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Labrador tea is a name for the dried leaves of Rhododendron groenlandicum, R. tomentosum or R. neoglandulosum (family Ericaceae, previously genus Ledum) as well as for the beverage native to North America, which is made from them. The above species are rich in the essential oil, which gives a conifer aroma to the tisane. Labrador tea is a valuable source of ascorbic acid, with tonic, improving digestion and relaxing activity. However, this beverage should not be drunk more than once daily because of the ledol and grayanotoxin toxicity. The common recipe for making Labrador tea is to add one teaspoonful of dried leaves to one cup of boiling water and to brew for 5 min. It is often sweetened or enriched with other flavors. Additionally, Labrador tea dried leaves are used to spice meat, soups, sauces, salads, beer, cakes and other dishes. In agriculture, its insecticidal properties can be useful for controlling pests. © 2014 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

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]