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Dietary Supplements: A Framework for Evaluating Safety
be assumed to have them even if grown under different conditions. Analyses that suggest specimens of a given plant species do not contain a hazardous phytochemical usually associated with the plant should be carefully considered to ensure that the analysis techniques are appropriately sensitive.
The presence of toxic compounds has been traditionally associated with a number of plant genera and families (e.g., Liliaceae are known to contain cardiac glycosides, Euphorbiaceae are known to contain phorbol esters and toxic diterpenes). The ability to anticipate the presence of specific classes of compounds based on plant family and genus knowledge may be helpful in predicting potential toxicity. Table 6-15 highlights some of the plant genera to which FDA may want to give attention. Also important are the nuances of information about each plant family, which are discussed in Appendix C. It is important to note that this table is not intended to provide a complete reference or to be inclusive, but it serves to provide FDA with a starting point of plant genera that warrant concern. The primary difficulty in using information about related plants to infer information about the toxicity of a particular plant arises when the family encompasses both valuable food plants and species capable of producing toxic compounds (see discussion of traditional use as a food plant below and specific examples in Appendix C).
Considerations Regarding Concerns Raised by Taxonomic Relationships or Chemical Constituents of Concern
There are a number of considerations that may mitigate or exacerbate concerns raised by the taxonomic relationship of a dietary supplement ingredient to a hazardous botanical or knowledge that a botanical contains chemical constituents of concern. These are described here, followed by discussion of how these and other factors should impact the use of historical consumption information as a mitigator of concern.
Chemical compounds are differentially distributed in various parts of plants. When secondary metabolites are biosynthesized for the purpose of
Note that association of these plants with toxic effects may well be a reflection of the degree of phytochemical examination to which they have been subjected, given that there is more reason to investigate plants that are cultivated for specific purposes. Other plant families may be relatively neglected (phytochemically), especially those that are of limited distribution or occur in remote areas.