Bioassays occupy a foundational position in pharmacology, toxicology, and plant-medicine research. Where purely chemical methods measure a molecule's presence or quantity, a bioassay measures what that molecule does in a biological context , a distinction that matters considerably when the activity of a compound depends on how it interacts with receptors, enzymes, or whole-organism physiology.
The general procedure involves exposing a standardised biological system (ranging from isolated receptor preparations and cell cultures to whole animals) to graded doses of a test substance, then recording the magnitude of a defined response. Results are typically expressed relative to a reference standard, allowing potency comparisons across batches, species, or preparations. Statistical models , most commonly log-dose/response curves , are applied to calculate parameters such as EC50 (the concentration producing 50% of the maximum effect) or LD50 in toxicity studies.
Bioassays are classified broadly as in vivo (conducted in living animals or whole plants), ex vivo (using tissues or organs removed from an organism), or in vitro (conducted in cell cultures or isolated biochemical systems). High-throughput screening assays used in cannabinoid and secondary-metabolite research are typically in vitro, offering speed and reduced animal use, though they carry limitations around predicting whole-organism behaviour. Regulatory bodies including the Therapeutic Goods Administration (TGA) specify which assay formats are acceptable for particular product classes under the Therapeutic Goods Act 1989.
In the context of plant-based medicine and cannabinoid science, bioassays are used to characterise how phytocannabinoids, terpenes, alkaloids, or peptide-derived compounds bind to and activate specific receptor systems; such as CB1 and CB2 cannabinoid receptors, without making claims about clinical outcomes. The distinction between a bioassay result and a therapeutic claim is, in regulatory and scientific terms, significant.
Sources:
- Bioassay Methods and Applications, National Center for Biotechnology Information (NCBI), National Library of Medicine
- Bioassays for Biological Medicines; Therapeutic Goods Administration (TGA)
- WHO Expert Committee on Biological Standardization: Guidelines for the Preparation and Establishment of Reference Materials for Biological Assays, World Health Organization (WHO)