Mass spectral analysis of some derivatives and in vitro metabolites of steviol, the aglycone of the natural sweeteners, stevioside, rebaudioside a, and rubusoside

Steviol ( ent ‐13‐hydroxykaur‐16‐en‐19‐oic acid), the aglycone of various plant‐derived glycoside sweeteners consumed by human populations, is known to be mutagenic toward Salmonella typhimurium strain TM677 when metabolically activated using a 9000 × g supernatant fraction derived from the liver of Aroclor 1254‐pretreated rats. Mass spectral analysis of this diterpenoid and some analogs revealed characteristic patterns reflecting differential stereochemistry at the C/D rings and variations in the nature of the substituents present. Such information has been used to help identify several in vitro metabolites of steviol in conditions known to produce a mutagenic response, when analyzed by human populations, is known to be mutagenic toward Salmonella typhimurium strain TM677 when metabolically be allylic oxidation and epoxidation. 15‐Oxosteviol, a product of oxidation of the major steviol metabolite, 15α‐hydroxysteviol, was found to be a direct‐acting mutagen.