Is 7-hydroxyphthalide a natural compound of oil gland secretions? – Evidence from Archegozetes longisetosus (Acari, Oribatida)
2011 - Volume: 51 Issue: 2 pages: 229-236DOI: 10.1051/acarologia/20112004
Keywordsgamma-acaridial 7-hydroxyphthalide chemical ecology artifact
The monophyly of a clade consisting of Astigmata and some of the glandulate Oribatida is supported by a synapomorphic set of five oil gland-derived secretion compounds (neral, geranial, neryl formate, 2-hydroxy-6-methylbenzaldehyde (=2,6-HMBD) and 2-formyl-3-hydroxybenzaldehyde (=gamma-acaridial)), known as ‘Astigmata compounds’. Another aromatic compound, 7-hydroxyphthalide, was reported for Astigmata and Oribatida, but is not known from any other source in nature. It was discussed whether this compound was a ‘natural’ part of oil gland secretions (and thus probably of phylogenetic significance) or an artifact. Here, we show that 7-hydroxyphthalide is the result of a post-extraction chemical transformation of gamma-acaridial, and not a natural compound of oil gland secretions. We compared time series of raw extracts from Archegozetes longisetosus stored at -20°C with extracts stored at +23°C and show that storage at room temperature conditions promotes the transformation. However, since this reaction is quantitatively coherent, summing the amounts of both components seems to be a suitable approximation for the quantity of gamma-acaridial in natural secretions, even if 7-hydroxyphthalide is found in the analyses.
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