Chemists Are Researching How to Utilise the Defensive Compounds of Plants in Preventing Climate Change

​At the moment, many plants are wakening from their winter hibernation. The plant cells start to produce their yearly chemical masterpiece, says Juha-Pekka Salminen, the Professor of Chemistry of Natural Compounds.

– We at the Department of Chemistry research the chemical diversity of plants, among other things. After each research, we understand better and better what kind of a vast the chemical effort the different plants have make, particularly in spring: they have to grow photosynthetic cells quickly and create an adequate chemical defence, says Salminen.

The plants develop defensive compounds, for example different kind of tannins, in their leaves and flowers against herbivore insects. According to Salminen, plants have become more skilful chemists than humans as they have had to develop increasingly various defensive compounds.

– In turn, we have become more skilful chemist in trying to understand the chemistry of these defensive compounds as well as utilising them for medicine, for improving the quality of food, and for reducing the greenhouse gas emissions.

The chemical composition of the defensive compounds of plants completely depends on the species. There can be hundreds of different kinds of natural compounds in one species of plants, which the plant uses against the attacks of herbivores and pathogens. For example, the plants defend themselves with certain tannin compounds against caterpillars and with others against elks and deer: the tannins cause an unsavoury taste or make the leaves feel unpleasant on mucous membrane.

The research group of the chemistry of natural compounds has ongoing research projects funded by the Academy of Finland and EU, which try to discover the operational mechanisms of the defensive compounds of plants, the occurrence of these compounds in different plants and how the evolution of active molecules has possibly evolved with the evolution of the plant species. The research projects study over 2000 species of plants from five different continents.

Cattle Causes Greenhouse Gases – the Natural Defensive Compounds Could Alleviate the Problem

The defensive compounds can be used in many ways. One of the most common uses is the advancement of health.

– Over half of the medicines used in the Western countries contain a compound originally separated from plants as one of the active ingredients at least. However, few people consider using the same compounds in improving the condition and state of cattle and the environment, says Salminen.

The animal protein produced with ruminants places a considerably larger strain on the environment than, for example, the protein that is produced with poultry. Firstly, the rumination process produces a significant amount of methane emissions, even 140 kilos per a dairy cow in one year. Secondly, ruminants also use the plant-based proteins ineffectually, whereupon the nitrogen that escapes during the rumination process ends up in urine and can transform into nitrous oxide, i.e. laughing gas, in nature. It is 200 times more potent greenhouse gas than carbon dioxide.

– In addition, synthetic drugs are used to protect the ruminants from parasites, but unfortunately the parasites are developing resistance against these drugs on a worldwide scale. Therefore the drug dosage has increased in general.  This in turn causes that the discharge of the synthetic chemicals in the environment increases and drug residues can appear in the food that we eat.

However, it is possible to significantly reduce the stress on the environment by choosing fodder that contains tannins from plants. The research group of natural compounds is currently studying which are the most efficient tannin compounds in reducing these detriments.

–There is a lot of work to be done as different problems require chemically slightly different tannin compounds. However, as the mechanisms of the positive impact of the tannins on the environment are better understood, it is possible to slowly discover which plants containing which tannins would make the most ecologically friendly way to feed ruminants.

The initial research results indicate that it is possible to reduce the greenhouse gas emissions and parasites of the ruminants by half with tannins.

The Analysis Method of the Department of Chemistry Reveals Hundreds of Defence Compounds in a Few Minutes

When the chemists have a good overall picture which of the natural compounds are the most effective as the defence compounds of plants or reduce the greenhouse gas emissions of ruminants the most, it is important to find out which species of plants produce great quantities of these chemicals.

The Department of Chemistry at the University of Turku has developed a new method where they use the liquid chromatography mass spectrometer, standard equipment in many modern laboratories, to do a molecule specific analysis of even 250 compounds in one minute.

– We could already measure the levels of a couple of hundred of the most effective defence compounds or parasite tannins in plants in one analysis if we only knew the molecule structure of all of these compounds. It can be difficult to wait, but scientific breakthroughs require time and patience and the research of plant chemistry is no exception to this rule. If the answers to our questions had been easy, they would have been found a long time ago, says Salminen.

The research is funded by the Academy of Finland (projects 258992 and 26080079) and EU (‘LegumePlus’; PITN-GA-2011-289377).

Text: Hannu Aaltonen and Juha-Pekka Salminen
Translation: Mari Ratia