An anti-mitotic compound, (+)-6-tuliposide A, isolated from the Canadian glacier lily, Erythronium grandiflorum.

The Canadian prairie ecosystem is subjected to abiotic and biotic conditions that induce plants to produce secondary metabolites that affect mammalian physiology. Extracts prepared from certain plant species native to Canadian prairie and montane cordillera ecosystems have previously been shown to have anti-mitotic activity on human cancer cell lines. In this study, we investigated the glacier lily, Erythronium grandiflorum (Liliaceae), in which the species was the most phylogenetically distant from Asteraceae and had anti-mitotic activity. When added to cell lines, E. grandiflorum extracts induced rounded cell morphology and arrested cells in the G2/M phase of the cell cycle. Of the cells that displayed a rounded phenotype, all were positive for phospho-histone H3 and contained a distorted mitotic spindle. This anti-mitotic activity was distinct from that of the compound colchicine, which has been previously isolated from the Liliaceae family. By biology-guided fractionation, we isolated the natural product (+)-6-tuliposide A and are the first to report its anti-mitotic activity. These results reveal a chemical motif in secondary metabolites and expand the range of Canadian prairie plants with anti-mitotic activity that can become new scientific tools or used in the development of anti-proliferative medicines.

Pulchelloid A, a sesquiterpene lactone from the Canadian prairie plant Gaillardia aristata inhibits mitosis in human cells.

BACKGROUND: The Canadian prairie ecosystem presents a rich source of natural products from plants that are subjected to herbivory by grazing mammals. This type of ecological competition may contribute to the production of natural products of interest in cell biology and medical research. We provide the first biological description of the sesquiterpene lactone, pulchelloid A, which we isolated from the prairie plant, Gaillardia aristata (Asteraceae) and report that it inhibits mitosis in human cells. METHODS AND RESULTS: We found that G. aristata (Blanket flower) extracts were cytotoxic to human cell lines and used phenotypic assays to characterize the bioactivity of extracts. Before dying, cells were characterized by a rounded morphology, phospho-histone H3 signals, mitotic spindles, and active Cdk1. By biology-guided fractionation of Gaillardia extracts, we isolated a sesquiterpene lactone named pulchelloid A. We used immunofluorescence microscopy and observed that cells treated with pulchelloid A have phospho-histone H3 positive chromosomes and a mitotic spindle, confirming that they were in mitosis. Treated cells arrest with an unusual phenotype; they enter a prolonged mitotic arrest in which the spindles become multipolar and the chromosomes acquire histone γH2AX foci, a hallmark of damaged DNA. CONCLUSIONS: We propose that pulchelloid A, a natural product present in the prairie plant Gaillardia aristata, delays cells in mitosis. There is a growing body of evidence that a small number of members of the sesquiterpene lactone chemical family may target proteins that regulate mitosis.

Extracts Prepared from a Canadian Toxic Plant Induce Light-Dependent Perinuclear Vacuoles in Human Cells.

We are investigating plant species from the Canadian prairie ecological zone by phenotypic cell assays to discover toxins of biological interest. We provide the first report of the effects of extracts prepared from the shrub Symphoricarpos occidentalis in several human cell lines. S. occidentalis (Caprifoliaceae) extracts are cytotoxic, and, strikingly, treated cells undergo light-dependent vacuolation near the nucleus. The range of irradiation is present in standard ambient light and lies in the visible range (400-700 nm). Vacuolization in treated cells can be induced with specific wavelengths of 408 or 660 nm at 1 J/cm2 energies. Vacuolated cells show a striking phenotype of a large perinuclear vacuole (nuclear associated vacuole, NAV) that is distinct from vesicles observed by treatment with an autophagy-inducing agent. Treatment with S. occidentalis extracts and light induces an intense lamin A/C signal at the junction of a nuclear vacuole and the nucleus. Further study of S. occidentalis extracts and vacuolation provide chemical tools that may contribute to the understanding of nuclear envelope organization and human cell biology.