Presence of natural products in Danish soils and ground water

Danish title: Forekomsten af naturstoffer i jord og grundvand som et resultat af dyrkning af klassiske såvel som gensplejsede afgrøder.

 

In the past decade, the risk of pollution of our ground water with chemically produced insecticides and herbicides has caused a lot of debate among politicians and in the general public. In contrast, the possible ground water pollution derived from natural products present in our crop plants and from weeds gained no or little attention. This situation changed dramatically, when the possibility arose to design transgenic crops that were made insect resistant by the transfer of a biosynthetic pathway for an insect repelling natural product from an insect resistant crop plant to a sensitive crop plant. This suddenly placed the risk of contamination of ground water by plant natural products high on the political agenda and a desire to evaluate the expected effects on the environment and human health. Previous work has shown that biomolecules such as Bt toxins from transgenic crops and natural carcinogenic ptaquiloside from bracken are transferred from plant to soil. The Soil and Environmental Chemistry Group at KVL has demonstrated that ptaquiloside is extremely mobile in soil and likely to leach to the ground water. In soil, ptaquiloside is degraded into a compound with antimicrobial effect. Preliminary investigations have demonstrated that cyanogenic glucosides are also weakly sorbed to soil and this may also be the case for the very similar rhodiocyanosides. Other nitrile glucosides are toxic to mammals, so the potential leach of such compounds to ground water may be harzardeous to humans. Furthermore, it is not known how sorption of cyanogenic glucosides and rhodiocyanosides and their respective aglycons to the soil matrix may affect the compounds persistence and effects in the soil ecosystem. Knowledge of plant-to-soil transfer, sorption characteristics and activity and availability to degradation of biomolecules widely present in our common crop plants would help to reduced undesired environmental effects from our current agricultural practises. Likewise, only natural products with undesirable properties should not be introduced in molecular breeding.

 

Linamarin, lotaustralin and rhodiocyanoside A and D have been isolated from Lotus japonicus and large scale chemical synthesis is in progress to enable direct testing of the behaviour of the compounds in different soil types. Soil samples from white clover fields have been collected so investigate their content of the cyanogenic glucosides linamarin and lotaustralin and cyanide released by degradation.

 

Researchers involved: Nanna Bjarnholt, Birger Lindberg Møller, Søren Bak

 

Foreign collaborators: Hans Christian Bruun Hansen

 

Financial support: KVL PhD stipendium, Danish Natioanl Research Foundation