Effect of five triterpenoid compounds isolated from leaves of Diospyros kaki on stimulus-induced superoxide generation and tyrosyl phosphorylation in human polymorphonuclear leukocytes

Background: The crude drug "kaki-yo" is a traditional medicine used in Japan as a hypotensive drug. Methods: The effect of five triterpenoid compounds, isolated from leaves of Diospyros kaki on stimulus-induced superoxide generation and phosphorylation of tyrosine residues of protein in human neutrophils was investigated. The five compounds examined were alpha-amyrin (A), uvaol (UV), ursolic acid (UA), 19 alpha-hydroxy ursolic acid (HU) and 19 alpha,24-dihydroxy ursolic acid (DHU). Results: When the cells were preincubated with these Compounds, the superoxide generation induced by N-formyl-methionyl-leucylphenylalanine (fMLP) was significantly Suppressed in a concentration-dependent manner. These compounds also Suppressed the Superoxide generation induced by arachidonic acid (AA) in high concentrations. In the case of the superoxide generation induced by phorbol 12-myristate 13-acetate (PMA), UA, HU and DHU suppressed the Superoxide generation but A and UV gave no effect. When the cells were incubated with fMLP in UA, HU and DHU, fMLP-induced tyrosyl phosphorylation of 45 kDa proteins of the cells was dose-dependently Suppressed in parallel to the Suppression of fMLP-induced superoxide generation. Conclusions: Triterpenoid compounds suppress stimulus-induced superoxide generation and tyrosyl phosphorylation and may have pharmaceutical applications. (C) 2002 Elsevier Science B.V All rights reserved.