[Development of technology for the substance of poly[3-(3,4-dihydroxyphenyl) glyceric acid] from Symphytum asperum].

Comfrey (Symphytum L.) is used to treat bone fractures, tendon injuries, ulcer lesions of gastrointestinal tract. It promotes wound healing, accelerates exudates resorption in lungs and reduces joints' inflammation. In Georgian folk medicine, herbal remedies from comfrey are used to accelerate regeneration processes. Comfrey contains hepatotoxic and carcinogenic pyrrolizidine alkaloids, besides the main active ingredient is poly [3 - (3,4-dihydroxyphenyl) glyceric acid] (PDPGA). The aim of present work was to develop a technology for the substance - poly [3-(3,4dihydroxyphenyl) glyceric acid] (PDPGA) from comfrey stems, free of toxic pyrrolizidine alkaloids. During the investigation the optimal conditions for extraction and purification have been established: on the first stage pyrrolizidine alkaloids were removed from plant material by supercritical extraction; then the crude polysaccharides' fraction was obtained by water extraction (raw materials/extragent ratio was 1:15 at 90oC, the procedure was carried twice for 60 and 90 minutes). The isolation of the final product - PDPGA from crude polysaccharides' fraction was carried out by ultrafiltration on membrane filters. Based on the results of the investigation the technological scheme for the substance has been developed.