Abstract:
Investigations of 2-alkyl-3-methoxypyrazines (2-isopropyl-3-methoxypyra2ine, 2-
secbutyl-3-methoxypyrazine and 2-isobutyl-3-niethoxypyrazine) in ladybug species
{Coleoptera: Coccinellidae) and wine samples have been conducted. Headspace sampling
coupled with gas chromatography-mass spectrometry was used to determine amounts
of 2-alkyl-3-methoxypyra2ines in the ladybug species. Hippodamia convergens had the
highest amount of alkybnethoxypyrazines, followed by Harmoma axyridis and the least
in Coccinella septempunctata.
Using a solvent extraction method, the precoccinelline alkaloid was found present in
Hippodamia convergens and Coccinella septempunctata but not Harmonia axyridis.
Steam distillation followed by a soHd phase extraction method as a sample
preparation technique, enhanced detection while the isotope dilution method
afforded accurate quantitation of the alkyknethoxypyrazines in the wine samples.
Both ladybug-tainted and commercial wine samples were found to contain the 2-
alkyl-3-methoxypyrazines. Wine samples prepared in 2001 generally contained higher
levels than the corresponding 2003 samples. Levels of the 2-alkyl-3-methoxypyrazines
found in the commercial wines ranged from a minimum value of 6 ng/L to 260 ±10
ng/L. Analyses revealed that for both ladybug species and wine samples, the 2-
isopropyl-3-methoxypyrazine had the highest concentration, followed by 2-isobutyl-
3-methoxypyrazine and the least being the 2-secbutyl-3-methoxypyrazine. Possible
contamination of the wine samples by ladybugs is thoroughly discussed.
Furthermore, attempts to remove or reduce the levels of the alkylmethoxypyrazines
with molecularly imprinted polymers from wine samples are presented in detail.
