This article byJennifer Farrer first appeared in APS Parramatta Hills Group newsletter Calgaroo. Part 1 is on early colonial uses of medicinal native plants.
The information is from a variety of sources including the book Australian Medicinal Plants by E.V. Lassak and T. McCarthy (Reed New Holland, 2011) gathered by Jennifer over many years as a guide with Boronia Tours.
Of all the Australian plants with medicinal properties only 30 have been exploited commercially and of these 20 are various species of Eucalyptus.
The pharmacist Joseph Bosisto migrated to Australia in 1848 and began the first serious investigation of the volatile oils of Australian flora. In 1854 he started the first commercial production of eucalyptus oil in Victoria. He used the process of steam distillation which is a process first developed in the Middle Ages. The leaves are placed in a vessel fitted with a lid and an outlet pipe connected to a water cooled condenser. After the addition of a certain amount of water the leaves are boiled and the steam enriched with the vapour is passed through the water cooled condenser. There the steam and the essential oil vapours are reliquefied. Since the oil and the water do not mix, the lighter-than-water oil can be skimmed off the surface of the condensed water. This method at its simplest is still being used by small distillers in country areas particularly Braidwood, Tumut, Cooma, and Casino in NSW and Bendigo in Victoria.
Of the 20 species of eucalypts used to produce this type of oil, the most commonly used is the blue mallee, Eucalyptus polybractea. Even though Australia is the home of the eucalypt, only 5% of Eucalyptus oil is produced here. Portugal and Spain account for 60% of the world’s production using the foliage of the Tasmanian blue gum Eucalypts globulus which was introduced into Europe last century as a timber tree and for paper production.
Tea tree oil
Another medicinal oil produced today on a commercial scale is that of medicinal tea tree (Melaleuca alternifolia). It is produced by a small number of distillers around Casino and Lismore by the same steam distillation process used to produce Eucalyptus oil. Apart from its bactericidal applications, the oil is used in the flavouring industry.
Commercial production of this oil faltered in the 1970s due to unreliable supply, inconsistent quality and lack of promotion. The foliage was hard to obtain as the species is found on swampy ground which made harvesting difficult especially in years of high rainfall. The oil content of the naturally occurring trees was also quite variable.
The situation changed in the 1990s. Manual harvesting of variable natural stands of Melaleuca alternifolia was eliminated. Highly successful efforts to improve the seed enabled huge plantations which could be harvested mechanically to be established along the eastern coast of northern NSW, southern Queensland and even inland. Australian tea tree oil is now well established in world trade and is even included in the International Standards ISO 4730.
The leaves of corkwood (Duboisia myoporoides) a native tree of the rainforests of northern NSW and southern Queensland contain a large proportion of an alkaloid (hyosine) which is used to treat stomach ulcers and sea sickness. The production of corkwood foliage on the north coast of NSW has been a steady if not large industry. The collected leaves are dried out of the sunlight and sold overseas to pharmaceutical firms to extract the alkaloidal constituents. Boehringer Ingelheim has an Australian plantation of 1,400 hectares in northern NSW which employs 20 people in the harvesting of Duboisia myoporoides leaves for the drug Buscopan.
The pale yellow resinous exudates from the cut trunks of the white and black cypress pines (Callitris sp) is sold overseas under the name of Australian sandarac. This resin is used to coat pills which are to dissolve in the intestine and not in the stomach.
The collection of the resin is a cottage industry. Parts of the forest which have been logged more than a year previously are visited to collect the resin which has now collected on the stumps in worthwhile quantities.
The future of the medicinal plant industry in Australia is bright as the world looks to become less dependent on the petroleum industry to produce synthetic organic chemicals. There are many potentially useful plants to be developed.
Note: Care should be taken in the medicinal uses of native plants which requires expert knowledge.