Populus nigra L. - Salicaceae - black poplar, Schwarz-Pappel
Deciduous tree, up to 10-25m high, native to the river banks of Europe; leaves nearly cordate; young branches round across; flowers at catkins (up to 12cm long), produced in early spring before the leaves.
The sweet-cented exudate of fresh P.nigra buds is collected by bees as the basis of their genuine product propolis, which is subject of medical interest.
„26 different compounds have been investigated experimentally for their sensitizing capacity in guinea pigs. 19 of these occur in propolis as well as in poplar bud exudates, and 14 of them are also found in balsam of Peru. 4 caffeates and benzyl isoferulate were found to be strong Sensitizers. 7 compounds were moderate, and 13 compounds showed only weak sensitizing potency. Methyl cinnamate was negative. Patch tests in 11 propolis-sensitive patients once more revealed 3-methyi-2-butenyl caffeate and phenylethyl caffeate as the major sensitizers.“
[Propolis allergy (IV) Studies with further sensitizers from propolis and constituents common to propolis, poplar buds and balsam of Peru., Hausen, B.M., Evers, P., Stüwe, H.T., König, W.A., Wollenweber, E., Contact Dermatitis, 26(1), 1992, 34-44]
„Fractions in which 37 organic compounds were identified by means of GC-MS method were isolated using extraction of four propolis samples and bud exudate from Populus nigra. Six of them were identified in propolis for the first time. They are: 4-hydroxybutyric acid (4-hydroxybutanoic acid), 3-hydroxybutyric acid (3-hydroxybutanoic acid), phthalic acid, 4-hydroxyhydrocinnamic acid (phenyllactic acid), imidazole and phenetole. The main components of propolis fraction are acids: benzoic, cis- and trans-p-coumaric, ferulic, caffeic and cinnamic… Propolis ethanolic extracts consisted of 3.5-8.8% of dry residue and 2.9% bud exudate extract from Populus nigra.“
[GC-MS and HPLC analysis of phenolic acids extracted from propolis and from Populus nigra bud exudate. Maciejeicz, W., Daniewski, M., Dzido, T. H., Bal, K., Chemia analityczna, Vol.47(1), 2002, 21-30]
„Volatile components from fresh and air-dried leaf-buds of Populus nigra L. (Salicaceae) were isolated by Likens-Nickerson apparatus and analyzed using GC/MS. Forty-eight components (ca. 95% of the total isolate) were identified among black poplar bud volatiles. Sesquiterpene alcohols β-eudesmol and α-eudesmol represented 26.3-28.7% of the oil. Other major sesquiterpene compounds were γ-selinene (7.6-8.8%), δ-cadinene (7.8-8.6%), α-elemene (3.3-5.2%) and γ-cadinene (3.9-4.2%). Hemiterpenes were also identified (2.2-7.6%). Monoterpenes were present in low percentages (1.6-5.7%). Aliphatic and aromatic alcohols, carbonyl compounds and aliphatic acids were identified among non-terpene volatiles (9.8-13.5%). The fresh buds contained 0.27% and dried 0.12% essential oil. Air-drying moderately effected the volatiles qualitative and quantitative composition.“
[Volatile compounds from leaf-buds of Populus nigra L.(Salicaceae). Jerković, Igor, and Josip Mastelić., Phytochemistry Vol.63(1), 2003, 109-113]
Phenylethyl caffeate, benzyl ferulate and benzyl-trans-4-coumarate are characteristic compounds found in propolis from various geographic origin.
[Chemical composition and antimicrobial activity of European propolis. Hegazi, Ahmed G., F. K. Abd El Hady, F. A. Abd Allah., Zeitschrift fur Naturforschung C 55.1/2, 2000, 70-75] http://zfn.mpdl.mpg.de/xtf/data/Reihe_C/55/ZNC-2000-55c-0070.pdf
Thomé,O.W., Flora von Deutschland Österreich und der Schweiz, Tafeln, vol.2 t.177 (1885)