Using Tox21 High-Throughput Screening Assays for the Evaluation of Botanical and Dietary Supplements

Abstract

Introduction: Recent nationwide surveys found that natural products, including botanical dietary supplements, are used by ∼18% of adults. In many cases, there is a paucity of toxicological data available for these substances to allow for confident evaluations of product safety. The National Toxicology Program (NTP) has received numerous nominations from the public and federal agencies to study the toxicological effects of botanical dietary supplements. The NTP sought to evaluate the utility of in vitro quantitative high-throughput screening (qHTS) assays for toxicological assessment of botanical and dietary supplements.Materials and Methods: In brief, concentration–response assessments of 90 test substances, including 13 distinct botanical species, and individual purported active constituents were evaluated using a subset of the Tox21 qHTS testing panel. The screen included 20 different endpoints that covered a broad range of biologically relevant signaling pathways to detect test article effects upon endocrine activity, nuclear receptor signaling, stress response signaling, genotoxicity, and cell death signaling.Results and Discussion: Botanical dietary supplement extracts induced measurable and diverse activity. Elevated biological activity profiles were observed following treatments with individual chemical constituents relative to their associated botanical extract. The overall distribution of activity was comparable to activities exhibited by compounds present in the Tox21 10K chemical library.Conclusion: Botanical supplements did not exhibit minimal or idiosyncratic activities that would preclude the use of qHTS platforms as a feasible method to screen this class of compounds. However, there are still many considerations and further development required when attempting to use in vitro qHTS methods to characterize the safety profile of botanical/dietary supplements.

Improving natural product research translation: From source to clinical trial

“…These include ligustilide (a constituent of dong quai), which is very unstable and prone to redox reactions and photo-induced dimerization; 43,116,117 desmethylxanthohumol, a chalcone found in Humulus lupulus, or hops, that forms the phytoestrogen, 8-prenylnaringenin, via Michael addition; 118 and curcumin, found in turmeric, which is known to form a myriad of degradation products and metabolites. 44 These chemical changes can modify bioactivity through a variety of mechanisms 97,119,120 and represent factors that appear to be minor (Residual Complexity, see go.uic.edu/resid ualco mplexity), but may significantly alter biological activities and therefore require monitoring. A number of organizations have published general guidelines for stability testing, which are relevant for dietary supplements and other NPs, including the NCCIH Policy on Natural Product Integrity 18 and guidelines published by the International Council for Harmonisation (ICH; ich.…”

“…[88][89][90][91][92] These approaches, as outlined by the Tox21 Federal collaboration and the U.S. Environmental Protection Agency's ToxCast program, [93][94][95][96] can be used to focus high-throughput in vitro and in vivo testing on compounds and concentrations that are more likely to be biologically active and appropriate for each model. 97,98 Such integrated approaches could be further developed to probabilistically model the pharmacological and toxicological kinetics and dynamics of complex NPs. 99 Speakers described several critical, often broadly applicable considerations for utilizing in silico models.…”

“…Data from more highly characterized products can be integrated into dynamic models, and in vitro to in vivo extrapolation (IVIVE) can be used to predict biological responses . These approaches, as outlined by the Tox21 Federal collaboration and the U.S. Environmental Protection Agency’s ToxCast program, can be used to focus high‐throughput in vitro and in vivo testing on compounds and concentrations that are more likely to be biologically active and appropriate for each model . Such integrated approaches could be further developed to probabilistically model the pharmacological and toxicological kinetics and dynamics of complex NPs …”

Improving Natural Product Research Translation: from Source to Clinical Trial

“…Data from more highly characterized products can be integrated into dynamic models, and in vitro to in vivo extrapolation (IVIVE) can be used to predict biological responses (87)(88)(89)(90)(91). These approaches, as outlined by the Tox21 Federal collaboration and the U.S. Environmental Protection Agency's ToxCast program (92)(93)(94)(95), can be used to focus high-throughput in vitro, and in vivo testing on compounds and concentrations that are more likely to be biologically active and appropriate for each model (96,97). Such integrated approaches could be further developed to probabilistically model the pharmacological and toxicological kinetics and dynamics of complex NPs (98).…”

“…These include ligustilide (a constituent of dong quai), which is very unstable and prone to redox reactions and photo-induced dimerization (42,116,117); desmethylxanthohumol, a chalcone found in Humulus lupulus, or hops, that forms the phytoestrogen, 8-prenylnaringenin, via Michael addition (118); and curcumin, found in turmeric, which is known to form a myriad of degradation products and metabolites (43). These chemical changes can modify bioactivity through a variety of mechanisms (96,119,120) and represent factors that appear to be minor (Residual Complexity, see go.uic.edu/residualcomplexity), but may significantly alter biological activities and therefore, require monitoring. A number of organizations have published general guidelines for stability testing, which are relevant for dietary supplements and other natural products, including the NCCIH Policy Natural Product Integrity (17) and guidelines published by the International Council for Harmonisation, ICH (ich.org).…”