Faculty of Food Technology and Biotechnology, University of Zagreb
Abstract
Recently special attention has been paid to dietary fibre-associated phytoestrogens such as plant lignans, which are related to the prevention of different hormone-dependent diseases. Therefore, phytoestrogens associated with dietary fibre and their metabolites are of interest for investigation. The aim of this work is to investigate the formation of enterolignans: enterolactone (ENL) and enterodiol (END) from their precursors by the action of intestinal microflora and their relationship with non-starch polysaccharides (NSP) in various cereal products from wheat, rye, barley and oats. For the investigation of the bioconversion of plant lignans, a technique of in vitro fermentation was used and the quantitative analysis of their metabolites ENL and END was performed by high-performance liquid chromatography (HPLC) with coulometric electrode array detection. The enterolignan formation in various cereal products ranged from 78.3 to 321.9 nmol/g depending on the product type: END from 8.7 to 149.3 nmol/g and ENL from 64.4 to 278.3 nmol/g. The lignan production in bran was about two times higher than that in whole flour of the same kind of cereals. Close correlations were found between the total NSP content and the total amount of enterolignans and ENL; between pentoses and the total amount of enterolignans and ENL; between arabinose or xylose and ENL; and between galactose and END values. Considering the correlations between hexoses and END as well as between pentoses and ENL found in cereals, it can be assumed that pentoses are closely related to the quantities of plant lignans in cereal products and their conversion to enterolignans.U posljednje se vrijeme sve više pozornosti posvećuje istraživanju lignana, tj. prehrambenih biljnih vlakana bogatih fitoestrogenima, koja sprečavaju razvoj različitih bolesti uzrokovanih hormonskim poremećajem. U radu su istraženi fitoestrogeni iz prehrambenih biljnih vlakana te njihovi derivati. Svrha je rada bila utvrditi ovisnost količine enterolignana, nastalih iz njihovih prekurzora pod utjecajem crijevne mikroflore, i to enterolaktona i enterodiola, o udjelu neškrobnih polisaharida u različitim žitaricama (pšenica, raž, ječam i zob). Pritom je provedena in vitro fermentacija žitarica, a nastali enterolaktoni i enterodioli kvantitativno su određeni pomoću visokodjelotvorne tekućinske kromatografije (HPLC) s kulometrijskim detektorom. Količina se lignana u raznim proizvodima od žitarica razlikovala od 78,3 do 321,9 nmol/g, i to od 8,7 do 149,3 nmol/g enterodiola i od 64,4 do 278,3 nmol/g enterolignana. Utvrđeno je da je količina lignana u mekinjama dvaput veća od one u integralnom brašnu. Ustanovljena je neposredna ovisnost udjela neškrobnih polisaharida o količini enterolignana i enterolaktona, zatim udjela pentoza o količini enterolignana i enterolaktona, udjela arabinoze ili ksiloze o količini enterolaktona, te udjela galaktoze o količini enterodiola. Dobiveni rezultati pokazuju da količina lignana u proizvodima od žitarica ovisi o udjelu pentoza i njihovoj konverziji u enterolignane
