ABSTRACT Herbal dietary supplements and medicines are used as the primary form of health care for about eighty percent of the world’s population. In the United States, the use of these botanicals is increasing, accounting for $11.26 billion in sales in the past year alone. Despite widespread and increasing use, herbal dietary supplements and medicines are severely underregulated compared to western medicine. Exact mechanisms, active compounds and metabolites, pharmacokinetics, and safety profiles are not fully understood. This study focuses on the top- selling herbal dietary supplement in the year 2020 in the United States, elderberry (Sambucus nigra L.), which exhibits antiviral effects. Many natural products can exhibit poor bioavailability and thus despite the promise of antiviral efficacy in vitro, do not equate to relevant pharmacological effects in vivo. Metabolic degradation products resulting from host metabolism or gut microbiome metabolism can, however, exhibit increased bioavailability and pharmacological effects. Few studies have examined the metabolic products, bioavailability, and pharmacological effects of metabolites of elderberry, and none have done so when regarding its antiviral activities. Thus, this proposal provides novel research training in pharmacokinetics and pharmacognosy to test metabolic biotransformation products of elderberry extracts for antiviral efficacy. This proposal will develop the methods and capabilities for host and gut microbial metabolism of complex botanical mixtures and provide pharmacological significance regarding the antiviral efficacy of elderberry. Metabolic products of elderberry will be characterized in vitro models and validated in vivo. Isolation of metabolites generated will be conducted using preparative high-performance liquid chromatography and their antiviral activity assessed against influenza models. Antiviral compounds and metabolites will be characterized using high-resolution mass spectrometry (HRMS), nuclear magnetic resonance (NMR), and X-ray crystallography where applicable. Bioavailability and contributions of the gut microbiome will be assessed using a gnotobiotic murine model. These studies will identify metabolites from elderberry exhibiting both antiviral capacities and bioavailability and help establish an infrastructure for metabolic assessment of other botanicals. This will advance the understanding and characterization of herbal medicines and promote the development of my career as an independent scientist capable of conducting relevant research in the fields of pharmacognosy and pharmacology to benefit human health.