School of Molecular Sciences, University of Sussex, Falmer, Brighton, UK.
15-Oxosteviol, postulated to be the mutagenic metabolite of steviol, was observed to be non-mutagenic in preliminary experiments using a number of different systems. Repetition of the original experiment in Salmonella TM677 failed to show any significant induction of 8-azaguanine resistant mutants by 15-oxosteviol even when the number of bacteria tested was greatly increased. Examination of the earlier positive result showed that it could not be justified from the data and revealed a commonly applied way of mishandling data obtained with the TM677 system.