Characterization of anti-complement compounds from Azadirachta indica

Area of Science:

• Immunology
• Natural Products Chemistry
• Biochemistry

Background:

• The human complement system plays a crucial role in innate immunity.
• Complement activation involves classical (CP) and alternative (AP) pathways.
• Azadirachta indica (Neem) is a medicinal plant with a history of therapeutic use.

Purpose of the Study:

• To investigate the inhibitory activity of Azadirachta indica bark extract on human complement activation.
• To isolate and characterize the active compounds responsible for complement inhibition.

Main Methods:

• Crude aqueous extract of Azadirachta indica bark was prepared.
• Purification involved methanol extraction, dialysis, ion-exchange, and gel-permeation chromatography guided by AP-inhibitory activity.
• Characterization of purified compounds (NB-I, NB-II) utilized color reactions, TLC, GLC, HPLC, and hydrolysis.

Main Results:

• The crude extract inhibited both classical (CP) and alternative pathway (AP) activation of human complement.
• Two peptidoglycan polymers, NB-I (high molecular weight, less active) and NB-II (low molecular weight, highly active), were isolated.
• NB-II contained 9.8% protein and predominantly glucose, with minor arabinose, galactose, and mannose.
• NB-I contained 5.5% protein and similar carbohydrate composition with only traces of minor sugars.

Conclusions:

• Azadirachta indica bark contains peptidoglycan compounds that inhibit human complement activation.
• The low molecular weight peptidoglycan NB-II exhibits significant inhibitory activity, suggesting its potential as an immunomodulatory agent.