estragole in fennel tea, the choice of the I.S. obviously is less important than the way of preparing the tea. In contrast to the common method for tea preparation, squeezing of the teabags increased the estragole content significantly by 50%.     

Selection for tolerance to volatile monoterpenoids in Sitophilus oryzae (L.), Rhyzopertha dominica (F.) and Cryptolestes pusillus (Schönherr)

Selection for tolerance to 8 monoterpenoids (linalool, camphor, γ-terpinene, S-carvone, geraniol, estragole, E-anethole, and fenchone) in three pests of stored rice, Sitophilus oryzae, Rhyzopertha dominica and Cryptolestes pusillus, as well as the metabolic mechanisms implicated, was studied. Strains were selected for tolerance towards each monoterpenoid from susceptible insect populations for each of seven generations.After selection, tolerance was observed towards linalool, S-carvone and estragole in S. oryzae and towards camphor in C. pusillus. Populations of R. dominica were not observed to develop tolerance to monoterpenoids.The activity of three enzymatic systems detoxifying these monoterpenoids, microsomal P-450 monooxygenase, esterase, and glutathione S-transferase (GST), were analyzed to study the metabolic mechanisms involved. Esterases could be involved in S. oryzae tolerance whereas P-450 monooxygenases could be involved for most monoterpenoids in selected populations of R. dominica and C. pusillus.     

Toxic compounds in essential oils of coriander, caraway and basil active against stored rice pests

Essential oils, distilled from seeds of Coriander sativum and Carum carvii and from leaves of five different varieties of Ocimum basilicum, were fractionated by column chromatography and tested in the laboratory for volatile toxicity against three stored rice pests (Sitophilus oryzae, Rhyzopertha dominica and Cryptolestes pusillus). The active fractions were analyzed by GC-MS. Coriander contained linalool (1617 ppm of the oil) as the main product active against the three pests. Camphor-rich fractions (over 400 ppm) were very toxic to R. dominica and C. pusillus. The caraway profile included carvone and limonene as expected but (E)-anethole, generally regarded as a minor product in the essential oil of this species, was also a major component, being present at 365 ppm. Carvone was the most effective (972 ppm) monoterpenoid against S. oryzae. In addition, (E)-anethole at 880 ppm was toxic to R. dominica while vapors of limonene (1416 ppm) and fenchone-rich (554 ppm) fractions killed adults of C. pusillus only. Three major essential oil profiles were present in the five varieties of O. basilicum analyzed: methyl eugenol/estragole, estragole and estragole/linalool chemotypes. The abundance of components had a strong influence on the outcome of the bioassays. Fractions, where combinations of products occurred with or without other minor compounds, were often more toxic than any one compound alone.     

Studies on the essential oil from guarana

The essential oil from guarana [Paullinia cupana H.B.K. var. sorbilis (Mart.) Ducke] was analysed. Nine components were identified, namely (2) methylbenzenes, (1) cyclic monoterpene and (2) cyclic sesquiterpene hydrocarbons, (2) methoxyphenylpropenes and (2) alkylphenol derivatives. The alleged psychoactivity of the essential oil is presumably due to the identified constituents estragole and anethole. Any contribution of aminated metabolites of estragole/anethole to the alleged psychoactivity of the essential oil of guarana can be excluded. Neither the psychoactive 4-methoxyamphetamine nortert-aminoketones could be traced in human urine after oral application of guarana.