Analysis of Phenolic Compound Concentrations in Over-the-Counter Herbal Preparations

Abstract

Many people rely on over-the-counter herbal extracts to treat a variety of health conditions from lethargy to respiratory or gastrointestinal stress to urinary tract infections. These preparations are relatively inexpensive and available from grocery stores, pharmacies, health-food stores, and online distributors. While the labels on these products usually indicate their plant sources and added ingredients such as sugars or alcohol, there is no standardization of their chemical composition. Most of the medical effects of herbal extracts have been attributed to phenolic and polyphenolic compounds, which differ in number, structure, and proportions from one plant preparation to another. Some polyphenolic compounds such as quercetin are antioxidants that can prevent heart disease while others such as baicalein are antimicrobial agents that can inhibit the growth of Gram-positive or Gram-negative bacteria. In this student project, students use a simple colorimetric assay with the Folin-Ciocalteu reagent to measure the total concentration of phenolic compounds in several over-the-counter extracts. These concentrations may vary greatly even among products from the same plant source. This project provides a good opportunity for students to practice experimental design, the use of micropipettes, the construction of standard curves, and quantitative analysis.