Ellagitannins in Finnish plant species – Characterization, distribution and oxidative activity

Abstract

<p> Ellagitannins are secondary metabolites that are produced by plants. Among other features, they are assumed to function as plants&rsquo; defensive compounds against plant-eating herbivores. This thesis focuses on a theory, which suggests that the biological activity of ellagitannins is based on their tendency to oxidize at the highly alkaline gut conditions of insect herbivores (oxidative activity).<br /> <br /> To study the biological activities of ellagitannins, a wide variety of structurally different ellagitannins were purified from different plant species by using liquid chromatographic techniques. The structures were characterized with the aid of spectrometric methods. Based on the acquired data, it was also possible to create a scheme, which enables the classification and even identification of ellagitannins from plant extracts without the need to isolate each compound for individual characterization.<br /> <br /> The biological activities of ellagitannins were determined with methods that are based on the abilities of the compounds to scavenge radicals, chelate iron ions, and on their rate of oxidation at high pH. The results showed that ellagitannins possess oxidative activities both at high and neutral pH, and that their activities depend on structure.<br /> <br /> The occurrence, distribution and content of ellagitannins in Finnish plant species were also studied. The specific ellagitannin profiles of the studied plant species were found to correlate well with their taxonomic classification.</p>