Immunodulatory compounds from Picrorhiza kurroa: isolation and characterization of two anti-complementary polymeric fractions from an aqueous root extract.

Two aqueous root extracts of Picrorhiza kurroa, one prepared by extraction at 4 degrees C and the other by refluxing, were purified using the guidance of modulation of classical (CP) and alternative (AP) pathway complement activity. By means of methanol extraction and gel filtration chromatography, two polymeric fractions were isolated from the cold water extract. A methanol-soluble polymeric fraction (CS1) was highly active in inhibiting CP complement activity exclusively, whereas a methanol-insoluble polymeric fraction (CI1) exhibited an inhibitory effect on both CP and AP complement activity. Preliminary chemical analysis of the anti-complementary fractions revealed the presence of structures of carbohydrate and of peptide nature in CS1 and CI1. The modulation of CP complement activity by CS1 was studied in more detail. Its inhibitory effect was proven to be based on complement consumption rather than on chelation of Ca2+ and/or Mg2+ or on stabilization of the target cells in the complement-assay. The purification of the aqueous extract prepared by refluxing, resulted in the isolation of a polymeric fraction with the same qualities as CS1. However, a fraction with properties similar to CI1 could not be isolated from this extract.