Seed dormancy breaking diterpenoids from the liverwort Plagiochila sciophila and their differentiation inducing activity in human promyelocytic leukemia HL-60 cells.

To obtain the structural diversity of bioactive compounds similar to cotylenins and fusicoccins that modulate 14-3-3 protein-protein interactions in eukaryotes, screening tests were carried out using the lettuce seed dormancy breaking-assay. An acetone extract of the liverwort Plagiochila sciophila exhibited significant activity against the seeds in the presence of the plant hormone abscisic acid. Activity-guided fractionation of the extract afforded the isolation of seven novel fusicoccane-type diterpenoids, named fusicosciophins A-E (1-5), 8-deacetyl (6) and 9-deacetyl fusicosciophin E (7). Their structures were determined by spectroscopic methods and X-ray crystallographic analyses. All the pure isolated compounds (1-7) exhibited moderate lettuce seed dormancy breaking activity. In addition, the differentiation-inducing activity and cytotoxicity of these isolates, together with fusicoccin A (FC-A) and all-trans retinoic acid (ATRA), were evaluated in human promyelocytic leukemia HL-60 cells and human mouth epidermal carcinoma KB cells, respectively. Fusicosciophins (2 and 4) and FC-A exhibited moderate differentiation-inducing activity (EC50 31.2-59.1 microM) compared with ATRA (EC50 0.3 microM), while 2, 4 and ATRA exhibited higher selectivity indices (IC50/EC50 >3.38-667) than FC-A (IC50/EC50 1.05). This is the first report on the isolation of fusicoccane-type diterpenoids from liverworts having seed dormancy breaking activity and differentiation-inducing activity in mammal cells.

Seed dormancy breaking diterpenoids, including novel brassicicenes J and K, from fungus Alternaria brassicicola, and their necrotic/apoptotic activities in HL-60 cells.

To find new metabolites similar to cotylenins and fusicoccins from the fungus Alternaria brassicicola, screening tests were carried out using the lettuce seed dormancy breaking assay. Activity-guided fractionation of the EtOAc extract from the culture using the assay afforded the isolation of two novel fusicoccane diterpenoids named brassicicenes J (1) and K (2), along with three known brassicicenes A (3), B (4), and F (5). Their structures were elucidated from extensive NMR spectral data and by comparison of these with those reported in the literature. Brassicicenes (1-5) exhibited weak to moderate seed dormancy breaking activities against lettuce seeds in the presence of abscisic acid. In addition, the necrotic/apoptotic activities of the brassicicenes (1-5), fusicoccin A (6) and cotylenin A (7) were evaluated by determining their cytotoxicity, cell viability and caspase-3/7 activation on the HL-60 cell line. Brassicicene K (2) exhibited similar cytostatic profiles to that of cotylenin A (7), and brassicicenes J (1), A (3), B (4), and F (5) exhibited necrotic activity. This is the first report of the seed dormancy breaking activity of brassicicenes in plants, and of necrotic/apoptotic activity in mammalian cells.