National Center for Natural Products Research
The University of Mississippi

Herbal medicines (or dietary supplements) are widely consumed products in both developed and developing countries. These are complex chemical mixtures prepared from different parts of plant materials in crude form or extract. Standardization of plant materials and herbal formulations are essential in order to assess the quality based on the concentration of active constituents or marker compounds.

Identification of chemical constituent’s composition has been studied by various chromatographic and spectrophotometric techniques and combination of these methods. In addition, studies of various parameters such as batch-to-batch variations, stability study, chemical profiling are considered essential. Other factors such as pesticide residues, aflatoxin content, heavy metal analysis contamination are also equally important. Furthermore, the combination of qualitative fingerprinting and quantitative multicomponent analysis is a novel method to address the issues of quality control of raw materials and dietary supplements.

Chemical Standardization

Chemical standardization involves all possible information with regard to the chemical constituents present in raw plant materials and dietary supplements. It includes the following chemical evaluation:

  • Preliminary checking for the presence of different chemical groups (like alkaloids, glycosides, tannins, steroids, essential oils, etc.)
  • Quantification of chemical groups of interest (e.g., total phenolics, total flavonoids, total alkaloids)
  • Multiple marker-based chemical fingerprint profiles
  • Quantification of active or marker chemical constituents
  • Method validation

Three basic activities involved in an analytical problem:

  • Sample handling
  • Sample preparation
  • Analysis using appropriate methods

Techniques in extraction of botanicals:

  • Supercritical fluid extraction (SFE)
  • Microwave-assisted extraction (MAE)
  • Ultra-Sonic extraction
  • Solid phase extraction (SPE)

Techniques in identification and characterization Separation techniques

  • Thin layer chromatography (TLC)/High performance thin layer chromatography (HPTLC)
  • High performance liquid chromatography (HPLC) and Ultra-High performance liquid chromatography (UHPLC)
  • Gas Chromatography (GC)
  • Supercritical fluid chromatography (SFC)
  • Inductively-coupled plasma-mass spectrometer (ICP-MS)
  • Metabolomics technique

Detection techniques

  • Photodiode array/Diode array (PDA/DAD)
  • Evaporative light scattering detector (ELSD)
  • Fluorimeter (FLU)
  • Mass Spectrometry (MS)
  • Nuclear magnetic resonance (NMR)

Analysis of adulterants and chemical contaminants

Over 70% of the world population uses herbal medicines and product for healthy living. This rise in the use of herbal product has also given rise to various forms of abuse and adulteration of the products leading to consumers’ and manufacturers’ disappointment and in some instances fatal consequences.

Due to varied geographical locations where these plants grow, coupled with the problem of different vernacular names these plants are known by, a great deal of adulteration or substitution is encountered in the commercial markets. In addition, there have been number of reported studies that reveal adulteration of dietary supplements with undeclared synthetic drugs, which may potentially cause serious toxic adverse effects.

In the majority of reported cases of contamination, the contamination is likely unintentional or intentional. The contaminant exists within the product to an extent that could cause harm if consumed, the product is deemed adulterated. Following are the parameters responsible for adulteration or contamination:

  • Name confusion, misidentification and mislabeling
  • Lack of knowledge about the authentic plant
  • Similarity in morphology and or aroma
  • Environmental contamination with heavy metals (lead in motor exhaust)
  • Insects feeding on the plant during the harvest
  • Pesticides/Insecticides
  • Microorganisms (bacteria, molds)
  • Short supply/Non-availability of the authentic plant (expensive) (Economic adulteration)
  • Synthetic or pharmaceuticals
  • Addition of inert material to add fill weight (Maltodextrin, Extracted marc)

Hyphenated techniques like liquid chromatography-PDA-tandem mass spectrometry (LC-PDA-MS/MS), gas chromatography-tandem mass spectrometry (GC-MS/MS), thin layer chromatography (TLC/HPTLC with MS), SFC-PDA-MS has become possible to detect plant adulterants or synthetic drugs and their structural analogues as adulterants even if they are present in small quantities.

Stability Studies

Chemical stability must be retained over time to prevent unwanted changes upon long term storage. Photo-irradiation, oxygen, humidity, pH, physical parameters, formulation and packaging can affect the overall chemical composition of botanical ingredients, enriched fractions or whole extracts. Stability studies are therefore necessary, in order to guarantee a consistent chemical composition over time. Stability studies are not only important for quality, but also for safety purposes.

In most cases, the manufacturer is responsible for development, validation and use of stability-indicating analytical methods and/or biological assays to monitor the stability of the botanical drug substance and drug product. Stress stability studies are required to identify and control degradation by-products and any adverse effects. Stability studies are particularly relevant in the field of volatile organic compounds (VOCs) that are used in cosmeceuticals, where extraction and purification steps may promote or accelerate the degradation of phytochemicals.  The resources at the NCNPR are well equipped to carry on a variety of experimental procedures for either forced degradation or long term stability studies.

Examples of studies conducted include:

  • Long term stability studies in solution and various pH by hyphenated chromatographic methods and NMR
  • Investigation of the impact of long term storage of commercial formulations on chemical composition of essential oils by CG-MS
  • Estimate the peroxide values of chemicals and characterization of suspected degradation products

Forced degradation studies to investigate the effect of oxygen and light exposure on the chemical stability of fragrance ingredients and implications to skin sensitization