Did you know that until the 1970s most drugs were discovered by chance?1
That’s right. By chance. The most notable example is the accidental discovery of penicillin, which has been attributed to laboratory carelessness of Sir Alexander Fleming, a Scottish researcher. After returning from vacation, Fleming noted that the mold growing in his petri dish secreted a compound capable of inhibiting the growth of Staphylococcus colonies. This compound was named after a genus of Ascomycetes fungi that produce penicilin, called Penicillium (Latin). The discovery of the first true antibiotic in 1928 revolutionized medicine and still profoundly affects it today. Let’s take a look at how the screening of biologically active compounds evolved over the years.
The trial-and-error approach was utilized in drug discovery all the way until the end of the nineteenth century.1 Since these early beginnings, the search for naturally-derived, biologically active compounds (BAC) with therapeutic potential has evolved to a systematic, step-by-step process with little or no room for ‘’chance’’ discoveries. Today, an efficient and cost-effective bioactivity testing scheme is utilized, which, like the funnel, systematically narrows down the pool of potential novel drug candidates. The approach to nutraceutical bioactivity testing is very similar in many aspects, because extensive testing mandated by the FDA must be performed before any health claims can be attributed to food/nutraceutical products.*
The first step in bioactivity testing is identification of interesting active constituent(s) from natural sources. This is often a single compound, or a group of compounds, whose application as food or use in traditional medicine, has already indicated some type of therapeutic potential. Following, the compound of interest is often isolated and purified from crude extracts and tested in a series of bioassays designed to assess its effects on specific biological functions. Finally, those candidates showing marked biological activity in bioassays are taken one step further and tested in animal model studies and clinical trials conducted on human subjects, thus completing the complicated and lengthy process.
The advantages and disadvantages of in vitro bioassays. In-vitro bioassays are designed to provide additional information about the test compound’s biological effects, bioavailability, and/or potential mechanisms of action. Over the years, a battery of assays focused on testing specific biological functions has been developed. Today, bioassays can be utilized to test antioxidant, anti-inflammatory, antiviral/antibacterial, anticancer and anti-aging effects, as well as bioavailability of the test substance.
Some of the advantages of bioassays include low cost, fast turnaround times and compliance with the non-animal testing policies of many food and nutrition companies. In addition, in comparison to the chemical ‘’test-tube’’ assays, bioassays are a better reflection of the test compound’s biological action and, therefore, yield better correlations with the in vivo effects.
As always in science, each technique has its shortcomings. Bioassays are no different in this regard. Some of their drawbacks include the inability to reproduce the complex environment of a human organism, accurately predict bioavailability, or account for the synergistic/antagonistic actions between the BACs and other interacting compounds. Since bioassays are conducted in a microenvironment outside the human body, they do not always correlate perfectly with a compound’s in vivo effects. In fact, certain studies have pointed to significant discrepancies between the in vitro and in vivo testing results. Consequently, responsible scientists have cautioned against loose interpretations and far-reaching projections based on the in vitro results alone. Therefore, the best way to utilize the results obtained from in vitro bioactivity testing it to treat them as useful diagnostic tools that point the researcher in the direction of the next logical step in the research process.
Types of human cell-based assays. Brunswick Labs offers a range of bioassays for biological functionality testing, such as the cellular antioxidant activity assay and the cellular Nrf2 activation assay for assessing the compound’s antioxidant effects. At Brunswick Labs, we can also test a compound’s anticancer effects by analyzing cancer cell viability, proliferation and apoptosis. Other assays covering anti-diabetic, anti-inflammatory, anti-aging, anti-allergy and immune-boosting properties, as well as bioavailability, are also available.
For example, a compound’s intestinal permeability and uptake can be assessed using the Caco-2 cell assay. In this assay, human intestinal cells are grown on a supportive membrane surface and the permeability of the test substance across the monolayer is monitored. The Caco-2 cell assay is considered to be the golden standard for in vitro prediction of in vivo human intestinal absorption and uptake of a nutraceutical substance or drug candidate.
In general, the testing principle of cell-based assays can be summarized in three simplified steps: 1) representative human cells or cell lines are used as a test model, and 2) treated with the test compound, while 3) their protective effects on cells are monitored using a range of specific biomarkers (for example, biomarkers of inflammation, aging, oxidation, cancer, etc.). Human cell-based assays have been used in preclinical testing in the pharma industry to provide guidance and identification of potential candidates for new product development. Due to the unavailability of specific human cells, some assays are performed using rat/murine cells, which have been established and verified as a suitable cellular model.
Taking things one step further. Upon completing in vitro bioactivity testing, promising compounds are taken one step further and subjected to animal-model studies or human clinical trials, designed to test a compound’s effect on specific biological function or disease state. Today, clinical studies are considered absolutely necessary before any definite conclusions can be drawn about the compound’s protective or therapeutic effects on the human body. On the path to clinical trials, bioassays conducted at Brunswick Labs offer an informative, cost-effective and quick way of identifying promising nutraceuticals.
- 1. Kaul, PN. Drug discovery: Past, present and future. Prog Drug Res. 1998; 50:9-105.
Jasenka Piljac Zegarac is a scientist and freelance writer. She holds a PhD in biology and a BS degree in biochemistry, and contributes on a regular basis to several health and science blogs. Her research articles have gathered more than 900 citations. She may be contacted for assistance with a variety of science and medical writing projects. Find Jasenka on LinkedIn.
*A legal/regulatory professional should be consulted for specific requirements.