Activity-guided isolation and identification of Azadirachta indica bark extract constituents which specifically inhibit chemiluminescence production by activated human polymorphonuclear leukocytes.

The A. indica crude aqueous bark extract inhibits the generation of chemiluminescence by activated human polymorphonuclear leukocytes (PMN). Guided by this activity the responsible compounds were purified by extraction with different organic solvents and HPLC. Gallic acid, (+)-gallocatechin, (-)-epicatechin, and (as a 2:1 mixture) (+)-catechin and epigallocatechin were isolated and identified by means of HPLC, TLC, MS, 1H-NMR, UV, and CD data. Commercial samples of gallic acid, (+)-catechin and (-)-epicatechin showed the same effects. To our knowledge the identified catechins have never been described as constituents of A. indica.