Investigation into the genotoxicity of water extracts from Hypoxis species and a commercially available Hypoxis preparation.

We performed an in vitro evaluation of the genotoxic potential of water extracts from four Hypoxis species (Hypoxis hemerocallidea, H. colchicifolia, H. rigidula, H. acuminata) and a commercial preparation thereof using the neutral red uptake (NRU) assay, the alkaline comet assay and the cytome assay in human hepatoma HepG2 cells. The relative cytotoxicity of these samples was established by determining their NI50 values (50% inhibition of NRU), and these results were used for dose-finding in genotoxicity tests. None of the tested extracts were identified as genotoxic in both the alkaline comet assay and cytome assay.

Testing chemical agents with the cytokinesis-block micronucleus cytome assay.

In order to evaluate the applicability of the cytokinesis-block micronucleus cytome assay in routine mutagenicity testing we investigated with this method different chemicals having different mechanisms of action: non-mutagens, direct-acting basealtering mutagens, direct-acting cross-linking mutagens, clastogens including a radiomimetic chemical, indirect-acting spindle poisons and indirect-acting enzyme inhibitors. We looked at the presence of micronuclei as biomarkers for either the loss of chromosome fragments (clastogen) or the loss of a whole chromosome (aneugen), nucleoplasmic bridges as biomarkers for complex rearrangements (e.g., dicentric chromosomes) and nuclear buds as biomarkers for gene amplification. The cytome assay proved to be a suitable tool to investigate genetic effects of environmental agents and to provide insight into their working mechanisms as all chemicals tested showed the expected response.