Essential Oils with Polyacetylene Compounds

Polyacetylene derivatives form a special group of compounds which are more and more often encountered. They are isolated preferably by extraction, however, since they are partly destroyed by steam distillation [134]. 

These compounds have been investigated thoroughly by Bohlmann s and Schulte s teams. Up to now, about 150 alkynes have been isolated [217, 333]. Schulte et al. [230] recommend sihca gel G layers for separating naturally occurring polyacetylene compounds which are 

Preparative TLC on silica gel HF254 layers can be employed for isolation of milligram amounts of the alkynes [15, 16]. Most polyacetylenes quench fluorescence and are, like the phenylpropane derivatives, easily detectable as dark zones. 

The following must be borne in mind in the microanalytical characterisation of essential oils with TLC and/or GC  

P) on the plant organ used (flower, leaf, bark or root). 

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Echinacea pallida roots contain a high amount (0.2-2.0%) of essential oil [5, 14, 15, 21, 67-69]. Main constituents are pentadeca-8Z-en-2-one [19], pentadeca-1, 8Z-diene (44% of the oil) and 1-pentadecene (Fig. 1) [17, 70]. In addition, pen-tadeca-8Z,llZ-dien-2-one, pentadeca-8Z, 13Z-dien-ll-yn-2-one and tetradeca-8Z-en-ll,13-diyn-2-one are occurring [14] and probably also (E)-lO-hydroxy-4,10-dimethyl-4,ll-dodecadien-2-one ( echinolon ) [18]. These ketoalkenes and ketoalkynes are also the major lipophilic constituents of . pallida roots. Other constituents of this type are pentadeca-8Z-ene-ll,13-diyn-2-one, pentadeca-8Z,11Z, 13 -triene-2-one, and pentadeca-8Z,ll ,13Z-triene-2-one (Fig. 7) [12, 19, 71]. According to Schulte et al. [19], who probably examined . pallida instead of . angustifolia only 2 mg% polyacetylenes (calculated on airdried material) with trideca-l-en-3,5,7,9,ll-pentayne and ponticaepoxide as main compounds are present. 

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