Delesseria sanguinea (Hudson) Lamouroux was shown to contain sulfated polysaccharides (D.s.-SP) with anti-inflammatory effects. This red macroalga turned out to dominantly populate an artificial reef in the southwestern Baltic Sea. An important aspect for its economical utilization is to obtain D.s.-SP in a reproducible quality. The aim of the study was to evaluate the seasonal variability of D.s.-SP; for this, algae batches were harvested monthly over the period of one year. Structural and pharmacological characterization of the isolated D.s.-SP showed that an optimized and standardized aqueous extraction (85 degrees C) leads to reproducible products without any significant seasonal variations of their elastase and hyaluronidase inhibitory activities. Besides the yields (from 17.9% in April to 6.12% in September), only the glucose content of the D.s.-SP batches seasonally varied (April, 7.48% +/- 1.00%, September, 22.8% +/- 1.2%) due to certain coextraction of starch-like glucans. In principle, algae material can be harvested throughout the year, but the optimum harvesting time is in spring.