Caffeic acid phenyl ester in propolis is a strong inhibitor of matrix metalloproteinase-9 and invasion inhibitor: Isolation and identification

Background: Propolis has been used as a folk medicine and has several proven biological activities. Herbal remedies recommended for cancer therapies in Korea. Methods: Matrix metalloproteinase (MMP)-9-inhibitory activity of propolis has been assessed. CAPE as an acting compound was isolated and molecular structure was determined. Anti-invasion activity of CAPE was assayed using hepatocarcinoma cells. Results: Propolis ethanol extracts showed a strong inhibitory effect of MMP-9 activity, which is known to be involved in tumor cell invasion and metastasis in a concentration-dependent manner on zymography. Assay guided fractionation led to the isolation of a caffeic acid phenyl ester (CAPE) as the compound responsible for the anti-MMP-9 activity. CAPE was obtained by reversed-phase HPLC, and its structure was elucidated by fast atom bombardment mass spectrometry and tandem mass spectrometry. The purified CAPE inhibited MMP-9 activity with the IC₅₀ of 1.0-2.0 nmol/l. Conclusions: CAPE possesses selective antiproliferative activity toward hepatocaricoma cell line Hep3B, but not primary cultured mouse hepatocytes.