FEMA 2795

Description

Various lichens belonging to the class Cryptogamia; they grow under cool, damp conditions on the trunks and branches of trees such as oak and fir. The lichens are used to prepare resinoids and concrete and absolute essences for a total yearly consumption of approximately 70 tons.
E. prunastri, the true oak moss, grows on the trunks and branches of oak trees. Like all ascolichens, the moss reproduces by fragmentation of soredia and grows by symbiosis yielding an erect, bushy, vegetative form. Other related lichen-E. furfuracea and Usnea barbata-that grow on spruces and firs are known by the more generic name of tree moss. Oak moss derivatives are light green and exhibit a rich odor, while tree moss derivatives have a grayish-green color and a slight resinous odor. E. prunastri yields the most valuable extraction products, while other tree mosses yield products of inferior quality. Oak moss is harvested mainly in France, Yugoslavia, Italy, Morocco, and Hungary. The harvested moss is pressed into bails and shipped to the extractive sites. The part used is the lichen. Oak moss has a delicate, pleasant, green, moss-like odor.
An essential oil can be obtained by steam distillation of the lichen; however, this product is of little commercial importance because of the very low yields (0.07%). Usually oak moss concrete and oak moss absolute are steam distilled, preferably under reduced pressure. Main constituents of the ether-extracted concrete include evernic acid, orcinol, phenols, acids (formic, acetic, stearic, palmitic, and oleic), α- and P-thujone, camphor, bomeol, cineol, naphthalene, ketones, terpene alcohols, and traces of vanillin.
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Chemical properties

Tree moss concretes and absolutes are prepared from Pseudevernia furfuracea (L.) Zopf (syn. Evernia furfuracea (L.) Mann; Parmelia furfuracea (L.) Arch.), a lichen growing on barks of Pinaceae, for example, on Cedrus species in Morocco. Their odors are different from those of the corresponding oakmoss products.
The extracts and absolutes are used in perfumery for nuances and as a fixative to give compositions a dry, sweet base note, for example, in fougére and chypre perfumes. Allergenic responses to oakmoss and tree moss products are probably caused by aromatic aldehydes such as atranorin and chloroatranorin and the corresponding products formed during the workup process as a result of transesterification and decarboxylation reactions, for example, ethyl hemmatomate, ethyl chlorohemmatomate, atranol, and chloroatranol.
Methods to obtain oakmoss and treemoss products of low allergenic properties have been reported. Treemoss extracts may also contain constituents that possibly cause allergenic reactions. As tree moss grows on conifers, it may be contaminated with some conifer rosin. This rosin usually contains resinic acids (abietic acid and similar constituents), which are known to be allergenic substances. Tree moss products free of these resinic acids can be obtained by treatment with selected solvents.

Chemical properties

As stated above, the absolute is obtained by alcoholic extraction of the concrete. Extraction requires approximately 5 hours.

Physical properties

The absolute is a dark-green liquid.

Occurrence

Found in the lichen, E. prunastri (L.) Ach. (Fam. Usneaceae), which occurs on the trunks of oak trees (Guenther, 1952; Naves, 1974).

The Uses of FEMA 2795

Oak moss absolute is an extract of oak moss. Extract made mainly from Evernia prunastri (oak moss) and Pseudevernia furfuracea (tree moss). Oak moss concrete is prepared by hydrocarbon solvent extraction of the lichen Evernia Prunastri, collected mainly from oak trees in Yugoslavia, France, Italy, Corsica, Morocco, Hungary, and various central European countries. Contains atranorin, evernic acid and usnic acid.

Preparation

By solvent extraction of E. prunastri; the solvent is evaporated and removed, usually under vacuum, and the resultant product is normally dispersed in benzyl benzoate or a similar diluent to facilitate handling. Commercially available oakmoss preparations are frequently compounded products (Chatelain, 1953).

Definition

Extractives and their physically modified derivatives. It is a product which may contain resin acids and their esters, terpenes, and oxidation or polymerization products of these terpenes. (Evernia prunastri, Unseaceae).

Essential oil composition

Extract of lichen contains camphor, α- and β-thujone, depsides, orcinol, sparassol, atranol, divarine and other monaryl derivatives of depsides.