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Highlights in Chemical Biology

Chemical biology news from across RSC Publishing.

Stressed sprouts hit back

05 April 2007

Brussels sprouts repel not only children, but fungi as well. Canadian scientists have discovered a novel antifungal compound in the plant, and hope to use the discovery to find ways to protect crops against pathogens.

"Brussels sprouts are less susceptible to this pathogen than cauliflower and broccoli, which do not seem to produce brussalexin A."
- Soledade Pedras

'Plants under stress synthesise antimicrobial compounds known as phytoalexins, which help the weakened plant defend itself against infection,' explained Soledade Pedras of the University of Saskatchewan, in Saskatoon. Pedras and her co-workers isolated a new phytoalexin, brussalexin A, from Brussels sprouts that had been stressed with UV radiation.

Niels Agerbirk, a plant biochemist at the University of Copenhagen in Denmark, praised Pedras' approach of using UV stress to discover new molecules in a plant that was believed to be well characterised already.

Structure of brussalexin A, superimposed on picture of child holding nose, about to eat a Brussels sprout

Brussalexin A contains an allyl thiocarbamate group, a structure not previously seen in phytoalexins. This puzzled the scientists because the compound's biosynthesis cannot be explained using currently known pathways. They proposed a new route - which Agerbirk called 'likely' - and will investigate their idea in future experiments. 'It is a tempting proposal, but we may be way off,' said Pedras.

Brussalexin A proved to be toxic towards several species of fungus, in particular Sclerotinia sclerotiorum, which causes stem rot in many plant families. 'Brussels sprouts are less susceptible to this pathogen than cauliflower and broccoli, which do not seem to produce brussalexin A,' said Pedras. However, she warned against concluding that brussalexin A is the main factor.

Pedras' group will investigate how fungal pathogens break down brussalexin A. Their aim is to treat crops with compounds that inhibit these detoxification routes, allowing the plants' natural defence mechanisms to work for longer. Alternatively, if the fungi do not break down brussalexin A, creating plants that make the compound in larger amounts could improve their pathogen resistance and boost crop yields, said Pedras. 

Daničle Gibney

Link to journal article

Efficient synthesis of brussalexin A, a remarkable phytoalexin from Brussels sprouts
M. Soledade C. Pedras, Qing-An Zheng and Mohammed G. Sarwar, Org. Biomol. Chem., 2007, 5, 1167
DOI: 10.1039/b702156a