This tobacco (Nicotiana tabacum) relative was first planted in the SCIence Garden in the summer of 2018. It was grown from seed by Peter Grimbly, SCI Horticulture Group member. Although normally grown as an annual, some of the SCIence Garden plants have proven to be perennial. It is also gently self-seeding across the garden. It is native to the south and southeast of Brazil and the northeast of Argentina but both the species and many cultivars of it are now grown ornamentally across Europe. Flower colour is normally white, but variants with lime green and pink through to darker red flowers are available.
Like many Nicotiana this species has an attractive floral scent in the evening and through the night. The major component of the scent is 1.8-cineole. This constituent has been shown to be a chemical synapomorphy for the particular section of the genus Nicotiana that this species sits within (Raguso et al, Phytochemistry 67 (2006) 1931-1942). A synapomorphy is a shared derived character – one that all descendants and the shared single ancestor will have.
This ornamentally and olfactorily attractive plant was chosen for the SCIence Garden to represent two other (arguably less attractive) Nicotiana species.
Firstly, Nicotiana benthamiana, a tobacco species from northern Western Australia. It is widely used as a model organism in research and also for the “pharming” of monoclonal antibodies and other recombinant proteins.
In a very topical example of this technology, the North American biopharmaceutical company Medicago is currently undertaking Phase 1 clinical trials of a Covid-19 vaccine produced using their plant-based transient expression and manufacturing technology.
Secondly, Nicotiana tabacum, the cultivated tobacco which contains nicotine. This alkaloid is a potent insecticide and tobacco was formerly widely used as a pesticide.
This vivid extract from William Dallimore’s memoirs of working at Royal Botanic Gardens, Kew illustrate how tobacco was used in the late Victorian era.
“Real tobacco was used at Kew for fumigating plant houses. It was a very mixed lot that had been confiscated by excise officers, and it was said that it had been treated in some way to make it unfit for ordinary use before being issued to Kew. With the men working in the house ten men were employed on the job. After the first hour the atmosphere became unpleasant and after 1 ½ hours the first casualties occurred, some of the young gardeners had to leave the house. At the conclusion there were only the two labourers the stoker and one young gardener to leave the house, I was still about but very unhappy. Each man employed at the work, with the exception of the foreman, received one shilling extra on his week’s pay.“
After a second such fumigation event it was reported that there was a great reduction in insect pests, particularly of mealy bug and thrips, with a “good deal of mealy bug” falling to the ground dead.
Health and safety protocols have improved since the Victorian era, but the effectiveness of nicotine as an insecticide remains. From the 1980’s through the 1990’s a range of neo-nicotinoid plant protection agents were developed, with structures based on nicotine. Although extremely effective, these substances have also been shown to be harmful to beneficial insects and honey bees. Concerns over these adverse effects have led to the withdrawal of approval of outdoor use in the EU.
Imidacloprid – the first neo-nicotinoid developed
In early 2020, the European commission decided not to renew the European license for the use of Thiacloprid in plant protection, making it the fourth neo-nicotinoid excluded for use in Europe.
Where the next generation of pest control agents will come from is of vital importance to the horticulture and agriculture industries in the UK and beyond and the presence of these plants in the garden serves to highlight this.
Elderflowers are in full bloom this month, both in hedgerows as well as gardens across the country. Whether they are the wild Sambucus nigra or a cultivated variety with green or black leaves they are all beautiful and useful plants.
The black leaved cultivar growing in the SCIence Garden has pink blooms, whereas the wild species has white flowers. It was purchased as ‘Black Beauty’, but is also sold as ‘Gerda’.
Sambucus nigra f. porphyrophylla ‘Black Beauty’ growing in the SCIence Garden
This cultivar, along with ‘Black Lace’ (Eva) was developed by Ken Tobutt and Jacqui Prevette at the Horticulture Research International research station at East Malling in Kent and released for sale in the horticulture trade in 2000. The leaves stay a dark purple throughout the year and the flowers have a good fragrance.
The shrub will tolerate hard pruning so is useful for smaller spaces and provides a long season of interest. The plant is also a forager’s delight, both in early summer (for the flowers) and in the autumn (for the berries).
Most commonly one may think of elderflower cordial, or perhaps even elderflower champagne, but an excellent alternative to the rose flavoured traditional “Turkish Delight” can be made - https://www.rivercottage.net/recipes/elderflower-delight. I can highly recommend it!
The chemistry of the elderflower aroma is complex. Analyses such as that in the reference below* have identified many different terpene and terpenoid components including nerol oxide, hotrienol and nonanal.
* Olfactory and Quantitative Analysis of Aroma Compounds in Elder Flower (Sambucus nigra L.) Drink Processed from Five Cultivars. Ulla Jørgensen, Merete Hansen, Lars P. Christensen, Karina Jensen, and Karl Kaack. Journal of Agricultural and Food Chemistry 2000 48 (6), 2376-2383. DOI: 10.1021/jf000005f
Another month starts in the SCIence Garden with no visitors to appreciate the burgeoning growth of fresh new leaves and spring flowers, but that doesn’t mean we should forget about it!
Hopefully in our absence the Laburnum tree in the garden, Laburnum x watereri ‘Vossii’ will be flowering beautifully, its long racemes of golden yellow flowers looking stunning in the spring sunshine!
Laburnum x watereri ‘Vossii’ in the SCIence Garden
This particular cultivar originated in the late 19th century in the Netherlands, selected from the hybrid species which itself is a cross between Laburnum alpinum and L. anagyroides. This hybrid species was named for the Waterers nursery in Knaphill, Surrey and was formally named in a German publication of 1893 (Handbuch der Laubholzkunde, Berlin 3:673 (1893)
The laburnum tree is found very commonly in gardens in the UK, and is noticeable at this time of year for its long chains of golden yellow flowers. However, the beautiful flowers hide a dark side to this plant. The seeds (and indeed all parts) of the tree are poisonous to humans and many animals. They are poisonous due to the presence of a very toxic alkaloid called cytisine (not to be confused with cytosine, a component of DNA). Cytisine has a similar structure to nicotine (another plant natural product), and has similar pharmacological effects. It has been used as a smoking cessation therapy, as has varenicline, which has a structure based on that of cytisine. These molecules are partial agonists at the nicotinic receptor (compared to nicotine which is a full agonist) and reduce the cravings and “pleasurable” effects associated with nicotine.
Cytisine is found in several other plants in the legume family, including Thermopsis lanceolata, which also looks stunning in early summer and Baptisia species, also growing in the SCIence Garden and flowering later in the year.
In 2018 there were 9.6 million deaths from cancer and 33% of these were linked to exposure to tobacco smoke.* Since the link between smoking and lung cancer was established in 1950, the market for smoking cessation therapies has increased enormously. In 2018 it was worth over 18 billion dollars annually worldwide and is projected to increase to 64 billion dollars by 2026.** Staggering! Varenicline, sold under the brand names Champix and Chantix, is one of the most significant smoking cessation therapies apart from nicotine replacement products.
If you see a laburnum tree whilst out on your daily allowed exercise this month, have a thought for its use as a smoking cessation therapy!
* Data from the Cancer Research UK website https://www.cancerresearchuk.org/health-professional/cancer-statistics/worldwide-cancer#heading-Zero accessed May 2020.
March in the SCIence Garden
Narcissus was the classical Greek name of a beautiful youth who became so entranced with his own reflection that he killed himself and all that was left was a flower – a Narcissus. The word is possibly derived from an ancient Iranian language. But the floral narcissi are not so self-obsessed. As a member of the Amaryllidaceae, a family known for containing biologically active alkaloids, it is no surprise to learn that they contain a potent medicinal agent.
Narcissus (and in particular this cultivar) are an excellent source of galanthamine, a drug more commonly associated with snowdrops (Galanthus spp.). Galanthamine is currently recommended for the treatment of moderate Alzheimer’s disease by the National Institute of Health and Clinical Excellence (NICE) but is very effective in earlier stages of the disease too.
Today, part of the commercial supply of this molecule comes from chemical synthesis, itself an amazing chemical achievement due to the structural complexity of the molecule, and partly from the natural product isolated from different sources across the globe. In China, Lycoris radiata is grown as a crop, in Bulgaria, Leucojum aestivum is farmed and in the UK the humble daffodil, Narcissus ‘Carlton’ is the provider.
Narcissus ‘Carlton’ growing on large scale
Agroceutical Products, was established in 2012 to commercialise the research of Trevor Walker and colleagues who developed a cost effective, reliable and scalable method for producing galanthamine by extraction from Narcissus. They discovered the “Black Mountains Effect” – the increased production of galanthamine in the narcissus when they are grown under stress conditions at 1,200 feet. With support from Innovate UK and other organisations, the process is still being developed. Whilst not a full scale commercial production process just yet, the work is ongoing. As well as providing a supply of the much needed drug, this company may be showing the Welsh farming community how to secure additional income from their land. They continue to look for partners who have suitable land over 1000 ft in elevation.
The estimated global patient population for Alzheimer’s in 2010 was 30 million. It is expected to reach 120 million by 2050. The global market for Alzheimer’s disease drugs for 2019 was US$ 2870 million.
One of the most beloved flowers in China (and elsewhere) this small tree was planted here in the SCIence garden to represent the Chinese UK group. It is in bloom from late winter and the bright pink flowers have a strong perfume. It is growing in the centre at the back of the main area of the garden.
There are 309 accepted species in the genus Prunus listed on the Plants of the World Online database (plantsoftheworldonline.org). The genus is distributed mainly across the Northern temperate zones but there are some tropical species.
The genus Prunus is generally defined based on a combination of characteristics which include: a solitary carpel (the structure enclosing the ovules – a combination of the ovary, style and stigma) with a terminal style, a fleshy drupe (fruit), five sepals and five petals and solid branch pith. The drupe contains a single, relatively large, hard coated seed (stone) – familiar to us in cherries, apricots, nectarines, peaches etc
This particular species, Prunus mume, originates from southern China in the area around the Yangtze River. The ‘Beni-chidori’ cultivar has been given an Award of Garden Merit by the Royal Horticultural Society.
Over 300 different cultivars of this species have been recorded in China, perhaps not surprisingly for a plant that has been domesticated for thousands of years due to its floral beauty. A recent study on the genetic architecture of floral traits across the cultivars of this species was published in Nature Communications.1
Prunus mume was introduced from China into Japan, Korea, Taiwan and Vietnam and it is now fully integrated into the cuisines of all these countries. In addition to its uses in many foodstuffs and drinks, extracts from the fruit are also widely used in traditional Chinese medicine and in the traditional medicines in Korea and Japan. Anti-bacterial, anti-oxidative, anti-inflammatory and anti-cancer properties have all been ascribed to the extract which has been used to treat tiredness, headaches, constipation and stomach disorders amongst other things. A recent review published in the Journal of Ethnopharmacology2 gathers together information from literature reports on the anti-cancer activity of Prunus mume fruit extract.
One standardised extract in particular (MK615) has shown antitumour activity against most common cancer types.
The anti-cancer activity has not been ascribed to a particular component. Compounds isolated from the extract include ursolic acid, amygdalin, prunasin, chlorogenic acid, mumefural and syringaresinol.
Like all the plants in the SCIence garden – there’s a lot more to this one than just its ornamental beauty.
1. Zhang, Q., Zhang, H., Sun, L. et al. The genetic architecture of floral traits in the woody plant Prunus mume. Nat Commun 9, 1702 (2018). https://doi.org/10.1038/s41467-018-04093-z
2. Bailly, C. Anti-cancer properties of Prunus mume extracts. J Ethnopharmacology 246, 2020, 112215. https://doi.org/10.1016/j.jep.2019.112215
Growing in just about the most challenging of locations in the SCIence Garden are a small group of Helleborus niger. They are planted in a very dry and shady location underneath a large tree sized Escallonia and although they struggled to establish when they were first planted (in May 2017) they are now flowering and growing well.
This plant was first featured as a Horticulture Group Medicinal Plant of the Month in December 2011 and as it is now in the SCIence garden I thought a reprise was in order.
Helleborus is a genus of 15 species of evergreen perennials in the buttercup family, Ranunculaceae. In common with most members of the family, the flowers are radially symmetric, bisexual and have numerous stamen.
Helleborus is the Latin name for the lent hellebore, and niger means black – referring in this species to the roots.
This species is native to the Alps and Appenines. Helleborus niger has pure white flowers, with the showy white parts being sepals (the calyx) and the petals (corolla) reduced to nectaries. As with other hellebores, the sepals persist long after the nectaries (petals) have dropped.
All members of the Ranunculaceae contain ranunculin, an unstable glucoside, which when the plant is wounded is enzymatically broken down into glucose and protoanemonin. This unsaturated lactone is toxic to both humans and animals, causing skin irritation and nausea, vomiting, dizziness and worse if ingested.
Protoanemonin dimerises to form anemonin when it comes into contact with air and this is then hydrolysed, with a concomitant ring-opening to give a non-toxic dicarboxylic acid.
Many hellebores have been found to contain hellebrin, a cardiac glycoside. The early chemical literature suggests that this species also contains the substance but later studies did not find it suggesting that either mis-identified or adulterated material was used in the early studies.
It is reported to contain many other specialized metabolites including steroidal saponins.
This plant has long been used in traditional medicine – in European, Ayurvedic and Unani systems and recent research has been aimed at elucidating what constituents are responsible for the medicinal benefit.
Extract of black hellebore is used sometimes in Germany as an adjuvant treatment for some types of tumour.
A recent paper* reports the results of a safety and efficacy investigation. The Helleborus niger extract tested was shown to exhibit neither genotoxic nor haemolytic effects but it was shown to have anti-angiogenetic effects on human umbilical vein endothelial cells (HUVEC), anti-proliferative effects and migration-inhibiting properties on tumour cells thus supporting its use in cancer treatment.
* Felenda, J.E., Turek, C., Mörbt, N. et al. Preclinical evaluation of safety and potential of black hellebore extracts for cancer treatment. BMC Complement Altern Med 19, 105 (2019) doi:10.1186/s12906-019-2517-5