During the last decade xylans were widely researched and several derivatives have been developed and analyzed. However, the application properties of these new products are still sparsely known. The main objective of the presented investigation was to examine whether sulfated xylans from different sources (hard wood and oat-spelt) possess antithrombotic properties and how their protonation/deprotonation behavior in water solutions influence these properties. Two types of xylans, glucuronoxylan derived from beech wood, and arabinoxylan from oat spelt, were sulfated. Infrared spectroscopy, elemental analysis, NMR and size exclusion chromatography were applied for analyzing the success of derivatization. Deprotonation/protonation behavior of xylan samples in water solutions was analyzed by titration methods and the antithrombotic properties were investigated using activated partial thromboplastin time determination. The results showed significant increases in negative charges for the sulfated samples, which were a consequence of introducing sulfated groups as strong acids. However, the increase of antithrombotic properties was not influenced only by the presence of certain amounts of sulfate functional groups but also by the total negative-charges originating from both sulfate and carboxyl groups. The later was proved by the high linear correlation between the activated partial thromboplastin time values, and the total charge of the samples. (C) 2013 Elsevier Ltd. All rights reserved.