Scientists in Canada have reported the discovery of naturally occurring aromatic isothiocyanates. 

Isothiocyanates are a remarkable family of natural products that are produced by various different species of plants. They are enzymatic products that are known to have crucial roles in the protection of plants against a range of diseases and pests. 

In a bid to understand how plants are able to deter their enemies, Soledade Pedras and colleagues from the University of Saskatchewan, Canada, investigated a previously unknown reaction between canola, important oil seed plants, and the microbes that cause white rust disease. They discovered that the infected leaves of the canola contained two unique isothiocyanates that showed strong inhibitory activity. This suggested that the isothiocyanates were playing a defensive role against the toxic white rust microbes. 

Using a combination of HPLC and NMR, the team were able to determine that the new isothiocyanates were plant metabolites biosynthesised by the canola plant in response to the stress of being infected by deadly microbes. They named them rapalexin A and B. The absence of rapalexin A and B in non-stressed plants confirmed their role as a counter-attack weapon. 

According to Pedras, further work is now needed to establish the biosynthetic precursors of rapalexins A and B. 'The biosynthetic pathway of rapalexins and related plant defences needs to be determined to assist in devising safer approaches to deter fungal pathogens,' she said. The team believe that their work will fuel new leads to the discovery of ways to protect plants in the future with the ultimate aim of creating a pharmacy for plants. 

Jenna Wilson