National Center for Natural Products Research
The University of Mississippi

Identification of biological activities within natural products is essential for understanding and discovering the therapeutic value of these materials. For botanicals and dietary supplements, proper characterization of biological activities is valuable for confirming the scientific basis of their medicinal/traditional use, discovering new applications and developing products that exhibit consistent efficacy. For pharmaceutical products, natural products serve as a reservoir for screening efforts to identify novel compounds and/or novel activities.

Cell-Based Screens

In vitro systems for detection of antimicrobial activities:

  • antifungal screens to detect natural products effective against Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus
  • antibacterial screens to detect natural products effective against Escherichia coli, Methicillin-Resistant Staphylococcus aureus, Klebsiella pneumoniae, Vancomycin-Resistant Enterococcus faecium, and Pseudomonas aeruginosa
  • anti-malaria screen to detect natural products effective against drug-sensitive and drug-resistant strains of Plasmodium falciparum and determination of therapeutic index of antimalarial activity versus cytotoxicity to mammalian kidney cells.

In vitro systems for detection of immune-enhancing, anti-inflammatory and anti-metabolic syndrome activities:

  • assays of detection of monocyte/macrophage activation
  • selective detection of pattern recognition receptor agonists or antagonists (e.g., TLR2, TLR4, dectin-1a, dectin-1b)
  • assays for detecting inhibitory effects towards iNOS, NF-kB and ROS generation
  • assays for detecting agonistic effects on NRF-2, NAG-1, LXR, PPARα and PPARg and activation of signaling pathways regulated by these receptors.
  • assays for glucose uptake, adipogenesis and anti-adipogenesis

In vitro systems for detection of anticancer activities:

  • a primary screen that employs an array of 14 luciferase reporter gene assays (transient transfection of Hela cells) that assesses the activity of many of the signal transduction pathways important for supporting tumor growth, invasion and spread.
  • assays for anti-cell proliferative effects against a panel of colon cancer, breast cancer, ovarian cancer, and melanoma cell lines.
  • assays for apoptosis, cell cycle, wound healing, cell migration and clonogenic effects.

In vivo models:

  • High Fat Diet Induced mouse (C57BL/6J) model for evaluating natural products for efficacy against diabetes
  • mouse model for evaluating natural products for efficacy against Cryptococcus neoformans
  • pharmacokinetic studies for different formulations
  • screening of natural products for their hepatotoxic potential in healthy and health compromised mice
  • guinea pig model for evaluating efficacy and toxicity of natural products against poison ivy
  • mouse (Balb/C and ND4) model for evaluating of natural products against H1N1 influenza virus
  • mouse (nude) model for evaluation of natural products against cancer

Mechanism of Action Studies

Investigations into the mechanism of action (MOA) of the active components of natural products are important not only for elucidating their molecular targets and facilitating their chemical optimization, but also for identifying potential markers of beneficial or toxic side-effects and for performing meaningful clinical evaluations. At the NCNPR, a combination of genomic and genetic approaches are being used to understand the MOAs of bioactive molecules. Molecular targets identified using these strategies are being validated using target-specific functional assays. These mechanistic approaches are also being used to identify the mechanism by which drug-potentiating compounds work, with the aim of discovering novel molecular pathways that can be exploited to develop new combination therapies. Our capabilities include:

Genomic approaches:

  • Transcript profiling analysis for identifying the molecular pathways that respond to drug treatment. The NCNPR has the required instrumentation for both microarray analysis as well as RNA-Seq analysis with next generation sequencing (NGS) technology.
  • NGS technology is also being utilized for drug target identification using whole-genome sequencing of drug-resistant mutants.

Genetic approaches:

  • Analysis of whole-genome yeast mutant collections consisting of deletion as well as overexpression mutants. This approach allows the identification of molecular pathways that are required for sensitivity to a bioactive molecule, and can be utilized to analyze molecules with activity against any eukaryotic organism.

Target validation studies:

  • Enzyme assays.
  • Metabolite analysis.
  • Elemental analysis.
  • Microscopy.

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.