An Immunomodulator from Terminalia Arjuna and Biological Evaluation of its Derivatives

Abstract

Detailed chemical investigation of Terminalia arjuna bark resulted in the isolation and identification of an immunomodulatory constituent, arjunic acid (1), which was converted into seven semi-synthetic derivatives (2–8). All the test compounds in 0.1, 1 and 10 μg/mL concentrations exhibited immunomodulatory effects in a dose dependant manner. 2-O-Lauroyl arjunic acid (3) and 2-O-palmitoyl arjunic acid (4) exhibited immunostimulatory response at all the tested concentrations, while arjunic acid (1), 2,3-di-O-acetyl arjunic acid (2), 2,3-di-O-benzoyl arjunic acid (6), and 2-O-p-anisoyl arjunic acid (7) exhibited immunostimulatory responses at lower doses, whereas at higher concentrations they exhibited immunosuppressive activity. Only 2,3-di-O-palmitoyl arjunic acid (5) showed immunosuppressive activity at all the concentrations; this is being reported for the first time.