Medicinal plants

CONTENTS

Spurge milkweed Euphorbia characias © Ita McCobb

Early use of medicinal plants

Plants and their extracts have been used since prehistoric times for treating human diseases and for their healing properties. Despite the ancient nature of the tradition, medicinal plants surprisingly still form the basis of traditional or indigenous health systems.

Physical evidence of the use of herbal remedies goes back around 60,000 years to a burial site at Shanidar Cave in Iraq in which a Neanderthal man was uncovered. Analysis of the pollen grains discovered with the corpse indicated that the plants from which they came were of medicinal value

China and India recorded descriptions of medicinal plants as early as 2700 BC. Egyptian, Greek, Roman and Arab physicians also described medicinal properties of plants.

Hippocrates, c.460-370 BC, a Greek physician known as the Father of Western medicine, used a number of medicinal plants. He is credited with having written, “Let your foods be your medicines, and your medicines your food.”

The first botanic gardens, which were purely for the academic study of medicinal plants, were the Physic gardens of Italy founded in the 16th century. These medicinal gardens soon spread to universities and apothecaries throughout central Europe.

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Opium poppy Papaver somniferum © Ita McCobb

Modern usage of medicinal plants

According to the World Health Organization (WHO), a medicinal plant is any plant that in one or more of its organs contains substances that can be used for therapeutic purposes, or which are precursors for chemo-pharmaceutical semi-synthesis.

This definition allows for a distinction between the already known medicinal plants whose therapeutic properties have been scientifically established and other plants used in traditional medicines and regarded as medicinal, but which have not yet been scientifically studied.

In 1985, WHO estimated that around 80% of the world’s population relied on medicinal plants as their primary health-care source.

Around 30% of the drugs sold worldwide contain compounds derived from plant material (UN Food and Agriculture Organization). Either these drugs currently contain plant-derived materials or synthesized materials from agents originally derived from plants.

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Chemicals in medicinal plants

Plants synthesize many compounds called primary metabolites that are critical to their existence. They also produce thousands of additional substances (secondary metabolites) that act as defence chemicals against predation or infection since they have medicinal properties proven to be beneficial to humankind.

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White willow Salix alba © Ita McCobb

Medicines from plants

Morphine, the first pure medicinal substance derived from plants, from the Opium poppy Papaver somniferumas, was the first alkaloid to be discovered.

Atropine is an alkaloid extracted from Deadly nightshade Atropa belladonna, and is used to treat certain heart conditions and to relax the muscles of the eye.

Quinine, an alkaloid from the bark of the Fever tree Cinchona succiruba, is used to treat malaria.

Salicylic acid, a phenol that comes from the bark of the Willow tree Salix species, is the active ingredient in aspirin. Aspirin is now synthesized in the laboratory.

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Monarch butterfly Danaus plexippus © J Hope-Morley

Plants and modern medicine

Many traditional herbal drug preparations are compounded from several plants and numerous medicines used today are extracted from plants.

In the developed world over 25% of all prescriptions contain materials isolated from plants. Others are synthesized copies of chemicals found naturally in plants or are modified from the initial natural product.

Despite the high reliance on plants in medicine less than 20% of species have been investigated for the presence of bioactive compounds.

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Nature’s self-medicators

It has long been known that animals such as chimpanzees seek out medicinal herbs to treat their diseases. Moths, ants and fruit flies also self-medicate.

Wood ants incorporate an antimicrobial resin from conifer trees into their nests, preventing microbial growth in the colony, while parasite-infected Monarch butterflies protect their offspring against parasitic growth by laying their eggs on anti-parasitic milkweed.

In an article entitled Self-Medication in Animals published in the journal Science in April 2013, the researchers stated that because plants remain the most promising source of new pharmaceuticals, studies of animal medication may lead to discovering new drugs to treat human ailments.

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Common thyme Thymus vulgaris © Ita McCobb

Loss of medicinal plants

Most of the world’s supply of medicinal herbs is obtained not by cultivation, but by collecting from the wild – so their growth security is under pressure.

In 2008, Botanic Gardens Conservation International reported that hundreds of medicinal plants were at risk from over-collection, deforestation, destruction of their habitats and global climate change.

Researchers warned that whenever a plant species becomes extinct there is a risk that cures for diseases such as cancer may be lost.

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Corsican pine Pinus nigra ssp laricio © Ita McCobb

Conservation of medicinal plants

The best means of conservation of medicinal plants is to ensure that they grow and evolve in the wild, in their natural habitats.

If conserved, medicinal plants will continue to provide benefits for health care, income and the support of our cultural heritage.

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References: The World Health Organization, WHO; World Wildlife Fund, WWF; plantlife.org.uk; Botanic Gardens Conservation International; Agriculture and Agri-Food Canada; University of Michigan; Missouri Botanical Garden.