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Medicines and minerals
Modern chemistry's unravelling of willow promises enough new medicines and materials to make even Hippocrates gasp. There is more to willow than asprin and cricket bats. And we're not talking fishing nets from 8000BC or munitions baskets used during the First World War, or even willow's primary use these days as afast-growing, high yielding, low-input source of biomass for sustainable energy generation.
The extra focus now is on adding value to that biomass chain and turning willow into a lucrative dual-purpose crop. Chemists are at the heart of this adventure, excited at the prospect of exploring such a chemically diverse plant to see what can be extracted before the material is burned as fuel.
Potentially useful chemicals, known as phenolic glycosides, can make up as much as 13% of willow’s dry weight (against ratios sometimes as low as 0.1% in other plants), and the compositional information is now so well catalogued that researchers can almost decide which chemical and therefore which species to focus on. Furthermore, extracting compounds is relatively cheap and easy.
Rothamsted Research is perfectly placed to Exploit the leads. It is custodian of the National Willow Collection, a vast repository of diverse willows, many of which might have been lost forever when tradiotionals uses, such as rural crafts in hurdle and basket making declined. Among the collection's 1500 different willows is a good representative of the 450 species, including ground hugging alpines, shrubs and trees up to 30m tall. A number of hybrids and populations have also been developed for research.
Tailoring plant metabolism is one of the Strategic Programmes at Rothamsted Research. The latest work comes under one of the institute’s five-year strategic programmes to 2022, known as Tailoring Plant Metabolism. TPM brings together two previous programmes on designing more nutritious seeds and on mitigating the impact of carbon on the environment.
Specialists in metabolomics and genetics are working together to understand the biosynthetic pathways that produce willow’s bank of phenolic gyclosides, which includes salicin, the analgesic ingredient behind aspirin. They are exploring three potential streams that could make the plant a more high-value crop.
Creating new materials
The first stream is looking for chemical building blocks that can be manipulated in hundreds of ways to form precursors for many industrial processes. Naturally, as these phenolic compounds are plant-based and found in willow’s bark or stem, they also offer an environmentally cleaner alternative to those traditionally derived from fossil fuels.
The second, associated stream tackles research into phenolic mixes, such as those used for phenolic formaldehyde resin, which is one of many synthetic bio-polymers that promise a range of new materials.
The third stream is the highest value one – and one that would delight Hippocrates, who is credited with formalising willow’s medicinal benefits in 400BC. Novel pharmacologies have been discovered for the potential treatment of cancers and neurological conditions, such as Parkinson’s and Alzheimer’s diseases, and depression. In TPM, the researchers will design new willow hybrids, using conventional breeding techniques, to optimise yield of these exciting compounds and to help identify the genes responsible for their production.