Seasonal variation of polyphenolics in<i>Ascophyllum nodosum</i>(Phaeophyceae)

Abstract

Thalli of the brown alga Ascophyllum nodosum were collected on the Scottish west coast and the phlorotannin content was measured once a month between January and December 2005. Due to the potential use of A. nodosum extract as a nutritional supplement or for medical purposes, our aim was to determine the most favourable time for collection of the algal material. For this purpose two different methods for quantitative phenol determination were used, i.e. the well-known spectrophotometric measurements with Folin–Ciocalteu's phenol reagent (FC-method) and for the first time quantitative 1H NMR spectroscopy (qHNMR). Qualitative variations regarding the composition of the polyphenolic fraction were analysed employing RP-HPLC and 1H NMR spectroscopy. Both quantitative and qualitative analysis of phlorotannins revealed variations over the course of the year. The highest phenol content during the year was reached in July.