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Rheum rhabarbarum L. - Polygonaceae
rhubarb, Rhabarber
Herbaceous perennial, 0.5-1.5m tall, native to China, cultivated in Asia and Europe; leaves triangular-ovate, subovate, broadly cordate, or narrowly triangular, large, 12-40 × 10-30cm, margin crispate or sinuate; flowers white-green or yellow-white.
http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=242343402
„Volatiles of rhubarb (Rheum rhabarbarum L.) stalks were isolated by means of vacuum headspace method and analyzed by capillary gas chromatography−mass spectrometry. Fifty-nine components were reported for the first time in rhubarb. A striking feature of the extracts obtained is the preponderance (∼65%) of compounds with C6 skeletons. In addition to unsaturated C6 aldehydes and alcohols, substantial amounts of the less common (E)-2- and (E)-3-hexenoic acid were detected. Gas chromatography−olfactometry and determination of odor activity values revealed the sensory importance of the C6 compounds to the aroma of rhubarb. Comparative experiments involving the inhibition of enzyme activities revealed that the initial spectrum of C6 components is changed due to subsequent isomerization and reductions. Thus, contributions of (Z)-3-hexenal and the unsaturated acids decrease, and (E)-2-hexenal/(E)-2-hexenol play major sensory roles.“
[Volatile constituents of uncooked rhubarb (Rheum rhabarbarum L.) stalks. Dregus, M., Engel, K. H., Journal of agricultural and food chemistry, Vol.51(22), 2003, 6530-6536]