Kōrero: Plant extracts

Whārangi 2. Toxic and commercial compounds

Ngā whakaahua me ngā rauemi katoa o tēnei kōrero

By isolating the active chemical in poisonous plants, researchers can work on remedies, treatments or possible beneficial effects of a poison. Poisonous plants may also contain chemicals new to science.


One plant that soon came under the microscope in New Zealand was tree tutu (Coriaria arborea) – sheep, cattle and horses died after browsing on its leaves. In 1900 the chemists Thomas Easterfield and Bernard Aston purified and identified tutin, a neurotoxin new to science.

Tutu poisoning via honey

An indirect form of tutu poisoning affected humans, through honey bees from the northern hemisphere. In some parts of New Zealand the bees occasionally produced honey that caused violent convulsions and death. Investigation of honey from the Bay of Plenty in the 1940s led to the discovery of mellitoxin, closely related to tutin. The connection to tutu was made when it was noticed that bees were collecting honeydew from vine hoppers, which were in turn feeding on tutu. Honey production is now controlled when tutu and vine hoppers are common.

Varnish from kauri gum

One of the first New Zealand natural plant products to be used commercially was kauri gum, a resin that oozes from kauri trees (Agathis australis), which grow in the far north.

Blended with linseed oil, the gum was used for varnish, and for the manufacture of floor coverings. A trial batch was sent to London in the 1830s and by 1899 gum production reached a peak of 9,979 tonnes.

Nearly 100 years later, in 1985, a processing plant was built at Kaimaumau north of Awanui to extract resins and waxes from kauri chips and dust from a peat swamp. The plan was to use the extracts for paper coatings and lipsticks that wouldn’t melt in the sun. However, there were technical problems and the factory closed in 1989.

A bite in the bush

Horopito grows throughout most of New Zealand, especially on bush margins. Chewing a tiny bit of the red-blotched leaf will show why this plant is also called pepper tree, and why it was sometimes used to treat toothache – or at least distract from it. The chemical producing the burning, pungent taste is called polygodial.

Steroids from poroporo

In Taranaki in the late 1970s and early 1980s, poroporo shrubs (Solanum laciniatum and S. aviculare) were grown for solasodine, a steroid used in contraceptives. When it proved cheaper to raise such plants overseas or use synthetic substitutes, poroporo was no longer cultivated in New Zealand.

Manool and totarol from conifers

Manool is extracted from dead logs of the small native conifer, pink pine (Halocarpus biformis). Manool is valued by perfumers because it can easily be converted into compounds with a powerful, sweet yet dry aroma similar to ambergris.

Totarol, as indicated by its name, was first found in tōtara (Podocarpus totara). This compound has an antibiotic effect and is being developed as a natural preservative.

The accumulation of compounds such as totarol and manool in the heartwood of long-lived conifers probably helps to protect the trees from rotting. When the timber is used for building, there is no need for additional antifungal treatments.

Me pēnei te tohu i te whārangi:

Nigel Perry, 'Plant extracts - Toxic and commercial compounds', Te Ara - the Encyclopedia of New Zealand, http://www.TeAra.govt.nz/mi/plant-extracts/page-2 (accessed 2 March 2024)

He kōrero nā Nigel Perry, i tāngia i te 24 Sep 2007