Tea Tree Oils of the Oceania Region.

Before proceeding to Drs Penfold and Morrisons monograph, it must be mentioned  that New Zealand is also home to two members of the Leptospermum i.e. L. ericoides (White Manuka) and L. scoparium (Red tea tree) 

Habitat, Range, and Occurrence.- This small tree grows on rocky ledges in  inaccessible parts of the Dividing Range of eastern Australia, and is very  sparsely distributed. Small stands occur at Copmanhurst, Macpherson Range,  Punchbowl, Whiteville, and Baryulgil, all in northern New South Wales, and at Spring brook and Palmwood in Queensland.

The authors are greatly indebted to Mr. H. H. G. McKern, Assistant Chemist,  and Mr. J. L. Willis, Botanical Research Officer, Museum of Technology and  Applied Science, Sydney, Australia, for their assistance in the preparation of  this chapter. 11. Proc. Roy. Soc. N. S. Wales 52 (1918) 175.

Planting and Cultivation.-It was early realised that this attractive  shrub, which had been grown as a garden hedge, would have to be cultivated if  commercial demands for its essential oil were to be met. Many experimental plots have been established in Australia, and much  information on cultivation is available. The only commercial plantations in the  British Empire are located in Kenya Colony, although Naves reports an  analysis of an oil sent to him from Rhodesia by the distiller. Outside of the  Empire, the tree is grown in Guatemala.

Yield of Oil.-One thousand pounds of leaves and terminal branchlets yield  from 10 to 15 lb. of a pale lemon colored oil containing from 75 to 85 per cent  of the aldehydes citral (45 to 50 per cent) and citronellal (35 percent)

Distillation.– Portable field stills, similar to those described in the  monograph on Australian Eucalyptus Oils, are employed for the distillation of  Leptospermum citratum. The general procedure of distillation resembles that of  the eucalyptus oils in every respect.

Physicochemical properties.

Use.- The oil is an excellent source of citral and citronellal. The  citral isolated from it is superior to that from any other source, with the  possible exception of Backhousia citriodora. The oil has also been used as a  fortifier or modifier in perfume compounds where citral or  citronellal-containing oils are employed. It has proved helpful in eau de  Cologne, toilet waters, hair oils, powder perfumes, hair washes, and shampoo  preparations.

Physiological Forms.-Aside from the Type oil discussed above, two  physiological forms of Leptospermum citratum were described in 1942. The two  forms are readily distinguished in the field by crushing the leaves between the  fingers. The leaves of variety A ” emit a terpene-like odor resembling  ‘Y-terpinene, whereas the foliage of variety “B” gives a rose-Iike odour  characteristic of geraniol and its esters.

Habitat, Range, and Occurrence.-Melaleuca alternifolia follows  water-courses and flourishes in swampy situations. The tree occurs in fairly  large stands in the Northern Rivers districts of New South Wales, from the  southern limit at Stroud, through the coastal rivers to southern  Queensland.

Distillation.-Two methods are employed in distilling the leaves of this species-namely, distillation in directly fired stills, and distillation of the  foliage with live steam generated in a separate boiler. The stills used for  direct firing resemble those described in the monograph on ” Australian  Eucalyptus Oils,” in the section on “Production.” Made of mild steel, and  holding from 1.5 to 2 tons of leaves, they are connected to a water tank of  approximately 1,500 gal. capacity, in which the condenser coil for cooling of vapors is placed. The distillation occupies about 6.5 hr

The large plants using live steam employ boilers ranging from 24 to 40  h.p. The stills used in this operation are slightly smaller than those employed  for direct firing, as they do not. require a water space in the bottom of the  stills. A wire tray to support the foliage. rests immediately on top ofthe steam  pipes, and live steam of about 15 to 20 lb. pressure is passed through the  leaves.

The oil and steam are condensed in the same manner as in the case of the  directly fired still. The methods of packing and emptying the still are  essentially the same, and there is no difference in the yield and quality of the oil.

The live steam unit consists of a steam boiler with three stills, each  with .its separate condenser tank. Overhead derricks or endless chain blocks are  used to empty the stills rapidly.

As regards the cineole content of the oil, an increase appears to occur in  the winter months, corresponding to the lowered yield.

Physicochemical Properties.
Specific Gravity at 15/15. 0.8950 to 0.9050
Optical Rotation. + 6 48′ to + 9: 48′
Refractive Index at 20 1.4760 to 1.4810
Ester Number. 2 to 7
Ester Number after Acetylation. ..80 to 90
Cineole Content. Under 10%
Solubility in 80% Alcohol (w/w) Soluble in 0.6 to 0.8 vol.

Use.-The complex mixture of substances constituting this oil possesses a  high germicidal value when tested against pure phenol, with B. typhosus as test  organism. The germicidal activity, the pleasant odor, and non poisonous, non  irritant, and non corrosive properties of the oil have resulted in its extensive application in surgical and dental practice. The great value of  the oil in medical practice is due to its property of penetrating pus, and of  mixing with it in a manner which causes it to slough off, leaving a healthy surface.

The following pathological conditions have responded to treatment, either  with the oil alone or with it in a water soluble emulsion: Perionychia, empyema,  gynaecological conditions, skin conditions, epidermophyton infection [psoriasis]  impetigo contagiosa, pediculosis, ring worm, tinea [ albuginea], throat and  mouth conditions, acute nasopharyngitis, catarrh, thrush, and “aphthous”  stomatitis, tonsilitis and ulcers of the mouth, sore throat, pyorrhoea,  gingivitis , diabetic gangrene, etc. It has also been demonstrated that the  water soluble emulsions of Melaleuca alternifolia oil not only retain their  activity in the presence of blood and organic matter, but actually increase in  effectiveness.

An interesting technical application of the oil is its incorporation  (about 1 per cent) in machine “cutting” oils, whereby skin injuries, .especially  abrasions to the hands by metal filings and turnings, have been reduced to a  minimum. Large quantities of the oil were used for this purpose in munitions  factories during World War II. The oil has also found use in perfumery as a  toner and blender, and as a flavoring and antiseptic agent in denture and mouth  washes.

Physiological Forms.-The occurrence of physiological forms was observed  in 1946, when investigations revealed oils containing a high content of cineole.  (A normal distillate of Melaleuca alternifolia contains about 10 per cent of  cineole. ) Since that date it has been noted that oils obtained from various  trees of Melaleuca alternifolia fall into the following three groups:

Type ………………….. 6 to 14 per cent of cineole
Type Variety ‘A’ …. 31 to 45 per cent of cineole.
Type Variety ‘B’ …. 54 to 64 per cent of cineole.

Warning on the Use of Oils Other than “Type” for Medicinal Purposes.~  Recent analyses have shown that the cineole content may vary from 5 to 15 per  cent in the Type oil, although the average of commercial consignments has been  approximately 10 per cent. In view of clinical evidence that the oil should  contain a minimum of cineole, it is imperative that the Type oil only be used  for medicinal and dental purposes.

Oil of Melaleuca linariifolia, Smith.
Botany, Habitat, Range, and Occurrence.-This tall, “Narrow-leaved” paper  bark “Tea Tree” has been fully described by Bentham. It occurs abundantly  throughout the coastal districts of New South Wales and Queensland, following  watercourses and flourishing in all swampy situations.

Yield of Oil.– One thousand pounds of leaves and terminal branch lets  yield from 15 to 20 lb. of a pale lemon colored oil. Distillation.-The  procedure is fully described in the monograph on “Oil of Melaleuca  alternifolia.

Physicochemical Properties.

Use.-Although the oil possesses a high germicidal value, the presence of  cineole in quantity renders it unsuitable for many of the applications described  under Melaleuca alternifolia. Nevertheless, the composition of the oil closely  resembles that of Melaleuca alternifolia, with the exception that cineole  largely replaces the alcohol I-terpinen-4-ol, The applications of Ithe oil,  therefore, are restricted to those where a high percentage of cineole is  unimportant, as, for example, in the manufacture of some germicides and soaps  other than those required for surgical, medical, and dental work.

Physiological Forms.-Many samples of this oil have been observed by ,the  authors to contain cineole in excess of 20 per cent, the figure often reach-  ling 60 per cent of cineole. As in the case of Melaleuca alternifolia this wide  variation in cineole content indicates the definite occurrence of physiologica1  forms of the species. We have already mentioned that physiological forms of  essential oil-yielding plants are those which are identical morphologically but  which yield oils of different composition.

Oil of Melaleuca viridiflora. Gaertner.

Introduction and Botany.-This species was named on the basis of specimens  collected by Banks and Solander during Captain Cook’s voyage to Australia in  1770. The species has generally been described as Melaleuca leucadendron and  some authors still retain this nomenclature.

Baker and Smith, in a critical study of the so-called , Broad leaved Tea  Trees,” not only separated the Australian tree from the New Caledonian but  declared Melaleuca l eucadendron Linn. extra-Australian. By reason mainly of  differences in chemical composition of the essential oils obtained from M.  viridiflora growing in different localities. Smith, established two new species,  Melaleuca maideni and Melaleuca smithii.

The present authors agree with the views of the botanists Cheel and White  that these are not distinct species but are closely related forms of M.  viridiflora.

Origin, Habitat, and Range.-Melaleuca viridiflora is trees of the genus,  reaching a height of 60 ft. It is usually found in low lying, sandy, swampy  country , not far from the sea. With its paper bark and compact bushy foliage,  consisting of rather stiff, flat parallel veined leaves, the species presents  little difficulty in identification. This broad leaved “Tea Tree” is widely  distributed, occurring all along the coastline of Australia from Port Jackson in the south to the Gulf of  Carpentaria in the north. The tree produces an excellent, pale, hard, close-  grained timber, suitable for boat and carriage building and general cabinet  work.

Physiological Forms.-Although Melaleuca viridiftora Gaertner is a  distinct botanical entity based on morphological evidence, the variations in the  chemical composition of the essential oil warrant its classification, for  commercial purposes, according to physiological forms. This procedure has  already been adopted with other essential oil-yielding plants which are  botanically identical, but which yield essential oils of diverse chemical  composition. The evidence available justifies the establishment of two distinct  physiological forms of Melaleuca viridiftora based upon differences in chemical  composition of the essential oils, viz., the Type, similar in chemical  composition to Cajuput oil of commerce (containing cineole and  terpineol), and Variety ” A ” (containing nerolidol and/or  linalool).

Yield of Oil.– The yield of oil obtained from the leaves and terminal  branchlets varies from 1 to 2.6 per cent, according to the physiological form. 

Variety ” A.”- The following constituents have been identified: Linalool,  nerolidol, some linalool monoxide, sesquiterpenes, citral, traces of phenol and  benzaldehyde.

(Cf. the preceding monograph on “Oil of Melaleuca viridiflora  Gaertner.”)

In New Caledonia, a French island possession in the Pacific, about 800 miles  off the east coast of Australia, the tree forms patches and sparse . forests  covering approximately two-fifths of the island. Hardy, resistant, and of great  vitality, it flourishes on swampy and rocky .soil alike, in the coastal lowlands  as well as on mountain slopes up to an altitude of about 1,000 ft. Its sturdy,  widespread roots split the schistaceous soil and in a way prepare the ground for  cultivation. It is almost impossible to exterminate the tree by root pulling or  burning, because new shoots soon reappear from those parts of the prolific root  system which have been left in the ground. The tree quickly invades uncultivated  land, and planters consider it a nuisance-also because it is liable to spread  bush fires.

Melaleuca viridiflora is quite a decorative tree and occasionally reaches  great dimensions. During certain periods of the year large quantities of fallen  leaves cover the ground, and, since they contain an essential oil which acts as  a strong disinfectant, the native population attributes the healthy air of New  Caledonia and the absence of malaria in certain sections to the occurrence of Melaleuca viridiflora in these localities.

Production of Oil.-The tree is not cultivated, as it grows profusely over  wide areas of the island. Since labor is quite scarce and relatively high  priced (it has to be imported from French Indo-China and the Netherlands East  Indies) , the production of Niaouli oil has remained a small family industry  among the settlers-some of them French, some Asiatic. Children and women collect  the leaf material, while the men attend to the actual distillation..

The center of production is in Gomen, whence the French term “Gomenol”  for Niaouli oil.
Production of Niaouli oil in New Caledonia.

Distillation.-Most of the stills, particularly those of small size, are  directly heated. From 500 to 1,000 kg. of-freshly cut leaves are packed into a  still, trampled down, some water is poured in, and the contents are distilled  for about 6 hr. The leaves are said to contain about 2.5 per cent of essential  oil, but in the rather primitive stills employed in New Caledonia the yield of  oil from fresh leaves ranges from only 0.6 to 1.0 per cent. It varies greatly  and depends upon climatic and seasonal conditions, the location, and most of all  upon the type of still used.

Yields of about 2.5 per cent have been obtained from the leaves of  Australian trees.

Physicochemical Properties.-Oil of Niaouli closely resembles oil of  Cajuput as regards physicochemical properties and chemical composition. The oil  possesses a slight by-odor of bitter almonds (due to the presence of  benzaldehyde) , which perhaps accounts for its popularity in France.

Gildemeister and Hoffmann recorded these properties for Niaouli oil :

Specific Gravity at 15C 0.910 to 0.929
Optical Rotation– Slightly dextro-, or (usually) laevorotatory , +  0! 42′ to 3. 34′ 
Refractive Index at 20C 1.465 to 1.472
Acid Number. Up to 2.
Ester Number. 2 to 9
Cineole Content. 50 to 60%
Solubility. Soluble in about 1 vol. of 80% alcohol; of 70% alcohol 4 to  25 vol. are required for clear solution In the experience of the present authors  the Cineole content of Niaouli oil ranges from 40 to 65 per cent.

Shipments of Niaouli oil received and examined by Fritzsche Brothers,  lnc., New York, had properties varying within the following limits:
Specific Gravity at 15/15, 0.912 to 0.922
Optical Rotation . 0.10 to +1.18′
Refractive Index at 20C. 1.4670 to 1.4722
Saponification Number. 3 to 5
Cineole Content. 52 to 57.8%
Solubility. Soluble in 1 vol. and more of 80% alcohol.

Adulteration.-In the producing regions oil of Niaouli is occasionally  adulterated with kerosene or with fatty oils. A very high cineole content may indicate the addition of eucalyptus oil, which is usually lower priced than  Niaouli oil.

The oil is exported from Noumea, the capital of New Caledonia, usually to  Marseilles, for distribution to various parts of Europe and transshipment to the  United States.

Use.-Because of its antiseptic properties, the oil is used, particularly  in France, as a substitute for oil of Cajuput and oil of eucalyptus in the  treatment of coughs, rheumatism, and neuralgia. Internally, it is given by mouth  or in the form of intramuscular injections, One part of niaouli oil being  diluted with four to ten parts of a sterilized fixed oil.

The oil has been recommended also in the treatment of chronic catarrhs of the  pulmonary membrane and especially of whooping cough. Behrens reported on the  application of a mixture of 5 g. of niaouli oil and 95 g. of paraffin oil when  building an oleothorax. Morin has claimed that a solution of 0;5 g. of niaouli  oil in 100 cc. of olive oil retards development of the tuberculosis bacillus.  Bernou recommends stronger solutions, ranging from 2 to 4 per cent, for blocking  the development of the tuberculosis. bacillus, and 4 to 10 per cent solutions in  cases of tubercular empyema.

The oil has always brought a high price in France, a matter of surprise to  the authors in view of the lower prices prevailing for medicinal eucalyptus oils  produced in Australia and Spain. Perhaps niaouli oil is simply a part of old  pharmaceutical formulas, and manufacturers hesitate to change them to eucalyptus  oil. Another reason for the consistently high price of niaouli oil may be that  the oil is a medium of exchange between France and New Caledonia. This factor  has probably encouraged the export of niaouli oil from the colony to France.  From a strictly technological point of view, the authors consider present-day  medicinal eucalyptus oils to be at least the equivalent of niaouli oil. This oil  could also be produced in Australia (New South Wales and Queensland} from  Melaleuca viridiflora growing there abundantly, but production has been  restricted because of the lower yield of oil compared with that obtained from  Eucalyptus species.

Oil of Melaleuca bracteata. F. von Mueller.
Introduction and Botany.-This tree, commonly known as the “Black Tea Tree,” occurs in small stands in the northern parts of New South Wales and  southern Queensland. It flourishes in favorable locations such as creeks and  watercourses. In general appearance it closely resembles another “Tea Tree,”  viz., Melaleuca trichyostachya. The leaves are small, being about 1 in.  in length. The tree possesses long terminal branchlets and calyxes ; the bark is  hard, compact, and furrowed; these characteristics distinguish it from other  paper bark “Tea Trees.” The species was first. described by Baron von Mueller.  The tree attains a height of 30 to 40 ft. Yield of Oil.-The leaves and terminal  branchlets yield from 0.4 to 1.0 per cent of a light amber colored oil,  heavier-than-water.

                                         Physicochemical Properties..
                                         Specific Gravity at 15/15C 1.025 to 1.039
                                         Optical Rotation at 20C – l!24′ to – 4.0′
                                         Refractive Index at 20C 1.529 to 1.535
                                         Acid Number 0.7to1.3 Ester Number 5.3 to 17.1
                                         Ester Number after Acetylation. 17.0 to 32.9
                                         Solubility in 70% Alcohol (w/w) …Soluble in 1.0 vol

Use.-As a source of methyl eugenol, as an insect repellent, and for  purposes similar to those described under “Huon Pine Wood Oil” .  Economics.-The comparatively low yield of oil (less than 1 per cent)  militates against the extensive use of this oil as a source of methyl eugenol in  competition with oil of Huon pine. The wood of this latter yields from 4 to 6  per cent of oil. Huon pine wood oil is becoming scarce, and an alternative  Australian source of methyl eugenol is urgently required. Experimental  plantations of Melaleuca bracteata are therefore being established by the  authors for the purpose of obtaining high yielding strains for commercial  plantations. That the potentialities of the oil are realized is evident from  reports on samples of oil distilled from Melaleuca bracteata grown in Kenya from  seeds sent from Australia.

Physiological Forms.-Recent work at the Museum of Technology and Applied  Science, Sydney, has shown the occurrence of physiological forms within this  species. Investigating the essential oils from the foliage of selected trees of  Melaleuca bracteata occurring throughout the eastern coast of Australia, the  present authors recently obtained very interesting results.

A number of the oils examined contained from 85 to 90 per cent of methyl  eugenol, whereas other oils contained equivalent percentages of methyl iso-  eugenol and elemicin, respectively. This is the first recorded occurrence of  methyl isoeugenol in Australian essential oils, and the first time elemicin has  been identified in oil of Melaleuca bracteata. As the trees, from which the oils  were obtained, grow in close proximity to each other, there would appear to be  no doubt about the occurrence of two physiological forms of Melaleuca bracteata.  The separate occurrence of different phenol ethers as major components, and  without admixture with each other, in oils derived from individual trees of this  species is a matter of considerable biological and economic significance.