National Center for Natural Products Research
The University of Mississippi

Bioassay Standardization Services

In vitro bioassays fulfill a critical need to quantitate the potency of active compounds present within botanicals so that these products can be manufactured to exhibit consistent therapeutic activity. Currently the NCNPR, in collaboration with Phytochemical Services Incorporated, has focused on development of in vitro bioassay services for standardizing the potency of immune-enhancing botanicals. These bioassays are capable of detecting high molecular weight compounds that activate the innate immune system.

Immune-enhancing dietary supplements

Current problem: immune-enhancing dietary supplements lack consistent efficacy
The raw materials used to manufacture immune-enhancing dietary supplements exhibit inherent variability due to numerous factors (e.g., genetic/phenotypic variations, differences in agronomic conditions during growth, harvesting practices, etc.). This variation in raw material can influence the level of active components and thereby result in lack of consistent quality of finished products. It is therefore likely that the inconsistent outcomes commonly reported for clinical trials on dietary supplements are due, in part, to variation in the level of active components within the products used in those studies.

Limitation of chemical standardization methods
To address the above quality control problem, chemical standardization methods are being used to verify that the levels of active compounds (when known) within these products are consistent. However, the most commonly identified substances thought to be responsible for the health benefits of immune-enhancing supplements are high molecular weight. High molecular substances can be extremely difficult to purify and cannot be standardized using analytical techniques because the physiochemical properties of these compounds do not fully predict their biological activity. An analogous problem existed in the field of pharmaceutical biologics until it was realized that bioassay-based standardization of these agents was necessary for consistent product quality. Although physicochemical techniques are valuable, the majority of biotherapeutic products require bioassays to quantitate activity/potency.

In vitro bioassays for quantitating the potency of immune-enhancing components
The NCNPR has adapted the concept of biological standardization to immune-enhancing botanicals in order to improve product quality (batch-to-batch consistency). Research discoveries at the NCNPR have been used to set-up in vitro cell-based bioassays that detect high molecular weight botanical components that activate macrophages. Macrophage activation was selected as the endpoint since most immunostimulatory extracts and fractions from dietary supplements activate this cell type. The components detected are relevant for standardization because research indicates that these active substances impact immune parameters in vivo and human clinical studies.

Dr. Nirmal Pugh (
Dr. David Pasco (