Characterization of anti-complement compounds from Azadirachta indica.

The crude aqueous extract of Azadirachta indica bark possesses an inhibitory activity on both classical (CP) and alternative pathway (AP) activation of human complement. Purification of the compounds with the guidance of the AP-inhibitory activity involved extraction with methanol, dialysis, ion-exchange procedures and gel-permeation chromatography. This sequence yielded two polymers, NB-I and NB-II, one a highly active compound with a relatively low molecular weight (NB-II) and the other a less active compound with a high molecular weight (NB-I). The polymers were characterized by using colour reactions, TLC, GLC and HPLC after hydrolysis and gel-permeation chromatography as peptidoglycans. The carbohydrate part consisted predominantly of glucose. Arabinose, galactose and mannose were present in minor amounts (NB-II) or only as traces (NB-I). Protein was present for 5.5% in NB-I and for 9.8% in NB-II.