Phenobarbital 5,6-benzoflavone

Inhibitors of cytochromes P-450 may be specific for only one form and SKF 525A, for example, is specific for the phenobarbital inducible form(s), whereas the inhibitor 7, 8-benzoflavone is specific for the polycyclic hydrocarbon-inducible form. 

In 1985 it was published [1] that stevioside was completely safe but that metabolically activated steviol was mutagenic in a "Forward Mutation Test". Steviol had to be applied together with the microsomal fraction of liver of animals treated with carcinogenic compounds (polychlorinated biphenyl or phenobarbital plus 5,6-benzoflavone). This publication has led to a confusing discussion between advocates and opponents of the use of Stevia or stevioside. To unravel the problem we must consider the opinion of authoritative international organisations such as OECD (Organisation for Economic Co-Operation and Development) and ICH (International Council of Harmonisation). To accept new substances as food three different mutagenesis tests are accepted and required by the OECD as well as by the ICH. These can be seen in Table 1. 

---