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 watereri ‘Vossii’ will be flowering beautifully, its long racemes of golden yellow flowers looking stunning in the spring sunshine!

 Laburnum x watereri

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)

 Laburnum tree

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 structure

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.

 Thermopsis lanceolata

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.

** https://www.businesswire.com/news/home/20200319005381/en/Global-Smoking-Cessation-Market—Expected-Reach