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Plant of the Month 2017

Flower_SCI Summer Reception 2017

In recent months Plant of the Month has taken inspiration from SCI’s SCIence Garden, which was launched in July of this year. Dr Alison Foster and committee members of SCI’s Horticulture Group played an integral role in bringing the Garden to life, with a diverse array of plants representing SCI’s technical and regional groups. The Garden also showcases the connections between all areas of chemistry related science and highlights the intrinsic role played by natural resources and the environment in industry.

Archive issues of the Horticulture Group newsletter, including Plant of the Month up to March 2017, can be found here.

December: Ricinus communis, Euphorbiaceae - Castor oil plant

How long will it last?

December is almost certainly not the month you would suggest if asked what month a castor oil plant would look at its best when growing outside in the UK. If that plant is growing in the SCIence garden at SCI headquarters in Belgrave Square you may have to reconsider though.

Ricinus - Communis, EuphorbiaceaeGrown from seed this spring and planted out in the garden in June, the castor oil plant has done particularly well. Perhaps it is the heat-retaining brick wall it is growing up against? Or the regular watering it received through the summer (many thanks to SCI staff member Sonia!)? It now stands at around 6ft tall and has flowered all summer producing a number of seeds ready for next year’s plants.

Ricinus communis is being grown at SCI because of the wealth of uses of castor oil, which is isolated from the seeds.

Although castor oil has many medicinal uses, there is also a deadly substance in the seeds - ricin, and that has made this plant rather infamous. Ricin is a lectin - a carbohydrate binding protein - which is a well-known toxin and has been used in a number of terrorist acts and also to murder the Bulgarian dissident Georgi Markov. More recently, a retired lady in the USA has been accused of testing home-made ricin on fellow residents in a retirement community!

On a more positive note, ricin is currently being investigated for potential use in anti-cancer therapies. The castor oil plant also has other claims to fame in the medicinal plant world.

Castor oil is an important solvent for many drug formulations but there is one drug that would never have made it through clinical trials testing and then to widespread use if it were not for the castor oil plant. The anti-cancer drug paclitaxel (also known as taxol) is a very insoluble substance but in order to get it into patients it must be formulated as a solution. Many solvents were tried and none worked and so the development of the drug was held up. Eventually a solvent called Cremophor EL was found to dissolve paclitaxel. Cremophor is a polyethoxylated castor oil substance. The clinical trials could then go ahead. Taxol is now used to treat patients with lung, breast and ovarian cancer. The downside to the use of cremophor is that it is fairly toxic in its own right and patients often are pre-medicated to alleviate potential adverse reactions to this solvent. However, many thousands of patients would not have received the life-saving treatment without it.

Today there are other formulations of paclitaxel available as well as Taxol. Abraxane, is a formulation of paclitaxel using nanoparticle albumin.

Ricinus communis is not the only “tender” plant that is growing in the SCIence garden. There are also citrus, cycads, and Dichroa febrifuga, none of which would survive a typical British winter in much of the country, but in the warmth of central London they should be fine.

It remains to be seen how well the castor oil plant will survive this winter outside at SCI - do pop out to the garden to take a look on your next visit. Whether this particular plant survives or not, Ricinus communis will be in the SCIence garden in 2018.

November: Eucommia ulmoides

Who needs flowers? It’s what is inside that matters…

At the outset of the project to rejuvenate the outdoors space behind SCI headquarters in Belgrave Square, there was a single imperative. Senior Arboricultural Officer at Westminster City Council, Barbara Milne, had given permission for the large Lawson cypress that dominated the 'garden' behind No 15 to be removed, but a suitable replacement tree 3-4m tall and of 12-14cm trunk girth must be planted.

Eucommia ulmoidesWhen asked for suitable tree suggestions almost the first to spring to mind with a strong connection to SCI interests was Eucommia ulmoides. This is the only hardy, rubber-producing tree. The name Eucommia derives from the Greek for true or good (eu) and kommi (gum). When the leaves are torn gently across, threads of rubber remain strong enough to support the torn portion. Barbara Milne was very supportive of the proposal, stating 'To the best of my knowledge Eucommia ulmoides is a very uncommon tree in central London, but it seems highly appropriate in the context of the SCI'.

Eucommia through the buildingThe Eucommia was the first plant into the ground of the new garden - in April of 2017. It was quite a challenge manoeuvring the required 3-4m tall specimen through the buildings and into the garden, but we succeeded!

The primary source of natural rubber is Hevea brasiliensis, the Para rubber tree, native to South America. Commercial cultivation of rubber began after seeds were smuggled out of Brazil in the late 19th century and made their way via Royal Botanic Gardens, Kew, to various tropical dominions of the British Empire and beyond. Today, Thailand, Indonesia and Malaysia are the largest producers of natural rubber. H. brasiliensis is not cultivated widely in South America due to the presence of a fungal disease known as South American leaf blight, caused by the ascomycete Microcyclus ulei.

Euphorbia characiasWhilst it is not possible to grow a Para rubber tree in the garden at Belgrave Square, we can grow other rubber producing plants successfully. Euphorbia characias grows in the back left corner of the new garden of No 15. It has grey-green narrow leaves, and when a leaf is broken or a stem snapped, a white latex is released as with all species in this genus. Gardeners are taught to avoid skin contact with Euphorbia sap, due to the phytotoxic reaction that causes skin discolouration and burns. However, this sap also has significant potential as a source of natural rubber.

Other rubber producing plants that do not yet feature in the SCIence garden include two plants in the daisy family - a Russian relative of one of the more common garden weeds and an evergreen shrub native to Texas and northern Mexico. Known as rubber sources for many decades and even used as commercial sources in the era of the second world war, these two plants are enjoying renewed commercial interest. They are being developed separately by two different tyre manufacturers as alternative natural rubber sources.

Continental are developing the production of commercial and domestic use tyres using Taraxagum™, a natural rubber sourced from Taraxacum kok-saghyz, the Russian dandelion. To date the company has won a series of awards for the ongoing development of this sustainable rubber source and are investing in a research facility for industrializing the cultivation and processing of the dandelion rubber. Their new research facility, Taraxagum Lab Anklum, will be based in the north east of Germany.

Bridgestone are focusing instead on rubber sourced from guayule, Parthenium argentatum. Parthenium argentatum USDARubber from this plant is very similar in make-up to that from Hevea brasiliensis. The Bridgestone Group have a research farm in Arizona where they are developing breeding programmes and cultivation techniques for guayule and a Biorubber Process Research Centre, also in Arizona, allowing them to develop in house the necessary processing techniques to allow manufacture of tyres from this alternative rubber source.

Yulex, founded in 2000, focus on developing natural rubber materials from a range of plant sources, including both the Russian dandelion and guayule. They have also developed a proprietary process to remove the proteins and other impurities that contribute to causing latex (natural rubber) allergies.

Could guayule be cultivated at SCI headquarters? Favouring arid climes, it should do well in a pot in a very sunny location through the summer, but may not fare so well the rest of the year.

By contrast, stopping dandelions from growing might be the bigger challenge for the garden at SCI!

October: Ammi visnaga - khella, Bishop’s weed, toothpickweed

Khella_Plant of the Month Oct 2017Currently in flower in the garden at SCI headquarters, is Ammi visnaga, a member of the carrot and parsley family. The seeds were sown in May this year, directly into the ground where it now flowers. With beautiful feathery foliage and stunning umbels of white flowers, this annual makes an excellent addition to any garden. Earlier flowerings would be achieved from seed sown in the previous autumn.

Also known as Bishop’s weed, khella, and toothpickweed, it is native to the Mediterranean region - from the Canary Islands and Morocco, eastwards to Egypt and Iran. It is commercially cultivated in Egypt, Morocco and Tunisia. Indeed, this plant was known to the ancient Egyptians for its antispasmodic properties, and has been shown to produce a chemical compound called khellin. Between 1958 and 1966 a drug discovery programme was undertaken in Belgium using khellin as the inspiration. Scientists synthesised and tested a large number of potential drug molecules with structures similar to that of khellin until finally one was shown to be an effective coronary vasodilator. Compound L2329 (amplivix, benziodarone) now known as amiodarone was born. It was initially used as a treatment for angina pectoris, (which translates from latin as a “strangling feeling in the chest”) but further research showed that it would be effective in treating heart arrhythmias. It became widely used for this purpose in Europe by the 1980’s but remained unapproved by the Food and Drug Administration (FDA) in the USA for any use. Physicians in America were prescribing the drug, but were forced to source it directly from pharmaceutical companies in Canada and Europe. The FDA relented and in 1985 approved the use of Amiodarone for the treatment of arrhythmias.

The dried flower stems (pedicels) of khella are sold in Egypt for use as toothpicks - hence the common name of toothpickweed. Ripe fruits (and standardised extracts thereof) are also used in herbal medicine in a range of cardiac, coronary and urological remedies. However, there are some concerns over its safety when used as a crude extract.

Khellin_Plant of the Month Oct 2017

Khellin

Amiodarone_Plant of the month oct 2017

Amiodarone

September: Amazing Maize

Zea mays - sweetcorn

Sweetcorn_SCIence Garden_croppedIt has been a good summer for growing sweetcorn. Many of us will be enjoying ample harvests from our gardens and allotments but sweetcorn is used for a lot more besides just eating!

When we take medications, in whatever form, how many of us realise that the active component is often only a small proportion of the formulation? The bulk of the medication (suppository, transdermal patch, solution, inhalation powder, tablet etc) that is not the active pharmaceutical ingredient has many different functions. Excipients facilitate the packaging of active ingredients. They can be used to enhance the absorption of the drug into the body, to alter the rate of absorption (i.e. to generate a slow release formulation) and to mask unpleasant tasting drugs.

Coatings are used to protect the contents from atmospheric moisture or to mask the bitter taste of the interior. Most tablets are coated with hydroxypropylmethylcellulose (HPMC), which is sugar free and does not contain potential allergens. Sometimes other coatings are used. One such is zein, a prolamine protein isolated from maize. Prolamine proteins are a group of plant storage proteins that have a high proline and glutamine content.

Maize is also an excellent source of starch - another commonly used excipient in tablets.

Proline

Proline

Glutamine

Glutamine

Sweetcorn and long term science?

On a recent visit to the University of Illinois at Urbana Champaign, whilst walking through the campus, I spotted what looked like a field of sweetcorn growing in the middle of the campus. Now, I know in Illinois, fields of corn are everywhere but on a university campus?

The Morrow Plots_University of IllinoisOn further investigation I found this sign. Another information panel informed me that these plots, which used to cover a larger area, were modelled on the experimental field plots at Rothamsted Research in Harpenden, which I visited just a few years ago. These plots were all designed to study the effect of long term crop production on soil properties including fertility.Rothamsted Reseach

Each sub-plot has been subjected to a different treatment - different levels of a range of nutrients, been part of a rotation system or not and above all everything is documented so the results can be further interpreted. Scientists have learnt that crop production does reduce the organic matter content of soils and lowers nutrient levels, requiring these to be added back in to the soil in order to maintain production levels.

July: Aloysia citriodora, lemon verbena, Verbenaceae

Lemon VerbenaThis lemon scented plant, not in the Citrus family, is native to South America. It is not reliably fully hardy in the UK, but should survive most winters although leaf loss will be observed when the temperatures reach 0°C. Unless the temperatures have plummeted to -10°C or below, plants should re-sprout the following spring.

Lemon verbena was first brought to Europe in the 18th Century and reached England when John Sibthorp, Sherardian Professor of Botany in Oxford (1784-1796) brought it back from Paris. By the end of the 18th Century it was being widely grown.

The lemon scent of the leaves when crushed is due to the presence of limonene, and the citral isomers neral and geranial.

The essential oil is said to have a wealth of beneficial properties from antiseptic to anti-depressant.

Whatever its potential medicinal benefits, the leaves definitely make a lovely and very refreshing tea. Try it some time!

Geranial

Geranial

Neral

Neral

Limonene

Limonene

June: Melaleuca citrina (Callistemon citrinus), lemon bottlebrush, Myrtaceae

Lemon bottlebrush Although perhaps more familiar to many people as Callistemon, the current accepted generic name for this plant according to the World Checklist of Selected Plant Families is Melaleuca. This “lumping” of Melaleuca and Callistemon follows a paper from 2006 by botanist Lyn Craven, where it was argued that the differences between the genera did not warrant them being maintained separately. However, not all Australian Herbaria have taken up this system.

Named Melaleuca citrina in 1802, this species was already reasonably widespread in cultivation in Britain by then, but to add even more confusion to the picture it was then known as Metrosideros citrina after an illustration was published in Curtis’ Botanical Magazine in 1794. This was one of the first Australian plants to be grown in Britain after being brought here by Joseph Banks in 1770.

The flower spikes, for which the plant gets its common name of bottlebrush, are made up of many individual small flowers. The petals are actually very short and insignificant and it is the coloured filaments which bear pollen on the anthers at their tips that make up the showy part of the flowers that give the plant the common name.

When the leaves are crushed they give off a citrus like odor. The major components of the essential oil derived from the leaves are 1,8-cineole and α-pinene. The essential oil shows strong antibacterial properties against a range of gram positive bacteria.

This plant, along with others in the myrtle family, contains another interesting chemical called leptospermone. This substance was first identified in 1927 and later isolated from a range of plants in the 1960’s. However, it was not until 1977 that it was first isolated from a plant of Melaleuca citrina (then known as Callistemon citrinus) growing in California. A researcher working for the Stauffer Chemical Company observed that very few plants were growing under these bottlebrush bushes. He took soil samples from underneath the plants and eventually identified the herbicidal component. However, it was not potent enough to be of practical use. A discover research programme followed based on the structure of leptospermone and the final outcome was the herbicide mesotrione, known under the brand names Callisto and Tenacity. This substance acts by inhibiting the plant enzyme 4-hydroxyphenylpyruvate dioxygenase (4-HPPD). This enzyme is involved in carotenoid biosynthesis. Without carotenoids to protect the chlorophyll in the leaves, sunlight degrades the chlorophyll and the plant dies.

Eucalyptol

2 different ways of drawing 1.8-cineole (also known as eucalyptol)

Leptospermone

Leptospermone

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