Dibenzylbutane- and Butyrolactone-type Lignans as Apoptosis Inducers in Human Hepatoma HuH-7 Cells

Seven lignans, previously isolated from Pycnanthus angolensis or obtained by derivatization, namely the dibenzylbutane-type lignans threo-4,4-dihydroxy-3-methoxylignan (1), 4-hydroxy-3,3,4-trimethoxylignan (2), (-)-dihydroguaiaretic acid (3), 3,3,4,4-tetramethoxylignan (4), 4,4-diacetyl-3,3-dimethoxylignan (5), heliobuphthalmin (6) and the butyrolactone lignan hinokinin (7), were evaluted for their ability as apoptosis inducers in human hepatoma HuH-7 cells. Cell viability assays, morphological evaluation of apoptosis and enzymatic analyses of caspase activity in HuH-7 cells were carried out. Using the lactate dehydrogenase lactate dehydrogenase (LDH) assay, it was demonstrated that the lignans (17) tested significantly reduced viability of HuH-7 cells. Morphologic evaluation of HuH-7 cells using Hoechst staining and fluorescence microscopy revealed that lignans 17 were strong inducers of apoptosis. In fact, HuH-7 cells developed morphological changes of apoptosis, including chromatin condensation, nuclear fragmentation and formation of apoptotic bodies. However, lignans 2 and 7 were the most promising compounds in this study, inducing 2.4- and 2.5-fold increases in apoptotic cells as compared to controls. Caspase-3-like activity assays confirmed the morphologic data. Copyright (c) 2011 John Wiley & Sons, Ltd.