compounds with established toxicity or closely related in structure to compounds with established toxicity, or whether the plant source of the botanical dietary supplement is itself a toxic plant or is taxonomically related to a known toxic plant.
It is well known that plants produce secondary metabolites with biological activities in mammals, and that plant toxicities are due to chemical constituents in plants. Indeed, the rationale for the use of botanical dietary supplements is that they are likely to affect human function. The challenge in assessing risk in the use of dietary supplements is to establish whether the plant compounds present a hazard to humans and, if so, whether the conditions of use suggest risk.
Risk is always considered a function of two factors: hazard and exposure. In the case of botanical ingredients, hazard relates to the presence of biologically active metabolites produced naturally by biosynthetic processes within the plant. In contrast, exposure may be a consequence of the amount of any particular substance produced by the plant, its concentration or dilution during manufacture, and user intake level and bioavailability (see Chapter 3). Thus consumption of a botanical containing a high level of potentially dangerous bioactive substances, consumed at high dosages or for prolonged periods, will significantly increase risk.
It is possible to make educated estimates of the potential hazard of any given botanical through consideration of the types of biologically active compounds that may be present in the plant (constituents of concern) and the nature of the plant (taxonomic relationships). The goal is to consider two likely scenarios that could provide some guidance regarding the possible toxicity of a botanical dietary supplement ingredient (1) where a known constituent of the plant is, or is structurally similar to, a known toxic compound; and (2) where a plant genus or species is, or is closely related to, a plant known to be toxic. When there is evidence that a botanical is taxonomically related to known poisonous plants and that particular constituents are established as having deleterious effects, the convergence of these factors compels detailed consideration of the potential risks associated with the use of the ingredient.
Information about the potential biological activity of a plant-derived dietary supplement ingredient is obtained by reviewing information about the plant’s individual chemical components to determine if any of the constituents raise concerns. Given that related plants have related chemical composition, with more closely related plants generally having more similar chemical constituents, it is therefore also appropriate to consider the activity of other plants in the same plant family or genus to predict composition and potential toxicity.