S03-04 Induction of genomic damage by natural plant constituents: development of genotoxicity testing strategies

Thirteen botanicals selected by the Botanical Safety Consortium as data-rich case studies were tested in four standard genotoxicity assays covering mutation and chromosome damage endpoints. The goal of this exercise was to determine whether the results from the four selected assays provided an assessment of genotoxicity consistent with the existing data for each case study, thereby supporting their use in generating genotoxicity profiles of botanicals. The four assays included the bacterial reverse mutation assay (Ames test), the in vitro micronucleus (MN) assay in TK6 cells and in HepaRG cells, and the ToxTrackerÒ assay. The Ames and MN tests were conducted in accord with their respective OECD Test Guidelines. Based on existing information for the 13 botanicals tested, aristolochia, comfrey, green tea, and milk thistle were expected to be positive in the Ames test and/or were expected to induce MN. Our results were consistent with the existing literature. Four Ames-positive botanicals were identified. The MN test in TK6 cells, conducted +/– S9, identified one botanical as positive while the MN test conducted using metabolically competent HepaRG cells identified four botanicals as positive or equivocal. ToxTrackerÒ assays identified four positives, consistent with previously published data. Our results suggest that currently available in vitro genotoxicity assays are suitable for testing botanicals. Currently, we are evaluating all the data to determine a recommended testing scheme. In addition, our test data will be compared with in silico predictions of genotoxicity that were made for each botanical based on their identified constituents to determine how to combine in silico data, in vitro test data, and human exposure data to produce a comprehensive assessment of genotoxicity.