Aktiviteetti: Tutkimustyypit › Väitöskirjan ohjaaja tai sivuohjaaja
soflavonoid phytoestrogens are secondary plant metabolites, which structurally or functionally resemble 17β-estradiol and they originally received attention due to breeding problems affecting ewes grazing on subterranean clover. Later research of phytoestrogens has been focusing on the possible beneficial effects as oestrogen agonists or anti-estrogens.
Due to their health promoting effects, the knowledge of the occurrence of isoflavonoids and their metabolites in food and biological fluids as well as the better understanding of their metabolic pathways have been the main aspects in the research field.
The literature review introduces the biological significance of isoflavonoids in plants along with various analytical techniques used for the determination of these compounds in biological matrices. This is followed by a discussion of the isoflavone metabolism in humans, rodents, and ruminants.
The experimental part focuses on the synthetic methods used for the preparation of the isoflavonoids, and on four studies in which they were used. In the first two studies cow milk was analysed. It was shown that commercial organic cow milk contains high levels of equol along with much lower levels of the other isoflavonoids typically found in milk and milk products. The levels of equol detected in organic milk were significantly higher than the levels found in normal milk which corresponds to the fodder that the cows are fed. In the following study five Finnish Ayrshire cows were subjected to a red clover rich diet in order to study the metabolism of the isoflavones futher. Equol and a hitherto unquantifed metabolite, 3 ,7-dihydroxyisoflavan was detected and quantitatively measured in milk samples.
In another study, the metabolisation of genistein fatty acid ester was studied after (oral or parenteral) administration to adult female rhesus monkeys. It turned that levels of genistein fatty acid ester levels depended of the form of administration, and it may be possible to introduce intact genistein ester molecules into plasma by parenteral, but not oral administration.
The last study, focuses on the metabolism of the soy isoflavones daidzein, genistein, and glycitein in humans. After oral administration of these isoflavones through ingestion of soy enriched food, daily urine samples of the volunteers were analysed. This led to identification of several metabolites and to the proposal of the metabolic pathways of the isoflavones ingested.
Antti Hoikkalan väitöstilaisuus 21.10. 2016
Title of thesis: Determination and identification of polyphenols and their metabolites in biological matrices