Part 3

(3) Sulphur-containing oils, a small group characterized by extremely disagreeable and offensive odors, such as those of mustard, asafetida, garlic, and onion. These oils contain as their chief constituents sulphids, sulphocyanates, or nitriles, and are used principally for medicinal purposes.

(4) Phenol and phenol-related oils, containing phenols or phenol derivatives and characterized by strong, persistent odors, some very pungent and others pleasant. Owing to their phenolic constituents the density of these oils is usually very high. Common examples of this class are the oils of thyme, cloves, cinnamon, sassafras, anise, fennel, and the monardas. The usefulness of phenol and phenol-related oils depends largely upon their antiseptic properties, the principal constituents being thymol, carvacrol, eugenol, anethol, chavicol, safrol, and their derivatives.

(5) Oils containing esters or alcohols, by far the largest group, consisting of the fragrant oils which are used principally for perfumery purposes, although some find a use in medicine. The chief constituents of these oils are usually alcohols and esters, some few containing aldehydes, ketones, oxids, and lactones. Prominent here are the alcohols menthol, linalool, geraniol, citronellol, sabinol and their esters, benzyl alcohol and its esters, and anthranilic acid and its esters, forming the chief constituents of the oils of peppermint, lavender, geranium and rose, citronella, savine, ylang-ylang, and orange flowers, respectively. Other constituents are the aldehydes citral and citronellal from lemon and lemon-grass oils, and the ketones thujone, menthone, pulegone, carvone, and methyl heptenone from the oils of wormwood, peppermint, pennyroyal, caraway, and rue. The oxid cineol from eucalyptus and many other oils, and the lactone sedanolid from celery oil are further examples.

All volatile oils capable of being isolated from wild aromatic plants will fall into one or more of the foregoing divisions although, it must be understood, the classification is far from being satisfactory. It will, however, serve to elucidate the fact that although plant odors are of a very variable character they still possess some relationship.

COMMERCIAL IMPORTANCE OF VOLATILE OILS AND THEIR CONSTITUENTS.

Not only do volatile oils as such find important uses in commerce, but the great variety of constituents, one of which in many cases forms the major part of an oil, find equally important uses commercially.

Such constituents as have antiseptic properties occur widely in plant oils and are of untold value to the medical profession, to the manufacturer of pharmaceutical preparations, and to the maker of toilet lotions and dentifrices. Many volatile oils also contain constituents which are recognized as very important in the perfumery industries, their value depending not so much upon their own inherent odor as upon the effect which they produce in modifying or toning the fragrance of a mixture of several components. The finest perfumes are often mixtures of odors blended together and frequently contain oils which in themselves would not be regarded as very agreeable or pleasing in odor. In some instances a single constituent, as for instance citral, the chief constituent of lemon-grass oil, is used in its own pure condition without the admixture of other odors, as in the scenting of fine toilet soaps.

As flavoring agents considerable use is made of many of the volatile oils or of their constituents. For example, the oils of sassafras, peppermint, cinnamon, and wintergreen are used by confectioners in the flavoring of candies. The chief constituents of these oils (safrol, menthol, cinnamic aldehyde, and methyl salicylate) can, with the exception of menthol, be used with equal efficiency.

Many essential oils and the compounds isolated from them have proven highly useful in therapeutics, and enter into a number of medicinal preparations. Such constituents as menthol from peppermint oil, eugenol from clove oil, methyl salicylate from wintergreen and sweet-birch oils, thymol from thyme and horsemint oils, camphor from camphor oil, borneol from Borneo camphor oil, cineol from eucalyptus oil, and many others, comprise a group of medicaments which are indispensable.

From the foregoing account of volatile oils and their important constituents may be observed the possibilities which lie in this field of investigation. It is probable that a thoroughgoing examination of the wild flora of the United States would reveal the presence of volatile oils in many plants which at present are not known to yield volatile products. This possibility should stimulate the search for these products with a view to their commercial utilization.

PLANT SOURCES OF CAMPHOR, BORNEOL, AND CINEOL (EUCALYPTOL).

Owing to the presence in large quantities of the compounds camphor, borneol, and cineol in the oils to be described in this bulletin, the usual sources of these compounds are herewith presented, together with their commercial uses.

The occurrence of camphor in the vegetable kingdom as a component of volatile oils has been noted chiefly in such plant families as the Lauraceæ, Compositæ, Labiatæ, and Zinziberaceæ. The source of commercial camphor at present is the camphor tree, Cinnamomum camphora (Laurus camphora), indigenous to Japan and Formosa. This tree has been introduced into the United States and experiments are now being conducted in Florida for the production of camphor, with some degree of success.

Two modifications of camphor occur in nature, the commercial variety, or dextrogyrate (rotating the plane of polarization to the right), and the levogyrate (having the opposite rotation). Comparatively few plants native to this country have been found to yield camphor. Whittelsey has recently succeeded in isolating and identifying levo camphor in considerable quantities from the oil of a western sagebrush (Artemisia cana Pursh., family Compositæ). Camphor has been observed in the native plant Sassafras variifolium (Sassafras officinalis), a tree belonging to the family Lauraceæ. According to Power and Kleber, sassafras oil contains from 6 to 8 per cent of dextro camphor. Traces of camphor have also been observed in tansy oil, obtained from Tanacetum vulgare, a plant which is cultivated in the Eastern States for its volatile oil.

Borneol, or Borneo camphor, is closely related to camphor and possesses very similar properties. It is derived chiefly from the Borneo camphor tree (Dryobalanops aromatica (D. camphora), family Dipterocarpaceæ), and is found in crude crystalline condition in the natural cavities of the wood. Blumea balsamifera (family Compositæ), a shrubby plant native to India, also yields considerable quantities of borneol, known to the natives as ngai camphor. The presence of borneol in plants native to this country is restricted to a few species, where it appears in the free condition only as a trace, being found more widely distributed as esters. It has been found in small quantities in the oil of red cedar (Juniperus virginiana), and in thuja oil from the arborvitæ (Thuja occidentalis), both trees being found abundantly in various sections of the United States. Small quantities have been found in the oils of other native plants, such as the goldenrod (Solidago canadensis), Virginia snakeroot (Aristolochia serpentaria), Texas snakeroot (Aristolochia reticulata), Canada snakeroot (Asarum canadense), tansy (Tanacetum vulgare), and sweet gum (Liquidambar styraciflua). As its acetic acid ester, it occurs in the oils of a large number of species of pines and firs.

Borneol and camphor occur occasionally together in the same oils. Their association is not surprising, since the relationship of the two compounds is very close. By oxidation borneol is readily converted into camphor. The two compounds have been observed together in the oil of cardamon, distilled from the seeds of Amomum cardamomum; also in the oil of rosemary, from the plant Rosmarinus officinalis, and in spike oil, obtained from Lavandula spica, the latter two belonging to the mint family.

Cineol, or eucalyptol, is found chiefly in the volatile oils from various species of the eucalyptus tree and is the principal constituent of many of these oils. The blue gum tree (Eucalyptus globulus), belonging to the family Myrtaceæ and introduced abundantly in the western part of the United States, furnishes a volatile oil of which more than one-half is cineol. Other important sources also are cajuput oil and niaouli oil from Melaleuca leucadendron (M. viridiflora), a plant indigenous to India. Only a few native aromatic plants are known to yield volatile oils which contain cineol and in only a very few cases has this constituent been found to be present in any quantity. It is known to occur in the oil of the California laurel, or mountain laurel (Umbellularia californica), where it is present to the extent of about 20 per cent. Among other native plants in which cineol is known to occur in small quantities is the composite Achillea millefolium, commonly known as milfoil or yarrow. Peppermint oil from Mentha piperita and sage oil from Salvia officinalis are said to contain small quantities of this constituent.

Camphor, borneol, and cineol are found in considerable quantities in volatile oils which have been distilled from three unutilized aromatic plants of the United States, which will be discussed fully in the subsequent pages of this bulletin.

COMMERCIAL USES OF CAMPHOR, BORNEOL, AND CINEOL.

As an article of commerce camphor is most useful, being employed extensively in the arts and in medicine. Its use in the arts is restricted principally to the manufacture of celluloid, a commodity which finds a great variety of uses. It also finds important uses in the manufacture of lacquers and pyrotechnics, in embalming, and, because of its odor, is used as an insectifuge. Camphor is also used to a great extent in medicine both for external and internal application, and enters into many pharmaceutical preparations.

Borneol, although closely allied to camphor, is much less used commercially in the United States, principally because of the difficulties encountered in its collection by the natives in Borneo and the Malay Archipelago. It would probably be used more extensively in this country if a sufficient supply could be obtained at reasonable prices, the high price of the article preventing its use for technical purposes.

Borneol is antiseptic and stimulant, and finds its main use in medicine, but is also in demand in the perfume industry, the esters being especially desirable. The acetic acid ester of borneol (bornyl acetate) is in fact the odoriferous principle of pine-needle odor. Borneol is used mainly as a base for the manufacture of bornyl acetate which is much used in the preparation of pine-needle odors by perfumers. It is in considerable demand in the Orient where, according to Janse, it is sought by the Chinese, who use it principally in religious ceremonies, but also in medicine and the perfuming of India inks. The Chinese are said to pay as much as $1.25 an ounce for it, and since the native producers are unable to supply the demand, a synthetic borneol, which is not a pure substance but a mixture of borneol and isoborneol, has entered the markets of the East.

Cineol, or eucalyptol, is a very important and valuable article of commerce. Its virtue as a remedial agent has placed it in a high position among the important drugs used in the treatment of human ailments. The uses of cineol are entirely medicinal. It is used both internally and externally, and also as an inhalant. It is administered internally in the form of various pharmaceutical preparations for the treatment of colds, pneumonia, bronchitis, and other respiratory affections. As an inhalant it is used for asthma, diphtheria, and throat troubles in general. Together with other medicaments cineol is applied externally in the form of ointments or liniments. Furthermore, it has a wide application in the manufacture of dentifrices, mouth washes, and other preparations where an antiseptic action is desired. At the present time pure cineol, as prepared from eucalyptus oil, commands a price of $1 to $2 a pound.

PURPOSE OF THE INVESTIGATION OF WILD AROMATIC PLANTS NATIVE TO THE UNITED STATES.

Since many valuable volatile oils and volatile-oil constituents have been discovered in plants growing wild in various parts of the world, it has been thought that an investigation of the wild aromatic plants of this country would reveal many, now practically useless and possibly classed as weeds, which might become of commercial value.

The economic value of these plants is determined not only by the proportion of oil which they contain, but by the constituents of the oil; hence careful analyses must be made in order to discover what these constituents may be. The present bulletin deals with the analyses of three heretofore unutilized plants, which may be grouped together, because the oils obtained from them are all of a camphoraceous character and because they contain several constituents in common. These, gathered from different sections of the United States from entirely different habitats and belonging to unrelated families, are as follows: Black sage (Ramona stachyoides) from California, wild sage (Artemisia frigida) from South Dakota, and swamp bay (Persea pubescens) from Florida.

SPECIAL INVESTIGATIONS.

BLACK SAGE.