In vitro Anti-inflammatory Activity of Ligustrum vulgare Extracts and Their Analytical Characterization

Interest in the anti-inflammatory effects of Ligustrum vulgare L., which has been used traditionally in China and Japan prompted us to determine anti-inflammatory effects of the plant's compounds in leukocytes. The leaves of L. vulgare were used to prepare a decoction which was successively extracted with organic solvents (dichloromethane (DCM), n-butanol, ethyl acetate) using liquid-liquid partition. Extracts were tested for inhibition of LTB4, resp. PGE(2) biosynthesis. Each extract was evaluated for its in vitro cyclooxygenase-1/2 (COX-1/2) inhibitory activity using assays with purified COX-1 and COX-2 enzymes, as well as for their LTB4 formation inhibitory activity using an assay with activated human neutrophil granulocytes. All extracts reported inhibitory actions against COXs in comparison with the synthetic inhibitors NS-398 (IC50 = 2.6 mu M) and indomethacin (IC50 = 0.9 mu M). The dichloromethane extract of privet leaves showed a considerable inhibitory effect against COX-1 and COX-2 enzyme activity. The DCM extract revealed 2.7 times higher inhibitory activity against LTB4 formation in comparison with the known specific LT inhibitor zileuton (IC50 = 5.0 mu M). Additionally, oleuropein and echinacoside were detected by HPLC-DAD and LC-MS in the Ligustrum vulgare leaves. Both compounds exhibited weak inhibitory activity on cyclooxygenases and leukotriene formation.