Chitin-containing complexes were obtained from the thalli of the foliose lichen Peltigera aphthosa by supercritical fluid extraction (SCFE) and acid-base hydrolysis. In an active designed experiment, the optimal SCFE conditions were determined, which made it possible to obtain a complex with a yield of 96% and a sorption capacity for methylene blue of 125 mg/g. The polyampholytic nature of the resulting sorbent complexes is shown, and their morphology and chemical composition are characterized. The processing of lichen raw materials to produce chitin-containing complexes by SCFE is shown to be more efficient than acid-base hydrolysis. supercritical fluid extraction, carbon dioxide, acid-base hydrolysis, epigean lichen, Peltigera aphthosa, chitin-containing complex, supercritical-fluid extraction, glucan complexes, activated carbon, usnic acid, optimization, chitosan, sorption, Physics