Evaluation of Quantitative Methods for the Determination of Polyphenols in Algal Extracts

Marine brown algae such as Ascophyllum nodosum and Fucus vesiculosus accumulate polyphenols composed of phloroglucinol units. These compounds are of ecological importance and, due to their antioxidative activity, of pharmacological value as well. In this study four methods for the quantitative determination of phlorotannins are compared: spectrophotometric determinations using Folin−Ciocalteuʼs phenol reagent or 2,4-dimethoxybenzaldehyde (DMBA), quantitative 1H NMR spectroscopy (qHNMR), and gravimetrical measurements. On the basis of the relative standard deviation and the F-test, the determination using Folin−Ciocalteuʼs phenol reagent and qHNMR proved to be the most reliable and precise methods.