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-Ciocalteu's phenol reagent or 2,4-dimethoxybenzaldehyde (DMBA), quantitative (1)H NMR spectroscopy (qHNMR), and gravimetrical measurements. On the basis of the relative standard deviation and the F-test, the determination using Folin-Ciocalteu's phenol reagent and qHNMR proved to be the most reliable and precise methods.

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Available online xxxx JEL classification: C5 G10 G1In this paper, we focus on the impact of short selling restrictions on stock returns volatility. In order to assess the potential effects econometrically, we apply two distinct versions of an asymmetric Markov-switching GARCH model to the short selling bans on stocks of financial enterprises in Germany, that were established between September 2008 and July 2010. We find empirical evidence that the financial crisis was accompanied by an increase in volatility persistence and that this effect was particularly pronounced for those stocks that were subject to short selling constraints. We interpret this finding as evidence of a destabilizing impact of short selling constraints on stock returns volatility.

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