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Marsh rosemary (Rhododendron tomentosum L. Stokes) H. Harmaja (formerly Ledum palustre) plants were collected at the flowering stage in marshes near Šulnys Lake (Šalčininkai District, Eastern Lithuania) in 2004. Essential oils were prepared by hydrodistillation and analyzed by GC and GC/MS. The major oil constituents were p-cymene (6.2-20.3%), isoascaridol (16.7-24.1%), palustrol (1.2-31.8%) and ledol (5.2-23.4%); and their percentage changed according to the sampling sites. Despite that the plant material was gathered from the limited area, significant compositional variability was observed in the essential oils. Ninety identified (two of them tentatively) compounds comprised up to 97.9% of the oils. [ABSTRACT FROM AUTHOR]

Wild Ledum palustre L. plants were collected near Juodupė (Rokiškis region) and Šilėnai (Vilnius region) villages. Essential oils from young and aged shoots, obtained by hydrodistillation, were analysed using GC and GC/MS. The major constituents were palustrol (31.4-42.8%), ledol (23.6-30.8%), cyclocolorenones (4.0-9.3%), myrcene (1.2-8.6%) and limonene (11.0%). The essential oil from plants growing near Šilėnai village differed from that of L. palustre near Juodupė by a higher content of compounds with the menthane carbon skeleton (10.9-18.0% and ≤1.2%, respectively) and by the content of limonene (3.7-11.0% and not detected, respectively). All essential oils included furyl containing monoterpenoids. Young shoots biosynthesized 3-4 times larger amounts of essential oils and contained larger quantities of terpenoids than did aged shoots. The content of palustrol in the essential oils of aged shoots was higher than of young ones. The dependence of ledol quantities on the age of shoots was opposite in the localities under study. The sixty nine identified compounds comprised 98.0-99.4% of L. palustre essential oils. [ABSTRACT FROM AUTHOR]