Finding the bad actor: Challenges in identifying toxic constituents in botanical dietary supplements

Abstract

Botanical-derived dietary supplements have widespread use in the general population. The complex and variable nature of botanical ingredients and reports of adverse responses have led to concern for negative human health impacts following consumption of these products. Toxicity testing of the vast number of available products, formulations, and combinations is not feasible due to the time and resource intensive nature of comprehensive testing. Methods are needed to assess the safety of a large number of products via more efficient frameworks. Identification of toxicologically-active constituents is one approach being used, with many advantages toward product regulation. Bioassay-guided fractionation (BGF) is the leading approach used to identify biologically-active constituents. Most BGF studies with botanicals focus on identifying pharmacologically-active constituents for drug discovery or botanical efficacy research. Here, we explore BGF in a toxicological context, drawing from both efficacy and poisonous plant research. Limitations of BGF, including loss of mixture activity and bias toward abundant constituents, and recent advancements in the field (e.g., biochemometrics) are discussed from a toxicological perspective. Identification of active constituents will allow better monitoring of market products for known toxicologically-active constituents, as well as surveying human exposure, two important steps to ensuring the safety of botanical dietary supplements.

Keywords: Active constituents; Bioassay guided fractionation; Dietary supplement.

Figure 1.. Bioassay Guided Fractionation

Botanical dietary supplements, containing extracts or raw material (whole plant, roots, aerials flowers, etc.), are extracted using multiple diverse solvents. The extracts are tested in a bioassay and active extracts are fractionated. Through an iterative process, the fractions are tested in the bioassay and active fractions may be further fractionated. Active constituents are then identified via other methods.

Figure 2.

Bioassay Selection. When the specific mechanism of toxicity is known for a particular botanical, a simple bioassay may be selected that will accurately predict the outcome of a more complex system. When less is known about the mechanism of toxicity a more complex bioassay is required to predict toxicity.

Figure 3.

Biochemometric Analysis of Alternaria sp. Mass Spectral Data and Bacterial Growth Inhibition. Reprinted with permission from “Biochemometrics for Natural Products Research: Comparison of Data Analysis Approaches and Application to Identification of Bioactive Compounds”, by J.J. Kellogg. 2016. Journal of Natural Products 79, 376–386. Copyright 2016 by American Chemical Society and American Society of Pharmacognosy. Reprinted with permission.