Lapachol and related naphthoquinones have been reported as constituents of mostTabebuiaspecies so far studied. A chemotaxonomic investigation, based on the presence of these compounds, was undertaken to assess the origin of commercial products sold in Canada as being derived fromTabebuiaspecies. Naphthoquinone standards, prepared by synthesis from lapachol and isolapachol, were used in the development of selective HPLC and GC-MS methods of analysis. Bark and wood samples from 3 authenticatedTabebuiaspecies and oneCarinianaspecimen were analyzed, and the naphthoquinones were identified by comparison with standards. Samples ofTabebuiabark were observed to contain no detectable amounts of lapachol while levels of less than 0.001 percent were observed in wood samples. The identity of naphthoquinones detected in bark differed significantly from the generally reported accounts. No naphthoquinones were detected in the non-bignoniaceousCarinianaspecies. A total of 15 commercial products sold in Canada (12 plant samples and 3 concentrates) and 2 products from Brazil (1 plant sample and 1 concentrate) were analyzed. Naphthoquinones were detected in all plant samples except 2. No naphthoquinones were detected in the 3 concentrates from Canada. Both products from Brazil contained lapachol with the woody material containing approximately 1.0 percent. The results suggest that most commercial products were likely ofTabebuiaorigin. The levels of constituent naphthoquinones, however, were highly variable, suggesting postharvest alteration of naphthoquinone content.
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