Story: Plant extracts
An infusion of mānuka leaves, to ease stomach complaints, was a traditional Māori herbal medicine. Kauri trees yield gum, which was exported in the 19th century for its use as a varnish. Chemists studying the ‘natural pharmacy’ of the forests have found unique compounds – including mānuka’s antibiotic leptospermone – which show promise as drugs and other products.
Full story by Nigel Perry
Main image: Mānuka beer label
The Short Story
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Plants contain chemicals (in their leaves, berries, bark or other parts) which can have interesting effects. For example, they can heal wounds, preserve wood, or keep insects away. Others cause skin rashes or poisoning. Scientists are interested in these chemicals, especially as some can be used in drugs and other commercial products.
New Zealand plants
Many New Zealand plants are found nowhere else. Some contain natural chemicals not found in any other plants.
Māori knew that many native plants had healing properties – mashed-up bark from the pukatea tree eased toothache, and you could treat skin sores with a mixture made from boiled twigs.
The tall kauri tree oozes a sticky gum that slowly builds up in the ground around the tree. Huge amounts of gum were found in swamps where kauri forests once grew. The gum was once used to make varnish and floor coverings.
Since the early 1900s, chemists have been analysing New Zealand’s plants. They have found interesting chemicals, including:
- bright red pigments in the flowers of the pōhutukawa tree
- the smelly sulfur compound released by crushed leaves of stinkwood
- the pungent-tasting leaves of horopito, the pepper tree.
So far, few of the chemicals being studied are on sale as products.
Mānuka: oil and honey
Māori people drank a tea made from its leaves to treat stomach problems. You can buy mānuka honey and oil from health food stores and supermarkets.
In the 1990s at East Cape, it was found that oil from the leaves of the local variety of mānuka acted as antibiotics (killing bacteria). Also, the honey from some areas works as an antibiotic. Scientists have discovered the chemical and hope to use it as a medicine.
Other products and possible uses
- Totarol, from the tōtara tree, helps stop timber from rotting.
- Mānuka honey is used in wound dressings.
- Manool, from a pine tree, can be used in perfumes.
- Horopito leaves are sold as herbal medicine to treat fungal diseases
- Prostratin, from a weed, could be used to treat HIV/AIDS.